Trend analysis of precipitation, watershed level, and river discharge in the Mashhad-Chenaran plain

The hydroclimatic data changes over time due to climate changes and human interventions. By examining trends in precipitation, river flow, and groundwater levels simultaneously, scientists and experts can plan water resource management at the watershed level with useful information. The aim of this study is to examine the trends in rainfall data, river flow, and groundwater levels in the Mashhad-Chenaran watershed. No significant trend was observed in the rainfall data on an annual scale, but there is a significant downward trend during the winter season. The results indicate a significant decrease in the annual data for stream-flow and groundwater table. According to the findings, the decrease in the discharge data is greater than the decrease in the precipitation data. Also, the trend of decreasing groundwater levels is greater than that of surface runoff. The environmental flow was finally determined by using Tasman's method. In almost all stations, critical flow conditions (less than the environmental flow) were observed according to the research results. According to the findings, the value of critical conditions increases with a decrease in station elevation and an increase in the area of the watershed upstream of the station.