Assessment Of Water Demand Pressure On Surface Water Resources In Burguret River Sub-Catchment Using IS SWAT

Abstract

Assessment water availability and use in any catchment is a preliminary key requirement for policy administrators and leaders to make an appropriate decision on water allocation. This ensures utilisation of water resources in a sustainable way thus understanding the quantity of water resources available over time. The study aimed at establishing water resources demand and availability at different seasons. In order to determine water available at different seasons in the Burguret Subcatchment as well as filling the missing data for river flow data, SWAT model was applied. Three-year period was applied to calibrate SWAT. Validation was done in a two-year period pegged on daily flow data. Calibration outcomes showed that, an acceptable degree among simulated and observed daily flows with NSE value of 0.63 while RSR was 0.63. The Performance Efficiency (R2) value for observed vs simulated daily flow data for the basin was 0.74 and 0.7 for the validation and calibration period respectively. Assessment of abstractions along Burguret River and analysis of the same was carried out to determine the water demand. To determine total water demand for irrigation every user/abstractor, a Demand-Based Estimate Method was used. The research showed that most of the water abstracted from Burguret subcatchment was mainly used for irrigation. There has been a huge increase in VII water demand over time. Out of 113 abstractions surveyed along Burguret River, only eight known abstractors have clear permit records. This indicated the little level of water utilization legality. It was also observed that 88% of water abstractors in the sub-catchment were small-scale farmers where most of them used portable pumps. The abstraction survey conducted during the dry season (normal flow period), the total abstracted quantity was found to be 20685 m3 per day. The authorized abstraction during normal flow is 149 m3 per day. This means water utilization is approximately 15 times the authorized quantities. With water demand for irrigation water being the highest and is increasing with time in the catchment, the situation was found to be worsened by inadequate water resources management as well as rainfall variability. Unwarranted abstractions of the river especially `during dry seasons have often resulted in reduced stream flow and highly affect the downstream users. The research study found that viable use of available surface water resources combined with better natural flow management is crucial. This can only be realised with the serious collaboration of farmers in the catchment for both communities and individual farmers. The study recommended that a comprehensive water allocation assessment in the catchment for all users should be carried out. This will manage demand that will improve water use thus improving returns from it whilst deterring crisis and