The Impact of Climate Change on Groundwater Recharge in Karkheh River Basin (Iran)
Department of Civil Engineering, Sharif University of Technology
In Iran, most research on the potential impacts of climate change on the hydrologic cycle has been directed at assessing the potential impacts on temperature, precipitation, and streamflow, while no significant research studies have reported on the impacts of climate change on groundwater resources, despite the fact that groundwater constitutes a significant proportion of freshwater supply in Iran. This paper represents the results of a study on the impact of climate change on groundwater recharge in the Karkheh River Basin in Khuzestan, Iran, using a physically-based methodology that can be used for predicting both temporal and spatial varying groundwater recharge. Recharge was estimated by using the Hydrological Evaluation of Landfill Performance (HELP3) water budget model. As the Karkheh River Basin is a semiarid region and all sectors of water demands, including domestic, rural, and irrigation, rely significantly on groundwater resources, it is essential that the potential impacts of climate change on the aquifers be identified for long-term sustainable integrated water resources management in the region. The Karkheh River Basin, with an area of 50,764 km2, has a population of around 4 million, of which 67 percent are living in rural areas. The mean annual precipitation varies from 150 mm in the south to 750 mm in the north and the climate is mainly semiarid. The future of the Karkheh River Basin and its people?s livelihoods clearly depends on natural resources like water. As water is the most limited natural resource in this basin, any increase in water productivity due to better water management will certainly benefit rural livelihoods. To ensure the sustainability of the improvements in water productivity, assessment of the possible impacts of climate change on hydrology and water resources in the basin is necessary. In this study, the potential impacts of climate change on groundwater recharge was modeled using two downscaled precipitation and temperature scenarios A2 and B2 due to CGCM2 and two large scale precipitation and temperature scenarios A1B and B1 due to CGCM3 model results for three periods: 2010-2039, 2040-2069, and 2070-2099. Results indicated that prediction of future recharge is very uncertain and highly depends on the scenario selected. While groundwater recharge is predicted to increase under B2 scenario, it will change slightly under other scenarios. The results also showed how groundwater recharge varies spatially, due to variations in land use and underlying soil characteristics.