IWRM - Planning and Decision Support Tools

Planning and Decision Support Tools

Planning and Decision Support Tools have been developed for the evaluation of water resources on the planning level river basin. They facilitate the identification and prioritization of WMUs (Water Management Units) with increased problem intensity and necessity for action through IWRM measures.


Figure 1: Planning and Decision Support Tools and their initial parameters and results

The Planning and Decision Support Tools consist of a water balance tool, a contamination risk tool and a ranking tool (figure 1, also cf. dissertation JOLK (2012), JOLK et al. (2010) as well as ZINDLER et al. (2010 & 2012)).

Water Balance Tool

The water balance tool serves to balance the water demand and water supply for each WMU, thus making possible giving statements on deficits and surplus. The calculation of the water balance is made in the MS Excel based water balance tool. Input data collection and result visualization is made in a geo information system (ESRI ArcGIS).


Figure 2: Components of water resources and water demands in a WMU

The water balance is carried out for each WMU of a river basin and includes calculations for all relevant components of a WMU’s water resources and water demands. The WMUs are interconnected in a cascade. A downstream WMU receives all surplus water of an upstream WMU. Figure 2 shows the water balance components for one WMU.

Contamination Risk Tool

The contamination risk tool can evaluate the contamination risk for water resources (ground and surface water). The contamination risk tool is GIS based. The actual contamination risk is captured by superimposing data on several different contamination potentials (agriculture, settlements, point sources) over the resource sensitivity (ground or surface water).
The resource sensitivity of water resources was evaluated in the following way in this context:


  • The groundwater resource sensitivity results from the groundwater aquifer runout in combination with their significance for water supply.
  • The surface waterbody sensitivity results from waterbody density, the local significance of surface waterbodies for water supply and possibly hillside inclination (potential erosion).

    The contamination potential is observed as follows:

  • The contamination potential of diffuse contaminant sources goes back to agricultural activities (fertilization, pesticides) as well as waste water discharge from settlements.
  • The contamination potential for point sources is based on commercial, industrial and communal activities (industrial and commercial facilities, dumpsites, gas stations etc.) with possible influx into groundwater or discharge into waterbodies.

    Additionally, three possible contamination paths are being distinguished (cf. figure 3):


Figure 3: System diagram for contamination paths (path 1: infiltration, path 2: erosive runoff, path 3: direct discharge)

An overview of processed aggregations of resource sensitivities and contamination potentials into contamination risks can be found in figure 4.

Figure 4: Aggregation of resource sensitivity and contamination paths into contamination risks

Explanations to figure 4 can be found below:

Path 1: Infiltration

  • The agricultural contamination potential is based on the assumption of the application of fertilizers and pesticides in agriculture.
  • The contamination potential from settlements is based in the overall lack in waste water treatment. Waste water treatment facilities for settlements are regarded as direct discharge (path 3). There is currently only one waste water treatment plant for household waste water in Da Lat.
  • The contamination potential from point sources is based on the possibility of contaminant infiltration close to industrial and commercial facilities.

Path 2: Erosive runoff

  • The agricultural contamination potential is based on erosive runoff and soil erosion. As there are generally no waste water canals and no waste water treatment plants in settlements, it is assumed that household waste water mostly influences the water resources through path 1 (infiltration). Otherwise they would be regarded as direct discharge (path 3).

Path 3: Direct discharge

  • The contamination potential from settlements is based in the direct discharge of waste water. An interposed waste water treatment plant would reduce the potential considerably.
  • The contamination potential of point sources is based on the direct discharge of industrial and commercial waste water. An interposed waste water treatment plant would reduce the potential considerably.


 

Ranking Tool

The ranking tool is used to prioritize the results from the water balance tool and the contamination risk tool. These rankings help to identify WMUs with increased problem intensity and increased necessity for action. Water balance ranking in WMUs is carried out regarding possible water surplus and deficit based on the results of the water balance tool. For this calculation, initially an index of “surplus/deficit” for each month was calculated in the water balance tool based on water resources and water consumption. Using this balancing process, water surplus and deficit for each WMU could be established. The ranking of the contamination risk is carried out based on the results of the contamination risk tool for each contamination potential (agriculture, settlements and point sources) for each of the contamination paths. The ranking results are delivered in tables and maps. Figure 5, for example, shows the result for the ranking of the contamination risk from settlements in path 3 in the upper Dong Nai river basin.


Figure 5: Ranking of the contamination risk from settlements in path 3 in the upper Dong Nai river basin

The Planning and Decision Support Tools have mainly been developed in the upper Dong Nai River basin, have also been tested, and adapted under two additional different natural conditions (Red River sub basin, Cuu Long sub basin (Mekong Delta).