The Effects of Climate Change on the Reuse of Agricultural Drainage Water in Irrigation

Climate change is projected to have a major impact on agricultural water resources availability. Comprehending the effects of climate change on water supplies for agriculture is an essential aid for the effective management of available water resources. A forecasting model, a surface water quality model coupled with an optimization algorithm have been used in forecasting agricultural water quality and to maximize the reuse of wastewater in the Osan watershed, South Korea. In forecasting water quality and streamflow parameters for a 30 year period, AutoRegressive Integrated Moving Average (ARIMA) was used. Both ARIMA model fit and model performance were within accepted levels. Water quality and quantity were simulated using the QUAL2Kw model. Jaya algorithm was executed to optimize the process for determining optimal quantities for agricultural drainage water (ADW) reused at withdrawal points. Simulations of water quality show that organic matter levels are key attributes in the management of the Osan drain. QUAL2Kw model calibration and validation show that the model can be applicable with values of Nash—Sutcliffe model efficiency (NSE) > 0.5 respectively. Water quality results show that Biochemical Oxygen Demand (BOD), Dissolved Oxygen (DO), Total Nitrogen (TN) and Total Suspended Solids (TSS) were within acceptable ranges. ADW is suitable for indirect irrigation in the Osan watershed as water quality standards meets Korea’s standards and Food and Agricultural Organization (FAO) Guidelines. Irrigation water demand will increase by 47.1 % for summer and by 16.5% for winter by 2050 due to an increase in temperature. The total agricultural ADW reuse amounts will increase by 47.4% for summer and 17.5% for winter by 2050 due to the creation of farmlands, as there will be an increase in food demand. Optimization results show that drainage water availability will increase by 31.6% and 21.3% respectively for summer and winter by 2050 due to climate change effects. Overall, the results show that the reuse of ADW demand and the available amounts is most likely affected by climate change.