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LIFE ENVIRONMENT STRYMON

Ecosystem Based Water Resources Management to Minimize Environmental Impacts from Agriculture Using State of the Art

Modeling Tools in Strymonas Basin

LIFE03 ENV/GR/000217

Task 2. Monitoring Crop Pattern, Water quality and Hydrological Regime

SHYLOC implementation in Strymonas basin

Volume 3

Period covered by the report: from 1/9/2005 to 31/8/2006

Date of submission of the report: 31/8/2006

The present work is part of the 4-years project: “Ecosystem Based Water Resources Management to Minimize Environmental Impacts from Agriculture Using State of the Art Modeling Tools in Strymonas Basin” (contract number LIFE03 ENV/GR/000217). The project is co-funded by the European Union, the Goulandris Natural History Museum - Greek Biotope/Wetland Centre (EKBY), the Prefecture of Serres – Directorate of Land Reclamation of Serres (DEB-S), the Development Agency of Serres S.A. (ANESER S.A.) and the Local Association for the Protection of Lake Kerkini (SPALK).

This document may be cited as follows: Hatziiordanou, Eleni. 2006. SHYLOC implementation in Strymonas basin - Volume 3. Greek Biotope/Wetland Centre (EKBY). Thermi, Greece. 42 p.

PROJECT TEAM

Greek Biotope/Wetland Centre (EKBY)

Dimitrios Papadimos (Project Manager) Iraklis Chalkidis (Agricultural Engineer)

Antonios Apostolakis (Geographic Information System Expert) Eleni Hatziiordanou (Geographic Information System Expert)

Prefecture of Serres – Directorate of Land Reclamation of Serres (DEB-S)

Christos Metrzianis (Scientific Coordinator) Athanasios Taousianis (Scientific Coordinator)

i

CONTENTS

CHAPTER 1: INTRODUCTION ........................................................................... 2

CHAPTER 2: METHOD ........................................................................................ 3

2.1 General ............................................................................................................ 3

2.2 Image acquisition............................................................................................. 4

2.3 Image preprocessing ........................................................................................ 5

2.4 Water quantity monitoring network.................................................................. 6

2.5 Third application of SHYLOC to the Strymonas River Basin........................... 9

2.5.1 Application of SHYLOC on SPOT Scene 9..............................................13

2.5.2 Application of SHYLOC on SPOT Scene 10............................................18

CHAPTER 3: RESULTS .......................................................................................23

3.1 Ditch indexes ..................................................................................................23

3.2 Results of water depth estimation....................................................................28

3.2.1 Measured water depths.............................................................................29

3.2.2 Satellite-derived water depths...................................................................29

3.3 Deviations between measured and satellite-derived water depths ....................32

3.4 Deviations between measured and satellite-derived water widths ....................37

CHAPTER 4: DISCUSSION AND CONCLUSIONS...........................................41

REFERENCES.......................................................................................................42

2

SHYLOC IMPLEMENTATION IN STRYMONAS BASIN VOLUME 3

CHAPTER 1: INTRODUCTION

The Strymonas River basin has significant values, in terms of biodiversity,

agriculture, tourism and economic assets. The irrigation and drainage of the

Strymonas River basin is elaborated through a dense network of canals and ditches.

Agricultural activities constitute the main threat to surface waters and groundwater in

the basin. One of the main problems occurring in the area is the unsustainable

management of surface waters with significant consequences: loss of water,

salinisation of agricultural soils, alterations in the hydroperiod of Lake Kerkini, high

nutrients concentration, sea intrusion.

The Life Strymon project aims at the sustainable management of surface waters and

groundwater in Strymonas River Basin. To accomplish that, a monitoring system for

the calibration of the modeling system of Strymonas River has been designed

(Chalkidis et al. 2004). A sufficient network of stage boards, sensors and sampling

stations for monitoring the quantitative and qualitative water flow properties is being

established. Spatial and temporal variations of the impacts of agricultural activities on

surface waters and groundwater are assessed using State of the Art Modeling Tools.

State of the art methods are also used to elaborate optimum water resources

management plans.

The objective of this work is to examine the possibility of using a satellite image

analysis method to provide water levels at certain positions in surface waters of the

Strymonas river basin. In particular, satellite images were used to estimate the water

widths of certain ditches and these values were correlated with the recordings of water

depth instrumentation at specific cross sections and on specific dates. The expected

output is to apply linear correlations in order to estimate water level at certain

positions of the drainage and irrigation network of the study area and use these

estimations to calibrate the modeling tools.

3

CHAPTER 2: METHOD

2.1 General

To assess water depth in surface waters of the river basin, 12 instruments measuring

water depths were installed at 12 cross sections of the irrigation and drainage network

of the Strymonas River basin. Satellite images that cover the basin area, were

processed and water widths of the parts of the irrigation and drainage network where

instrumentation is installed, were derived. These water widths were correlated with

ground measurements of water depths from different dates, in order to test the

accuracy of the SHYLOC results and examine the possibility of using them for the

calibration of the MIKE SHE/MIKE 11 models. Satellite-derived water depths were

also estimated using the SHYLOC water width calculations, taken into account that

most ditches have trapezoid cross sections and their inclinations and bases are known.

Ten satellite images have been processed so far, covering the Strymonas river basin.

The images were acquired at different dates covering spring and summer periods of

2004, 2005 and 2006.

Both satellite image processing and the calculation of the ditch water depths were

performed using SHYLOC (System for HYdrology using Land Observation for model

Calibration). The functionality of this software has been described in “SHYLOC

Implementation in Strymonas Basin-Volume 1”.

The satellite images were firstly geo-processed and then used to estimate the water

width of rivers, through SHYLOC. The first application of SHYLOC was performed

to satellite imagery of 2004 and is described in the first SHYLOC technical report

(Hatziiordanou and Papadimos 2004). SHYLOC application to the remaining satellite

images of 2004 and those of 2005, was implemented in 2005 and is described

thoroughly in the second SHYLOC technical report (Hatziiordanou 2005). The

present report describes the SHYLOC application to two satellite images that were

acquired in summer of 2006.

The processing stages and the results of the third SHYLOC application are described

in the following chapters.

4

2.2 Image acquisition

The selection of the appropriate satellite imagery was based on its spatial resolution,

its coverage and its ability to distinguish water from land. SPOT (Satellite Pour l’

Observation de la Terre) imagery outweighed other space and airborne remote sensing

data on all the above matters. A further advantage of SPOT is that its images can be

acquired under exact acquisition programming request.

Thus, 10 panchromatic SPOT images that cover the whole study area were requested

to be acquired at certain time periods (Table 2.2.1). The programming request

included detailed descriptions and technical requirements of the imagery needs, such

as survey period, survey area and repeated acquisitions at specified time intervals for

crop monitoring. The image acquisition was programmed for the spring and summer

of 2004, 2005 and 2006, in order to avoid cloud and ice coverage. More precisely,

five sets of images were purchased, each including two scenes, one from the

northeastern part and one from the southwestern part of the basin. Most of them were

acquired by SPOT-4 and some by SPOT-5, depending on the time availability of the

satellite’s pass at the requested time period. A minimum radiometric correction was

already performed to them by ‘SPOT Image France’ (level of processing: 1A).

Table 2.2.1 Technical information and exact date and time of acquisition of the

satellite images.

Set Scene Satellite Instrument Resolution Acquisition date

Acquisition time

1 1 SPOT 4 HRVIR 2 10 m 23 April 2004 09:44:54

1 2 SPOT 4 HRVIR 1 10 m 29 April 2004 09:29:25

2 3 SPOT 4 HRVIR 1 10 m 25 May 2004 09:29:34

2 4 SPOT 4 HRVIR 2 10 m 14 June 2004 09:45:09

3 5 SPOT 5 HRG 2 10 m 14 July 2004 09:41:40

3 6 SPOT 5 HRG 2 10 m 25 August 2004 09:34:04

4 7 SPOT 5 HRG 2 10 m 22 June 2005 09:43:44

4 8 SPOT 4 HRVIR 2 10 m 9 July 2005 09:46:14

5 9 SPOT 5 HRG 2 10 m 17 June 2006 09:18:50

5 10 SPOT 5 HRG 2 10 m 7 July 2006 09:34:14

5

2.3 Image preprocessing

SPOT images of the fifth set were georeferenced to the Greek Geodetic Reference

System EGSA�871. “Image to map” and “image to image” coordinate transformations

were applied using well defined ground control points from topographic maps (scale

1: 50.000) and the first order polynomial method. The bilinear interpolation was

selected for the image resampling, because of its better spatial accuracy and its

suitability for SHYLOC application against other available methods (Hatziiordanou

and Papadimos, 2004). Figures 2.3.1 and 2.3.2 display the resulted images. The

images had to be reprojected to the Word Geodetic System (WGS84)2, in order to be

used as input in SHYLOC.

Figure 2.3.1 Scene 9 (June 17, 2006) that covers the NW part of the study area,

georeferenced to EGSA�87.

1 The Greek Geodetic Reference System (EGSA�87) is a Tranverse Mercator projection that uses the

spheroid of GRS80 and a scaling factor of 0.9996. It is the main reference system that is used in Greece

and it measures in meters.

2 The World Geodetic System 1984 (WGS84) is a geocentric geodetic datum used for the determination

of geographical coordinates developed by the United States Department of Defence.

6

Figure 2.3.2 Scene 10 (July 7, 2006) showing the SE part of the study area,

georeferenced to EGSA�87.

2.4 Water quantity monitoring network

The main objective of the water level monitoring network is to provide an adequate

number of water depth time series for the calibration and validation of the hydraulic

model of the catchment (Chalkidis et al. 2004).

The network includes 12 water level auto-recorders that are established at the inlets

and outlets of either the natural water bodies (e.g. Strymonas River, Lake Kerkini, etc)

or the irrigation and drainage networks in the Strymonas basin (Figure 2.4.1). Four of

them (No 9, 10, 11 and 12) are installed at earthen canals, whereas the remaining 8

(No 1 to 8) are installed at concrete canals.

The 1st water level recorder (No 1) has been established in Strymonas River just

upstream the flow control structure “Ypsilon 1 (Y1)” aiming at the monitoring of

Strymonas inflows into the catchment.

7

Figure 2.4.1 The water quantity monitoring network (yellow spots) and the study area (orange line).

8

Three water level recorders (No 2, 3 and 4) have been established in the upper end of

the canals of “Kentriki dioriga”, “Anatoliki dioriga” and “Ditiki dioriga”, aiming at

monitoring the discharges that are supplied to the 1st irrigation network of Serres plain

and to the region of “Hrisohorafa”.

Water level auto-recorder No 5 has been established about 3 km downstream the

upper end of the canal “2K” that supplies the irrigation networks of Sidirocastro

region.

The 6th water level recorder (No 6) has been established just downstream the flow

control structure “Ypsilon 2 (Y2)” under the bridge of “Enotiki Dioriga” that supplies

with water the 2nd irrigation network of Serres.

The 7th water level auto-recorder (No 7) has been established downstream the

“Ypsilon 3 (Y3)” flow control structure through which water diverts to the “5K”

canal. The canal “5K” supplies with water the 4th irrigation network of Serres and the

“Dimitritsi” irrigation network.

The 8th, 9th and 10th water level auto-recorders (No 8, 9 and 10) are located in

“Belitsa” drainage ditch. Instrument No 8 has been established in “Belitsa” ditch just

before the outlet of “Annageniseos” ditch, aiming at the monitoring of the water flow

at its upper end. Instrument No 9 has been established under the bridge near the

villages “Ano Mitrousi” and “Kato Mitrousi”. The water flow at this point comes

from drainage water from the upstream cultivated areas during the summer while

during the rest period, comes mainly from the upstream torrents. Instrument No 10 is

located under the bridge of village “Skoutari”.

The 11th water level auto-recorder (No 11) has been established at “Agitis” River near

the “Agistas” Railway Station. At this point the net inflow of “Agitis” into the

catchment can be estimated.

Water level auto-recorder No 12 has been established 2 km upstream of Strymonas

outlet into Strymonikos Gulf aiming at monitoring the total runoff of Strymonas

catchment into the sea.

9

2.5 Third application of SHYLOC to the Strymonas River Basin

The third application of SHYLOC involved application to the fifth set of SPOT

images, acquired on summer of 2006 (Table 2.5.1 and Figure 2.5.1).

Table 2.5.1 SPOT images that were used for the third SHYLOC application.

Set Scene Satellite Resolution Band used for the

SHYLOC application Acquisition

date

5 9 SPOT 5 10 m 4 17 June 2006

5 10 SPOT 5 10 m 4 7 July 2006

The 4th spectral band (Short Wave Infrared) of SPOT was used for the SHYLOC

calculations, due to the ability that offers to distinguish water from land, as it takes

advantage of their different reflectance at this spectral range. Figure 2.5.2 displays the

study area (highlighted in orange polyline), the hydrographic network (highlighted in

blue polyline) and the 12 instruments (in red) on Band 4 of the fifth set of images.

The SPOT images were opened at SHYLOC in SceneType and their corner

coordinates were entered in WGS84 Longitude/Latitude. They were then saved in

bitmap format and opened in Shyloc Type mode from the SHYLOC Calculation bar.

The ditch4 data (polyline vector of the hydrographic network in shapefile format)

were transformed from EGSA’87 to WGS84, to overlay the SPOT images.

4 Although instruments were installed in canals, the term “ditch” will be used hereafter, due to its

compatibility to SHYLOC.

10

Figure 2.5.1 Fifth set of SPOT images. Scene 9 at the left (June 17, 2006) and scene 10 at the right (July 7, 2006) displayed in RGB

combination, using the 4th and 2nd spectral bands.

11

Figure 2.5.2 The study area (orange polyline), the hydrographic network (blue polyline) and the 12 instruments (red symbols) on Band 4 of Set

5 (9th SPOT scene at the left and 10th SPOT scene at the right).

12

SHYLOC was applied to 10 of the 12 water level recorders of the water level

monitoring network. It was not applied to instruments 8 and 1, because the 8th water

level recorder could not be detected by the satellites and the 1st is established at an

orthogonal ditch. It should be noted that SHYLOC calculations for water level

recorders No 9, 10, 11 and 12 that are installed at earthen ditches are not accurate,

because these ditches do not have stable cross sections. Nevertheless SHYLOC was

applied to water level recorders No 2, 3, 4, 5, 6 and 7, that are installed at trapezoid

concrete ditches with known inclinations and bases.

For the SHYLOC calculations the land reference value was automatically computed

by the software for each cross section on the images. The pure water reference value

was stable for each image. The water widths of the cross sections that were computed

for each land method were used to estimate the corresponding water depths. The

water depths that were estimated by SHYLOC were compared with the measurements

of water depths from the water level recorders at the exact day and time that the

satellite passed over the instruments.

To identify the ditch carrying pixels and calculate the ditch index and the ditch width,

10 boundaries where drawn around the locations of the 10 instruments, using the

Polyline Editor tool of SHYLOC. Thus the ditch index and wet ditch width

calculations were limited to the ditch carrying pixels located within the defined

boundaries.

The SHYLOC Calculation bar (Figure 2.5.4) was used for raster and vector data

input. Raster data (Image file) had to be in bitmap format, vector data that represents

hydrographic network (Ditch Data) had to be in shapefile format and vector data that

represents the defined boundaries around the instruments (Boundary) had to be in

DXF format.

A slight shift of the images was necessary, in order to optimise the fit between the

satellite image and the vector ditch data. The “Shift/rotate” tool of SHYLOC was used

in order to recalibrate the images.

13

Figure 2.5.4 Input of raster and vector data in Shyloc Type mode, to the SHYLOC

calculation bar.

2.5.1 Application of SHYLOC on SPOT Scene 9

The 9th SPOT Scene that was acquired on 17 June of 2006, covers the NW part of the

study area. Nine water level recorders are installed at ditches around the area covered

by the image (Figure 2.5.5). The 8th and the 1st water level recorders were excluded

from the SHYLOC calculations. Thus, SHYLOC was applied to 7 cross sections

(around water level recorders No 2, 3, 4, 5, 6, 7 and 9).

Image pre-processing included a shifting of the image, in order to optimise the fit

between the satellite image and the vector ditch data. Figure 2.5.6 (up) shows a detail

of the image where the digitized hydrographic network (vector file outlined in red) is

not overlaying well the ditches (shown in black color on the satellite image).

Recalibration was applied using the “Shift/rotate” tool in SHYLOC and the fit

between the image and the overlaying vector file was improved (Figure 2.5.6 down).

14

Figure 2.5.5 The 9 water level recorders (red spot) on SPOT Scene 9 (June 17, 2006).

15

Figure 2.5.6 Up: Detail from the 9th SPOT scene (June 17, 2006) where the digitized

hydrographic network (outlined in red) is not overlaying well the

satellite image (ditches shown in black). Down: The same scene, after its

coordinates have been modified using the shift tool.

To enable faster and easier data processing, the image was cut in smaller areas defined

by selections, using the rectangle selection tool. The areas surround the boundaries

that were drawn around the water level recorders. (Figure 2.5.7).

16

Figure 2.5.7 Detail from the boundaries (in yellow) that were drawn with the Polyline

Editor around the water level recorders 2, 3, 4, 5, 6, 7 and 9 for SPOT

scene 9.

2nd 3rd

4th 5th

6th

9th

7th

17

Following the image pre-processing, the Pure Water Reference Value and the Land

Reference Value were determined.

The Pure Water Reference Value was determined using the rectangular selection

button, by defining an area inside Kerkini Lake. The minimum digital number inside

this area corresponds to the value of the reference water pixel (W) and was found to

be 0 (Figure 2.5.8).

Figure 2.5.8 Selected pure water area and minimum digital number (highlighted at

the pixel selector table) of pixels found inside this area. This minimum

number corresponds to the pure water reference number of the 9th

SPOT scene.

Regarding the calculation of the digital number of the land reference value (Li), the

automatic method was applied to calculate it, using eight methods (described at

section 2.4 of “SHYLOC Implementation in Strymonas Basin-Volume 1”). The main

scope was to examine the effects of the different land calculation methods upon the

statistical relationships between satellite-derived and measured water depths, obtained

on the day of the satellite overpass.

A SHYLOC calculation index was applied to the 7 user-defined boundaries around

the ditches where water level recorders are installed. The calculation was applied 8

Selected pure water area

Highlighted pure water DN at the pixel editor window

18

times for each one of the boundaries. In all cases the same water reference value was

declared at the calculation bar, but the land reference value was dependent on the

selected land calculation method. In some cases, editing of the ditch pixels was

necessary in order to correct some slight errors, caused by inaccurate digitization.

2.5.2 Application of SHYLOC on SPOT Scene 10

The 2nd SPOT Scene was acquired at 29 April 2004. It covers the NW part of the

study area. Four water level recorders are installed at ditches around the area covered

by the image (Figure 2.5.9). The 9th water level recorder was excluded from the

SHYLOC calculations, because it was located at the edge of the image. Thus,

SHYLOC was applied to 3 cross sections around water level recorders No 10, 11 and

12 that were all installed at earthen ditches.

During the SHYLOC application, a slight shift of the image was needed for

improving the overlay with the vector ditch data. Figure 2.5.10 displays an example

where the digitized hydrographic network did not overlay well the ditches (shown in

black color on the satellite image).

19

Figure 2.5.9 The 4 water level recorders (red spots) on SPOT Scene 10 (July 7, 2006).

20

Figure 2.5.10 Up: Detail from the 10th SPOT scene (July 7, 2006) where the digitized

hydrographic network (outlined in red) is not overlaying well the

satellite image (ditches shown in black). Down: The same scene, after

image shifting.

The image was then cut in smaller areas around the 3 water level recorders for faster

and easier data processing (Figure 2.5.11).

21

Figure 2.5.11 Detail from the boundaries (in yellow) that were drawn with the

Polyline Editor around the water level recorders 10, 11 and 12 for

SPOT scene 10.

The Pure Water Reference Value for the 10th SPOT scene was determined by defining

an area inside Kerkini Lake, using the rectangular selection button. The minimum

digital number inside this area that corresponds to the value of the reference water

pixel (W) was found to be 0 (Figure 2.5.12).

10th 11th

12th

22

Figure 2.5.12 Selected pure water area and minimum digital number (highlighted at

the pixel selector table) of pixels found inside this area. This minimum

number corresponds to the pure water reference number of the 10th

SPOT scene.

The automatic method was applied to calculate the digital number of the land

reference value (Li), using all eight available methods. Finally, a SHYLOC

calculation index was applied to the user-defined boundaries around the ditches where

water level recorders are installed. The calculation was applied 8 times for each one of

the 3 boundaries, using the same water reference value (W=0) and the land reference

value that was calculated from 8 land calculation methods. Editing of the ditch pixels

was necessary in order to correct digitization errors.

Selected pure water area

Highlighted pure water DN at the pixel editor window

23

CHAPTER 3: RESULTS

3.1 Ditch indexes

SHYLOC calculation of the “Ditch Index” includes determination of the wet ditch

width inside user-defined boundaries. The “Ditch Index” calculations were applied to

both satellite images, for user-defined boundaries around all water level recorders

situated at certain ditches that were detected at the images. The calculation, which was

made for each one of the water level recorders and for each of the images, was

repeated 8 times, using the pure water reference digital value of each image, and each

time the land reference digital value that was calculated using 8 methods.

All automatic methods of the software were used to calculate the land reference value:

(1) moving average 5x5, (2) moving average 3x3, (3) fixed average inside boundary,

(4) maximum average inside boundary, (5) fixed average in 1 nearest pixel, (6)

maximum average in 1 nearest pixel, (7) fixed average in 2 nearest pixels and (8)

maximum average in 2 nearest pixels. The reason for using all the methods was to

find out which give tighter correlations between the water depths that are derived by

SHYLOC and those derived by the water level recorders.

The results from the SHYLOC calculation applied to the 6th water level recorder for

SPOT scene 9 and the 10th for SPOT scene 10 are displayed in Figures 3.1.1 and

3.1.2 correspondingly. The different colored pixels indicate the percentage of the

pixel water coverage. The deeper the color of the category, the greater the pixel water

content is. Orange color indicates dry pixels. The default value (100 %) of the

maximum pixel water coverage was used for the calculations.

Tables 3.1.2 and 3.1.4 that follow, show the water widths (in meters) that were

derived by SHYLOC applications on both images for cross sections 2, 3, 4, 5, 6, 7, 9,

10, 11 and 12, using as land reference values those that were calculated by 8

automatic methods. The results of the land reference values are shown at Tables 3.1.1

and 3.1.3

24

moving average 5x5 moving average 3x3 fixed average inside boundary

maximum average inside boundary fixed average in 1 nearest pixel fixed average in 2 nearest pixels

maximum average in 1 nearest pixel maximum average in 2 nearest pixels

Figure 3.1.1 The ditch index calculation for the 6th instrument, calculated using the 8

automatic land calculation methods for SPOT scene 9 (June 17, 2006).

25

moving average 5x5 moving average 3x3 fixed average inside boundary

maximum average inside boundary fixed average in 1 nearest pixel fixed average in 2 nearest pixels

maximum average in 1 nearest pixel maximum average in 2 nearest pixels

Figure 3.1.2 The ditch index calculation for the 10th instrument, calculated using the

8 automatic land calculation methods for SPOT scene 10 (July 7, 2006).

26

Table 3.1.1 Land reference values derived by 8 calculating methods for selected boundaries corresponding to instruments 2, 3, 4, 5, 6, 7

and 9 of the 9th SPOT scene (June 17, 2006).

Cross Section

Date of SPOT image

overpass

Moving average 5x5

window

Moving average 3x3

window

Fixed average inside boundary

Maximum value inside boundary

Fixed average in 1 near pixel

Maximum value in 1 near pixel


Maximum value in 2

near pixels 2 17 June 161.4 152.44 179 255 159 231 168 255 3 17 June 163.68 146.2 157 255 147 211 162 255 4 17 June 175.083 160.125 203 255 175 255 184 255 5 17 June 132.778 124.444 134 255 127 192 137 255 6 17 June 36.8061 22.497 106 234 36 137 57 162 7 17 June 103.023 91.0747 126 238 98 171 111 204 9 17 June 133.438 107.884 204 255 128 236 160 255

Table 3.1.2 Water widths (m) corresponding to instruments 2, 3, 4, 5, 6, 7 and 9, derived by a SHYLOC application to the 4th band of

the 9th SPOT scene (June 17, 2006). The water reference value used for the calculation is W=0 and the land reference

values are shown in Table 3.1.1.

Cross Section

Date of SPOT image

overpass

Moving average 5x5

window

Moving average 3x3

window






Maximum value in 2

near pixels 2 17 June 6.22 4.25 9.74 18.74 6.09 16.53 7.81 18.74 3 17 June 7.32 4.78 6.84 16.13 5.20 13.03 7.59 16.13 4 17 June 5.40 3.16 8.78 13.05 5.44 13.05 6.62 13.05 5 17 June 3.29 1.94 3.55 13.06 2.46 9.61 3.99 13.06 6 17 June 59.82 54.52 64.90 66.95 58.07 65.75 61.68 66.20 7 17 June 9.32 5.98 14.65 25.46 8.66 20.69 11.69 23.43 9 17 June 16.61 11.19 24.17 27.18 15.23 26.21 20.03 27.18

27

Table 3.1.3 Land reference values derived by 8 calculating methods for selected boundaries corresponding to instruments 10, 11 and 12

of the 10th SPOT scene (July 7, 2006).

Cross Section

Date of SPOT image

overpass

Moving average 5x5

window

Moving average 3x3

window






Maximum value in 2

near pixels 10 7 July 111.841 99.3175 147 255 110 187 127 198 11 7 July 99.3651 93.8008 148 255 98 211 106 211 12 7 July 71.336 61.856 152 238 73 127 87 152

Table 3.1.4 Water widths (m) corresponding to instruments 10, 11 and 12 derived by a SHYLOC application to the 4th band of the 10th

SPOT scene (July 7, 2006). The water reference value used for the calculation is W=0 and the land reference values are

shown in Table 3.1.3.

Cross Section

Date of SPOT image

overpass

Moving average 5x5

window

Moving average 3x3

window






Maximum value in 2

near pixels 10 7 July 10.01 5.85 18.00 28.79 9.51 23.45 13.99 24.56 11 7 July 0.01 0.01 0.04 0.07 0.01 0.06 0.02 0.06 12 7 July 20.00 12.23 44.87 53.04 20.87 40.42 28.03 44.87

28

3.2 Results of water depth estimation

SHYLOC water width calculations were used to estimate the water depths of cross

sections. These depths were then compared with the depths that were measured by the

water level recorders at the exact days that SPOT satellite passed over the study area.

This enabled examining the effects of different land calculation methods upon the

statistical relationships between satellite-derived and measured depths.

Satellite-derived water depths were estimated from the water width calculations, taken

into account that ditches are trapezoids with known inclinations and bases (Figure

3.2.1). Table 3.2.1 shows the inclinations of the side walls (c) and the widths of the

bottom base (b) of the concrete ditches where water level recorders No 2 to 7 are

installed. Water level recorders 9, 10, 11 and 12 are installed at earthen ditches that do

not have stable dimensions.

Figure 3.2.1 Representation of a trapezoid shaped water ditch, filled with water. The

water depth (measured quantity) is symbolized with the letter d, the

water width with w, the inclination of the side walls of the ditch (known

value) with c and the small base of the trapezoid (known value) with b.

Table 3.2.1 Inclinations of side walls and widths of the bottom base of the concrete

covered trapezoid ditches.

Water level recorder ID Inclination of side walls Bottom base width (m) 2 1 1.5 3 1.49 0.6 4 1.55 0.6 5 1.5 2 6 2 23.6 7 1.53 4.8

c

b

d

w

29

3.2.1 Measured water depths

Table 3.2.2 shows the measured water depths for the acquisition date of SPOT scene 9

(June 17, 2006) and Table 3.2.3 for the acquisition date of SPOT scene 10 (July 7,

2006).

Table 3.2.2 Ground measured water depths (in meters) from the 7 water level

recorders that were located at the area covered by SPOT scene 9 at the

exact date and time of the SPOT image acquisition.

Table 3.2.3 Ground measured water depths (in meters) from the 3 water level

recorders that that were located at the area covered by SPOT scene 10 at

the exact date and time of the SPOT image acquisition.

3.2.2 Satellite-derived water depths

The next step was to estimate the water depths at each cross section, by using the

SHYLOC-derived water widths, for those water level recorders that were detected by

SPOT scenes 9 and 10.

Regarding water level recorders 2, 3, 4, 5, 6 and 7 that are located in concrete

trapezoid ditches, the water depth was easily computed. The resulted water depths

corresponding to the 8 different land methods are included in Table 3.2.4.

Instrument Measured water depth on June 17, 2006 (d) 2 0.51 3 0 4 1.048 5 0.776 6 1.789 7 1.81 9 0.82

Instrument Measured water depth on July 7, 2006 (d) 10 1.1 11 0.992 12 0.877

30

Table 3.2.4 Satellite-derived water depths D (in meters) for concrete cross sections

where instruments No 2 to 7 are installed. The measured depths (in

meters) for the day of 17th of June 2006 that the 9th SPOT scene was

acquired are included in Column 2. Columns 3 to 10 show satellite-

derived water depths, estimated from the water widths, for 8 different

land calculation methods.

Regarding those water level recorders (No 9, 10, 11 and 12) that were installed at

earthen ditches, that do not have stable dimensions, water depth could not be easily

computed. Thus, the effectiveness of the land calculation method was tested using the

satellite-derived water widths and the water widths that were estimated from the

measured depths. It should be mentioned that these widths are not very accurate, since

they were estimated graphically, using sketches of the 4 cross sections (Figures 3.2.2

to 3.2.5).

0.00

1.00

2.00

3.00

4.00

5.00

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0

Figure 3.2.2 Cross section at Belitsa Ditch where the 9th water level recorder has

been established (Chalkidis et al. 2004).

Cross Section

Measured depth (d)

D1 Moving average 5x5

window

D2 Moving average 3x3

window

D3 Fixed

average inside

boundary

D4 Maximum

value inside

boundary

D5 Fixed

average in 1 near

pixel

D6 Maximum value in 1 near pixel

D7 Fixed

average in 2 near

pixel

D8 Maximum value in 2

near pixels

2 0.51 2.36 1.38 4.12 8.62 2.30 7.52 3.16 8.62 3 0 5.01 3.11 4.65 11.57 3.43 9.26 5.21 11.57 4 1.048 3.72 1.98 6.34 9.65 3.75 9.65 4.67 9.65 5 0.776 0.97 -0.05 1.16 8.30 0.35 5.71 1.49 8.30 6 1.789 36.22 30.92 41.30 43.35 34.47 42.15 38.08 42.60 7 1.81 3.46 0.90 7.54 15.80 2.95 12.16 5.27 14.25

Water level recorder No9

Bridge at Mitrousi

31

0.001.002.00

3.004.005.006.00

7.008.00

0 5 10 15 20 25 30 35 40 45

Figure 3.2.3 Cross sections at Belitsa Ditch where the 10th water level recorder has

been established (Chalkidis et al. 2004).

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

0 10 20 30 40 50 60 70

Figure 3.2.4 Cross sections of Agitis River at “Agistas” Railway Station where the

11th water level recorder has been established (Chalkidis et al. 2004).

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 10 20 30 40 50 60 70

Figure 3.2.5 Cross sections at Strymonas River where the 12th water level recorder

has been established (Chalkidis et al. 2004).

Bridge at Skoutari Water level

recorder No10

Agiti’s Bridge Water level recorder No11

Water level recorder No12

Ground Level

32

Tables 3.2.5 and 3.2.6 show the satellite-derived water widths and the estimated

widths for water level recorders No 9, 10, 11 and 12 that are installed at earthen

ditches for scenes 9 and 10.

Table 3.2.5 Satellite-derived water widths W (in meters) for earthen cross sections

where instrument No 9 was installed. The estimated widths (in meters)

for the day of 17th of June 2006 that the 9th SPOT scene was acquired

are included in Column 2. Columns 3 to 10 show the satellite-derived

water widths.

Table 3.2.6 Satellite-derived water widths W (in meters) for earthen cross sections

where instruments No 10 to 12 are installed. The estimated widths (in

meters) for the day of 7th of July 2006 that the 10th SPOT scene was

acquired are included in Column 2. Columns 3 to 10 show the satellite-

derived water widths.

3.3 Deviations between measured and satellite-derived water depths

The SHYLOC-derived water depths were thereafter compared to measured depths.

This resulted in a comparison of each land method’s effectiveness.

Figures 3.3.1 to 3.3.6 indicate the variation of depths derived by the 8 land methods

for cross sections 2, 3, 4, 5, 6 and 7 and their comparison with the depths that were

measured by the water level recorders for the day that SPOT scene 9 was acquired (17

Cross Section

Estimated width (w)

W1 Moving average

5x5 window

W2 Moving average

3x3 window

W3 Fixed

average inside

boundary

W4 Maximum

value inside

boundary

W5 Fixed

average in 1 near

pixel

W6 Maximum value in 1 near pixel

W7 Fixed

average in 2 near pixel

W8 Maximum value in 2

near pixels

9 23 16.61 11.19 24.17 27.18 15.23 26.21 20.03 27.18

Cross Section

Estimated width (w)

W1 Moving average

5x5 window

W2 Moving average

3x3 window

W3 Fixed

average inside

boundary

W4 Maximum

value inside

boundary

W5 Fixed

average in 1 near

pixel

W6 Maximum value in 1 near pixel

W7 Fixed

average in 2 near pixel

W8 Maximum value in 2

near pixels

10 21 10.01 5.85 18.00 28.79 9.51 23.45 13.99 24.56 11 26 0.01 0.01 0.04 0.07 0.01 0.06 0.02 0.06 12 47 20.00 12.23 44.87 53.04 20.87 40.42 28.03 44.87

33

June 2006). D1 to D8 correspond to the depths (in meters) derived by SHYLOC using

each one of the 8 land calculation methods.

Figure 3.3.1 Water Depths for cross section 2 that were derived by SHYLOC using

the 8 automatic land calculation methods. The blue discontinuous line

represents the depth (d=0,51 m), measured by the water level recorder

at June 17, 2006 (date of SPOT Scene 9 overpass).



represents the depth (d=0 m), measured by the water level recorder at

June 17, 2006 (date of SPOT Scene 9 overpass).

1,38

4,12

8,62

2,3

7,52

3,16

8,62

2,36

0

1

2

3

4

5

6

7

8

9

10

Land calculation methods

Wat

er d

epth

(m)

Series1

D1D2

D3

D4

D5

D6

D7

D8

D cs 2

d=0,51

SPOT Scene 9 (17/6/2006) - Cross section 2

3,11

4,65

11,57

3,43

9,26

5,21

11,57

5,01

-2

0

2

4

6

8

10

12

14


Wat

er d

epth

(m)

Series1

D1

D2

D3

D4

D5

D6

D7

D8

D cs 3

d=0


34









1,98

6,34

9,65

3,75

9,65

4,67

9,65

3,72

0

2

4

6

8

10

12

Land Calculation methods

Wat

er d

epth

(m)

Series1

D1

D2

D3

D4

D5

D6

D7

D8

D cs 4

d=1,048


1,16

8,3

0,35

5,71

1,49

8,3

-0,050,97

-1

1

3

5

7

9


Wat

er d

epth

(m)

Series1

D1

D2

D3

D4

D5

D6

D7

D8

D cs 5

d=0,776


35









30,9234,47

38,08

42,15

36,22

43,35

41,3

42,6

0

5

10

15

20

25

30

35

40

45

50


Wat

er d

epth

(m

)

Series1

D1

D2

D3D4

D5

D6

D7

D8

D cs 6

d=1,789


3,46

15,8

2,95

12,16

5,27

14,25

7,54

0,90

2

4

6

8

10

12

14

16

18


Wat

er d

epth

(m)

Series1

D1

D2

D3

D4

D5

D6

D7

D8

D cs 7

d=1,81


36

As indicated by the above Figures (3.3.1 to 3.3.6), the correlations between the

SHYLOC-derived water depths and those depths measured by water level recorders

are not good. The differences appear to be independent of the land calculation method

that was used. Apart from that, at cross section 5 the estimated depth, computed using

the ‘moving average 3x3 window’ land calculation method, was found to be negative.

This depth is not realistic and indicates the ineffectiveness of this method.

Table 3.3.1 that follows, shows which land calculation methods were found to be

most appropriate for calculating water depths at cross sections 2 to 7 for SPOT scene

9. It should be mentioned though, that water depths that were computed using some

land reference methods resulted in significant deviations from measured depths. These

methods were the “maximum value inside boundary”, the “maximum value in 1

nearest pixel” and the “maximum value in 2 nearest pixels”. On the other hand, the

“moving average 3x3 window” method and the “fixed average in 1 nearest pixel”

method, resulted to better correlations between SHYLOC-derived depths and

measured depths. Nevertheless, at some cases (cross sections 3 and 6) none of the

land calculation methods was proved effective.

Table 3.3.1 Effectiveness of land calculation methods on calculating water depths at

cross sections 2 to 7 for SPOT scene 9. Symbol “*” indicates most

appropriate methods and void cells indicate methods that resulted to bad

correlations between SHYLOC-derived and measured depths.

SPOT SCENE 9

Cross section

Moving average

5x5 window

Moving average

3x3 window

Fixed average inside

boundary

Maximum value inside

boundary

Fixed average

in 1 near pixel


Fixed average

in 2 near pixel

Maximum value in 2

near pixels

2 * 3 4 * 5 * * * 6 7 * *

37

3.4 Deviations between measured and satellite-derived water widths

The water widths that were computed by SHYLOC for cross sections 9, 10, 11 and 12

were compared with those water widths that were estimated by the measured depths.

The effectiveness of the land calculation methods that were used at SHYLOC was

then examined.

Figures 3.4.1 to 3.4.4 indicate the variance of water widths derived by the 8 land

methods for cross sections 9, 10, 11 and 12 and their comparison with the widths that

were measured by the water level recorders for the days that SPOT scenes 9 and 10

were acquired. W1 to W8 correspond to the widths (in meters) computed by

SHYLOC using each one of the 8 land calculation methods. It is noticeable that bad

correlations exist between SHYLOC-derived water widths and those widths estimated

by measured depths and differences appear to be independent of the land calculation

method.

Figure 3.4.1 Water widths (W) for cross section 9 that were derived by SHYLOC

using 8 automatic land calculation methods. The blue discontinuous

line represents the width (w=23 m), estimated by the water level

recorder measurements at June 17, 2006 (date of SPOT Scene 9

overpass).

11,19

24,17

27,18

15,23

26,21

16,61 20,03

27,18

0

5

10

15

20

25

30

35


Wat

er w

idth

(m)

Series1

W1

W2

W3

W4

W5

W6

W7

W8

W cs9

w=23


38




recorder measurements at July 7, 2006 (date of SPOT Scene 10

overpass).





overpass).

5,85

18

28,79

9,51

23,45

10,01 13,99

24,56

0

5

10

15

20

25

30

35


Wat

er w

idth

(m

)

Series1

W1

W2

W3

W4

W5

W6

W7

W8

W cs10w=21


0,060,010,070,040,010,01 0,02 0,06

-5

0

5

10

15

20

25

30


Wat

er w

idth

(m

)

Series1

W1 W2 W3 W4 W5 W6 W7 W8

W cs11

w=26


39





overpass).

Table 3.4.1 shows which land calculation methods were found to be most effective to

calculate water widths at cross sections 9 to 12 for SPOT scenes 9 and 10.

Water depths that were computed using some particular land reference methods

resulted in significant deviations from measured depths. These methods were the

“moving average 5x5 window”, the “moving average 3x3 window”, the “fixed

average in 1 nearest pixel” and the “fixed average in 2 nearest pixels” methods. On

the other hand, the “fixed average inside boundary” method resulted in better

correlations between the SHYLOC-derived depths and the measured depths. For cross

section 11 none of the land calculation methods was proved effective.

12,23

44,87

53,04

20,87

40,42

20

28,03

44,87

10

15

20

25

30

35

40

45

50

55


Wat

er w

idth

(m

)

Series1

W1

W2

W3

W4

W5

W6

W7

W8

W cs12

w=47


40

Table 3.4.1 Effectiveness of land calculation methods appropriate for calculating

water widths at cross sections 9 to 12 for SPOT scenes 9 and 10. Symbol

“*” indicates the most appropriate methods, whereas void cells indicate

methods that resulted in bad correlations between SHYLOC-derived

widths and estimated widths.

SPOT SCENE 9

Cross section

Moving average

5x5 window

Moving average

3x3 window


boundary


boundary

Fixed average

in 1 near pixel


Fixed average

in 2 near pixel

Maximum value in 2

near pixels

9 * SPOT SCENE 10

Cross section

Moving average

5x5 window

Moving average

3x3 window


boundary


boundary

Fixed average

in 1 near pixel


Fixed average

in 2 near pixel

Maximum value in 2

near pixels

10 * * 11 12 * *

41

CHAPTER 4: DISCUSSION AND CONCLUSIONS

The calculation of the water depth with SHYLOC demonstrates the importance of

using remote sensing data to determine surface water stored in a network of ditches.

Main obstacles that were met during the third application of SHYLOC in Strymonas

River basin were related to digitization inaccuracies that resulted to bad estimation of

some water carrying pixels. The software interface was proved week to deal with the

problem, as it required a lot of manual and time-consuming editing processes.

Most of the land calculation methods that evaluate the digital land reference value

produced week statistical correlations between the satellite-derived depths and the

measured ones. It is possibly caused on the land pixels that correspond to the

vegetation that surrounds those ditches were instrumentation is installed. It is possible

that either dense vegetation may dominate some of the ditches, or deciduous trees

(e.g. aspens) may cover part of them and prevent water detection by the satellite.

At the upcoming time period, all 3 SHYLOC applications to satellite images of the

years 2004, 2005 and 2006 will be compared and their results will be summarized.

The best fit linear equations between satellite-derived water widths and measured

depths will then be selected. The examination of the temporal variation of the pure

water and land reference values and the comparison of the image histograms of the

defined areas at different years or at different months of the same year will enable an

integrated multi-temporal analysis.

Based on the results, the possibility of using SHYLOC for providing water levels at

certain positions in surface waters for the calibration of MIKE SHE/MIKE 11 will be

decided.

42

REFERENCES

Chalkidis, I., D. Papadimos and Ch. Mertzianis. 2004. Water quality and hydrological

regime monitoring network. Greek Biotope/Wetland Centre (EKBY). Thermi, Greece.

21 p.

Hatziiordanou, Eleni. 2005. SHYLOC implementation in Strymonas basin - Volume

2. Greek Biotope/Wetland Centre (EKBY). Thermi, Greece. 88 p.

Hatziiordanou, Lena and D. Papadimos. 2004. SHYLOC implementation in

Strymonas basin - Volume 1. Greek Biotope/Wetland Centre (EKBY). Thermi,

Greece. 52 p.

Khudhairy Al D.H.A, V. Hoffmann and C. Leemhuis. 2001. SHYLOC user manual,

EUR 19745 EN, European Commission.

Khudhairy Al (D.H.A.), C. Leemhuis, V. Hoffmann & I.M. Shepherd (JRC), J.R.

Thompson, H. Gavin & D. Gasca Tucker (UCL), G. Zalidis & G. Bilas (AUT), H.

Refstrup Sørenson & A. Refsgaard (DHI), D. Papadimos (EKBY) and A. Argentieri

(ESA-ESRIN). 2001. SHYLOC final report, EUR 19755 EN, European Commission.

Shepherd, I., G. Wilkinson and J. Thompson. 2000. Monitoring surface water storage

in the north Kent marshes using Landsat TM images. International Journal of Remote

Sensing. Volume 21, no 9: 1843–1865.

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