Quantifying the impacts of land use/land cover change on groundwater depletion in Northwestern China - A case study of the Dunhuang oasis

In recent decades, the Dunhuang oasis in the arid Northwest China has been undergoing significant changes due to social-economic development and expanded irrigation for agricultural production. Groundwater table was found to have significantly declined during the period of 1987-2007 owing to greater pumping. We analyzed the impacts of land use/land cover (LU/LC) changes on the groundwater fluctuations in the study area. The LU/LC types were derived from the satellite images for the years of 1987, 1990, 1996, 2001 and 2007. The water consumptions associated with the LU/LC types were estimated using the FAO-Penman-Monteith method. Results show that during the period of 1987-2007, the area of agricultural land sharply increased by 98.7 km2, and the cash crops were the main contributor. Under the current market system, farmers had much more autonomy and greater incentives to shift the cropping pattern from the traditional food crops to the high value cash crops with greater water consumption. The total water consumption of the cash crops accounted for 14.1% of the total water consumption in 1987, but increased to 71.6% in 2007, becoming the largest water consumer. The agricultural land use was the main cause of the declining groundwater table during the period from 1987 to 2007.