Applicability Of SWAT Model Study In Wangmo River Basin

Based on the Wangmo river basin which has frequent geological disasters from mountain torrents, the author carried out the test, and built the SWAT hydrological model to analysis the applicability of the SWAT model in the Wangmo river basin. And by using the SWAT model to simulate the hydrological conditions in the study area, to analyze spatial and temporal distribution of water in the basin, climate changing, land using and land covering and so on, so that the author can analyze this various factors’ influences on Wangmo river basin runoff variation.To explore the SWAT model’s suitability in Wangmo river basin, the author got the following main conclusions.(1)The monthly runoff and daily runoff of Wangmo river basin simulated by the SWAT model is consistent with the actually measured value. The coefficients of Ens in calibration period and validation periods of are all above 0.5, and R2 are all higher than 0.79, and the absolute values of Re are less than 15%, achieving the standard of class C. SWAT model, as an effective tool for hydrological simulation, is applicable to Wangmo river basin, and can be use in other river basins.(2)The rainfall and runoff distribution in the study area has obvious regularity, from south to north, gradually increasing. The large rainfall areas mainly distributed in the upstream areas of higher elevation. Runoff influenced by rainfall intensity, the greater the rainfall, the greater the runoff.(3)To simulate the runoff in the condition of 4 kinds of land using and covering changing, we can learn that the increasing of broad-leaved forests and grasslands in Wangmo river basin will make the runoff increase. But the broad-leaved forests’ increasing amplitude is small, the grasslands’ is big.The increase of coniferous forest and shrubbery area will reduce the runoff, and the simulation results is close to the actual values. This suggests that in Wangmo river basin, the effect of arbor for conservation of water and reducing the runoff is better than grassland, and the effect of coniferous forest and shrubbery is better than broad-leaved forest.(4)Combined with Mann Kendall trend analysis, the highest temperature, lowest temperature and average temperature from 1960 to 2013 had an obvious rising trend. The lowest temperature and the annual average temperature has a significant upward trend. The lowest temperature’ change rate is 0.32℃/10 a, and the change rate of the average temperature is 0.37℃/10 a.The highest temperature’s rising trend is not very obvious, and the temperature’s change rate is 0.07℃/10 a. Through the analysis of weather scenario simulation, the runoff in Wangmo river basin has close relationship with temperature and rainfall. Relationship between runoff and temperature were positively correlated. The runoff increases as temperature rise. In the future, the change of precipitation in the study area is the main reason affecting the annual runoff, and the influence of the temperature is not very obvious.(5)The changes of land using and covering and climate in the Wangmo river basin all affect the changes of the runoff. Among climate factors, the influence of rainfall on runoff is greater than the influence of the temperature on runoff. So to prevent geological disasters from mountain torrents to Wangmo, people should take measures of conservancy engineering. Through water conservancy, to shunt of runoff, delay the time of runoff and confluence and the confluence volume, so as to reduce the damages to the downstream.