漫湾库区多陡坡，断层发育，地表破碎，雨量集中，生态环境较为脆弱，易退化。通过实地调查及野外资料分析，介绍了该库区生态退化的几个表现：①景观变化，原994m以下河谷地带的村落、耕地、陆生动植物全部被淹没，在1000～1800m的谷坡地带，原有林地、草地、坡度稍缓的地方，均被新开垦的坡耕地和新建的聚落环境所取代。生态环境较以前脆弱，但因蓄水后库区水热配置条件的改变，使1000～1300m地带的植被条件变好，促进了库区植被的恢复；②1984年以后，库区及上游地区地表水土流失加剧，长系列年径流量含沙量增加36.6%，年输沙量增加37.3%；③库容损害严重，1998年调查，水库建成的3年时间里，总库容淤损率已达到原设计标准的第5年水平，有效库容淤损率已达到15年的水平；④水土流失、滑坡、泥石流、山地洪水、崩塌等山地灾害频繁。并进一步分析了造成生态退化的人为因素，认为：①建库后坡地开垦，造成库区植被的减少，以及水土流失的加剧；②水库蓄放水造成库周边稳定性变弱，引起崩塌和滑坡；③因公路、水沟等水库相关工程设施建设引起泥石流等山地灾害；④库外上游环境恶化是库区泥沙、水质生态环境的重要影响因素。最后，例举库区生态环境恶化对地方生产、生活以及水库工程本身造成危害，提出库区生态环境治理和维护的对策：①对库区内生态环境严重退化地区的环境贫困人口和受滑坡、泥石流等山地灾害危害的人口，必须移民到库区外进行安置，以减少环境压力。目前，库区属于此方面影响的人口约1000人，需要重新安置费约3000万元；②以小流域为生态单元，将土地合理利用、灾害治理和社区发展相结合，进行小流域综合治理，重点在南涧公郎河和凤庆黑河小流域；③加大库周移民安置区重点山地灾害危害区的工程治理；④提高漫湾电厂库维资金的额度，直接用于库区移民安置区的绿化工程建设、农村能源建设和扶贫开发建设；⑤治理库区外大理市及兰坪县境内的水污染企业，改善入流水质；⑥结合小湾大型电站的建设，加大澜沧江中上游干流河谷两岸的天然林建设和水土流失治理。

Western China includes 12 provincial divisions (the 7 provinces of Sichuan, Guizhou, Yunnan, Shangxi, Gansu, Qinghai and; 5 autonomous regions of Tibet, Ningxia, Xinjiang, Inner Mongolia and Guangxi; and one city of Chongqing), which comprise 71.4% of the national land area, 28.5% of the national population and produce 17.5% of the national GDP in China. There are 17 countries that have riparian relationships with wester n China, most of which are water -short countries. All are listed by UN ESCAP as countries with potential water crisis. The co-operative development and coordinated management of international rivers in western China is an important step toward the implementation of the national Great Western Development program. Taking into account of the national strategy and object hierarchy, as well as the development demand of the western region, it is necessary to pursue the multi-disciplinary study of the equitable allocation, utilisation, and eco-environment protection of transboundary water resource in the region. Such efforts will undoubtedly provide scientific evidence and support for the decision-making of the environmental protection and ecological construction and management in the western region, the enforcement of the sub-regional economic co-operation, mitigation of trans-boundary conflicts, and enhancing bio-diversity conservation.

China possesses over 110 international rivers and lakes, among which 41 are major ones and 15 are of great importance. With the highest concentration of international rivers, the northeast, northwest and southwest regions of China enjoy abundant transboundary resources aad pose complicated ecological security issues. Following the 1950s, relevant studies on international rivers fall into three periods: 1) the planned economy period of the 1950s 1980s when border development mad basic research were scant; 2) the reform mad opening up period from 1980 to the end of 20th century. Along with the drive of economic globalizafion mad regional cooperation, development of international rivers was thriving, which filled blanks in the research and nanowed gaps with international standards. Relevant studies also provided national mad local governments with important scientific grounds for making decisions; 3) since the start of the 21st century, China has integrated its international river studies across sectors mad across international borders. Now both government mad scientific institutions pay great attention to transboundary environmental issues.

The western part of China borders on South and Southeast Asia. Of the numerous well known international rivers sharing with the two regions, the Lancang2Mekong River has been most extensively studied in the world for its important strategic position, rich resources, prosperous potential market as well as considerable opportunities for investment and development. The sustainable multipurpose development in this area has increasingly become the focus of international regional cooperation, and great attention has been paid to this area by the international society. Up to now, at least 10 major actions in the international regional cooperation are expected in this area. This paper intends, at the angle of geography and with the overall target of promoting the sustainable development in the basin through international cooperations, to study the international position, the potential and the prospects for development of the Lancang-Mekong River, to analyze the main problems in this international cooperation, to propose targets and prospects for such cooperation, and to indicate the way for geographers to participate in such research.

Through analyzing the difference and complementarity in the thydrogengraphic characteristitcs, socioeconomic conditions, water resources development objectives and relative problems between regions in the Lancang-Mekong River Basin, an integrated multiobjective optimum utilization planning of water resources is proposed, so as to reduce the damage to environment and to facillatte the sustainble development of the basin.