The Effects of the Mountain Forest Changes on Hydrology in Northwest Arid China

摘要

The research on the relationship between vegetation and water budgets in mountainous area occupies an important niche either in hydrology or ecology. Based on GIS, using 15 years' (from 1987 to 2001) hydrological databases and forest investigation databases, we evaluated the hydrological effects of forest changes in the Qilian Mountains of northwest arid China with the cases of mo catchments (DYK and HCB). In this paper, Landsat ETM{sup}+ remote sensing satellite data (1:50000) taken in May 2001, forest map (1:50000) and topographic map (1:50000) were used to produce the forest landscape map. The forest spatial pattern and area had changed very little in the two catchments, and the main changes were the forest growing stock during the 10 years (from 1989 to 2001). The growing stock increased 50926m{sup}3 in DYK and 34282m{sup}3 in HCB. The result of analyzing the forest change and hydrological databases indicated that, from 1989 to 2001, with a certain forest area in the two catchments, the runoff modulus and the dry season runoff percentage increased with the forest growing stock increasing. Runoff modulus increased 5.41mm per 10000m{sup}3 forest growing stock in DYK and 5.7mm in HCB. The mean dry season runoff percentage of DYK was 10.14% during 1989 to 1995 and 11.9% during 1996 to 2002, and which was separately 7.23% and 8.48% in HCB, which means the forest growing in the catchments should improve its hydrology adjusting function especially in arid mountains.