Modeling and evaluation of optimal management of water consumption in the agricultural sector using WEAP software

Case study of Injil District, Herat Province

Abstract

Considering the scarcity and limitation of water resources, it seems necessary to use them efficiently. To achieve optimal management, it is necessary to know the status of these resources and plan based on their changes. The study area of Injil district in Herat province, having surface water sources such as the Harirud river, faces a shortage of water resources in various sectors, especially for agricultural purposes, due to mismanagement and lack of optimal management of water resources and uses. Therefore, in this research, it was tried to provide solutions for the optimal management of resources and uses of this watershed by modeling the range and implementing different scenarios. The purpose of this research is to investigate and model the existing conditions of the study area of Injil district using software (WEAP) and also implement different scenarios such as the scenario of 15% increase in agricultural efficiency (S1), changing the cultivation pattern of the study area (S2), Evaluating the effects of climate change on surface water resources and meeting needs (S3) and examining the effect of climate change and changing the cultivation pattern in the study area (S4) in current and future conditions (year 2030) to examine the supply or non-supply of the area's needs . To achieve this goal, in this research, in the first step, different climate models were examined. Among the investigated models (GFDL-ESM2M, IPSL-CM5A-LR and CSIRO-MK3.6), the CSIRO-MK3.6 climate model is the selected model of this research to simulate the maximum and minimum temperature parameters and the precipitation parameter during the statistical period of 2021- 2030 was selected. By forecasting temperature and precipitation for the upcoming period, the runoff of the upcoming period was simulated with the help of the IHACRES runoff precipitation model. The output of the IHACRES model as the discharge of the Harirod River during the years 2021-2030 was entered into the Comprehensive Water Resources Planning and Management (WEAP) model. The simulation results of precipitation parameters and minimum and maximum temperature for the upcoming period determined that the monthly average temperature is increasing compared to the base period (1986-2005) (historical data of climate models are available until 2005) and the precipitation parameter did not follow a specific trend. It increases in some months and decreases in some cases. The runoff forecast also showed that there is no special pattern for different months, but in general, the amount of runoff will decrease for the coming period. The results of the implementation of scenarios S1, S2, S3 and S4 in the WEAP model showed that increasing agricultural efficiency can be effective, but a comprehensive and optimal management of resources and uses in this area is needed. Scenario S2 showed that by changing the current cropping pattern to the suggested optimal cropping pattern, which is accompanied by an increase in efficiency, the needs of Injil district can be met to a large extent. Also, the results of the implementation of S3 and S4 scenarios showed that the discussion of climate change in the future can have a negative effect on the supply of drinking and agricultural consumption in this area.