Evaluation of the Effects of Temporal Variations of Temperature, Precipitation and Water Harvesting on Groundwater Resources in Mehrgerd basin of Semirom

Mehrgerd region of Semirom county has faced the water shortage for several years. The emergence of drought has led to a decline in water resources in recent years; and there are various reasons for climate change and increased consumption in order to reduce water resources. The present study aimed to investigate the process of temperature and precipitation variations and its possible effects on groundwater resources. Therefore, the Mann–Kendall test was applied to the climatic data of five selected stations during a 28-year statistical period as well as the groundwater level statistics of 33 observation wells. Effects of temporal temperature and precipitation variations on water resources were assessed using the correlation between climatic parameters, SPI drought index and water resources statistics. Results indicated that the average monthly temperature had an ascending trend in Mehrgerd region especially in winter and it could lead to changes in types of precipitation and early snow melting. The precipitation had no significant trend in most months (except for the observed precipitation reduction in January and March). Groundwater resources had a significant descending trend in almost all months of year. The study on relationships of precipitation parameter and water resources of region indicated that the precipitation parameter affected groundwater resources with a delay of 6 months. The effects of wet and dry periods on the status of groundwater level are quite obvious; and the groundwater level of plain has had an annual decline since the onset of a drought period in 2008. Despite the fact that this level has fluctuated with the severity and weakness of drought in subsequent years, but the reduction of water level has been the overall trend of groundwater level in Mehrgerd plain.