Modelling water demands and efficient water use in river Malaba catchment.

Abstract

The places traversed by Malaba River Catchment in Uganda have been constrained by acute scarcity of water due to the increasing water demands, which is occasioned by the industrial growth, increasing population and changing land uses. This study applied Soil and Water Assessment Tool (SWAT) to assess water supply and and Water Evaluation and Planning (WEAP) model to evaluate past trends and simulate current demand scenarios and water management scenarios for the purposes of planning by authorities in regard to future use demand for the period 2015 to 2050 by simulation. The hydrology of the catchment was studied using Soil and Water Assessment Tool (SWAT). SWAT model was calibrated using data from 2002 to 2008 and then validated using data from 2009 to 2013. The model was successfully calibrated with NSE of 0.77 and the R2 0.79 and for validation with NSE of 0.55 and 0.7 for the R2.The calibrated model was then used to estimate the available water resources which was later an input for WEAP model. This study also used WEAP model to forecast demand and analyze scenarios on water use in Malaba river catchment. WEAP model schematic was set to develop current and reference scenarios. Parameters used to run WEAP model were a GIS map of the sub-catchment, Head flow obtained from SWAT modelling and water demand data from NWSC and from the field. High population growth was predicted to increase water demand while reuse though not practiced, was found by the model to be the most effective approach to manage unmet demands as compared to reduced conveyance losses and increased demand managent scenarios. The study concluded that water reuse through exploitation of wastewater could be a viable solution to Malaba river catchment water problems.