土地利用变化情景下牧羊河水文响应研究

HYDROLOGICAL CHANGES RESPONDING TO LANDUSE CHANGES IN THE MUYANG RIVER

土地利用方式变化影响水量平衡各要素的分配,进而导致流域水源涵养能力发生变化。选用长江流域金沙江水系下段牧羊河小流域内及周边气象站气象资料,植被、土壤以及地形数据,构建了研究区SWAT水文模型,分析其在牧羊河适用性后,结合1986～2009年的土地利用以及设置的人类活动增强和生态环境改善的4种土地利用变化情景,用率定好的SWAT模型分析了土地利用变化下牧羊河水文响应。结果表明:径流依次按1986、2000、2009、1995年土地利用方式减小,而蒸散依次按2009、1986、2000、1995年土地利用方式减小,土地利用对径流和蒸散的影响在汛期大于非汛期,随着林地面积的增加径流将减小;将现有耕地变为林地或变为草地都有助于减少径流,从流域水源水量涵养角度出发,构建适宜的生态系统将有助于减少径流和蒸散,而增加入渗。这一结果为牧羊河水源涵养林建设提供科学依据。

Different landuse types influnce the surface runoff, the infiltration and evapotranspiration in the soil. Changes of landuse patterns would impact the elemental distribution of water balance, as well as the changes of water conservation capacity. The hydrological response to landuse t~）pes was the basis of studies on water resource management and ecological remediation. It is important,therefore, for the reasonable uti- lization of water resources and the sustainable development of ecological system. The Muyang River water- shed refers to the lower part of the Jinsha Jiang River basin,and is chosen as the study area in this paper. Taking the meteorological data within and nearby the study area,combining with the landuse,soil and to- pography data in this area as the basis, a SWAT model was built. The feasibility of the model in the Muy- ang River watershed was evaluated afterwards. The landuse data from 1986 to 2009 were collected. By pre- supposing four different scenarios of landuse changes with the intense human activities and the improving ecological system,the hydrological responses to the landuse changes in the watershed were analyzed using the SWAT model. The results indicated that the modelling error in the Muyang River watershed was4- 10% ,and the Nash-Sutcliffe efficiency coefficient was larger than 0.75 both in the calibration period and the validation period, which proved the SWAT model was suitable for the evaluation of the hydrological re- sponse in the Muyang River. The runoff decreased in accordance with the landuse pattern of 1986,2000, 2009 and 1995 ,and the evapotranspiration decareased by the order of 2009,1986,2000 and 1995. The influ- ence of landuse changes on runoff and evapotranspiration in the flood season was greater than that in the dry season. The runoff would decrease with the increasing area of forest. Changes of the present arable lan- duse type to forest or grass landuse type would contribute to the decrease of the runoff. The evapotranspi- ration in forest area was higher than that in grass land. Therefore,the construction of the composite forest- and-grassland system was favorable for the decrease of runoff and evapotranspiration, and for the increase of infiltration. All the results will provide scientific knowledge for the water resource protection and the construction of the forest for conservation of water supply.