Planning Model

The model is a combined hydrological- environmental-economic water management model (Fig. 7.1), which compares varying alternatives of -water supply for drinking and for irrigation and different water treatment alternatives. The goal was to identify the optimal treatment and reuse methods that- will ensure a sustainable and economic management of groundwater. The hydrological model, shown in Fig. 7.2, simulates two processes:

• Contaminants flow through the unsaturated zone of the soil.

• The effect of irrigation with wastewater on chlorides in groundwater.

Fig. 7.1 The planning model
Fig. 7.2 The hydrological model

Water use

Chloride level in groundwater

Irrigation water

^ Crop yields

Chloride level in groundwater

Drinking water

Enhancement of desalination

Energy use f

Alternative energy sources

Fig. 7.3 The environmental model

When chloride concentration increases and reaches a predefined threshold, water sources are desalinated and combined with freshwater sources, to reach the permitted salinity level. The assumptions and mathematic description of the model are outlined in a separate paper [4].

The results of the hydrological model then serve as inputs to estimate the environmental impacts through the environmental model (Fig. 7.3). Finally, the hydrological and environmental model outputs then serve as inputs for the economic model that calculates the total cost of three factors:

• Desalination

• Wastewater treatment, storage and conveyance

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