Effects of land use change on water balance in the Sanjiang Plain

Land use (LU) change and large-scale exploration and utilization activities of water resources have resulted in apparent disturbance on the hydrologic circle in the Sanjiang Plain. To identify the water balance characteristics and problems, this paper, based on the hydrologic baseline model, which can reflect the continuous change of land use from 2000 to 2014 (dynamic LU scenario or actual scenario), established a hypothetical model and a predictive model to simulate the hydrologic processes under the 2000 LU (2000 static LU scenario) and the 2014 LU (2014 static LU scenario), respectively, by replacing the LU data of the baseline model, and then compared the simulated water balance in the three scenarios. The results showed that if active LU control measures were taken since 2000, meaning the LU kept constant since 2000, the dependence on external water resources would have been effectively reduced compared to the actual scenario. The groundwater overdraft problem could be largely alleviated, and the groundwater storage in plain areas could even increase by 308 million m³/a in the following 15 years. However, if the LU control measures were implemented after 2014, meaning the 2014 LU was used for the whole simulation period, it would cause the annual groundwater deficit in the plain areas to be as much as 1426 million m³. The water storage in the whole region would have turned from positive to negative, with an average annual deficit of 425 million m³. To achieve water balance at various levels in the Sanjiang Plain, it is imperative to carry out more active allocation of water resources and construction of relevant water projects while taking immediate measures to contain excessive growth of high-water-consuming LU types.