Impact of Climate Change on Groundwater in Cham Anjir Aquifer

AbstractGroundwater and aquifers play a crucial role in sustaining human life and ecosystems, serving as vital sources for drinking water, agriculture, industry, and regulation of water and land systems. This study focused on Cham Anjir Basin representative of the Karkheh River to assess the impact of climate change on water resources. We utilized hydroclimatic data, including discharge, water levels, well discharge, number of wells, precipitation, temperature, and groundwater quality parameters, covering the statistical period from 1991 to 2020. To estimate the effects of climate change on water resources, we applied the output from the Lars-WG7 exponential microscale model for the two future periods of 2021-2040 and 2041-2060 under optimistic, realistic, and pessimistic scenarios. Our findings indicated significant increases in well withdrawals, temperature, Total Hardness (TH), Sodium Adsorption Ratio (SAR), and sodium percentage in groundwater, alongside a significant decline in discharge. According to the HadCM3 model outputs, rainfall in the basin was projected to increase from 2021 to 2060 compared to the observed period (1991-2020). However, a decrease in rainfall was expected from 2041 to 2060 relative to the previous period (2021-2040). Discharge was anticipated to decline consistently from 2021 to 2060. The regression model relating discharge and precipitation suggested that groundwater levels would decrease during 2021-2060, while groundwater quality indicators (anions, cations, and electrical conductivity) were expected to rise. Given the reliance on groundwater due to limited surface water resources, the impacts of climate change on both the quality and quantity of groundwater were significant. Therefore, advancements in water management, technology, and education would be essential in mitigating the effects of climate change on groundwater resources. Keywords: Aquifer, Climate Change, Discharge, Cham Anjir, Water Quality. IntroductionGroundwater and aquifers are essential for the survival of humans and other living organisms, serving as vital sources for drinking water, agriculture, industry, and regulation of ecosystems. Given their importance, it is crucial to protect these resources. Over-extraction of aquifers, pollution from industrial and agricultural effluents, and impacts of climate change are significant factors threatening the quantity and quality of groundwater resources. Climate change poses a serious challenge to water resources as various climatic, human, and geological factors jeopardize groundwater availability. Poor management and over-exploitation of natural resources, particularly in water management, have led to declines in both the volume and quality of water in river headwaters. This issue is particularly evident in the Karkheh River Basin. This study aimed to assess the effects of climate change on groundwater quality in the upper reaches of the Karkheh River, specifically in Cham Anjir Sub-basin in Lorestan Province. Changes in precipitation and temperature, along with the over-extraction of groundwater, had resulted in a decrease in reservoir levels in Cham Anjir Basin. Variations in water levels, precipitation, and discharge also indicated frequent droughts and water shortages in the area. Concurrently, there was a significant upward trend in both minimum and maximum temperatures, while discharge levels were significantly declining. Additionally, recent statistical data revealed an increase in the number of wells in Cham Anjir Basin, highlighting the growing demand for groundwater resources. Materials & MethodsTo investigate the effects of climate change on the quantity and quality of groundwater resources in Cham Anjir Basin, we utilized hydroclimatic data, including discharge, water table levels, well discharge, water quality parameters, precipitation, and temperature. These data were sourced from hydrometric stations, observation wells, meteorological stations, and the statistical yearbook of Lorestan Province, covering the period from 1951 to 2021. For analyzing the future impacts of climate change on water quantity, we employed scenarios SSp1-2.6, SSP2-4.5, and SSP5-8.5 from the sixth climate change assessment report, focusing on two timeframes: 2020-2040 and 2040-2060. The LarsWG7 microscale model was also used in this analysis.In this study, we applied the Z-score method to identify trends in climatic data and water quality parameters and detect data anomalies. Pettitt's Test was utilized for homogenization to determine the turning points in the data. We used correlation coefficients and regression models to identify the most