Determining the monthly utilizable water volume from Zahre River to secure drinking water of Handijan city

Assessment of river flow variation and trends is important in surface water resources management and utilization. In this study, the changes of Zahre river flow regime was assessed in Polfloor, Kheirabad, and Dehmola gauge stations using Mann-Kendall, Sen-estimator in monthly time scale, quarterly and annually during the years 1996 to 2015. The Tennant method was used to determine the environmental flow requirement, and subtracted from the recorded river flow data of the Dehmola station (adjacent to Handijan city), the volume of water taken from the river for drinking water supply of the Handijan city were determined at monthly scale. Results indicate that the flow amount in April and May had the highest volume at all stations during the year. Also, the Polfloor and Kheirabad stations had the greatest volume of discharge in spring season. While, the high river flow discharge of Dehmola station was observed in winter season. According the Mann-Kendall and Sen`s estimator the decreasing trend were observed in almost all seasons, and the steepest decreasing trend slope occurred in the spring. The results of Mann-Kendall and Sen`s estimator tests also suggest a decreasing trend in the annual flow discharge at all studied stations. Finally it was realized that the November, December, January, February and March are the wet months and suitable for water withdrawal/harvesting to supply drinking water from the river. In contrast, the summer months of June, July, August and September are low flow months and there is no water to exploit, and the base flow of the river should be maintained to support and protect the river environment and its dependent ecosystems.