Drought Risk Assessment for Surface Water Distribution Systems in Irrigation Districts

This study puts forward a practical risk assessment framework for agricultural Surface Water Distribution Systems (SWDS) operation under drought conditions. It accounts for situations when the diverted flow from the diversion dam fails to cover the total water rights within the districts. The risk probability is based on drought analysis and the Stream Drought Index (SDI) classification using the DrinC calculator. The risk consequence is determined based on SWDS operational performance appraisal, which includes hydraulic simulation by HEC-RAS, temporal analysis of adequacy, efficiency, and equity indices, spatial assessment in GIS, and combining performance evaluation indices using the Simple Weighted Sum (SAW) method. SWDS risk assessment is conducted considering the probability and consequences of drought hazard on the monthly and annual time scales. The obtained results show the monthly and yearly risks vary between (73.7, 76.1) % and (46.3, 63.9) % under the extreme-critical condition; (46.0, 53.2) % and (38.1, 51.1) % under the critical condition; (24.4, 35.1) % and (18.7, 27.5) % under the semi-critical condition; and (16.6, 25.5) % and (10.7, 16.6) % under the normal condition. The outcomes of the present study can empower dam owners, utility companies, and irrigation district managers to have realistic water planning, emergence action, and recovery plans for optimum surface water distribution between the hydraulic off-take structures.