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EVALUATION OF THE OPTIMAL EVALUATION OF THE OPTIMAL LOCATION OF MONITORING LOCATION OF MONITORING SITES BASED ON SITES BASED ON HYDROLOGIC MODELS AND HYDROLOGIC MODELS AND GIS TECHNOLOGY GIS TECHNOLOGY

De De Girolamo Girolamo A.M., Lo Porto A., A.M., Lo Porto A., Passarella Passarella G., G., Garnier Garnier M. M.

Water Research Institute Water Research Institute -

• CNR, BARI

CNR, BARI – – ITALY ITALY

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INTRODUCTION (1) INTRODUCTION (1)

• Surface water represents an important

source of drinkable supply.

• Protecting such a resource from

contamination processes is a task of increasing importance.

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INTRODUCTION (2) INTRODUCTION (2)

• Diffuse pollution from intensive

agricultural practices is the main responsible of nutrients and pesticides intake in the hydrologic cycle.

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INTRODUCTION (3) INTRODUCTION (3)

• Pollution of surface water systems caused

by agricultural activities is strongly conditioned by soil physical and chemical properties, geomorphology, land use, management practices, and climate.

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INTRODUCTION (4) INTRODUCTION (4)

• The availability of schematic and

synthetic tools to assess surface water quality is an urgent demand of the River Authorities everywhere in the world.

• Any managerial tool needs monitored
• data. (i.e. models require data for

calibration and validation).

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INTRODUCTION (5) INTRODUCTION (5)

• Existing monitoring networks in surface

water can be extensively used to gather water quality information.

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PROBLEM (1) PROBLEM (1)

• Monitoring networks are often designed
• n the basis of already existing or easy to

reach monitoring sites in a watershed; this approach often increases the sampling cost but sometime does not means more extensive and reliable information.

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PROBLEM (2) PROBLEM (2)

• The first step to correctly define a

monitoring program is the identification

• f the optimal location of monitoring

points among several candidates to keep under control the evolution of the water quality.

• The second step consists in defining the

temporal frequency of sampling campaigns.

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OBJECTIVE OBJECTIVE

• To propose and test a methodology for

locating the optimal position of monitoring points within a watershed.

• The parameters to be monitored, the

location of the monitoring points and the sampling temporal frequencies can be determined through the definition of several critical points.

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METHODOLOGY METHODOLOGY

• The methodology consists in using SWAT

coupled with GIS technologies to evaluate the optimal location of monitoring sites within a watershed.

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STUDY AREA (1) STUDY AREA (1)

• River length:

River length: River length: River length: 99 km 99 km 99 km 99 km

• Catchment area:

Catchment area: Catchment area: Catchment area: 884 km 884 km 884 km 884 km2

2

• Annual rainfall:

Annual rainfall: Annual rainfall: Annual rainfall: 950 mm 950 mm 950 mm 950 mm

• Annual snow

Annual snow Annual snow Annual snow prec prec prec prec.: .: .: .: 60 cm 60 cm 60 cm 60 cm

• Mean flow:

Mean flow: Mean flow: Mean flow: 10 m 10 m 10 m 10 m3

3/s

/s /s /s

• Fe

Fertilize rtilizer application: application: Fe Fertilize rtilizer application: application: – – 50 kg/ha P 50 kg/ha P 50 kg/ha P 50 kg/ha P – – 170 kg/ha N 170 kg/ha N 170 kg/ha N 170 kg/ha N – – 10 t/ha/year of dairy 10 t/ha/year of dairy 10 t/ha/year of dairy 10 t/ha/year of dairy cattle and pig manure cattle and pig manure cattle and pig manure cattle and pig manure

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STUDY AREA (2) STUDY AREA (2)

• Enza River is moderately clean.
• Diffuse pollution from agriculture is by

far the primary cause of pollution.

Major activities in the catchment Estimation of % contribution to total load of Nitrogen Estimation of % contribution to total load of Phosphorus Agriculture 60 50 Aquaculture Domestic sewage 10 5 Industry 30 45 Others

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AVAILABLE DATA AVAILABLE DATA

• DEM

DEM

• Vector contour lines layer

Vector contour lines layer

• General

General-

• purpose maps

purpose maps

• Raster topography

Raster topography

• Land

Land-

• use map

use map

• Soil map

Soil map

• Temperature and precipitation

Temperature and precipitation

• Flow and water quality

Flow and water quality

• Management input

Management input

• Management and crop parameters

Management and crop parameters

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LAND LAND-

• USE MAP

USE MAP

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SOIL MAP SOIL MAP

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RESULTS AND DISCUSSION RESULTS AND DISCUSSION (1) (1)

• Only one HRU per sub-basin was

considered, assigning the most common landuse/soil type combination to the whole subbasin.

• According to this scheme, 44 sub-

basins (HRU) where defined within the catchment.

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RESULTS AND DISCUSSION RESULTS AND DISCUSSION (2) (2)

• The automatic GIS tracing of the

The automatic GIS tracing of the Enza river network produced Enza river network produced reliable results only in the reliable results only in the upstream course of the river where upstream course of the river where its steepness is relatively high but its steepness is relatively high but it failed in the flat part of the basin it failed in the flat part of the basin where the mean land gradient is where the mean land gradient is less than 1%. less than 1%.

PROBLEM PROBLEM

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RESULTS AND DISCUSSION RESULTS AND DISCUSSION (3) (3)

• The SWAT

The SWAT-

• GIS interface greatly

GIS interface greatly improved the correspondence improved the correspondence between the real and the modelled between the real and the modelled stream when a digitalized stream stream when a digitalized stream shapefile shapefile was was “ “burned burned-

• on
• n”

” the the DEM. DEM.

SOLUTION SOLUTION

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RESULTS AND DISCUSSION RESULTS AND DISCUSSION (4) (4)

SWAT produced: SWAT produced: 1. 1. predicted values of water balance, predicted values of water balance, erosion, nutrient and pesticide fate, erosion, nutrient and pesticide fate, crop grow crop grow in every sub in every sub-

• basin/HRU

basin/HRU; ; 2. 2. discharge and water quality parameter discharge and water quality parameter values values at each sub at each sub-

• basin outlet and at

basin outlet and at several several key nodes key nodes. .

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RESULTS AND DISCUSSION RESULTS AND DISCUSSION (5) (5)

• In order to calibrate

In order to calibrate and validate the and validate the model results, key model results, key nodes were nodes were associated to four associated to four river cross sections river cross sections where water quality where water quality and discharge were and discharge were monitored. monitored.

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RESULTS AND DISCUSSION RESULTS AND DISCUSSION (6) (6)

• It was performed

It was performed comparing comparing simulated and simulated and monitored flow monitored flow data, firstly at the data, firstly at the most upstream most upstream monitoring station monitoring station ( (Vetto Vetto) and then at ) and then at the following the following stations along the stations along the stream. stream.

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RESULTS AND DISCUSSION RESULTS AND DISCUSSION (7) (7)

• At basin scale the model output revealed

the contribution of each considered land use type to every component of the water balance.

Deciduous forest (FRSD) Corn (CORN), sugar beet (SGBT) Winter wheat (WWHT), Alfalfa (ALFA) Highly responsible for: water yield Poor contribution for: evaporation, surface runoff, sediment load Highly responsible for: percolation, evaporation, surface runoff, sediment load Poor contribution for: water yield Intermediate behaviour

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RESULTS AND DISCUSSION RESULTS AND DISCUSSION (8) (8)

• At HRU scale the model output

highlighted which land use/soil combinations are responsible for the greatest dump of pollutants to the stream.

Sediment Sediment bound P Soluble P Leached nitrogen

• CORN/silty clay
• SGBT/coars sand
• CORN/silty clay
• SGBT/coars sand
• WWHT/sandy clay
• CORN/silty clay
• CORN/silty loam
• CORN/f. sandy loam
• ALFA/sandy loam
• CORN/silty clay

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RESULTS AND DISCUSSION RESULTS AND DISCUSSION (9) (9)

20 40 60 80 100 120 140 160

sedim.P kg/ha sedim.N kg/ha" Sediment t/ha

sedim.P kg/ha 3,2 2,8 1 ,0 1 ,6 0,5 9,6 0,9 0,1 0,2 0,0 0,1 5,5 0,5 4,3 2,5 2,7 6,1 2,3 1 ,6 sedim.N kg/ha" 1 7,7 22,9 8,1 1 2,6 4,0 1 5,8 7,0 1 ,0 1 ,4 0,3 0,7 1 6,2 2,3 23,6 21 ,4 1 3,4 33,7 8,7 7,2 Sediment t/ha 6,7 5,3 2,0 2,8 1 ,9 1 1 7,5 2,6 1 ,0 0,8 0,3 0,4 87,2 1 ,5 24,6 25,9 1 8,2 33,6 1 7,9 7,2 ALFA coars e sand ALFA sandy loam ALFA silty clay ALFA v.f.san dy COR N silt loam COR N silty clay COR N v.f.san FRSD coars e sand FRSD sandy loam FRSD silty clay FRSD v.f.san dy SGBT coars e sand SGBT silt loam SGBT v.f.san dy SWR N v.f.san WWH T coars WWH T sandy WWH T silty clay WWH T v.f.san

Sediment and sediment bound nutrients per HRU Sediment and sediment bound nutrients per HRU

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RESULTS AND DISCUSSION RESULTS AND DISCUSSION (10) (10)

• The location of such HRUs was known

thanks to GIS database, consequently those which are mainly responsible for the pollution in the area were easily located.

• This leaded to the reaches selection were

monitoring devices should be placed or manual sampling activities should be carried out.

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RESULTS AND DISCUSSION RESULTS AND DISCUSSION (11) (11)

Sediment load map Sediment load map Arrows indi Arrows indicate outlet where moni cate outlet where monito toring stations should be ring stations should be placed placed

• Several sites were

selected as possible monitoring places because representative

• f sub-basin

contribution, in terms

• f pollutants load.

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RESULTS AND DISCUSSION RESULTS AND DISCUSSION (12) (12)

Nit Nitrogen load in leachate

• gen load in leachate

Arrows indi Arrows indicate outlet where moni cate outlet where monito toring stations should be ring stations should be placed placed

• Also monitoring

station should be placed in a critical position that included between very loaded areas and more clean

• nes.

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CONCLUSIONS CONCLUSIONS

• Integrated use of GIS and hydrological

models (SWAT) is suitable to evaluate the response of a natural system to the agricultural land use.

• This tool could strongly support Water

Management Authorities in operating actions to reduce pollution.

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CONCLUSIONS (2) CONCLUSIONS (2)

• The methodology described operates a

good screening for the right location of the monitoring sites, giving a valuable aid in terms of costs and effectiveness.