Analyze The Impact Of Human Activities On Runoff And Flood Forecasting Based On Multi-Source Information

Water resources problem, which has a close relationship to human survival and society development, is the most important issue of resource and environment of the world in the 21st century. The safety of water supply and flood control is the graveness task and important guarantee, which is decided by the basic characteristics of the water resources problem in our country:deficiency of water resources quantity per capita and unbalanced spatial-temporal distributing. In the last few decades, along with the population explosion and development of economy and society, the profound variation of water resources mechanism can be found because of human activities. Decreasing the stream flow, increasing the flood frequency, the problem of water supply and flood control will be more stand out. Many new problem of water resources were brought by these variations, such as, runoff change and the balance between water supply and water demand, flood forecast and control under the human-natural driving model. According to these problems, this paper choose Biliu river reservoir basin as study case, analyze the impact of climate change and human activities on large-size reservoir's runoff which assignment is provide water to cities; choose Fengman river reservoir basin as study case, analyze the impact of middle- and small-size reservoirs on flood forecasting. The study content and result are as follows:(1) Impact factors of human activities are divided into three classes according to the impact of human activities on runoff and flood. The first class of factor is the impact on condition of runoff yield and concentration, such as land use change, runoff yield and concentration, river regulation, and so on. The second class is directly water use, which are mainly contain water diversion project(such as inter-basin water transfer and irrigation district), groundwater exploitation, and so on; The third class is the impact on runoff process, such as the impact of sluice projects like reservoirs and ponds. Analyze the impact characteristic of human activities on Biliu river reservoir basin and Fengman river reservoir basin, aiming at the three classes of factors above.(2) Qualitative analyze the factors of runoff change, by analyzing the variation trend of hydrometeorological data in study area used Kendall rank correlation method, Spearman rank correlation method and linear regression test. On this basis, according to the variation of precipitation and temperature, the method of total amount control and random distribution is used to calculate the reduced precipitation series. This method, first calculate the total amount of reduced precipitation by its variation trend, and then calculate the average precipitation days of each month of representative station in three typical years(wet, normal and dry), finally, random distribute the reduced precipitation to each month according to the calculated precipitation days of each month. The method of total amount control and proportional amplifying is used to calculate the reduced temperature series. This reduced temperature series can be calculated by original temperature series multiplied by reduction coefficient, which is calculated by comparison the temperature variation between before and after reduction. Only periodicity characteristic can be found in the reduced precipitation and temperature series, the trend characteristic is eliminated.(3) The SWAT model of Biliu river reservoir basin is established used DEM, soil, land use and hydrometeorological data. In this study, the author adopted a multi-site and multi-variable approach based on the water balance control to calibration of SWAT model. Under the optimization criterion of total amount control and annual distribution, according to the attribute of each hydrologic station, calibrate the parameter from upstream to downstream successively. The calibrated SWAT model can reflect the water cycle process in Biliu river reservoir basin.(4) The GLUE method use Nash-Sutcliffe coefficient (Ens) as single likelihood criterion, which may lead large simulation error, and then affect the uncertainty analyze. In this study, the author adopted a multi likelihood criterion, which contain three criterions (Nash-Sutcliffe coefficient (Ens), relative error (Re) and determination coefficient (R2)), to improve the GLUE method. And the posterior likelihood function of the improved GLUE method is calculated by multi-objective fuzzy optimization model. Then, the uncertainty analyze method of SWAT model is established. The application shows that, for 90% confidence interval, the width of an interval for improved GLUE method is more narrow than unimproved method, which indicate the smaller uncertainty of SWAT model. The uncertainty of precipitation is found relative less by the method of precipitation randomization change, which got the same conclusion of parameter uncertainty analyze.(5) The method of genesis analysis is adopted to calculate the impact of climate change and human activities on runoff, through the hydrometeorological data reduction method and SWAT model scenario simulation. Firstly, the author find the change-point of human activities by analyze the GDP and population change. The contribution rate of climate change and human activities are calculated by analyze the runoff series pre-and post the change-point and the reduction runoff series simulated by SWAT model. Applying this method to Biliu river reservoir basin, the result shows that, for 1981-2005, the impact of climate (precipitation and temperature) change and human activities on runoff are take the percentage of 39% and 61% respectively. Aiming at scenario 1980s and scenario 2000s of SWAT model in Biliu river reservoir basin, scenario simulation method is used to simulate the runoff of different scenarios which contains different land use and weather consider mid-and small-size reservoirs. It is easy to found that, the main reason of human activities induced runoff decrease is directly water use and detention of the reservoir in up-stream, the impact of land use change is relative less.(6) Combining remote sensing data (Landsat TM/ETM+) and traditional hydrometeorological data, a method for determining the flood detention quantity of ponds and small reservoirs based on remote sensing data was proposed. This method choose sub-watershed as basic calculation unit, and according to the water surface area extracted by remote sensing data and the measured volume of small reservoirs which has measured data, capacity-area relationship of ponds and small reservoirs is established in different category of sub-watershed divided by average slope. Based on the two scenes remote sensing data that contains the flood period, the water surface area change is calculated by analyze the water surface area of two scenes remote sensing data and the variation of precipitation and potential evaporation in corresponding time period. The flood detention quantities can be calculate by convert the water surface variation to volume variation, through the capacity-area relationship. This value can be used to adjust the primary flood forecasting model. The application in Fengman subarea II basin shows that, the flood detention quantity of the entire basin is 4389.6×104m3. Using this value to adjust the primary flood forecasting model, the relative error decreased from 31.8% to 10.1%.(7) The analyze method of detention and discharge mechanism for ponds and small reservoirs based on single scene remote sensing data is proposed, and applied in 7 floods of Fengman subareaⅡbasin. This method, Firstly, the initial volume of ponds and small reservoirs are calculated in the use of remote sensing data, and then choose the initial volume, phase of flood season and precipitation as three factors, analyze the flood detention mechanism in the different condition. The result can be used for real-time flood forecasting adjustment.Finally, a summary is given and some problems to be further studied are discussed.