Study On The Effect Of Human Activities And Climate Change On Hydrology And Water REsources

Recorded runoffs in many rivers in China have been decreasing, particularly in northwest region. How to identify the quantitative effect of climate change and human activities on runoff is a hot topic, a difficulty problem as well. Since the eighties, the reduction of water resources due to human activities and climate change has intensified the contradiction of water supply and demand, also further resulted the ecological environment deterioration in the region. With development and application of modern scientific technology and computer, the original runoff that can only give qualitative study of the formation mechanism and the process has reached the stage of mathematical model simulation and prediction. To research and improve the distributed basin hydrological model, it becomes an important task in hydrological forecasting and planning, which play an important role in achieving sustainable economic development in the region.View of the already existing deterioration of the ecological environment in Ebinur Lake Basin, this research choose Jinghe Basin in Xinjiang (named valley, one of the main components of Ebinur Lake Basin) for the typical study area researched for a long term. It is explained that the major drivers of runoff change is climate change and human activities and that the representation of the hydrological and meteorological data in the valley. In this thesis, on the basis of hydrographical and meteorological data for 52 years (1957～2008), the variation features of precipitation and runoff and their response relationship are analyzed with the methods of nonparametric test (Mann-Kendall) and correlation analysis. This research reveals that the change characters of climate and runoff in the valley for 52 years, which can provide some reference for the further hydrological simulation study.This research achieved a limited area numerical meteorological prediction based on Regional Climate Model RegCM3 with regarding NNRP2 as the initial field and lateral boundary conditions and choosing appropriate physical programs. Based on the systematic study of natural environment, runoff course and hydrological characteristics in the study area, this research chose the hydrological and meteorological data from 1957 to 2008 in Jinghe Basin, and analyzed the stages of annual runoff changes using the cluster method and determined human activities affecting the hydrological sequence marked a turning point in 1981 according to change character of the annual runoff coefficient and analysis results of watershed hydrological characteristics, which is regarded the natural sequence of hydrological prior to the 1981.The average annual runoff depth is regarded as background prior to the 1981 by accounting the actual situation of the study area, and this research calibrated and validated the SWAT Model using the measured values prior to the 1981.It is simulated for the watershed runoff according to the calibrated model parameter and measured values after 1981 and calibrated meteorological data in missing year. The individual effect of human activities on annual runoff was forecasted combining the numerical meteorological forecast results of regional climate model RegCM3 and the spatial information technology ("3S") by SWAT model. Based on the calculation of annual runoff series and calibrated watershed situation by specialist organization, this research probably predicted annual runoff situation of Jinghe Basin under assumed scenarios by the hydrological frequency analysis method.Key findings include as follows:(1) This research achieved a limited area numerical meteorological prediction based on Regional Climate Model RegCM3 with regarding NNRP2 as the initial field and lateral boundary conditions and choosing appropriate physical programs. By comparison of the measured average values in 9 stations, simulating results showed that various indicators are less than 10% error range, forecasting results are better. Which not only provide the theoretical basis on the interpolation of the latter hydrological simulation in the study area, but also offer an important reference for hydrological forecasting, water resources management and program in the areas without data. (2) This research extracted a large number of surface data and parameters required by SWAT Model based on "3S" technology, and calibrated and validated the SWAT Model using measured values prior to the 1981,the model simulation period was divided into trial period (1957-1959) in order to decreasing human errors, calibration(1960-1969) and validation (1970-1980) periods. Results indicated that the annual runoff simulated by SWAT Model corresponded very well with measured values. The largest relative error is less than 10%, and the average relative error is less than 5%,all of the Nash-Sutcliffe simulation efficiency E in the model is above 0.85. Therefore, the watershed runoff simulation by SWAT Model is very feasible. The watershed runoff was simulated according to the calibrated model parameter, measured values after 1981 and calibrated meteorological data.(3) Based on previous study and the actual situation of the study area, the quantitative separation method of human activities and climate change on annual runoff was put forward. The individual effect of human activities and climate change on annual runoff was separated with the quantitative separation method by comparison of background values, measured values, forecasted values and the simulated values in hydrological model.By comparison and analysis, the results indicated that the relative impact of human activities in the downstream is the most obvious in the 80's and over the past 10 years, which reduced 85% of the total downstream reduction; the impacts of climate change on runoff is about 10% of the downstream runoff reduction in the 90's. Overall, human activities are main reasons of runoff reduction in the downstream,which is 85.7% of the downstream reduction (290.2mm). Although the impacts of climate change has a slight rise in annual precipitation, but higher temperatures makes the evaporation increase, which has affected the reduction of runoff too.The climate change is a major factor of runoff reduction in the mountainous catchments of the valley according to watershed runoff spatial distribution; human activities are main reasons of runoff reduction in the plain region of the valley. The total annual runoff of Jinghe and Bortala River flowing Ebinur Lake have been decreased under the ecological limited value (5×108m3) based on the forecasting results by specialist organization. So human beings in Ebinur Lake region have to face the lack of water resources and the environmental deterioration, it is hard to change this situation only by decreasing water waste, improving industrial and agricultural structure and technology integration and so on. Then, it is necessary to transfer water from other basin.(4) This research simulated runoff process according to the regulated model by the recent data and a long series of measured precipitation and temperature. This runoff process represents the "reproduction" 1981-2008 multi-year rainfall runoff according to recent level of human activity. It assumed that the precipitation of 1981-2008 can represent the future rainfall and human activities maintained the level of the late 20th century. According to the calculation of annual runoff series, this research predicted annual runoff situation in Jinghe Basin under assumed scenarios by means of the hydrological frequency analysis and based on calibrated watershed situation(Cv=0.12,Cs/Cv=2.00). Results indicated the required water quantity in basin is 8.62 x 108m3 for short-term goal and 14.39 x 108m3 for long-term goal in order to ensure the rate of p=75%. It shows that the inter-basin water Transfer may meet the actual demand water.In a word, as the valley population growth and socio-economic development as well as the massive shift of population from outside, the intensity of water resources development and utilization continued to increase. Particularly in large-scale human activities, land reclamation farming, which made serious water depletion in spring. By quantitative analysis of the influence of human activity and climate change on annual runoff, it can be inferred that basin water shortage is largely resulted in human activities. And the strong evaporation with rising temperatures also made valley's annual runoff quantity reduce.In the light of the hydrological characteristics, spatial distribution of water resources and present situation of the ecological environment in the study area, the construction of water conservancy projects in the valley such as demand water, store water and inter-basin water transfer will directly change the river runoff, And thus, the watershed runoff will increase and could also gradually improve the entire basin environment. Through the above analysis and research and the valley's annual runoff predicted results, it is recommended to increase the funding of water conservancy facilities in Jinghe Basin, to carry fully out water-saving construction in the valley. It is also necessary to implement inter-basin water transfer and the water resources optimal allocation, and to solve thoroughly the valley's water resources shortage, seasonal water scarcity, the conflicts between ecological and economic water requirement and so on.The process and results of this research on the one hand lay a theoretical foundation for further analysis of watershed runoff in the future. On the other hand, it offers very important practical significance in regulating the uneven spatial and temporal distribution of water resources, improving the water utilization efficiency, modifying ecological environment, developing eco-sustainable agriculture, promoting building of regional cycle economy and sustainable development.