Hydrology of the Tukituki Catchment Flow metrics for 17 ... · temperate climate2 under the Koppen...

Hydrology of the Tukituki Catchment

Flow metrics for 17

sub-catchments

September 2012 ISSN 1179 8513

EMT 12/18

HBRC Plan No. 4405

4405 EMT 1218 Hydrology of the Tukituki Catchment.docx

Resource Management Group

Environmental Science

Hydrology of the Tukituki Catchment Flow metrics for 17 sub-catchments

September 2012 ISSN 1179 8513

EMT 12/18 HBRC Plan No. 4405

© Copyright: Hawke’s Bay Regional Council

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Executive Summary

The Tukituki River originates in the Ruahine Ranges. These forested mountains and foothills receive more rainfall than the Ruataniwha Plains and are the source of much of the rivers’ flow and gravel bed load. The drier Ruataniwha Plains lie at the base of the ranges, having formed from sediment that has eroded from the mountains. The Waipawa, Makaretu and upper Tukituki Rivers lose water as they traverse the plains because the channels are perched above the aquifer on permeable gravels deposited by the rivers. The water that was lost to groundwater subsequently re-emerges, together with direct rainfall recharge, in spring-fed streams of the Ruataniwha Plains (e.g. Kahahakuri Stream). At the eastern edge of the Ruataniwha Plains, both gaining and losing tributaries come together to form the mainstem of the Tukituki River. The Tukituki River then flows through Hill Country of soft sedimentary rock where inflowing tributaries have more variable flows and less groundwater contribution.

Relatively higher rainfall and lower evaporation increases river flows in winter. In addition to seasonal cycles, river flows respond to longer-term climate cycles. El Niño events reduce rainfall, and increase the risk of drought, because the moisture from more prevalent westerly winds is intercepted by the Ruahine Ranges before reaching the Ruataniwha Plains. El Niño events can last several years and occur more commonly during the positive phase of the Interdecadal Pacific Oscillation. The Tukituki River experienced lower mean flows during the positive phase of the Interdecadal Pacific Oscillation (1978-1998), relative to the negative phase (1947-1977). The loss and gain of flow to groundwater also varied from decade to decade, as demonstrated along a length of the Tukipo River that lost flow to groundwater in 1973, but gained flow from groundwater in 2009.

This report provides flow metrics for 17 sub-catchments of the Tukituki River, summarised in Table 1 and Table 2. These flow metrics describe the size of the stream (mean annual flow, median flow) and more extreme flow events (mean annual low flow, mean annual flood flow). We have more confidence in the flow metrics for those sites with long-term measured flow records, compared to the sites where flow records were synthesised using correlated flow measurements (see ‘Method’ column in Table 1). Flow metrics were also estimated in the absence of water abstraction (termed ‘naturalised flows’) for four sub-catchments that were delineated as Management Zones (Table 2).


Table 1: Metrics of existing flow (L/s) for sub-catchments of the Tukituki River.

Flow metrics include MAF (mean annual flow), Median flow, MALF (mean annual low flow) and MAFF (mean annual flood flow) in litres per second. The Method column distinguishes the more precise Rated flow records with long-term records, from measured records that were extended in time using Vector Transformation (Rated+VT), and the less precise Correlated synthetic records (* denotes extrapolated flows). River Environment Classification (REC) provided an approximate estimate for the remaining sites where abstraction pressure is low.

Code Site Method Record MAF Median MALF MAFF

T1 Waipawa River at RDS/SH2 Rated 1987-2011 14,949 8,655 2,839 479,775

T2 Mangaonuku Stream U/S Waipawa

Correlated 1987-2011 5,200* 3,121 1,170 160,000*

T3 Kahahakuri Stream at Lindsay Rd Correlated 1987-2011 1,700* 1,425 1,064 21,000*

T4 Tukituki River at Waipuk Onga Rd Correlated 1987-2011 4,386 2,458 344 145,000*

T5 Tukipo River at Ashcott Rd Correlated 1977-2011 7,700* 3,947 1,043 387,000*

T6 Makaretu Stream at State Highway 50

Correlated 1987-2011 2,191 1,308 340 67,000*

T7 Porangahau Stream at Oruawhara Rd

Rated+VT 1977-2011 546 148 30 60,316

T8 Maharakeke Stream at State Highway 2

Correlated 1977-2011 1,300* 570* 218 111,000*

T9 Mangatarata Stream at Farm Rd Rated+VT 1983-2011 500 55 2* 23,000*

T10 Mangamahaki Stream REC 3,800 NA 29 NA

T11 Papanui Stream at Middle Rd Correlated 1968-2011 1,200* 320* 63 72,000*

T12 Mangarara Stream REC 500 NA 4 NA

T13 Makara Stream Correlated 1968-2011 500* 207 14 18,000*

T14 Hawea Stream REC 700 NA 6 NA

T15 Tukituki River at Tapairu Rd Rated 1987-2011 15,150 9,130 2,534 454,492

T16 Tukituki River at Red Bridge Rated 1968-2011 44,544 21,586 5,902 1,397,762

T17 Makaroro River at Burnt Bridge Rated+VT 1968-2011 6,661 3,680 1,394 144,199

Table 2: Naturalised flow metrics for major sub-catchments of the Tukituki River.

Code Site MAF Median MALF

T1 Waipawa River at RDS/SH2 14,970 8,991 3,009

T15 Tukituki River at Tapairu Rd 15,830 9,829 2,865

T16 Tukituki River at Red Bridge 44,505 22,022 6,258

T17 Makaroro River at Burnt Bridge 6,661 3,680 1,394

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Table of Contents

EXECUTIVE SUMMARY ................................................................................................................................ I

TABLE OF CONTENTS ............................................................................................................................... III

1 INTRODUCTION ................................................................................................................................... 1

1.1 SCOPE/PURPOSE .................................................................................................................................. 1 1.2 CATCHMENT OVERVIEW ........................................................................................................................ 1

1.2.1 Geology ............................................................................................................................................ 1 1.2.2 Climate ............................................................................................................................................. 3 1.2.3 Stream types of the Tukituki catchment ...................................................................................... 9 1.2.4 Losses and Gains to Groundwater ............................................................................................ 11 1.2.5 Notable channel changes ............................................................................................................ 15 1.2.6 Minimum flows .............................................................................................................................. 15

2 METHODS ........................................................................................................................................... 17

2.1 RIVER FLOW RECORDS ........................................................................................................................ 17 2.1.1 Correlated gauging method ........................................................................................................ 17 2.1.2 Vector Transformation method ................................................................................................... 18 2.1.3 Naturalised flow records .............................................................................................................. 18 2.1.4 REC flow metrics .......................................................................................................................... 18

2.2 FLOW DURATION CURVE - FDC ......................................................................................................... 22 2.3 DESCRIPTION OF FLOW METRICS ........................................................................................................ 22

2.3.1 Mean Annual Flow - MAF ............................................................................................................ 22 2.3.2 Median Flow .................................................................................................................................. 22 2.3.3 Monthly Mean Flows .................................................................................................................... 22 2.3.4 Mean Annual Flood Flow - MAFF .............................................................................................. 22 2.3.5 Mean Annual Low Flow - MALF ................................................................................................. 23

2.4 SECURITY OF SUPPLY .......................................................................................................................... 23

3 RESULTS ............................................................................................................................................. 24

3.1 FLOW SUMMARIES ............................................................................................................................... 24 3.2 COMPARISON OF MAJOR SUB-CATCHMENTS ....................................................................................... 24 3.3 COMPARISON OF FLOW DURATION CURVES BETWEEN STREAM TYPES ............................................ 25 3.4 SEASONAL PATTERN OF FLOW ............................................................................................................ 25

4 CONCLUSIONS .................................................................................................................................. 28

5 REFERENCES .................................................................................................................................... 29

APPENDIX 1 – VECTOR TRANSFORMATION METHOD ...................................................................... 32

APPENDIX 2 - FLOW NATURALISATION METHOD ............................................................................. 33

APPENDIX 3 - FLOW METRICS FOR EACH MONITORING SITE........................................................ 36

APPENDIX 4 – TUKITUKI LIDAR ELEVATION IMAGERY .................................................................... 66

1 INTRODUCTION

1.1 Scope/Purpose

This report provides a summary of river flow information for the Tukituki catchment, to inform policy development. This report focuses on the quantity of surface water that flows through the Tukituki River and its tributaries (i.e. hydrology of the Tukituki). New or revised flow metrics are presented for the sub-catchments. We have also summarised the results from existing reports that are vital for understanding the hydrology of the Tukituki catchment, such as groundwater interactions and long term trends. Minimum flows required to protect instream values are summarised for completeness. The report does not address security of supply for abstractive users of surface waters - readers are referred to Waldron & Baalousha (2012).

1.2 Catchment Overview

The Tukituki River flows into Hawke Bay, south of Napier and Hastings. The map in Figure 1 displays the catchment location and some key landmarks, such as the Ruataniwha Plains.

River flow originates from rainfall, some of which is lost to evaporation or temporarily stored as groundwater before reaching streams and rivers. Understanding river flow therefore requires an understanding of climate and geology, which are summarised in this section, together with existing information on how the flow regime varies across the catchment.

Figure 1: Map of the Tukituki catchment.

1.2.1 Geology

The Tukituki River receives much of its runoff from the Ruahine Ranges, where the hard greywacke has a low capacity for water infiltration (Figure 2). The majority of gravel in the

Tukituki River also originates from the ranges, where gravel production is high and the rock is harder (Grant, 1982; Grant 1989). The Ruataniwha Plains lie at the foot of the ranges, representing a basin filled with material derived from the rapidly eroding Ruahine Ranges (Part 1.4 in HBRC 2003).

Classifying geology at the level of ‘Rock Group’ (Figure 2) provides an overview of land systems at a catchment scale. Important sub-classifications must also be recognised within each Rock Group. The gravel group on the Ruataniwha Plains can be sub-divided into the older and thicker Salisbury Gravels and the Young Gravels (Baalousha, 2010). The soils of some older river terraces have formed a cemented clay pan (Part 1.3 in HBRC 2003), which can limit infiltration of water to more permeable alluvium beneath. The Young Gravels have high permeability and form a thinner layer over the Salisbury Gravels. McGuinness (1984) proposed that the groundwater-surface water interaction is associated with the shallow, unconfined aquifer housed in these Young Gravels. More recent research indicates that interchange also occurs between the shallow aquifer and the more confined deep-aquifer (Undereiner, et al. 2009; Section 3.1 in Baalousha, 2012).

A limestone ridge (Ruakawa & Turiri Ranges) forms the eastern boundary of the Ruataniwha Plains. The Hill Country east of the Ruataniwha Plains is comprised of soft sedimentary rock (mudstone, sandstone and limestone), producing rapid runoff from steep slopes. Broad alluvial valleys traverse the Hill Country, indicating the present and historical course of waterways.

Figure 2: Geology of the Tukituki catchment.

Major ‘Rock Groups’ from Lee et al. (2010). Tukituki sub-catchments are overlain (white outline), together with streams draining a watershed >30km2. Sub-catchments are coded T1 to T17, as defined in Table 4.

1.2.2 Climate

The Hawke’s Bay Region experiences a predominantly mild climate, buffered by sea temperatures. Snowmelt is therefore a minor contributor to the flow of most rivers (Grant, 1973), despite the mid-latitude location (38.5° to 40.4° south). Hawke’s Bay is generally drier than most other regions of New Zealand (Figure 3), lying in the rain shadow of the mountain ranges that intercept moisture from the prevailing westerly winds (Coulter, 1961).

Rainfall in the Tukituki catchment exemplifies this pattern (Figure 4, Figure 5), with higher rainfall from westerly systems intercepted by the Ruahine Ranges (average rainfall greater than 2,000 mm/yr). There is typically less rainfall (less than 1,000 mm/yr) to the east at lower elevations, but coastal hills that are more exposed to easterly weather systems can receive more rain (e.g. average rainfall greater than 1,500 mm/yr on Kahuranaki, Figure 5).

Mean annual temperature varies less than rainfall across the catchment, except for cooler temperatures at the top of the ranges (Figure 4). Cooler temperatures translate to less evaporation (Figure 5). Grant (1973) estimated that 80% of baseflow for the Tukituki River

originated from the Ruahine Ranges and foothills, despite occupying less than a third of the catchment. In agreement with Grant’s (1973) calculation, we estimated that 73% of mean annual low flow for the Tukituki River is sourced from the Ruahine Ranges and foothills1. This bias becomes less pronounced as flows increase, with 53% of mean annual flow originating from the ranges.

The seasonal distribution of rainfall is relatively even for the Ruataniwha Plains, when considered in terms of monthly totals (Figure 6). The climate may be described as a maritime temperate climate2 under the Koppen Classification (see Peel et al. 2007). Winter is typically the wettest season, with the highest monthly total rainfall occurring in July (Figure 6). This winter contrast was more pronounced in the Hill Country (Te Kaihi rain gauge, Figure 6).

There is less evaporation in winter (Figure 7), increasing the contrast in stream flow between summer and winter. The measure of evaporation used here (PET - potential evapotranspiration) is an estimate of the maximum potential loss of moisture from wet surfaces and from plant transpiration (see Tait & Woods 2007). Actual evaporation is typically lower than PET when surfaces are dry.

1 Calculated from River Environment Classification attribute data (described by Woods et al. 2006)

summed for streams at the 1,400 mm rainfall contour that are second-order or greater, contrasted to the Tukituki River at the coast.

2 Mediterranean climates that have drier summers.

Figure 3: Seasonal rainfall for Napier contrasted to other New Zealand locations.

The seasonality of Napier rainfall is less pronounced than Auckland, as demonstrated by monthly total rainfall (main plot) and the number of wet days per month (top right plot, days with >1mm rain). Annual total rainfall is specified in the legend for each location. Mean values for 1981-2010 were sourced from NIWA.

Figure 4: Profile of rainfall and temperature along the Tukituki River channel.

This profile runs from the coast (Haumoana – 0 km) to the headwaters (Ruahine Ranges). Note that this is not an elevation profile. Rainfall is much higher in the forested ranges, which contribute disproportionately to flow. Mean temperatures are less variable over the length of the catchment, with only a short length in the headwaters less than 10 °C.

Figure 5: Map of annual rainfall minus PET (potential evapotranspiration), as an indicator of runoff across the Tukituki catchment.

Sub-catchments are coded T1 to T17, as defined in Table 4. Map data provided by K. Kozyniak (HBRC).

Figure 6: Seasonal rainfall pattern in the Tukituki catchment.

Means of the monthly total rainfall are plotted for three monitoring sites that were selected to represent the Ruahine Ranges (Moorcock 1988-2010, 770 m elevation), Hill Country (Te Kaihi 1981-2010, 183 m) and Ruataniwha Plains (Onga Onga 1981-2010, 170 m). Site locations are mapped in Figure 5. Te Kaihi and Onga Onga data from NIWA.

Figure 7: Seasonal evaporation on the Ruataniwha Plains (Onga Onga climate station).

Potential evapotranspiration estimated for each month over the period Nov 2007 – Jun 2012. Irrigation demand was estimated from metered data by Harkness (2009a) for the Tukituki catchment (expressed as a percent of the maximum abstraction rate specified in resource consents).

This report focuses on average flows for the Tukituki catchment (e.g. low flows averaged across several decades). It is important to recognise that climate varies from year to year, with direct consequences for river flows. The IPO (Inter-decadal Pacific Oscillation) provides a measure of longer-term climate trends, with a positive phase lasting from 1978-1998, and a negative phase from 1947-1977. The El Niño pattern is more likely to develop (and be more severe) during positive phases of the IPO. La Niña climate patterns can last several years, and are associated with increased rainfall in the Hawke’s Bay region (including ex-tropical cyclones) because of increased easterly winds during summer months (see Section 3.2 in MfE, 2008). In contrast, El Niño events reduce rainfall, and increase the risk of drought, because the moisture from increased westerly winds is intercepted by the Ruahine Ranges before reaching the Ruataniwha Plains. Changes in climate resulting from increased concentrations of greenhouse gases in the atmosphere, may be of the same order of magnitude as IPO variability (MfE, 2010).

Harkness (2009b) examined the influence of this inter-decadal climate pattern on Hawke’s Bay rainfall and river flow by contrasting the 1978-1998 positive phase of the IPO with the 1947-1998 negative phase of the IPO (see Kozyniak, 2012, for climate patterns post 1990). The Harkness report mostly confirmed3 predictions from MfE (2008) of less rain during the positive phase IPO (1978-1998), compared to the negative phase IPO (1947-1977). This held true for annual total rainfall and number of rain days in the Tukituki catchment, where climate change predictions include increased drought severity (Mullan et al. 2005). Despite the decline in annual total rainfall, Harkness (2009b) did not detect a change in annual maximum daily rainfall.

The decrease in annual total rainfall translated to reduced river flow. Harkness (2009b) detected a net decline in mean annual flow for the lower-Tukituki (at Red Bridge) and upper-Tukituki River (at Taiparu Road, Figure 8) during the positive phase IPO (1978-1998). Low flows (mean annual low flow) were typically below average for 1978-1998 for the upper Tukituki (at Tapairu Road). The pattern was less pronounced for the Waipawa River (at SH2) and lower Tukituki (at Red Bridge). Seasonally, rainfall is expected to decrease over the summer-autumn period during El Niño conditions (Kozyniak 2012). It is not clear to what extent westerly rain spills over to the eastern slope of the Ruahine Ranges to feed higher elevation tributaries during El Niño conditions. Harkness (2009b) reported a decline in the number of rainy days for the foothills of the Ruahine Ranges over the past 120 years (from 190 to 120 days4 >0.1 mm rain at Gwavas). This decline was correlated with an increase in air temperature (latitudes 44° to 64° south, NASA data) over the same period (R2=0.77, p-value<0.0001, for 5 year means). In contrast, the number of rainy days at Napier increased slightly over the same period (from 100 to 120 days >0.1 mm at Nelson Park).

Harkness (2009b) did not detect a change in annual maximum flows, which is consistent with the lack of pattern he observed in rainfall maxima. MfE (2010) predicted that the biggest increases in flooding will occur in regions where rainfall is expected to increase (decrease predicted for most of the Tukituki catchment). Extreme flow data are more variable and the metrics are based on few data points (annual maxima are 1 day of data, compared to 365 days for mean annual flow). This reduces the power to resolve any subtle changes that are taking place.

3 The IPO appears less important, or produced increased rainfall, for some areas in northern Hawke’s

Bay (Wairoa at Waiputaputa Station), which is arguably consistent with predictions from Mullan et al. (2005) for that particular area.

4 This pattern was less pronounced at a higher rain threshold, reducing 25 days at a 1 mm threshold

for rain days at Gwavas (compare 70 day decline using 0.1 mm threshold).

http://data.giss.nasa.gov/gistemp/

The reductions in rainfall and river flow observed during the positive phase IPO demonstrate the potential for climate change to further decrease flows.

Figure 8: Changes in MAF (mean annual flow) over time for the Tukituki River.

This plot is reproduced from Harkness (2009b). The change is represented as a cumulative percent deviation from the long-term mean flow for all sites. Flows exhibited a net decline over the positive phase of the IPO (1978-1998, green bar on x-axis) – a period when dry El Niño events were more common than 1947-1977 (negative phase, red bar on x-axis).

1.2.3 Stream types of the Tukituki catchment

Wood (1998) identified three general stream types in the upper Tukituki catchment:

Gravel Streams originating from the wet Ruahine Ranges with a large bedload of gravel and more reliable baseflows.

Hill Country Streams originating from sedimentary rock with low infiltration rates and less reliable baseflows. Bed material varies from gravel to silt.

Groundwater Streams fed by aquifers such as the Ruataniwha, with more stable baseflows. Substrate is often silt and organic matter.

The magnitude of gravel load is sufficient to cause braiding (multiple wet channels among bare gravel islands) where the Tukituki and Waipawa rivers spill out onto the Ruataniwha Plains. At these transition zones, the rivers change from erosional to depositional because the reduced slope denies them the power necessary to carry the entire bedload of gravel (Ludecke, 1988). Further downstream, braiding is less pronounced where the channel is more confined (e.g. through limestone outcrops in the Hill Country). Some reaches of Gravel Streams have intermittent flow where water is lost to groundwater (see Section 1.2.4).

For this report, we produced a similar classification of stream types using a flow variability index (Figure 9). This index uses attributes from the River Environment Classification (Snelder et al. 2004), and was calculated as the MALF divided by the MAF (the synthesis of these flow metrics are described by Woods et al. 2006, Henderson et al. 2004). Flow variability is an important driver of river processes (e.g. channel morphology, ecology). The index also reflects the more fundamental physical drivers that dictate flow variability (flows were modelled from rainfall, temperature, vegetation, geology and soils). The streams shown in red in Figure 9 are likely to have more variable flows (i.e. a smaller ratio), and correspond well with the Hill Country stream classification from Wood (1998). The streams that are

shown in blue (Figure 9) drain the high-rainfall Ruahine Ranges, and overlap with the Gravel Stream classification.

The flow variability index was derived from predicted flows, rather than measured flows. Hence it does not distinguish groundwater losses or gains beyond the moderating effect of alluvial deposits (such as the Ruataniwha Plains) on the flow variability of streams shown in green (Figure 9). These streams typically gain groundwater, with some exceptions (see Section 1.2.4). The streams shown in green (Figure 9) represent a mix of Groundwater Streams and Gravel Streams, reflecting varying stream slopes and varying groundwater influence. Streams shown in blue change from perennial to intermittent flow as they cross the Ruataniwha Plains (notably the Waipawa, Tukituki and Makaretu Rivers), reflecting substantial losses to groundwater (see Section 1.2.4). The classification in Figure 9 therefore represents large-scale drivers of flow (climate, geology, etc.) as a useful starting point for more detailed investigations (e.g. concurrent gauging to measure flow losses and gains).

Figure 9: Stream types of the Tukituki catchment.

The index of flow variability was calculated from flow attributes of NIWA’s River Environment Classification (MALF/MAF). The red streams are expected to have more variable flows (i.e. a smaller ratio), and the blue streams less variable (larger ratio). Streams with a mean flow greater than 50 L/s are displayed, with names for sub-catchments overlaid (outlined in grey).

1.2.4 Losses and Gains to Groundwater

Several rivers originating from the Ruahine Ranges transition to intermittent streams as they flow across the Ruataniwha Plains because water soaks through the permeable gravels into the groundwater aquifer. Johnson (2011a) investigated the loss and gain of stream flow to groundwater, based on concurrent gaugings across the Ruataniwha Plains during 2009. A key output from that report was the spatial distribution of streams that lose or gain flow (Figure 10). In particular, the Waipawa, Tukituki and Makaretu Rivers lost flow over considerable lengths of stream (orange and red lines on Figure 10). These three rivers tend to lose flow as they traverse more recent alluvial deposits of the eastern Ruataniwha Plains (HBRC 2003). These Young Gravels are a product of historic and ongoing deposition by the river (T&T 2012). As a result of this deposition, the river channel can become perched higher than the surrounding land (e.g. Figure 10 left plot, and Appendix 4) and hence higher than the groundwater level.

The lost flow was regained at the eastern edge of the Ruataniwha Plains as well as from spring-fed tributaries (blue lines on Figure 10). Those spring-fed tributaries must intersect the groundwater aquifer by way of a more incised channel (e.g. Figure 10 right plot) and/or traversing lower elevation areas (e.g. Figure 11). The water level of the shallow groundwater aquifer slopes from the western plains down to the east and is recharged from local rainfall, in addition to lost river flow (Baalousha, 2010). Using chemical signatures, Undereiner et al. (2009) concluded that springs closer to the Waipawa have a more direct connection to river water via the shallow aquifer. The lower elevation Mangaonuku Stream intercepts springs on the eastern edge of the plains that drain both the shallow aquifer and the deep aquifer (Undereiner et al., 2009).

The Tukituki River downstream of the Waipawa confluence (not shown in Figure 10) demonstrated little gain or loss of flow during 2009 gaugings. Johnson (2011a) attributed the lack of loss/gain in the lower river to the small alluvial aquifer, which is bounded by basement rock within a narrower valley.

Figure 10: Gaining and losing reaches for the upper catchment (2009).

The map (from Johnson, 2011a) distinguishes reaches that lose flow to groundwater (orange line), from those gaining flow from groundwater (blue), or with negligible flow loss/gain (green). This map encompasses the catchment above the Tukituki-Waipawa confluence. The cross-section plots include a drying reach of the Tukituki River (left plot) where the stream (red points) is perched above surrounding land, plus a gaining section of the Mangaonuku Stream (blue points on right plot) with a more incised channel (see Appendix 4 for LiDAR imagery).

Figure 11: Elevation profiles for the Waipawa River and Mangaonuku Stream.

The Waipawa River loses flow to groundwater, whereas the Mangaonuku River gains flow from groundwater over this section (2003 LiDAR elevations).

Johnson (2011a) found that losing and gaining reaches had a similar extent under different flow conditions. From gaugings undertaken from September 2008 to June 2009, the Waipawa went to zero flow (above the Mangaonuku confluence) when flow upstream of the losing section (at SH50) dropped to about 3,500 L/s. Johnson (2011) further reported that a section of the Tukituki ran dry when flows above the losing section (at SH50) dropped to about 1200 L/s.

We can say with certainty that some rivers lose flow to groundwater as they cross the Ruataniwha Plains. It is also clear that the Tukituki, Waipawa and Makaretu Rivers are more prone to flow loss than most other rivers. In contrast, other streams on the Ruataniwha Plains benefit from sustained inputs of shallow groundwater – these streams are likely to have more stable flow and temperature regimes as a consequence (Section 5.2 in McGuinness, 1984).

The length of losing and gaining sections was less consistent between-decades, with a shorter stream length identified as losing water in 2009 relative to either the 1973 or 1997 results (compare the extent of orange and red lines between maps in Figure 12). The Tukipo River indicated the strongest contrast. During 1973 the Tukipo River lost water to groundwater over a considerable length, whereas water gain was measured over the same length in 1997 and 2011. Johnson (2011a) suggested inter-decadal changes may be related to sediment processes (e.g. aggradation, degradation, changing bed permeability). Gravels eroded from the Ruahine Ranges are transported down the channel at a slower speed and more intermittently than surface water (mostly during floods). Cross-section monitoring by HBRC reveals the high inter-annual variation in gravel flow for the upper Tukituki (see Section 5.2 in T&T, 2012). Dr Patrick Grant proposed the current episode of river aggradation started in 1950 (‘Waipawa Warm Erosion Period’, Chapter 14 in Grant, 1996). Extraction of aggraded gravel from the Tukituki and Waipawa channels is managed by HBRC to maintain the flood capacity of the stopbanks. Gravel bars are also raked to increase the mobility of gravel during floods - this could maintain bed-permeability. The extent of drying will depend on the magnitude of river flow that reaches the plains (Johnson, 2011a). The effect of changes in groundwater level and bed permeability was investigated by Waldron & Baalousha (2012) in order to predict the effects of groundwater abstraction on surface flow.

Figure 12: Gaining and losing reaches of the Ruataniwha Plains, compared between decades.

Investigations in 1973 and 1996/97 are compared to 2008/2009 concurrent gauging programme (for legend, see Figure 10). Maps are adapted from Johnson (2011a).

For the present report, we investigated flow losses and gains in tributaries east of the Ruataniwha Plains. Tributaries of the Papanui and Mangatarata sub-catchments were distinguished as a different class of stream in Figure 9 (green lines, compared to red lines for surrounding Hill Country streams). This difference in classification reflects more extensive alluvial gravels in these catchments.

The Papanui Stream is separated from the Waipawa River by a stopbank (located 0.7 km upstream of the Tukituki-Waipawa confluence), which prevents Waipawa surface flow from entering the Papanui (for channel changes, see Section 1.2.5). But the Papanui Stream appears to gain groundwater that originates as a loss from the Waipawa River. Alluvial gravels of the historic Waipawa River bed likely connect the groundwater across the catchment boundary. This proposal is supported by the lower elevation of the Papanui Stream relative to the Waipawa River (>2 m lower across 300 meter distance, using 2003 LiDAR elevations). Similar water quality of the Papanui and Waipawa also supports a link between the two (Ludecke, 1988). Flow gaugings near the source (Papanui at Pourere Rd) revealed much more flow than expected from the small catchment area (REC annual water balance prediction of 4 L/s, compared to 60 L/s measured from two gaugings). Further downstream at Newman’s ford, long-term monitoring (1979-1991) provided MAF estimates in the order of 400 L/s for the Papanui Stream, which is more than double the flow predicted from a water balance estimate (REC MAF estimate of 150 L/s). Flows in the Papanui Stream are most likely supplemented by the Waipawa River, but we have not quantified how this subsidy varies along the stream length over time.

The potential exists for input of groundwater to Lake Hatuma that originate from the Tukituki River. Lake Hatuma is just south of Waipukurau and discharges to the Mangatarata Stream, which flows into the Tukituki River below the Waipawa confluence. The lake surface is at a lower elevation than the Tukituki River (lake at 127.5 m ASL, compared to Tukituki at 129 m at Waipukurau at time of LiDAR). Alluvial gravels provide a potential groundwater connection across the 3 km that separate the lake from the Tukituki River5. This connection was not supported by measured flows (at the Farm Road monitoring site) that were lower than those

5 If the groundwater table was at the level of the Tukituki River, then springs would arise in Hatuma

feeder drains between the railway and racecourse, according to LiDAR elevations.

1973 2009 1997

indicated by a water balance (observed mean 640 L/s; REC annual water balance 1,100 L/s). Ludecke (1988) discussed the potential for large evaporative losses from Lake Hatuma, which may contribute to the lower than expected water balance.

1.2.5 Notable channel changes

To understand flow patterns in the Tukituki catchment, it is useful to understand major channel changes that have taken place. Flood control using stopbanks and gravel management started in 1969 (Grant, 1982). Most stopbanks are confined to the eastern Ruataniwha Plains (Waipawa, Tukituki and Tukipo Rivers), with a shorter length of stopbanks where the river traverses the Heretaunga Plains.

Historically, there were more wetlands (vegetated by toetoe and raupō) and springs on the Ruataniwha Plains, according to Wakefield et al. (2012). Native forest was present on the higher alluvial terraces of the plains (Grant 1996). In the lower catchment, catastrophic winds may have confined tall forest to the few remnants that were encountered by European settlers (Grant, 1996).

The Waipawa River historically followed a different path through the Hill Country, flowing down what is now the Papanui Stream (sub catchment T11, Figure 2) to a more distant confluence with the Tukituki River. The Papanui Stream was referred to as the Waipawa River as recently as 1888 (Worthy, 2000, p41 in Wakefield et al., 2012). From discussion with local land-owners (Peter and Tony Kittow), the Waipawa was diverted in the late 1800’s (about 1897) by a prominent local6. A stopbank now divides the Waipawa from the Papanui, located 0.7 km upstream of the Tukituki-Waipawa confluence. A groundwater connection may still exist (via shallow alluvial gravels), supplementing flows of the Papanui Stream (see Section 1.2.4). The Waipawa River may have alternated between the Papanui channel and its present course over the centuries - diverted by its own gravel deposits.

Within the Papanui catchment, Te Aute Swamp/Lake (syn. Roto-a-Tara) was drained about 18887, perhaps in association with the Waipawa River diversion. The large area of swamp and lake deposits that remain today (shown as peat in sub-catchment T11, Figure 2) will continue to exert an influence on the flow regime of the Papanui Stream (particularly the Te Aute drain).

Hatuma Lake (synonym Whatuma), located south of Waipukurau, was historically larger (p36 in Wakefield et al., 2012) and is now managed as a wetland. The residence time of water flowing to the Maharakeke Stream has likely decreased. The lake lies at the base of what appears to be an alluvial fan of the Tukituki River, raising the prospect of a prehistoric surface water link between the lake and river.

1.2.6 Minimum flows

Minimum flows are set in the Hawke’s Bay Regional Resource Management Plan (HBRRMP) to maintain existing aquatic ecosystems (Policy 73a, 2006). These are reproduced in Table 3, along with the revised minimum flows proposed by Johnson (2011b). Security of supply for irrigators was investigated by Waldron & Baalousha (2012).

6 Reverend Williams was Anglican Arch Bishop of Waiapu - though it is not clear which of the three

generations of Reverend Williams oversaw these works.

7 Bones of giant moa, takahe and Haast eagle were exposed when drainage ditches were excavated

through Te Aute Swamp/Lake in 1888 (Worthy, 2000).

Table 3: Minimum flows for streams in the Tukituki catchment.

The left column values are as specified in the HBRRMP (Table 9 from 2006 Operative Plan). Proposed minimum flows, based on more recent technical investigations are also presented. Technical reports are tabulated that provide more information on the flow recommendations.

River Site Minimum flow– HBRRMP Minimum flow - proposed

(L/s) Technical report (L/s) Technical report

Tukituki Red Bridge 3,500 Wood (2006) 5300 Adult rainbow trout 5800 Torrentfish

Johnson (2011b)

Tukituki Tapairu Road

1,900 See Wood (1998)

2200 Johnson (2011b)

Waipawa RDS/SH2 2,300 See Wood (1998)

2400 Adult rainbow trout 2500 Juvenile longfin eel

Johnson (2011b)

Papanui Middle Road

45

Maharakeke Station Road

140

Tukipo SH 50 150 Wood (1998) 175 Adult rainbow trout 187.5 Torrentfish

Johnson (2011b)

Makaretu Watson reach

170

2 METHODS

This section describes the methods we chose to estimate flow metrics for sub-catchments of Tukituki River, including the synthesis of flow records (Section 2.1) and the calculation of flow metrics from flow records (Section 2.2 & 2.3).

2.1 River flow records

HBRC, and its forebears (e.g. catchment boards), established an extensive network of flow and water level records for Hawke’s Bay streams for the purpose of:

State of Environment monitoring (to define state and detect trends over space and time).

Minimum flow monitoring (to identify when restrictions on water use should be imposed as flows drop below minimum flows scheduled to maintain instream values).

Flood warning and flood control.

Targeted investigations for project-specific outcomes were also undertaken. A subset of flow monitoring sites was selected to best represent the 17 sub-catchments of the Tukituki River (Figure 13, Table 4, Table 5). Flow monitoring data are subject to formal quality assurance procedures, including external audits by experienced hydrologists (Arnold, 2011; Keane, 2012; Waugh, 2011). Sites with flow records that were adequate for calculation of flow metrics were not available for every sub-catchment. For those sub-catchments where long-term records exist, not all measurement sites coincide with the downstream boundary for the sub-catchment. The differences between sub-catchment boundaries and flow measurement sites reflect:

the diverse objectives of HBRC flow monitoring programmes, plus

the practical requirements that determine the suitability of a site for flow monitoring (requires successful calibration of water level to derive continuous flow).

We were able to develop synthetic flow records for some sub-catchments that lack measured flow records (Table 5). These were developed using one of two methods: the correlated gauging method and the vector transformation method. These methods are described below, and the application of these methods is defined on a site-by-site basis in Table 5 (see column – “Synthetic Flow Method”).

2.1.1 Correlated gauging method

This method requires a number of flow measurements that were made concurrently at two sites: the site where a synthetic record is required, and a donor site, for which an adequate continuous flow record exists. Flows measured at the synthetic site were related to those recorded at the donor site using least squares regression. The data were carefully scrutinised and suspect flow records were removed, along with flow records that were obtained during periods of rapidly changing flows when the sites may be at different stages of the flood hydrograph.

Standard functions available in Microsoft Excel were used - a linear function normally provided the best fit. Visual inspection and R2 values were used to identify alternative functions (e.g. power function) that provided a better fit to the data. The equation describing the relationship was then applied to each time step in the donor flow record to derive a synthetic record for the new site. After various data checking techniques were applied, flow metrics were calculated from that synthetic flow record.

2.1.2 Vector Transformation method

A vector transformation was used, instead of the correlated gauging method, if an overlapping period of continuous flow record was available for the donor and synthetic site. This method was used to extend the flow record for sites where the existing flow record was too short to use on its own. We followed the method described by Tonkin & Taylor (2011) (reproduced in Appendix 1), which included the following steps:

FDC (Flow Duration Curves - see Section 2.2) were derived using the period of data overlap between the donor site and synthetic site. This provided a list of exceedences and associated flows for each site.

We used Hilltop Rating software to derive a relationship between flow values for the donor and synthetic site, paired by matching exceedence value (e.g. 200 L/s exceeded 90% of the time at donor site, corresponding to 25 L/s exceeded 90% of time at the synthetic site).

This relationship was then applied to the entire flow record from the donor site in order to derive a synthetic record that represented the new site.

Flow metrics were calculated from that synthetic flow record, after various data checking techniques were applied (following T&T, 2011).

2.1.3 Naturalised flow records

Flow metrics were also estimated in the absence of water abstraction, and these are termed ‘naturalised flows’. These detailed site-specific analyses are described in Appendix 2 (page 33) for those sub-catchments that delineate Management Zones. In addition to correcting for estimated surface water abstraction, the consequence of groundwater abstraction for surface flows were estimated using groundwater models.

2.1.4 REC flow metrics

Flow metrics could not be calculated or synthesized for three sub-catchments because insufficient data existed (Mangamahaki, Mangarara, Hawea). Estimates of MAF and MALF were derived from the REC river attributes (Woods et al. 2006, Henderson et al. 2004) for these Hill Country sub-catchments where abstraction pressure is lower.

0 Kahahakuri Stream at Lindsay Road 9 Papanui Stream at Middle Road

1 Kahahakuri Stream at Ongaonga Rd Br. 10 Papanui Stream at Newman’s Ford

2 Maharakeke Stream at Limeworks Stn Rd 11 Porangahau Stream at Oruawhara Road

3 Maharakeke Stream at State Highway 2 Br 12 Tukipo River at Ashcott Road

4 Makara Stream at St Lawrence Rd 13 Tukipo River at State Highway 50

5 Makaretu Stream at State Highway 50 14 Tukituki River at Red Bridge

6 Makaroro River at Burnt Bridge 15 Tukituki River at Tapairu Rd

7 Mangaonuku Stream U/S Waipawa 16 Tukituki River at Waipuk Onga Road

8 Mangatarata Stream at Farm Road 17 Waipawa River at RDS/SH2

Figure 13: The Tukituki catchment, showing the monitoring sites used in this report.

Each site is numbered, corresponding to a site name in the above table. For more site details, see Table 4 and Table 5.

Table 4: Stream and catchment descriptors.

Sourced from the REC (River Environment Classification) and FENZ (Freshwater Environments NZ) for the river confluence.

Stream Code River Environment Classification Freshwater Environments NZ

Area (km

2)

Geology (flow weighted dominant)

Annual water

balance (MAF-L/s)

Flow variability (low flow /

mean flow)

Channel slope (catchment

mean)

Pasture %catchment

(flow weighted)

Waipawa T1 313 hard sedimentary 12,650 21.1% 36% 44%

Mangaonuku T2 359 alluvium 5,040 16.2% 13% 80%

Kahahakuri T3 79 alluvium 920 17.2% 5% 98%

Upper Tukituki T4 185 hard sedimentary 5,790 22.3% 35% 70%

Tukipo T5 214 alluvium 4,330 17.4% 14% 94%

Makaretu T6 75 alluvium 2,280 20.6% 31% 67%

Porangahau T7 72 alluvium 1,110 13.8% 6% 98%

Maharakeke T8 158 alluvium 2,260 10.6% 10% 98%

Mangatarata T9 191 soft sedimentary 1,780 5.2% 10% 96%

Mangamahaki T10 267 soft sedimentary 3,810 0.8% 14% 97%

Papanui T11 164 soft sedimentary 360 8.5% 10% 95%

Mangarara T12 39 soft sedimentary 500 0.7% 15% 95%

Makara T13 127 soft sedimentary 1,910 1.1% 15% 94%

Hawea T14 49 soft sedimentary 730 0.8% 22% 78%

Upper Tukituki T15 765 alluvium 15,960 18.6% 22% 86%

Lower Tukituki T16 2,500 alluvium 44,070 15.2% 22% 83%

Makaroro T17 121 hard sedimentary 5,850 20.7% 43% 12%

Table 5: Flow monitoring sites used in this study to represent each sub-catchment.

Multiple sites were used for some sub-catchments where the long-term monitoring sites were not located close to the river confluence. In that case, synthetic records were derived closer to the river confluence (VT = Vector Transformed). See Appendix 3 for additional method details.

Code Sub-Catchment Flow Site Existing Flow Record Synthetic Flow Method

T1 Waipawa RDS/SH2 Rated

T2 Mangaonuku U/S Waipawa Synthetic (Correlated) Correlated from Waipawa River at RDS

T3 Kahahakuri Ongaonga Rd Br. Rated + Synthetic (Vector Transformed) VT Flow from Tukituki River at Tapairu Rd

Lindsay Road Synthetic (Correlated) Correlated from Kahahakuri Stream at Ongaonga Rd Br.

T4 Upper Tukituki Waipuk Onga Road Synthetic (Correlated) Correlated from Tukituki River at Tapairu Rd

T5 Tukipo State Highway 50 Rated

Tukipo at Ashcott Rd Synthetic (Correlated) Correlated from Tukipo River at State Highway 50

T6 Makaretu State Highway 50 Synthetic (Correlated) Correlated from Tukituki River at Tapairu Rd

T7 Porangahau Oruawhara Road Rated + Synthetic (Vector Transformed) VT Flow from Maharakeke Stream at Limeworks Stn Rd (derived from Tukipo River at State Highway 50)

T8 Maharakeke Limeworks Stn Rd Rated + Synthetic (Vector Transformed) VT Flow from Tukipo River at State Highway 50

Maharakeke State Highway 2 Br Synthetic (Correlated) Correlated from Maharakeke Stream at Limeworks Stn Rd

T9 Mangatarata Farm Road Rated + Synthetic (Vector Transformed) VT Flow from Tukituki River at Tapairu Rd

T10 Mangamahaki Confluence REC

T11 Papanui Newman’s Ford Rated + Synthetic (Vector Transformed) VT Flow from Tukituki River at Red Bridge

Papanui Middle Road Synthetic (Correlated) Correlated from Papanui Stream at Newman’s Ford

T12 Mangarara Confluence REC

T13 Makara Brooklands Rated + Synthetic (Vector Transformed) VT Flow from Tukituki River at Red Bridge

Confluence REC

T14 Hawea Confluence REC

T15 Upper Tukituki Corridor

Tapairu Rd Rated NA

T16 Lower Tukituki Corridor

Red Bridge Rated NA

T17 Makaroro Burnt Bridge Rated + Synthetic (Vector Transformed) NA

2.2 Flow Duration Curve - FDC

Most flow metrics represent one aspect of flow, be it low flow, high flow or typical flow. A FDC (Flow Duration Curve) is a plot of each flow increment against the percentage of time that increment is equalled or exceeded (over the period analysed). This condenses information across the entire flow range into one plot. An “instantaneous” time series was used (actually recorded at 15 minute intervals), so the curve represents the percent of time that the flow is exceeded (rather than % of days or years). The results of this analysis were summarized as tabulated flow magnitudes across a range of percentiles.

Many flow metrics can be read directly from a FDC (e.g. median flow is the 50% exceedance flow). The shape of the FDC can be compared between sites (e.g. after standardising by median flow), or the change in flow distribution over time can be compared (e.g. before and after a flow diversion). The duration of flows that are greater than a particular magnitude (e.g. minimum flow for instream habitat) can also be read off the plot to estimate the proportion of time that restrictions on abstraction are likely.

2.3 Description of flow metrics

We adopted flow metrics from a report completed by NIWA for Horizons Regional Council (Henderson and Diettrich, 2007). Most flow metrics are calculated for a water year that starts July and ends June, instead of a calendar year (i.e. January to December), to avoid splitting a single dry-season across two years. Deviations from the July to June water year are described in the flow-metric descriptions.

2.3.1 Mean Annual Flow - MAF

The MAF (Mean Annual Flow) was calculated over the period of record. The term “annual” refers to the minimum data period over which flow is averaged. The MAF is a useful measure of the annual water balance for the catchment, defining how much of the water falling as rain actually reaches the stream (after losses to evaporation and transpiration). The long period of averaging (>1 year) also reduces sensitivity of MAF to the lag between rainfall and flow (from groundwater or lake residence time). The margin of error on this flow metric is therefore low (Kennard et al., 2009), and this metric is subject to less influence from land use and geology relative to flow metrics associated with more extreme flows. The MAF was the first flow metric modelled for all streams of New Zealand (Woods et al. 2006), and can be accessed as a REC (River Environment Classification) attribute.

2.3.2 Median Flow

The MAF does not represent the ‘typical’ flow that might be observed on any day of the year. A large proportion of water flows over a short period of time after heavy rain for the majority of streams in the Hawke’s Bay region. Median flow better represents the typical flow in a stream because it is calculated as the flow that is equalled or exceeded 50% of the time over the period of analysis. The median flow is less than mean flow.

2.3.3 Monthly Mean Flows

To understand the seasonal variability of flows, monthly mean flows were plotted for each site. To calculate a monthly mean flow, the flow was averaged within each month across all years.

2.3.4 Mean Annual Flood Flow - MAFF

To calculate the MAFF (Mean Annual Flood Flow), the maximum instantaneous flow (15 minute time-step) was collated from each calendar year to create a new dataset of maxima (excluding years that were missing record at a time when the maximum flood could have occurred). The MAFF was then calculated as the mean of this reduced data set.

Instantaneous maximum flows are inherently variable, so require a longer period of record to achieve the same precision as MAF (Kennard et al. 2009). Monitoring equipment is also more likely to be washed away during floods. Channel shape can also change over the duration of a large flood (as gravel is mobilised at very high velocities), so it is difficult to accurately estimate the flow associated with a measured water level. For these reasons, estimates obtained for MAFF are more approximate.

2.3.5 Mean Annual Low Flow - MALF

The MALF (Mean Annual Low Flow) was included to describe the magnitude of typical low-flows. The MALF was adopted by Jowett (1992) as an indicator of low flow conditions that potentially constrain fish populations. The water year was defined as July to June for this metric, to prevent a single drought event (e.g. 15 December to 20 February) from being counted twice in two separate calendar years. The instantaneous time-step (15 minute interval) was converted to a 7-day mean (7 day moving average), before identifying the minimum for each water year. An average was then calculated from the new dataset of annual low-flows (excluding years with missing record at a time when the minimum flow could have occurred).

2.4 Security of supply

Security of water supply for abstractive use was specifically investigated by Waldron & Baalousha (2012), and is not re-stated here.

3 RESULTS

3.1 Flow summaries

Flow metrics are tabulated for each site in the Tukituki catchment in Appendix 3 (page 36). Summary tables of sites near confluences are also included with the Executive Summary. Of the 17 sub-catchments, the most reliable flow metrics were derived for three sites with continuous rated flow records (Tukituki at Red Bridge, Tukituki at Tapairu Road and Waipawa at SH2). We were able to extend the continuous flow record for two of the remaining sub-catchments using the Vector Transformation method (Porangahau at Oruawhara Rd; Mangatarata at Farm Rd), following the methods used previously for the Makororo sub-catchment by Tonkin & Taylor (2011). The flow metrics for eight of the sub-catchments relied on correlations between gaugings at the target site and a donor site. These correlations employed measurements over a limited flow range (specified in Appendix 3), and hence estimates at higher flows are approximate (i.e. predicted MAFF was extrapolated).

3.2 Comparison of major sub-catchments

Three important monitoring sites are: the Waipawa River upstream of the Tukituki confluence (RDS/SH2); the upper Tukituki River upstream of the Waipawa confluence (at Tapairu Road); and the lower Tukituki River (at Red Bridge). Together, the Waipawa and upper Tukituki account for much of the rivers total flow, accounting for 57% of flow at Red Bridge in June and 90% of flow in November (Figure 14).

There is some evidence of water transfer from the Waipawa River to the Tukituki River, via groundwater, before they leave the Ruataniwha Plains. The two rivers are very similar in size at their confluence (Figure 14) – more similar than expected. The REC provides an estimate of MAF and MALF that are based on rainfall, watershed area, temperature and other factors. The REC was a good approximation (within 10%) of the naturalised flows for the Tukituki River upstream of the Waipawa River confluence (Tapairu Rd), and at the coast (Red Bridge). But naturalised flows in the Waipawa River were 15-20% lower than the REC estimate. Possible explanations include:

the REC values are inaccurate, or

there is water transfer from the Waipawa River to the upper Tukituki River.

The Kahahakuri Stream could provide the connection between the Waipawa and Tukituki, given that Undereiner et al. (2009) concluded the Kahahakuri received Waipawa water (via shallow groundwater) before discharging to the upper Tukituki. Transfer does not explain why measured Tukituki River flows were close to the REC flow estimate for Tapairu Rd – flows should exceed the expected flow by as much as the Waipawa River was short of flow.

Figure 14: Monthly mean flow for the Tukituki River at three important monitoring sites.

Red Bridge is used to represents total river flow as it is closest to the coast. Tapairu Road and SH2 are sites a short distance above the Waipawa-Tukituki confluence.

3.3 Comparison of Flow Duration Curves between stream types

The FDC (Flow Duration Curve) is useful for comparing flow regimes between stream types as shown by the example in Figure 15. The flow regime of the Makororo River, which drains the Ruahine Ranges, was more variable than that of the Kahahakuri Stream, which is fed primarily by groundwater on the Ruataniwha Plains. This difference is small when the flow characteristics of these two catchments are contrasted with those of the Mangatarata Stream, which drains the Hill Country and has highly variable flow. This contrast in flow regime is consistent with the stream types described in Section 1.2.3.

3.4 Seasonal pattern of flow

The higher rainfall in July (see Section 1.2) translated to higher flow at all sites during winter (Figure 16). Stream flows reached a pronounced minimum during the warmest months (January to March). We attribute this minimum to higher evaporative loses, given that the seasonal contrast in rainfall was less pronounced. The Hill Country streams produced more of a contrast between summer and winter flows, as demonstrated by the Mangatarata Stream (Figure 16). Averaging the flow data at a monthly time step was sufficient to mask the contrast in seasonality between the groundwater-fed stream (Kahahakuri) and flows from the Ruahine Ranges (Makororo) (Figure 16).

Figure 15: Comparison of Flow Duration Curves across three sites.

A steeper curve indicates more variable flows. These sites were selected to provide a contrast between flashy streams of the Hill Country (Mangatarata at Farm Road), stable groundwater-fed streams of the Ruataniwha Plains (Kahahakuri at Ongaonga Rd) and streams of the Ruahine Ranges (Makaroro at Burnt Bridge). Flows were divided by the median flow for each site, to better visualise the contrast in flow regime between sites (rather than flow magnitude). The MALF is also plotted for each site.

Figure 16: Comparison of flow seasonality across stream types.

These sites were selected to provide a contrast between the Hill Country (Mangatarata at Farm Road), Groundwater fed streams of the Ruataniwha Plains (Kahahakuri at Ongaonga Rd) and streams of the Ruahine Ranges (Makaroro at Burnt Bridge). Monthly mean flows were divided by the mean annual flow for each site, to better visualise the contrast in flow regime between sites (rather than flow magnitude). The lower plot of monthly total rainfall is reproduced from Figure 6 for comparison.

4 CONCLUSIONS

This report provides a summary of river and stream flow for selected monitoring sites in the Tukituki catchment. Flow metrics were derived for these sites and are presented in Appendix 3 to provide hydrological information for each sub-catchment. These flow metrics represent our best estimates. We have more confidence in the flow metrics for sites with long-term measured flow records, compared to sites where correlated flow measurements were used to synthesise a flow record.

The Waipawa, Makaretu and upper Tukituki Rivers lose water as they traverse the Ruataniwha Plains because the channels are perched on gravels deposited by the rivers. The loss and gain of flow to and from groundwater varied from decade to decade, as demonstrated by the Tukipo River, which was a gaining river during 2009 but a losing river in 1973. The water that was lost from the rivers then re-emerges, together with local rainfall recharge, in spring-fed streams of the Ruataniwha Plains (e.g. Kahahakuri Stream). At the eastern edge of the Ruataniwha Plains, both gaining and losing tributaries come together to form the mainstem of the Tukituki River. The Tukituki River then flows through Hill Country of soft sedimentary rock where inflowing tributaries have more variable flows.

Lower rainfall conditions are associated with El Niño conditions, increasing the risk of drought. El Niño events reduce rainfall, and increase the risk of drought, because the moisture from more prevalent westerly winds is intercepted by the Ruahine Ranges before reaching the Ruataniwha Plains. El Niño events can last several years at a time and these are more common during the positive phase of the Interdecadal Pacific Oscillation. The Tukituki River experienced lower mean flows during the positive phase of the Interdecadal Pacific Oscillation (1978-1998), relative to the negative phase (1947-1977).

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http://dx.doi.org/10.1002/rra.1249

http://www.mfe.govt.nz/publications/climate/climate-change-effect-impacts-assessments-may08/index.html

http://www.mfe.govt.nz/publications/climate/climate-change-effects-on-flood-flow/index.html

http://www.mfe.govt.nz/publications/climate/drought-risk-may05/index.html

http://www.hydrol-earth-syst-sci.net/11/1633/2007/hess-11-1633-2007.pdf

http://www.mfe.govt.nz/environmental-reporting/about/tools-guidelines/classifications/freshwater/

Tait, A.; Woods, R.A. (2007). Spatial interpolation of daily potential evapotranspiration for New Zealand using a spline model. Journal of Hydrometeorology 8(3):430-438.

Tait, A.; Henderson, R.D.; Turner, R.; Zheng, X. (2006). Spatial interpolation of daily rainfall for New Zealand. International Journal of Climatology 26(14): 2097-2115.

T&T. 2011. Development of a synthetically extended Makaroro at Burnt Bridge flow record. Memo to Hawke’s Bay regional Council from Candice Band and David Leong, Tonkin & Taylor Ltd, dated 14 November 2011. T&T Project No: 27690.200.

T&T. 2012. Ruataniwha Water Storage Project sedimentation assessment. Tonkin & Taylor Ltd. T&T Project No: 27690.600. File link

Undereiner, G., P.A. White, C. Meilhac. 2009. Groundwater-surface water interactions along the Waipawa River, Ruataniwha plains, Hawke’s Bay. GNS Report 2009/37, GNS Science Wairakei.

Wakefield B., M. Apatu, M. Hape D. Moffatt, J. Maaka, D. Whitiwhiti, B. Wakefield, H. Maaka. 2012. Tukituki River catchment cultural values and uses. Te Taiwhenua O Tamatea in Partnership with Te Taiwhenua O Heretaunga. File link

Waldron, R. Baalousha, H. 2012. Ruataniwha Water Storage Project. Tukituki River Catchment. Assessment of potential effects on groundwater and surface water resources. Hawke’s Bay Regional Council. Plan Number 4370 WI 12-08.

Waugh, B. 2011, Data Audit Review Tukituki River at Tapairu Rd. Prepared for Hawke’s Bay Regional Council, NIWA.

Wood, G. 1998. Sustainable Low Flow Project: Ruataniwha Rivers Waipawa – Tukipo – Tukituki. Hawke’s Bay Regional Council Environmental Management Group Technical Report EMT 98/2.

Wood, G. 2006. Lower Tukituki River instream habitat assessment. EMT 06/06 HBRC Plan Number 3851. File link

Woods, R.; Hendrikx, J.; Henderson, R.; Tait, A. 2006. Estimating mean flow of New Zealand rivers. Journal of Hydrology (NZ) 45 (2): 95-110 2006

Worthy, T.H., 2000. Two late-Glacial avifaunas from eastern North Island, New Zealand - Te Aute Swamp and Wheturau Quarry. Journal of the Royal Society of New Zealand 30(1): 1-26. adelaide.academia.edu

http://www.hbrc.govt.nz/HBRC-Documents/HBRC%20Document%20Library/Tukituki%20River%20Catchment%20Values%20and%20Uses%20July%2012.pdf

http://adelaide.academia.edu/TrevorWorthy/Papers/606597/Worthy_T.H._2000._Two_late-Glacial_avifaunas_from_eastern_North_Island_New_Zealand_-_Te_Aute_Swamp_and_Wheturau_Quarry._Journal_of_the_Royal_Society_of_New_Zealand_30_1_1-26

Appendix 1 – Vector Transformation method The following text and figure are reproduced from Appendix 1 of T&T (2011):

The key output from this process is a rating curve that is applied to the donor site data that transforms the flow data at that site into an equivalent flow record at the site we wish to generate data for (viz. Makaroro at Burnt Bridge).

As an example, using Tukituki at Red Bridge as the donor site for Makaroro at Burnt Bridge:

- Say the flow at Red Bridge at a particular point in time is 28 m³/s

- From its flow duration curve, this flow would correspond with an exceedence percentile of 40% (indicated by the dashed blue line in Figure A1)

- The corresponding flow at this exceedence percentile (40%) from the flow duration curve for the Makaroro at Burnt Bridge record is 4.0 m3/s (indicated by solid brown arrow).

The implicit assumption in this method is that flows for the two sites used are completely coherent and synchronised in time.

Figure A1 Flow duration curve depicting vector transformation method.

Appendix 2 - Flow Naturalisation Method The following methodology outlines the process used to generate naturalised flow records for the Tukituki River at Tapairu Rd, Waipawa River at RDS and Tukituki River at Red Bridge (reproduced from Waldron & Baalousha, 2012).

Components of the Tukituki River at Tapairu Rd Naturalised Flow: 1) Tukituki River at Tapairu Rd extended synthetic daily mean flow record from 1969-2011

(combines periods of audited rated flow record with periods of synthetic flow record derived by MWH for the HBRC).

a) Surface water abstraction dataset accounting for Surface water abstractions within the Tapairu Rd catchment (sub-catchments T3-T8 & T15) based on estimated use (Harkness 2012). Length of record is from 1969-2008.

b) A dataset produced by the HBRC Ruataniwha Transient groundwater (groundwater) model (Baalousha 2010) which represents the impact of groundwater abstraction on river flow within the Tapairu Rd catchment and inside the groundwater model boundary based on current groundwater abstraction (estimated as at 2009, Baalousha 2010). Length of record is from 1990-2008. Pre 1990 is assumed to be natural (refer to assumptions).

c) Stream depleting groundwater abstraction dataset accounting for stream depleting abstractions within the Tapairu Rd catchment but outside of the groundwater model boundary. Length of record is from 1969-2008.

1+a+b+c = Tukituki River at Tapairu Rd naturalised daily mean flow record (1969-2008)

Components of the Waipawa River at RDS Naturalised Flow: 2) Waipawa River at RDS extended synthetic daily mean flow record (MWH) from 1969-

2011 (combines periods of audited rated flow record with periods of synthetic flow record derived by MWH for the HBRC).

a) Surface water abstraction dataset accounting for Surface water abstractions within the RDS catchment (sub-catchments T1-T2 & T17) based on estimated use (Harkness 2012). Length of record is from 1969-2008.

b) A dataset produced by the HBRC Ruataniwha Transient groundwater model (Baalousha 2010) which represents the resulting impact of groundwater abstraction on river flow within the RDS catchment and inside the groundwater model boundary based on current groundwater abstraction (estimated as at 2009, Baalousha 2010). Length of record is from 1990-2008. Pre 1990 is assumed to be natural (refer to assumptions).

c) stream depleting abstraction dataset accounting for stream depleting abstractions within the RDS catchment but outside of the groundwater model boundary. Length of record is from 1969-2008.

2+a+b+c = Waipawa River at RDS naturalised daily mean flow record (1969-2008)

Components of the Tukituki River at Red Bridge Naturalised Flow: 3) Tukituki River at Red Bridge audited rated daily mean flow record from 1969-2011.

a) Surface water abstraction dataset accounting for Surface water abstractions within the Red Bridge catchment (sub-catchments T1-T17) based on estimated use (Harkness 2012). Length of record is from 1969-2008.

b) A dataset produced by the HBRC Ruataniwha Transient groundwater model (Baalousha 2010) which represents the resulting impact of groundwater abstraction on river flow within the RDS and Tapairu Rd catchments inside the groundwater model boundary based on current groundwater abstraction (estimated as at 2009, Baalousha 2010). Length of record is from 1990-2008. Pre 1990 is assumed to be natural (refer to assumptions).

c) stream depleting abstraction dataset accounting for stream depleting abstractions within the RDS and Tapairu Rd catchments but outside of the groundwater model boundary. Length of record is from 1969-2008.

d) stream depleting abstraction dataset accounting for stream depleting abstractions D/S from RDS and Tapairu Rd which.

e) Otane groundwater abstraction dataset accounting for groundwater abstractions within the Otane groundwater zone. All Otane groundwater abstractions have been treated as stream depleting abstractions for the purpose of naturalising flows at Red Bridge (Gordon, D 2011, pers. comm., 11-Nov-11).

3+a+b+c+d+e = Tukituki River at Red Bridge naturalised daily mean flow record (1969-2008)

Assumptions ▪ It was assumed that prior to 1990 there was no significant impact on river flow arising

from groundwater abstraction. ▪ stream depleting abstractions were identified in the HBRC consents database and

classed as stream depleting abstractions based on the ‘Larking Method’ (Larking 2004a & 2004b). Stream depleting abstractions were assumed to have a 100% connection to the river.

▪ Surface water abstraction was calculated based on available metered water use data (MWH 2012).

▪ groundwater abstraction was based on current groundwater abstraction (estimated as at 2009, Baalousha 2010)

Additional Notes ▪ Baalousha (2010) has developed a groundwater model for the Ruataniwha Basin

(Baalousha 2010). This model was used to produce a dataset that shows the impact of groundwater abstraction (all groundwater abstractions including those classed as stream depleting) on the groundwater contribution to river flows from 1990 to 2010. It was based on past and current estimates of groundwater abstraction derived from available metered well data and crop water demand studies. This dataset was incorporated into the flow naturalisation process for Tukituki Catchment river flows.

▪ Naturalised flow records were generated using all available audited rated flow records as follows: ▫ Tukituki River at Red Bridge:

- NIWA completed an audit of the Red Bridge flow record from 1969-2011 (Arnold 2011). The audited rated flow record from 1969-2008 was modelled using the method above to produce a naturalised flow record.

▫ Tapairu Rd & RDS: - Audits of the Tapairu Rd (Waugh 2011) and RDS (Keane 2012) flow records have

been completed. Audited Tapairu Rd record is available from 1987-2011 and audited RDS record from 1987-2011.

- These audited records were used to naturalise the Tapairu Rd and RDS flow records. Extended synthetic flow records were produced for Tapairu Rd and RDS sites which combine the available audited rated flow records (1987-2011) with periods of synthetic record (1969-1987) produced by MWH (2012). These

extended synthetic records were used in the naturalisation process to create naturalised flow records for the period 1969-2008.

- For the Tapairu Rd site, naturalised flow data for the period 1976-1987 was derived using a correlation with data for the Tukipo at SH50, this period remains the same as no changes have been made to the SH50 record. The period 1969-1976 for Tapairu Rd was derived using an AWBM model, which used rainfall data to derive flow records at Tapairu Rd (refer to MWH 2012 and OPUS 1997). Modelled AWBM flows were calibrated by comparisons to available rated flows recorded over a short period (1987-1990). The modelled flows showed an error in annual minimums up to 33% - A discussion with Mike Harkness at MWH confirmed that if audited flow data was used to recalibrate the AWBM modelled flow record (pers. comm., 24-Feb-12), it is likely that similar error or uncertainty would be associated with the modelled flow record. It is likely that by using audited flows to re-calibrate modelled flow data, these audited flows would not affect the production of modelled flow records for 1969-1976 (i.e. the errors would be retained).

- For RDS, data for the period 1976-1987 were derived using a correlation with the Tukipo at SH50. This period remains the same as no changes have been made to the SH50 record. The period 1969-1976 for RDS was correlated from a synthetic Tukipo at SH50 record which was derived using an AWBM model. As with Tapairu Rd, modelled Tukipo flows used to produce the correlated RDS record (1969-1976) were calibrated by comparisons to available rated flows records.

- The periods of Tapairu Rd and RDS records correlated from Tukipo at SH50 (1976-1987) were derived using an un-audited Tukipo flow record.

▪ The lengths of the naturalised records were limited by the shortest dataset modelled. The Surface water abstraction datasets were the shortest (1969-2008), so the naturalised records cover the period 1969-2008.

Appendix 3 - Flow Metrics for each monitoring site This Appendix provides tables summarising the flow metrics calculated for sites in each sub-catchment, including the site intended to represent each sub-catchment plus any sites used for calculating synthetic records. The first table summarises the methods used for each site, including synthetic derivation, formula and donor sites. Flow metric acronyms are defined in Section 2.3.

Min Max

T1 Waipawa River at RDS/SH2 Rated Audited rated record

T2Mangaonuku Stream U/S

WaipawaSynthetic (Correlated) Synthetic record correlated from audited record

Waipawa River at

RDS/Waipawa SH2587 4135 21

y = 0.3355x +

217.12R² = 0.8741

Kahahakuri Stream at

Ongaonga Rd Br.

Rated + Synthetic (Vector

Transformed)

Un-audited rated record with synthetic record vector

transformed from audited recordTukituki River at Tapairu Rd

Kahahakuri Stream at Lindsay

RoadSynthetic (Correlated) Synthetic record correlated from another synthetic record

Kahahakuri Stream at

Ongaonga Rd Br.805 1510 13

y = 2.0307x +

546.61R² = 0.8309

T4Tukituki River at Waipuk Onga

RoadSynthetic (Correlated) Synthetic record correlated from audited record Tukituki River at Tapairu Rd 7 4949 32

y = 0.3204x -

467.7R² = 0.9057

Tukipo River at State Highway

50Rated Un-audited rated record

Tukipo River at Ashcott Road Synthetic (Correlated) Synthetic record correlated from un-audited rated recordTukipo River at State

Highway 50786 3955 18

y = 4.819x +

310.78R² = 0.8644

T6Makaretu Stream at State

Highway 50Synthetic (Correlated) Synthetic record correlated from audited rated record Tukituki River at Tapairu Rd 169 2348 93

y = 0.1467x -

31.406R² = 0.9061

T7Porangahau Stream at

Oruawhara Road


Transformed)

Large uncertainty in high flow range, synthetic record correlated

from another synthetic record

Maharakeke Stream at

Limeworks Stn Rd


Limeworks Stn Rd


Transformed)

Large uncertainty in high flow range, un-audited rated record

with synthetic record vector transformed from un-audited

records

Tukipo River at State

Highway 50

Maharakeke Stream at State

Highway 2 BrSynthetic (Correlated)

Large uncertainty in high flow range, synthetic record correlated

from another synthetic record


Limeworks Stn Rd111 407 9

y = 1.9892x -

16.507R² = 0.9366

T9Mangatarata Stream at Farm

Road


Transformed)


transformed from audited recordTukituki River at Tapairu Rd 12 677 16 y = 8.2527e0.0003x R² = 0.6697

T10

Papanui Stream at Newmans

Ford


Transformed)


transformed from audited recordTukituki River at Red Bridge

Papanui Stream at Middle

RoadSynthetic (Correlated) Synthetic record correlated from another synthetic record

Papanui Stream at

Newmans Ford52 256 10

When donor flow

≤ 49.65 l/s

y =

0.0691x1.7531 R² = 0.8874

When donor flow

> 49.65 l/s

y = 3.0565x -

86.832R² = 0.7854

T12

Makara Stream at BrooklandsRated + Synthetic (Vector

Transformed)


transformed from audited record Tukituki River at Red Bridge

Makara Stream at St

Lawrence RoadSynthetic (Correlated) Synthetic record correlated from audited record Tukituki River at Red Bridge 3 468 22

y = 0.0126x -

65.188R² = 0.8476

T14

T15 Tukituki River at Tapairu Rd Rated Audited rated record

T16 Tukituki River at Red Bridge Rated Audited rated record

T17Makaroro River at Burnt

Bridge


Transformed)


transformed from audited records

Tukituki River at Tapairu Rd

and Red Bridge

T8

Existing Flow RecordSite NameCode

T13

T11

T3

T5

Correlation Formulae and R² ValueValid Flow Range No. of Paired

GaugingsExisting Record Comments Donor Site

Waipawa River at RDS/SH2 T1

Existing Flow Statistics

Flow Record Details

Record Type: Rated Instantaneous

Period of Record: 1987-2011

Flow Statistic Flow (L/s)

Min 1836

Max 941805

MAF 14949

Median 8655

3 x Median 25965

MALF 2839

MAFF 479775

Flow Distribution Percentiles

Percentile Flow (L/s)

0 (Maximum Recorded) 941805 5 41554 10 27471 20 17472 25 (Upper Quartile) 15011 30 13073 40 10456 50 (Median) 8655 60 7140 70 5703 75 (Lower Quartile) 5099 80 4514 90 3347 91 3243 92 3135 93 3023 94 2902 95 2797 96 2684 97 2568 98 2442 99 2264 100 (Minimum recorded) 1836 Biological Disturbance Indicators

MAF/MALF 169

MAF/Median 55

Waipawa River at RDS/SH2 T1

Naturalised Flow Statistics

Flow Record Details

Record Type: Naturalised (Daily Mean Flow)



Min 1358

Max 656271

MAF 14970

Median 8991

3 x Median 26974

MALF 3009

MAFF -



0 (Maximum Recorded) 656271 5 40995 10 26974 20 17264 25 (Upper Quartile) 15043 30 13167 40 10755 50 (Median) 8991 60 7369 70 5945 75 (Lower Quartile) 5307 80 4709 90 3425 91 3299 92 3130 93 2966 94 2835 95 2701 96 2583 97 2482 98 2341 99 2116 100 (Minimum recorded) 1358

Mangaonuku Stream U/S Waipawa T2


Flow Record Details

Record Type: Synthetic Instantaneous



Min 833

Max 316193

MAF 5233

Median 3121

3 x Median 9363

MALF 1170

MAFF 161182



0 (Maximum Recorded) 316193

5 14158

10 9434

20 6079

25 (Upper Quartile) 5253

30 4603

40 3725

50 (Median) 3121

60 2613

70 2130

75 (Lower Quartile) 1928

80 1732

90 1340

91 1305

92 1269

93 1231

94 1191

95 1156

96 1118

97 1079

98 1037

99 977

100 (Minimum recorded) 833

Biological Disturbance Indicators

MAF/MALF 138

MAF/Median 52

Kahahakuri Stream at Ongaonga Rd Br. T3


Flow Record Details

Record Type: Rated + Synthetic Instantaneous



Min 124

Max 22438

MAF 579

Median 433

3 x Median 1298

MALF 255

MAFF 10005




5 1301

10 916

20 623


30 526

40 479

50 (Median) 433

60 393

70 353


80 318

90 281

91 277

92 273

93 270

94 266

95 261

96 257

97 251

98 244

99 232



MAF/MALF 39

MAF/Median 23

Kahahakuri Stream at Lindsay Road T3


Flow Record Details




Min 799

Max 46111

MAF 1722

Median 1425

3 x Median 4275

MALF 1064

MAFF 20864




5 3188

10 2406

20 1812


30 1615

40 1519

50 (Median) 1425

60 1345

70 1264


80 1192

90 1117

91 1110

92 1102

93 1095

94 1087

95 1077

96 1068

97 1057

98 1042

99 1018



MAF/MALF 20

MAF/Median 15

Tukituki River at Waipuk Onga Road T4


Flow Record Details




Min 0

Max 394293

MAF 4386

Median 2458

3 x Median 7373

MALF 344

MAFF 145152




5 12817

10 8521

20 5451


30 4046

40 3159

50 (Median) 2458

60 1915

70 1433


80 1015

90 541

91 503

92 466

93 424

94 382

95 342

96 301

97 243

98 184

99 124



MAF/MALF 422

MAF/Median 59

Tukipo River at State Highway 50 T5


Flow Record Details

Record Type: Rated



Min 54

Max 260744

MAF 1538

Median 755

3 x Median 2264

MALF 152

MAFF 80145




5 4940

10 2994

20 1817


30 1288

40 972

50 (Median) 755

60 573

70 421


80 293

90 192

91 183

92 173

93 163

94 154

95 143

96 135

97 122

98 109

99 95



MAF/MALF 528

MAF/Median 106

Tukipo River at Ashcott Road T5


Flow Record Details




Min 570

Max 1256838

MAF 7724

Median 3947

3 x Median 11840

MALF 1043

MAFF 386531




5 24118

10 14737

20 9066


30 6517

40 4994

50 (Median) 3947

60 3074

70 2339


80 1724

90 1237

91 1190

92 1142

93 1098

94 1052

95 1002

96 961

97 900

98 838

99 767



MAF/MALF 528

MAF/Median 106

Tukipo River at SH50 T5


Flow Record Details




Min 54

Max 94659

MAF 1551

Median 847

3 x Median 2540

MALF 184

MAFF -




5 4831

10 3069

20 1924


30 1390

40 1075

50 (Median) 847

60 656

70 495


80 348

90 221

91 207

92 195

93 183

94 170

95 159

96 147

97 134

98 120

99 100


Makaretu Stream at State Highway 50 T6


Flow Record Details




Min 178

Max 180716

MAF 2191

Median 1308

3 x Median 3924

MALF 340

MAFF 66643




MAF/MALF 196

MAF/Median 51

Porangahau Stream at Oruawharo Road T7


Flow Record Details




Min 5

Max 217896

MAF 546

Median 148

3 x Median 444

MALF 30

MAFF 60316




MAF/MALF 2027

MAF/Median 408

Maharakeke Stream at Limeworks Stn Rd T8


Flow Record Details




Min 48

Max 155023

MAF 658

Median 295

3 x Median 884

MALF 118

MAFF 55803




MAF/MALF 473

MAF/Median 189

Maharakeke Stream at State Highway 2 Br T8


Flow Record Details




Min 79

Max 308354

MAF 1292

Median 570

3 x Median 1709

MALF 218

MAFF 110987




MAF/MALF 509

MAF/Median 195

Mangatarata Stream at Farm Road T9


Flow Record Details




Min 0

Max 56399

MAF 500

Median 55

3 x Median 165

MALF 2

MAFF 23052




MAF/MALF 15308

MAF/Median 420

Mangamahaki at confluence T10

Flow Record Details

Record Type: None

Period of Record:


Min

Max

MAF (REC – 3800 L/s))

Median

3 x Median

MALF (REC – 29 L/s)

MAFF



0 (Maximum Recorded) 5 10 20 25 (Upper Quartile) 30 40 50 (Median) 60 70 75 (Lower Quartile) 80 90 91 92 93 94 95 96 97 98 99 100 (Minimum recorded) Biological Disturbance Indicators

MAF/MALF

MAF/Median

Flood frequency (FRE3)

Papanui Stream at Newman’s Ford T11


Flow Record Details




Min 0

Max 74596

MAF 408

Median 131

3 x Median 394

MALF 46

MAFF 23676




MAF/MALF 515

MAF/Median 180

Papanui Stream at Middle Road T11


Flow Record Details




Min 0

Max 227915

MAF 1161

Median 315

3 x Median 945

MALF 63

MAFF 72280




MAF/MALF 1147

MAF/Median 229

Papanui Stream at Middle Road T11


Flow Record Details




Min

Max

MAF

Median

3 x Median

MALF

MAFF



0 (Maximum Recorded) 5 10 20 25 (Upper Quartile) 30 40 50 (Median) 60 70 75 (Lower Quartile) 80 90 91 92 93 94 95 96 97 98 99 100 (Minimum recorded)

Mangarara at confluence T12

Flow Record Details

Record Type: None

Period of Record:


Min

Max

MAF (REC – 500 L/s))

Median

3 x Median


MAFF




MAF/MALF

MAF/Median


Makara Stream at St Lawrence Rd T13


Flow Record Details




Min 0

Max 38293

MAF 496

Median 207

3 x Median 620

MALF 14

MAFF 17547




MAF/MALF 1256

MAF/Median 85

Makara Stream at Brooklands T13


Flow Record Details




Min 1

Max 340701

MAF 673

Median 132

3 x Median 397

MALF 13

MAFF 669




MAF/MALF 53

MAF/Median 5

Hawea at confluence T14

Flow Record Details

Record Type: None

Period of Record:


Min

Max

MAF (REC – 700 L/s)

Median

3 x Median


MAFF




MAF/MALF

MAF/Median


Tukituki River at Tapairu Rd T15


Flow Record Details




Min 1426

Max 1232087

MAF 15150

Median 9130

3 x Median 27390

MALF 2534

MAFF 454492




MAF/MALF 179

MAF/Median 50

Tukituki River at Tapairu Rd T15


Flow Record Details




Min 1307

Max 582126

MAF 15830

Median 9829

3 x Median 29486

MALF 2865

MAFF -




Tukituki River at Red Bridge T16


Flow Record Details




Min 2561

Max 3044306

MAF 44544

Median 21586

3 x Median 64759

MALF 5902

MAFF 1397762




MAF/MALF 237

MAF/Median 65

Tukituki River at Red Bridge T16


Flow Record Details




Min 2871

Max 2104360

MAF 44505

Median 22022

3 x Median 66067

MALF 6258

MAFF -




Makaroro River at Burnt Bridge T17


Flow Record Details

Record Type: Synthetic (Rated + Synthetic)



Min 474

Max 297903

MAF 6661

Median 3680

3 x Median 11040

MALF 1394

MAFF 144199




MAF/MALF 103

MAF/Median 39

Makaroro River at Burnt Bridge T17


Flow Record Details

Record Type: Naturalised (Instantaneous)



Min 474

Max 297903

MAF 6661

Median 3680

3 x Median 11040

MALF 1394

MAFF 144199




MAF/MALF 103

MAF/Median 39

Appendix 4 – Tukituki LiDAR Elevation Imagery This image uses colour to represent elevation of a short section of the Tukituki River at the same location (centred at NZTM 1,898,264 - 5,570,635) where a cross-section profile is provided in Figure 10 (cross-section of the dashed line shown on this map). The Tukituki channel was elevated above the land outside the stopbanks, with elevation dropping toward adjacent streams (Black Stream tributary in north-east corner was about 2 meters lower than the Tukituki River). LiDAR elevations from 2003 provided this snapshot of a river channel form that experiences ongoing changes, together with the more stable valley form. The blue arrow indicates direction of flow (i.e. top left to bottom right).

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