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In the wake of global and regional climate change and heightened human activities, runoff from some rivers in the world, especially in the arid and semi-arid regions, has significantly decreased. To reveal the varying characteristics leading to the change in runoff, detecting the influencing factors has been important in recent scientific discussions for water resources management in drainage basins. In this paper, an investigation into attributing the runoff response to climate change and human activities were conducted in two catchments (Wushan and Shetang), situated in the upper reaches of Weihe River in China. Prior to the identification of the factors that influenced runoff changes, the Mann-Kendall test was adopted to identify the trends in hydro-climate series. Also, change-points in the annual runoff were detected through Pettitt's test and the precipitation-runoff double cumulative curve method. It is found that both catchments presented significant negative trend in annual runoff and the detected change-point in runoff occurs in 1993. Hence, the pre-change period and post-change period are defined before and after 1993, respectively. Then, runoff response to climate change and human activities was quantitatively evaluated on the basis of hydrologic sensitivity analysis and hydrologic model simulation. They provided similar estimates of the percentage change in mean annual runoff for the post-change period over the considered catchments. It is found that the decline in annual runoff over both catchments can be mainly attributed to the human activities, the reduction percentages due to human activities range from 59 to 77 %. The results of this study can provide a reference for the development, utilization and management of the regional water resources and ecological environment protection. [ABSTRACT FROM AUTHOR]

To study the impact of the uncertainties existed in nature and management on the ecological planning and the achievement of the planning objective under uncertainty, the General restoration planning of Shiyanghe river basin, which is for Shiyanghe river basin located in an arid inland area in China, is selected as the research object. The general thought of the essay is to get the probability of the objective achievement of ecological planning by analysing the floating region and possibility distribution of the uncertainties which is of the critical factors in achieving the planning objective. Firstly, the uncertainties of the critical factors are identified and analysed separately. Secondly, the two uncertainties are combined to study its impacts on the achievement of planning objective in each scenario. Lastly, the probability and the possible deviation of ecological objective achievement are analysed in each scenario. The methods used in the study include the scenario analysis, BPF based on BP neural network, PPCC analysis and interval analysis. The results show that the achievement of ecological objective is greatly influenced by the uncertainties, the objective achievement could be get only in the scenario of water resources utilization and management meet the planning requirement and high flow year in planning year, the results also show that the greater volume of local water resources and the higher level of local water resources utilization and management lead to the higher probability of achieving ecological objective and the lower possible deviation. [ABSTRACT FROM AUTHOR]

As one of the most important climatic variables, annual evapotranspiration ( E) reflects the complex interactions between atmosphere, vegetation, soil and hydrological process at global and regional scales. It is largely determined by potential evapotranspiration ( E) and precipitation ( P). Aridity index ( E/ P) which can be defined as the ratio of annual potential evapotranspiration to annual precipitation, can be used to represent annual evapotranspiration. As result it has become an important indicator to assess water-related climate change. This study utilizes the aridity index to reveal the recent climate change patterns in the Lancang River Basin, China. A new non parametric estimator of climate elasticity has also been developed. Using the daily meteorological records (1961-2005) of precipitation, air temperature, wind speed, relative humidity and sunshine hours from 35 stations, changes in spatial and temporal characteristics of P, E , E, and E/ P are analyzed. The results reveal some important new findings, which can be summarized as: (a) new findings show that the spatial distribution of, and the correlation coefficients between P, E, E, and E/ P possess strong latitude zonality; (b) high consistency in the temporal variation of P and E has been detected. The main periodicity of the E and E/ P series varies greatly for the three sub basins, and an anti-phase relationship between them has also been found; (c) our newly developed nonparametric estimator of climate elasticity can be successfully used in assessing the sensitivity of climate system. Climate elasticity of E in relation to E and P increases for most of the regions in the study area, suggesting that E becomes more sensitive to changes in the corresponding climatic variable during the study period. The study demonstrates the importance of the aridity index in the water-related climate change studies which has been neglected for a long time by most hydrologists and managers. [ABSTRACT FROM AUTHOR]