Evaluation of the Use of Non-Conventional Waters on the Runoff and Sedimentation of the Tajen Basin Using the SWAT Model

Lack of water resources in Mazandaran province and the volume of effluent produced in different sectors, ‎has caused that in order to reduce the withdrawal of surface and groundwater resources in the province, the ‎use and management of unconventional water resources, much attention is paid. The purpose of the present ‎study is to evaluate the application of unconventional water use scenarios on the amount of runoff and ‎sediment in six stations (including Kordakhil, Garmroud, Varand, Vastan, Parvijabad and Aliabad stations) in ‎the Tejn watershed during the years 2000 to 2017 using the SWAT model. Recalibration and validation of the ‎model using data from 2003 to 2012 and 2013 to 2017 and then to evaluate the scenarios of allocating 30% of ‎the available wastewater for agriculture (scenario one), allocating 30% of unconventional water to feed ‎aquifers in the conditions of applying scenario one (scenario two) and a 20% reduction in the extraction of ‎underground water sources for irrigation and the use of unconventional water sources as alternative sources ‎to meet environmental needs (scenario three).‎‏ ‏Evaluating the efficiency of the model using R2 and NSE ‎coefficients shows the proper performance of the model in simulating these two parameters. The results ‎indicate that the application of scenario one did not affect the amount of runoff and sediment in the basin, but ‎with the application of scenario two, the amount of runoff and sediment decreased by 13.4% and 9.1%, ‎respectively. Applying Scenario three should be 10 to 20% of the annual discharge for the second six months ‎and 30 to 40% of the average annual discharge for the first six months of the year in order to meet the ‎environmental needs. The results obtained from the present research show that the use of non-conventional ‎water, in addition to solving the water shortage, also reduces the problems caused by the flow of runoff and ‎the settling of sediments.‎