近50年来河西走廊区域生态环境变化特征与综合防治对策

近50年来,河西走廊地区在人类活动强烈作用和区域气候变化双重驱动下,区域水文与生态环境发生了一系列变化。①区域出山径流过程表现为走廊东段的石羊河流域出山流量多年变化呈显著减少趋势,河西走廊中、西段的黑河流域和疏勒河流域年均出山流量则呈现递增趋势,但下游河流水量锐减并呈现明显的人为水文过程特征,水体盐化和污染趋势加剧,其中Ⅳ～Ⅴ级污染河道长度达到208km。②南部祁连山区森林面积减少约16.5%,自20世纪90年代以来逐渐有所恢复;北部天然荒漠森林则持续衰退,天然林加速消亡,仅额济纳和民勤两地减少林地34.31×104hm₂。草地生态呈现以面积减少、草地荒漠化和载畜能力降低等为特征的持续退化趋势,河西地区总体退化草地面积达46.86%。③近50年来河西土地沙漠化发展十分强烈,其发展速度在80年代初期最高达到年递增2.15%,80年代后期至90年代,全区域土地沙漠化过程出现明显的减缓。以流域为单元,进行水资源统筹利用规划与管理,统筹兼顾不同区域经济发展与生态环境建设对水的需求,以生态系统健康发展为原则,遵循生态规律来进行土地资源的开发利用,系统开展流域为单元的生态功能保护与建设是提高区域可持续发展能力的根本途径。

Features of eco-environmental changes in Hexi Corridor Region in the last50years and comprehensive control strategies

A series of changes have taken place in the last50years in regional hydrology and e-co-environment in Hexi Corridor region due to dual driving force of intense human activities and regional climate changes.(a)Regional runoff processes flowing out from mountains showed that mean annual outflow of the Shiyang River from mountains at the east section of the corridor tended to decrease significantly;annual outflow of the Heihe River and the Shule River at the middle and west sections of the corridor tended to increase,but the downstream discharge sharply decreased and displayed obvious anthropogenic hydrological features.Water salinization and pollution tended to be exacerbated,of which theⅣ～Ⅴgrades of polluted river course reached208km.(b)Forest area in the south Qilian Mountain region decreased by16.5%but it has gradually increased since the1990s.However,natural desert forest in the northern part of the corridor continuously degraded and rapidly disappeared,only in Minqin and Ejin counties about 34.31×10 4 hm 2 of woodland have disappeared.Grassland ecology showed a continuous degradation tendency,grassland area decreased,desertification exacerbated,carrying capacity re-duced and total area of degraded grassland in Hexi corridor region occupied46.86%.(c)Land de-sertification in Hexi corridor region developed rapidly in the last50years and reached a highest an nual rate of2.15%in the early1980s,but from the late1980s to the1990s its develop ment rate significantly reduced.The essential ways to improve regional sustainable development capa-bility are identified as to take river basin as an unit,make overall plans of water use and man-agement by taking water demand for economic development and eco-environmental construction of different regions in to consideration;to take healthy development of ecosystem as the principle,follow ecological laws to exploit and utilize land resources;and to take river basin as an unit,conduct systematic work to protect the ecological function.