长江上游干支流的水沙变化及其与森林破坏的关系

本文以长江上游支流岷江、嘉陵江和长江上游干流控制站宜昌站的长系列水文资料对长江上游森林生态系统的环境功能、水文效应和森林破坏后的影响进行了分析。表明，森林可以显著增大枯水流量，可以显著削减中小洪水的洪峰流量，但对全流域性长历时暴雨所造成的特大洪水的削减作用是有限的。长江上游支流岷江和嘉陵江的输沙变化表现出一定的趋势，森林破坏和坡地开垦使河流泥沙增多；水库修建后，因水库的拦沙作用而使河流输沙量减少。但干流宜昌站则看不出明显的趋势性变化。解决洪水泥沙问题，单靠森林生态系统恢复是不够的，应该生物措施与工程措施(重点为修建水库)并重。

Runoff and sediment variations in the upper reaches of Changjiang River and its tributaries due to deforestation

Based on the long term hydrometric records from the Minjiang River, Jialingjiang River and the upper reaches of Changjiang River, an analysis is made to reveal the effects of deforestation on the hydrological regimes. The results show that forest can significantly elevate the runoff in low-water season and reduce the flood discharge, but its effect of reducing large floods caused by long durating rainstorms covering the whole river basin is limited. The deforestation and slope land cultivation lead to an increase in sediment load, but the interception of sediment by reservoirs built in the river basin makes sediment load decreased. However, the long-term hydrometric record at Yichang Station indicates no trend of changes in sediment load. It seems that it is necessary to adopt not only the reforestation but also the biological and engineering measures to solve the flood and sediment problems in Changjiang River.