Effects Of Land Use Change On Runoff Of The Fenghe River Basin Based On SWAT Model

The Fenghe River is the first grade tributary flowing of the south bank of Weihe River, the drainage basin of the Fenghe River is facing the severe situation of preventing flood, and at the same time, the utilization of water resources is unreasonable, so the ecological environment needs further improvement. Population growth, urbanization, industrial, mining construction and other human activities cause land use/cover changes, which will affect the water cycle and the water balance of the drainage basin. So the study of the hydrological response of the drainage basin due to the land use/cover changing gives the further acquaintances of characteristics and evolution law of the runoff, at the same time, the related studies have important actual meanings for the planning, configuration and reasonable use of water resources during the changing environment. The paper chose the distributed hydrological model SWAT which was coupling with GIS on the basis of the analysis to the change trend of main meteorological hydrological elements in the study area, in order to discussed the effects of the change of land use on the runoff by the means of carrying on contrasts of the different runoff from the simulation of the annual runoff and the distribution runoff of different land use types. The paper drawing the conclusion as follows:(1) The precipitation of the Fenghe River was gradually decreases, and the temperature kept rising tread in the whole from 1958 to 2014. The annual runoff of the Fenghe River had a remarkable decrease trend in 1958-1990, however, in the period of 2001-2012, the annual runoff with the wavelike increasing trend. The annual runoff of the Fenghe River showed a response for the climatic factors, specifically, which has a positive correlation with the precipitation, but has a negative correlation with the temperature.(2) The runoff simulations results shows that there is a good credibility at the year scale and the month scale, the years scale is prior to monthly scale, so the SWAT model can be applied to simulate the runoff changes in this region.(3) For different land use types in the Fenghe River Basin, the forest area is has the largest proportion, and the second is plough, and then the land use of grassland and construction, nesting a little water area and unused land into this region. There is a frequent conversions between different land uses in 2000-2005. However, above 98% land use had no significant changes in 2005-2010. This indicates that: arable land, grassland basin constitute the dominant process to convert forest land, part of arable land into construction land is its dynamic performance.(4) The remote imagines in 2000,2005 and 2010 were chosen to simulate runoff in three time periods, the results showed that the land use change degree sequence is 2000> 2005> 2010. Changes in runoff became clear after 2007. This suggested that the role of water conservation by forest had a lag effect in the land water balance.(5) The trend of the annual and the monthly runoff have the consistence in different land uses, its difference is mainly manifested in the size of the runoff. The results showed that the cultivated land will lead to the increase of runoff, and the forest and grassland will reduce runoff, and the role of woodland will be more significant, which would reduce the amount of flooding in some certain degree. In the dry season, the store and delay effect of different land use types on runoff is not as evident during the rainy season. It was seen more sensitive to the effects of land use change on the basin runoff during the rainy season. The policy of returning farmland to forest can be effective in stabilizing runoff basin. It is conducive to regional soil and water conservation and the improvement of the ecological environment.