| The issue of water is a dominant theme in the study with the population and productivity increasing highly. Upstream catchments construct numerous middle and small-sized hydraulic projects in order to relieve this contradiction between flood control and irrigation, which changed runoff processes entering large reservoirs. A flood forecasting and hydrologic calculation model must reflect the continually changing runoff situation. The Fengman basin is a major tributary of the Songhua River basin (SRB), located in the northeast of China. In the past half century, the climate in the SRB has became warmer and drier and a large area of wetlands has degraded while farmland has been increased rapidly. Many hydraulic projects as reservoirs, ponds, paddy fields and soil and water conservation engineering projects have been constructed to improve utilization of water resource in upstream of Wudaogou station basin in recent years. The local hydrological characteristics of the basin and the flood runoff and process are changed. Study on historical flood recurrence under the impacts of hydraulic engineering is important for scientific guiding ideology river basin flood control, making plan for design food of basin and reservoir and assure the flood control security. It is an important issue waiting to resolve in water conservancy industry of Song-Liao rivers basin. In this paper we take the Subarea ? of the Fengman basin as an example and analyse the impacts of such human activities as the changes of land use/land cover and the construcion of water conservancy project on flood process and simulate the historical flood process on current hydraulic projects. The study content and result are as follows:(1) Qualitative and quantitative analysis the variation trend of hydrometeorological data in study area using Man-Kendall rank correlation, Sequential clustering and linear regression test method. According to the test results, the variation trend of climate and hydrology is different. Then, the dominant factors of ruoff and flood changing were analyzed. Impact factors of human activities are land use change and hydraulic projects, while climate factors are precipitation, evaporation, temperature, pressure, sunshine, wind speed and relative humidity. These factors are analyzed quantitatively and results show that streamflow changes due to hydraulic projects activities and climate variability. Meanwhile, the local hydrological characteristics of the basin and the flood runoff and process are changed impacting by reservoirs and hydraulic projects activities especially. The influence must be considered in flood forcasting.(2) Using the multi-objective and semi-structural decision-making fuzzy recognition theory and model, the results prove that there were few changes in the land use/cover between 1980s and 2000s. The elasticity of streamflow with respect to precipitation and potential evapotranspiration was calculated using four methods:two non-parametric estimators, an estimator based on the Budyko hypothesis and a one-parameter Budyko model. Climate change accounts for a decrease of annual streamflow from 1957-2010 by an estimated 43.3 mm (51% of total streamflow decrease 85.4mm) using the climate elasticity model. Hydraulic projects decreased runoff by 42.1mm (49%). Decreases in runoff from hydraulic projects activities were calculated respectively in three sub-periods and the relationship between annual streamflow decrease and hydraulic projects was established.(3) The sensitivity and uncertainty of parameters of the TOPMODEL was analyzed. The simulated image of aggregated reservoir's holding and discharging (ARHD) is presented to reflect the relationship between model parameters and effects of hydraulic projects on flood. The TOPMODEL with the dynamic soil moisture storage capacity and ARHD-TOPMODEL are used to simulated floods influenced by small and mid-sized hydraulic engineering of SRB ?. Results show that floods process simulated by ARHD-TOPMODEL are more suitable to observed process and the flood forecasting for the large reservoir can be supported by the study results.(4) Establish the flood recurrence method under the influence of the water conservancy project operation based on ARHD-TOPMODEL. The historical flood on current hydraulic projects were simulated and summarize the influence law of current hydraulic projects on historical floods in Fengman reservoir. Comparison and analysis the change between the process of historical flood forward restore and the measurement process, the simulation flood process and runoff show a decreasing trend and special extreme flood will become more severe. It will be meaningful to the current flood control in basin. |
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