Evolution Of The Water Resources And Its Rational Allocation In The Taolai River Basin Of Northwest China

Along with the intensive human activities, climate change and heterogeneity of geomorphology-hydrogeology make frequent exchanges between the surface water and groundwater, and then the high complexity of the water resources evolution in the arid inland river basins in the northwest of China. Nowadays, there is still large insufficiency in the fields of water sciences such as dynamics of hydrology and rational water resources allocation, especially in the arid regions, which might have influenced the efficient utilization of water resource for a long time. From this point, studies of arid hydrology under the background of climate change at the scale of basin are of great significance for people to understand the evolution of water resources and to reduce the water related crisis for the sustainable development of the whole society.In this study, a typical inland river system named Taolai river basin was selected for the case study of the characteristics of water resources evolution, Knowledge and methods integrated in the research covered communities of geography, hydrology and water resources and information sciences. First, the nonparametric Mann-Kendall test method was adopted to examine the characteristics of hydrometeorology in the Taolai river basin, and then the impact from key climatic factors such as temperature and precipitation on mountainous discharge was assessed based on the regressive relationship among variables above. Second, the groundwater system dynamic was simulated by coupling the GIS technique and the finite element based Feflow model and the risk of the groundwater abstraction was determined spatially. At last, the amount of water resources across the whole basin was calculated and a dual structure water resource model was developed for better management of the local water resources. Main conclusions have been made as follows:1. It was found that the temperature had an overall rising tendency since the middle of 1950s, while obvious differences occurred between time stages in different regions such as in the mountains and across the northern plains. As the whole, duration continued with a time scale of 11 or 5 year for the temperature. For precipitation, it was not clear for more or less in the whole statistic duration, meant that there was no continuous increase or decrease of the precipitation in the Taolai river basin. When compared to the durations of temperature, status of the precipitation presented more complicated. Results from simulations based on the regression of temperature/precipitation and the runoff modulus revealed a negative impact of temperature to runoff while a positive one of precipitation. While the precipitation rises with percentages of 10%,20% and 30%, the increase of the runoff correspondingly are up to extensions of 13%,43% and 100%; when under the condition of an increase of 10% for the precipitation, as the temperature rises with values of 0.5,1.5 and 2.5℃, the total of the runoff will have incremental percentages of 6.70%,6.61% and 5.80%, respectively.2. A finite element based groundwater model named Feflow was applied in the relatively independent hydro-geological structure for the groundwater dynamic simulation. The Jiuquan basin was illustrated into a 3-dimensional space based on histograms and hydro-geological section maps.The sink and source was determined by experiential or physical methods for the parameterization of the groundwater simulations. When compared with the observed well data, results of the simulation turned into a relative satisfactory accuracy. Numbers of the simulated groundwater level with the relative error below 0.5 m occupied a ration of 60% to the total while those occupied with the relative error between 0.5-2m were of 20%. resulted that the Feflow model is suitable for the calculation in the arid northwest of China. Based on the simulated results, the groundwater resources with their spatial characteristics were described at the scale of the irrigated districts, people could do something according to the water relationship between those districts.3. Simulations by Feflow revealed that the source and sink, together with the horizontal exchange from upper to lower in the groundwater system, strongly influence the groundwater resources in different irrigation districts. One example is the simulations in the large water demand districts located at northern plains. It resulted that although the water balance based on source and sink to the groundwater system was with a negative number of-14149.51×104m3, the horizontal exchange form upper groundwater contributed positively with an amount of 29515×104m3, both led to the final sink total of 15567.30×104m3 to the district. This part of study could be a support to the local water allocation and optimization. We also did some regional illustration for the groundwater risk assessment assisted with the spatial distribution of the coefficient of variation of long term observed well data, which could be used to guide the water resources utilization in the region.4. Water price in the arid inland Taolai river basin was discussed based on the analysis of the water resources demand and supply. The range scale of the optimal price was determined for optimizing regime of the water allocation. Especially, to the water price for irrigation we concerned factors most broadly such as the cost on project invest, original resource value of the water as well as its environmental effectiveness, profits and taxes in the market and,even water transferring cost for compensation among different time stages. The reflective price method and the boundary occasion approach were coupled for the irrigation water price in the basin and resulted in prices of 0.13 and 0.15 Chinese Yuan in 2005 and 0.16 and 0.18 Yuan in 2015, the form price was for the surface water and the later, the groundwater.5. Based on the understanding of the methods of water allocation and optimization and analysis of their application for the specific region, a dual structure water allocation model including social and hydrology was adopted to quantify the local sector occupation under different optimizing schemes for lowest unsatisfactory to improve the efficiency of the water utilization. It is concluded that the optimized water use scheme for 2015 would fell in a whole amount of 12.58×108 m3 for the total supply and 12.62×108m3 m3 for the total demand. Water for irrigation in the scheme presents a reduction and goes down to the amount of 10.37x 108m3, contradiction between water supply and demand in the region will be remitted to a certain extent and water for land surface ecology will supply more, which is effective for the sustainable development of the compound society-economy-ecology system across the Taolai river basin.