Crowsnest River –4 th order, around 3-4 m 3 /sec—10-20 m wide DA around 400 km2

32
Fish and other aquatic biota that live in rivers and streams have to contend with the variability of the flow regime. How variable is runoff/discharge? From year to year? From month to month From day to day

description

Fish and other aquatic biota that live in rivers and streams have to contend with the variability of the flow regime. How variable is runoff/discharge? From year to year? From month to month From day to day. Crowsnest River –4 th order, around 3-4 m 3 /sec—10-20 m wide DA around 400 km2. - PowerPoint PPT Presentation

Transcript of Crowsnest River –4 th order, around 3-4 m 3 /sec—10-20 m wide DA around 400 km2

Page 1: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2

Fish and other aquatic biota that live in rivers and streams have to contend with the variability of the flow regime.

How variable is runoff/discharge?

From year to year?

From month to month

From day to day

Page 2: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2

Crowsnest River –4th order, around 3-4 m3/sec—10-20 m wide DA around 400 km2

Page 3: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2

0

2

4

6

8

10

12

14

1982 1987 1992 1997 2002 2007

Annual mean discharge of the Crowsnest River at Frank

m3/s

20

Page 4: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2

0

2

4

6

8

10

12

14

1982 1987 1992 1997 2002 2007

Annual mean discharge of the Crowsnest River at Frank

m3/s

Exceedence probability

0.90

0.50

0.25

0.10

0.75

90 percentile

75 percentile

50 percentile

25 percentile10 percentile

1995 12

1991 9.8

2005 8.7

1993 6.3

2002 6.2

1996 5.9

1992 5.5

2004 4.6

1999 4.4

1994 4.2

1986 4.1

1990 3.8

1988 3.7

1989 3.5

1998 3.1

1987 2.5

1997 1.7

2003 1.5

2000 1.4

2001 1.2

Page 5: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2

10.0

1.0

100

oo

o

We can now plot these data on cumulative probability paper

Non-exceedence probability (percentiles)

Based on this plot we can estimate that 1 year in 100 there will be a year wetter than 20m3/s and a year drier than 0.8 m3/s, if there is no-longterm climate change

Dischargem3/sec

Exceedance probability (percentiles)

99.9 99 90 70 50 30 20 10 1 0.1

o

o

Recurrence interval is the reciprocal of the probability

Page 6: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2

1 yr out of 4 discharge is above this line

3 yr out of 4 discharge above this lineAnnual average 2.7 m3/s

2 yr out of 4 discharge above this lineAnnual average 4.1 m3/s

Annual average 6.0 m3/s

Page 7: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2

River Management can significantly alter the seasonal hydrograph

Before Ottawa R dams

After Ottawa R dams

Page 8: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2

St.Lawrence River Flood Plain at Lac St. Pierre—has rarely been flooded since the late fifties—What effect might this have on the river?

Page 9: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2
Page 10: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2

The hydrographShort-term response to a precipitation event

How would you expect deforestation to influence this response?---Consider the terms of the hydrological balance equation

Page 11: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2

Human activities can markedly influence the shape of the hydrograph

Deforestation •reduces the lag time •raises the peak• reduces the base flow

Fig 5-2 in your text

How does deforestation affect the hydrological balance[P-E]DA – S/t

Page 12: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2

We can explain the effects of deforestation on the hydrograph in terms of the hydrological balance, mainly in terms of changes in Evaporation and storage.

Evaporation directly from the soil surface increases when plant cover is reduced, but usually transpiration from plant leaves is decreased more than surface evaporation increases.

•leads to increased runoff—more area under the hydrograph curve

Storage is reduced—water stored in plant tissues is removed, and the water holding capacity of soils is reduced by the death of roots.

•Thus less of the water from the precipation event goes into recharging storage pools (S is less), & more water enters the stream directly, reducing the lag time on the rising limb, and giving a higher and sharper peak in the deforested watershed.

•Recession will also be faster and base flow lower in the deforested watershed since there will be less storage to sustain the stream flow after the rain stops.

Page 13: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2

Biological Impacts that generally occur when watersheds are hydrologically disturbed by deforestation

Scouring—increased flashiness of the hydrograph can scour and shift gravels.Siltation—shortening of hydrological lag time (usually associated with increased overland flow vs percolation--influx of fine particulate matter to streams.

•plug up interstitial spaces in gravels & reduce water percolation and oxygen supply to interstitial benthic organisms & fish eggs in the gravels.

•Siltation + increased dissolved organic material can reduce light penetration

Nutrient enrichment—hydrological changes usually also increase the influx of Nitrogen & Phosphorus to the stream leading to increased algal growth on the substrate.

Increased temperature & illumination—reduced forest cover, depending on how near to the stream bank trees are cut, can increase light penetration, warming the stream & changing the composition of benthic communities, by reducing survival of cold-water species.

•increased illumination can also contribute to increased benthic algal growth on rocks.

Page 14: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2

Patterns in stream flow and how they generate habitat diversity in streams

•Annual discharge patterns—floodplain habitats

•Stream meander—pool/riffle alternations

•Stream channel changes over time—oxbow lakes, braided streams

Page 15: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2

Flood plain habitats greatly increase biodiversity in river systems. They contribute mostly temporary wetlands, but some remain as permanent because of groundwater inputs.•Important for•Waterfowl, mammals, amphibians, fish, aquatic insects, molluscs etc.

•Most of the species found in flood plain wetlands would be lost from the river if the floodplain were not allowed to be flooded regularly.

Flood plains depend on seasonal variability in river discharge

Page 16: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2

Oxbow lake and the Chippewa River. Eau Claire, Wisconsin.http://www.uoregon.edu/~millerm/meander.html

River flood plains often undergo extensive urban development

Page 17: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2

Many are also strongly impacted by agriculture

Page 18: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2

Meander pattern of the Sacramento River, CA, note old abandoned channels and oxbows, and the encroachment of agriculture on the river channel.http://www.uoregon.edu/~millerm/meander.html

Page 19: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2

http://vernalfishandwildlife.fws.gov/vernalfloodplain.jpg

Such restoration can involve breaching of levees and removal of dams with the aim of.re-establishing natural floodplain vegetation and habitat

Green River, Wyoming

Page 20: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2

meandersIn streams and rivers of different sizes

Page 21: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2

Rivers meander when they are traveling on top of a relatively flat surface.

•a straight line is not the most efficient path for water to flow. A meandering river will dissipate more energy through friction with the riverbed than one that flows straight

•The meander pattern shifts constantly since the river is cutting the bank on the outside of meander loops and depositing alluvial sediment on the inside.

Page 22: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2

http://www.kented.org.uk/ngfl/rivers/River%20Articles/meander.htm

Streams flow down hill and take the path of least resistance, however the path is usually a meandering instead of straight

Page 23: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2
Page 24: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2

It takes more velocity to suspend and move larger particles

Page 25: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2

Oxbow lake forming from a river meander

The erosion that occurs during a flood even may cause the river to take a shortcut from one loop to the next--thus cutoff loop will remain as an oxbow lake.

Page 26: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2

Oxbow lakes and braided channels on the Upper Amazon River

http://muller.lbl.gov/travel_photos/AmazonWebPages/AmazonWebPages-Thumbnails/1.jpg

Page 27: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2

http://waterknowledge.colostate.edu/meander.htm

An important reference on River MeandersLeopold, L.B., and M.G. Wolman, 1960,River Meanders: Geol. Soc. America, Bull., v. 71, pp. 769-794.

The physical stresses on the river bed during floods often cause a river to change course.

The river valley contains many old channels superimposed on each other

Page 28: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2

A good example of braiding in the river channel

Rivers often simultaneously occupy several of their historical channels at once.We call this type of river channel braided

Page 29: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2

Oldman RBelow Summerview

Showing old river channels

Page 30: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2

When rivers cut deeply into the landscape the meander pattern becomes entrenched and from then on shifts downward only.

http://courses.missouristate.edu/EMantei/creative/WeathStrem/entrenched.jpg

Page 31: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2

If you want to learn more about the landforms and deposits created by running water, with particular reference to western Canadian watersheds, take

Geography 3035Fluvial Geomorphology—Hester Jiskoot

Other courses of relevence are

Geography 4015Integrated Watershed Management—Jim Byrne

AndGeography 4012Hydrology—Stefan Kienzle

Page 32: Crowsnest River –4 th  order, around 3-4 m 3 /sec—10-20 m wide   DA  around 400 km2

Sutcliffe, W.H. 1973Correlations between seasonal river discharge and landings of American Lobster and Atlantic halibat in the Gulf of St. Lawrence.

J.Fish. Res. Bd. Can. 30:856-859.