Water Security In Arid Northwest China:A Case Study Of Dunhunng Oasis

Water is a precious, unique resource that is important for life and is a commodity for which no substitute exists, ensuring an adequate supply of water is essential for human well-being and socioeconomic development. However, the limited nature resource security is threated by increasing population, expanding irrigated agriculture, high water use lifestyle and fast growing economic development model in the worldwide, particular in the arid region. Water has become the main constraints of regional sustainable development.Dunhuang is located in the westernmost of Silk Road in Gansu Province, adjacent to the eastern edge of the Kumtag Desert. Since the Han-Tang Dynasty, Dunhuang is an important area of economic and cultural exchanges between China and western countries.The famous UNESCO World Heritage Site Mogao Grottoes, Mingsha Mountain (sounding sand dunes) and Crescent Spring, are all located in the Dunhuang oasis. In recent decades, ecological water use has been declining due to rapid economic development. The ecological crisis of Dunhuang oasis includes: shrinking terminal lakes, declined groundwater level, and expansive desertification. The speed and criticality of ecological environment deterioration must be taken seriously. Dunhuang ecological crisis has gradually evolved into the ecological environment of national and international problems.Taking the Dunuang oasis as a case study, this research used Landsat-5 TM remote sensing data, meteorological data, oasis groundwater table data, socioeconomic data and other related regional water resources planning material, and combining the field crop structure survey, remote sensing digital image processing, GIS spatial analysis, reference crop evapotranspiration, single value crop coefficient method, DPSIR framework, system dynamic model. This research aims to fully analyze the evolution of oasis agricultural water use, ecological water use and social economy water use, on this basis, we select many suitable water resources security evaluation index to establish evaluation system, and under the background of current region water resources planning, we apply the system model to predict the future evolution of oasis water structure under different scenarios. The basic conclusion and understandings from the research are as follows:Firstly, during the 1987-2007, the area of 8 classes land use/cover type are all changing in different degree, and the main change characteristics are urban land and farmland increased rapidly, the grassland area decreased in some certain degree. Specifically, the maximum increased farmland has an increase of 98.71 km2, and the increment speed in 1996-2007 is over twice than that in 1987-1996. The urban land has a small increase of 9.76 km2 but has a maximum increase speed. The transformation for farmland is mainly grass land and bare land, and the incoming is more than outgoing. Among the three classes grassland, high coverage grassland turn into medium-low coverage grassland and bare land, and medium turn into low, and the low coverage grassland transferred into bare land and farmland. The urban land is mainly transferred from farmland and bare land. The expansion of the artificial oasis oasis reduction in natural vegetation areaSecondly, the estimated total water consumption of the study area increased from 4.00×108m3 in 1987 to 4.75×108m3 in 2007, representing an average annual increase of 3.6%. Agricultural water consumption has been the largest of all classes during the period from 1987-2007. The proportion of the natural vegetation had been declining. Although the water consumption of the domestic-industrial uses was growing rapidly, their proportion in the total water consumption is very small. The rapid expansion of high water consumption cash crops depleted most of water from the headwater to irrigation canal system, and the canal lining further reduces the infiltration and leakage to groundwater, which accounting for up to 60% of the total groundwater recharge. Eventually leaving little recharge to groundwater. Agricultural land use was the main cause of the decline of the groundwater table during the period from 1987-2007.Fourthly, DPSIR comprehensive evaluation results show that the water resources security of Dunhuang oasis under an unstable condition, mainly reflected in the:Decreased natural oasis stability, declined groundwater level. The response indicators show that the local water management measures should be strengthened, especially in fundamentally solving the problem of groundwater exploitation excessive in irrigation area.Fifthly, in the current development situation of scenario 1, the total water consumption of Dunhuang oasis will progressively increase, and agricultural water consumption remains stubbornly high, the oasis ecological security will face a great threat. In the scenario 2, after implementing agricultural water saving measures, the agricultural water consumption will decrease almost 5.3 ×107m3. The additional water allocated from the inter-basin water diversion project plays a very important role in alleviating the oasis ecological water crisis.