Function And Value Of Water Conservation In Beiluohe Basin

Ecosystem has a variety of functions in providing natural resources to human beings, as well as in maintaining the life support system of the earth. The functions include soil conservation, water conservation, and climatic regulation, etc. Furthermore, in the arid and semi-arid regions, the water conservation areas play a very important role in alleviating the erosion of water and maintaining the amount and quality of water. This article aims to explore how to calculate the amount of water conservation.The principle of water amount balance is the most used and effective way to calculate the amount of water conservation, which believe that the amount of precipitation minus evapotranspiration and other consumption is just the amount of water conservation. In this thesis, the amount of water yield (the amount of precipitation minus evapotranspiration) in the study area was calculated through the In VEST model. Meanwhile, the amount of the surface runoff (other consumption) has been obtained by applying the SCS model. Based on the result of the two models, the amount of water conservation will be calculated.By analyzing the results of the calculation, the conclusions are as follows. a)The average amount of precipitation in this area is 516.5 mm, the evapotranspiration is 372.8mm. The average amount of water yeild is 143.7mm, totaled 3.359 billion cubic meters, which has the trend of decreasing from the southeast to northwest. Water yield is related to precipitation、 soil type、vegetation、leaf area index、 solar radiation and temperature, which influence the water yield by changing the evapotranspiration. For the same amount of precipitation, the water yield will be decreased as a result of the higher temperature、greater leaf area index、 more intense solar radiation、 deeper root and more loose soil texture. b)The average depth of surface runoff in the study area is 43.9mm per year, which has the trend of decreasing from the southeast to the northwest. The amount of surface runoff is related to soil moisture before the rainfall、land use and land cover、soil texture. Surface runoff will be decreased as a result of the lower soil moisture before rainfall、more loose soil texture, especially in the areas covered with forests and shrub, where the precipitation is liable to infiltrate. c) The average amount of water conservation depth in the study area is 99.89mm per year. The areas have the strongest ability of conserving water distribute across the south of the study area, where covered with forest and shrub or have more rainfall and more loose soil texture. In the meanwhile, the north of the study area could conserve more water because of its lower evapotranspiration. From the aspect of aggregate quantity of water conversation, basins that have stronger ability and lager area could conserve more water than any other basins. At the same time, the amount of water conservation of various land uses is different, in order of most amount, it goes:forest、shrub、grassland、farmland、desert. d) The water conservation service value of the study area is 13.987 billion yuan by the method of shadow engineering. e) Based on the InVEST model and SCS model, the amount of water conservation and the discrepancy conservation capacities of different land uses can be acquired scientifically and quantificationally. InVEST model is well-developed for calculating the water yeild, while SCS model requires further investigation because of its empirical relation among parameters.