Estimation and Analysis of Ecological Water Requirement in the Jinghe Watershed

Jinghe Watershed is the second-branch of the Yellow River with a length of 450 km and coverage of about 45 421 km~2. Due to dry climatic conditions and human activities, there is only thin vegetation there. Serious soil and water loss caused by degraded vegetation ecosystems is one of the most serious problems in the Loess Plateau and main silt sources floating into the Yellow River. Therefore, ecological water requirement in the watershed will be of importance to regional ecological restoration and construction. In this paper, ecological water quota of high, middle and low coverage grasslands were determined based on analysis of grassland ecological water requirement and the influential factors and through correction of temperature and precipitation data at different regions. Then, grassland ecological water requirements were calculated in accordance with the quota and the area of grassland interpreted from 1∶100 000 land use map. The results show that total grassland ecological water requirement is about 569 706×10~4 m~3, of which water requirement of grassland with middle coverage is roughly 434 674×10~4 m~3, occupying 76.3% of the total; followed by grassland with low coverage, the water requirement and percentage are 78 326×10~4 m~3and 13.8%, respectively; water requirement and percentage of grassland with high coverage are only 56 706×10~4 m~3 and 9.9% respectively. Because of difference in grassland types and grassland areas, variations in ecological water requirements exist among the regions.