Assessing the impact of future water demand on River Rwizi

Abstract

Due to effects of increasing demand oil water, attributed to increasing population and increased industrialization, sustainable development in terms of water management has become a big challenge to, meet the demands of the Mbarara municipality; proper planning for careful use of limited resources is essential. This research has been carried out to determine the availability of 'water in micro Mbarara municipality catchment. The analysis has been carried out by using Arc SWAT for time period of 21 years from 1993 to 2014, Integrated management planning network was also developed based on Water Evaluation and Planning(WEAP) to evaluate the impact of future water demand on the river under different scenarios W.E.A_P. was used to investigate, major stresses on demanded supply in terms of water availability in the river Rwizi. A customized WEAP model of Rwizi catchment was developed, taking into account the different water users in the municipality as demand points (municipal, rural and livestock), The: model was calibrated for year2014 using several quantitative statistics (coefficient of. determination, R2 Nash-Sutcliffe efficiency, NSE and Percent bias, PBlAS). Measured stream flow and simulated stream flow was used for calibration, the trend of supply and demand in the municipality was evaluated under four scenarios from year2014 to year2040 these include; reference scenario, higher growth rates scenario, climate variation scenario (extended wet and seasons under reference . scenario, extended wet and dry season under higher growth rates) and demand management options scenario. Demand management scenario was divided into reduction of non-revenue water (NRW)from 31.2% to 28% and demand management programs with a reduction of 20% of total annual water demand in the municipality, Results show that the available water in micro Mbarara municipality by 2014 was 1.74m 3/s The water demand will continue to increase over the coming years which is majorly due to the urbanization of the municipality (municipal water use contributed 86.3% and 88.2% of the total water demanded by 2040 under reference scenario and higher growth-rates-scenario respectively) and the river will only be able to sustain the varying demanduptoyear2029underextendedwetclimate, uptoyear2028underextendeddryclimate and up to year 2033 under normal climate considering both demand management options of reduced NRW, and demand management programs