| Flood disaster not only brings a great threat to human production and living, but also has huge harm to social and economic development. Since the mid-20 th century, frequent floods caused the attentions of the countries all over the world. Flood process is influenced by the underlying surface which restrained and limited by various factors such as geographical condition, hydro meteorology condition and human activity, therefore, floods have a high degree of randomness, fuzzification and complexity, and showed some regularity. In order to better control and manage the flood, we need to better understand the cause of the flood process, and perfect the relevant mechanism of hydrological process.Nowadays, there are many researches about influences of vegetation coverage condition for low water and flood peak, and develop a lot of conclusions. The regulation function of vegetation coverage condition for flood peak and low water runoff due to different soil types, the vegetation coverage and vegetation structures. Tangshan mountains are the most important water containing area in Xingjiang. It has a big significance of researching the influence of the changes in vegetation cover for the runoff process in the Tianshan mountains.This paper focused on catchments of the upstream watershed in Kaidu River where located in Bayanbulak basin of middle Tianshan mountains, from the angles of runoff, rainfall, and the meteorological and hydrological coupling, forecasted and analyzed the characteristics of peak flow and low water runoff, revealed the influences of the mountain vegetation coverage. Main conclusions are as follows:NDVI has a good representation of regional forest coverage condition. From the analysis on time variation, the interannual variation of NDVI in Bayanbulak basin has a tendency of rising steadily year by year, distribution between 0.21 ~ 0.26. Although shows a tendency of steady rise, it has obvious periodic changes. From the analysis of the spatial distribution, the surface vegetation distribution in the west Bayanbulak basin is superior to the vegetation distribution in the east. Besides, riparian zone and wetlands around the Kaidu river have good vegetation distribution. From the analysis on the change tendency of NDVI, from 1982 to 2013, improve areas of vegetation coverage are bigger than the deterioration area in Bayanbulak basin. From the analysis on the change sustainability of NDVI, the vegetation coverage in Bayanbulak basin can keep a stable tendency. The researchers need to continue to pay attention to the continuous degradation area and where did not have a clear tendency in the future. By analyzed the relationship between NDVI and runoff volume, the NDVI and peak discharge show a negative correlation. A high vegetation coverage has played a certain action to reduce the flood peak. The NDVI and low water runoff show a positive correlation. The improve of forest vegetation coverage can significantly increased low water runoff.Different parameterize combining scheme of WRF has a different sensibility to each climatic elements simulating in Bayanbulak basin. This paper preferred choice 16 combining scheme simulatings, in view of the rainfall, more stable parameterize combining scheme as follows: YSU scheme, Kain-Freitsch scheme, WDM6 scheme, Dudhia/RRTM. In view of the air temperature, more stable parameterize combining scheme as follows: YSU scheme, Kain-Freitsch scheme, Thompson scheme, Dudhia/RRTM. In view of the wind speed, more stable parameterize combining scheme as follows: QNSE scheme, Kain-Freitsch scheme, Thompson scheme, Dudhia/RRTM. Those Physical schemes have a considerable value to the machine rational researches of the weather process such as rainfall in Bayanbulak basin. After numerical modeling the heavy rainfall event 2013J18 P, preferring choice scheme,and analyzing difference result caused by each combining scheme, we can get the conclusion that : the outcome bias of model simulation can not Greatly reduce by change the parameterize scheme,that also means The improve of results precision of model simulation closely related to ambient field of Numerical simulation of drive mode. A series of methods can be utilized to improve the prediction accuracy. Such as assimilates the observation data into ambient field to do the correcting action. On the other hand, combining the characters of high and cold basin and complete the physical process of schemes to improve the prediction accuracy.Create different scenarios, application of distributed hydrological model DHSVM to simulate the vegetation influence on runoff. Respectively to simulate the process of daily runoff changes under different vegetation coverage. Simulation results show that: From the angles of daily runoff changes and hours runoff changes comprehensive verification and evaluated the applicability of DHSVM hydrological model which has a same trend with the actual measurement process. Certainty coefficients are between 0.85 to 0.92. Simulation error of daily runoff(the difference between the simulated values and measured values)is within 34.50%,mean absolute error is about 10.27%. Simulation error of hour runoff(the difference between the simulated values and measured values)is within 15.00%,mean absolute error is about 7.07%. Certainty coefficients are between 0.90 to 0.91. This provides a scientific basis for the model application research in the future.Comparing with two vegetation coverage situations, when vegetation coverage area is relatively small, the flood peak induced by heavy rain is short in time and strength in change. The middle and later periods of runoff simulation model show a simulated runoff is higher than the actual runoff. The possible reason is due to rainfall supply continues to decline, Soil water remain at a relatively low level, The amount of rainfall infiltration supplement soil moisture relative increase The amount of Rain infiltrate into soil, so the surface runoff is less than the earlier periods. When the vegetation coverage area is larger, there was a decrease in the peak flow, and shows a phenomenon of water slowly decrease. It is due to a great Rainfall intercept ability of the surface vegetation layer, to some extent, weakened the rain directly to the surface.Coupling the numerical weather pattern WRF and distributed hydrological model DHSVM,to forecast the flood caused by heavy rainfall in vegetation dense coverage area. The forecast runoff process is basically tallies with practical observation(R2=0.8019,RMSE=2.16,E=0.8955), it shows that DHSVM has an applicability in the high and cold basin,can reproduce the process of heavy rains caused flooding. But there is a considerable error in some periods(the difference between simulated values and measured values.) Swelling process has an over estimate in earlier periods. The maximum error is about 2.69 m3?s-1(absolute error is 5.8%).Swelling process has an over estimate in later periods. The maximum error is about 5.8 m3? s-1(absolute error is 9.8%). The coupling simulation results can effectively implement warning and forecast of intense rainfall flood. |
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