陕西省子午岭生态功能区水源涵养能力研究

应用InVEST模型和SCS模型，计算得出研究区多年平均水源涵养量约为3×108 m3，涵养深度69.79 mm，表明研究区具有比较突出的水源涵养服务功能，特别是在森林和灌丛分布相对集中的子午岭自然保护区内，水源涵养能力处于较高水平。不同土地利用类型的水源涵养能力有较大差别。由于灌丛具有较好的降水截留能力和较小的蒸腾作用，水源涵养能力最强；而森林由于蒸腾旺盛，加之冠层截留的大部分降水用于蒸发而无法积累，使其水源涵养能力稍低于灌丛；草地和农田覆盖地区，降水极易流失，因而草地和农田的水源涵养能力较差，对区域总水源涵养量的贡献也最小。此外，研究区多年平均产水深度139.4 mm，整体趋势是从东南向西北方向减小，与区域降水量空间变化趋势一致，在土地利用类型的影响下，这一趋势更加明显；多年平均径流深度71.1 mm，空间上大致由南向北减少，同时，由于径流深度还受到降水时间分配、土地利用类型、土壤质地的影响，因此呈现出较为复杂的空间分布特征。

Water conservation function of Ziwuling Ecological Area in Shaanxi Province

With the development of the society and economy，the contradiction between the growing demand of water and the shorter supply of water resources is increasingly intensified，which has resulted in the serious water shortage of many areas，and in turn，the serious water shortage can be the major restricting factor of the local social and economic development. The functions of ecosystem 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 paper 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. In this paper，the amount of water yield（the amount of precipitation minus evapotranspiration）in the area of Ziwuling Ecological Area in Shaanxi Province，China was calculated with the InVEST 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：（1）The average amount of water yield in this area is 139.4 mm per year，which has the trend of decreasing from the southeast to northwest. The cause of this general trend is that in the southeastern part of Ziwuling area，there concentrate the majority of the settlements and farmlands of the whole area. As is known，the precipitation is more likely to become the surface runoff than to infiltrate in the area of towns and settlements. On the other hand，the amount of water yield will be increased as a result of the decreasing amount of evaporation which is caused by the low content of water in the soil of farmlands. While in the northern area of Ziwuling，there are the densely distributed forests and shrubs，which has led to a significant evapotranspiration and less precipitation. All these factors are supposed to contribute to the low amount of water yield. （2）The average depth of surface runoff in the area is 71.1 mm per year，which has the trend of decreasing from the south to the north and it is roughly consistent with the specific distribution of water yield in the area. However，the distribution of the average depth of surface runoff displays a very complicated feature because the depth of surface runoff is also influenced by the following factors as the time distribution of precipitation，the land utilization types and the quality of the soil. （3）The average amount of water conservation in the area is approximately 300 million m3. And the average depth of water conservation is 69.79 mm，showing an outstanding feature of excellent water conservation function. Generally speaking，the depth of water conservation in the central part of the area of Ziwuling is greater than that of the north and the south part，which results from a concentration of forests and shrubs in the central part，and these two types of land possess a high capability of water conservation. （4）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. （5）InVEST model is well-developed for calculating the water yeild，while SCS model requires further investigation because of its empirical relation among parameters．