Optimal Management And Protective Measures Of Groundwater Resources In China Based On Vulnerability Assessment Under The Changing Environment

Groundwater is one of the most valuable natural resources, which supports human health, economic development and ecological diversity. However, overexploitation and poor management have contributed to infamous groundwater depletion problems and less publicized groundwater quality deterioration. Moreover, changes in water quantity and quality are considered to have strong environmental and socio-economic consequences. Under the intensive human activities and environmental changes, groundwater pollution control becomes an arduous issue for groundwater management. In the process of climate change and urban expansion, at the same time to protect natural resources, will be the main theme of the country development in the future. Groundwater vulnerability is an effective tool for groundwater resource management. It provides a method for evaluating sensitivity of groundwater to contamination and scientifically defensible information for decision makers. In this paper, based on the results of groundwater vulnerability assessment in the changing environment, we study the future protection and management of groundwater resources in China. We(1) pred ict the net recharge and the depth of water table in China under the climate change scenarios, and predict the future groundwater vulnerability of China under the climate change scenarios with the DRASTIC model;(2) provide insights about the urbanization of China under future condition that provide the plan for urban planners while protect the groundwater quality, the groundwater vulnerability is employed as a special terms to restrict urban expansion;(3) combine the results of groundwater vulnerability o f China under the climate change scenarios and the results of urbanization of China under future condition, to predict the vulnerability of groundwater in the changing environment(climate change and urbanization);(4) apply modern portfolio theory(MPT) t o formulate an optimal stage investment of groundwater contamination remediation in China, to generate optimal weights of investment to each stage of the groundwater management and helps maximize expected return while minimizing overall risk in the future. The results indicated that(1) Climate change is forecasted to impact groundwater recharge and DTW strongly in most part of China with increases of net recharge in ranging from 1 to 2 cm and DTW in ranging from 1 to 3 m. And they are increasing over time. Compared with baseline, projected groundwater vulnerability patterns are expected to shift significantly under all future scenarios. The greatest increases in groundwater pollution potential are projected to occur in southern China which may face higher groundwater pollution risk in the near future. In the future, areas with moderate, high and very high vulnerability will dramatically expand, and areas with low or very low vulnerability will substantially shrink. The variations from 2010 to 2050 in vulnerability class of low, very low, moderate, high and very high were-5.31%,-3.03%,-1.2%, 4.47% and 5.32%, respectively;(2) The results indicated that there has been a notable and uneven urban growth between 2010 and 2050 in China. Future groundwater vulnerability is expected to shift significantly under future climate change scenario. The proportion of urban land is expected to change from 1.18% in 2010 to 2.95% in 2030, and 3.17% in 2050. The land replaced by urban is up to 305400 km2 by 2050 in China, which is as 2.7 times as it in 2010. The total area, which land changed to urban, is the same. However, with the restriction that the land of very high groundwater vulnerability cannot be replaced by urban, the urban land pattern shows obvious difference;(3) the results show that despite high uncertainty surrounding the future groundwater management. In the lowest risk situations, the investment weights of three managed stages are 0, 37% and 63% respectively. However, in the highest expected benefits situatio ns, all investment should be invested in the first stage. The expected value of groundwater vulnerability index increases from 0.6118 to 0.6230 following with the risk of uncertainty increased from 0.0118 to 0.0297. But the results of investment allocation will help China learn how to control its pollution in a more effective way under the high uncertainty attached to the climate change and urbanization. This is an important step in the process of making an effective national policy for groundwater.