塔里木河流域水资源开发利用及其环境效应

近30a来,由于塔里木河流域水资源无序的开发利用,导致了严重水土环境退化.从20世纪50-70年代,下游300km河道逐渐干涸,致使下游水文过程和生态环境严重破坏.1960-1980年下游水位由2～4m下降到4～10m;1980年后,水位年降速率是20cm.1958-1978年,塔里木河流域胡杨减少了2/3,生物量下降了1/2;1950-1990年代,塔里木河下游主要树种胡杨林减少了3820km²,而灌木和草地面积减少了200km².这种水文变化已导致水环境的明显恶化,并引起了土地沙漠化,1960-1990年代形成沙漠化土地12300km².塔里木河的盐分含量逐渐升高,1960年的最大含盐量是1.28g·L^-1,但1981-1984年达到4g·L^-1,到1998年达7.8g·L^-1.根据对沙漠化土地有机碳含量推算,近30a塔里木河流域土壤由于退化向大气中释放的有机碳多达112Tg,且28.3%来自表层0～1.0m土壤.人类活动的强度干扰是导致以上水环境变化的重要原因,解决问题的关键是提高对水资源与水土环境监测、观测、管理和恢复的科学与技术水平.

Utilization of Water Resources and Its Environment Effect in the Tarim River Basin

Increases in exploitation and utilization of water resources over the last thirty years have led to significant environmental and hydrological degradation of the Tarim River basin. Water of the lower reaches has been seriously compromised. The lower reaches, 300 km in total, have dried up since the 1950s-1970s. The water table decreased from 2～3 m to 4～10 m from 1960 to 1980, and the decreasing rate of the water table is 20 cm per year from 1980 to the present. Populus euphtatica declined by two-thirds and the biomass decreased by one-half from 1958 to 1978 in the basin. From the 1950s to the 1990s, the forest area of P. euphratica and E. angustifolia, the main tree species in the basin, declined by 3820 km² in the lower reaches in the basin, and the shrub and meadow area declined by 200 km². The hydrological change results in a marked degradation of aquatic habitats, and causes substantial land desertification. A total of 12300 km² of desertified lands formed from the 1960s to the 1990s. During the past 30 years, the salt content of the Tarim River increased gradually according to the observation in the Alar Hydrological Station. The maximum salt content was 1.28 g·L^-1 in 1960, but reached 4.0 g·L^-1 in 1981-1984 and 7.8 g·L^-1 in 1998. Based on the present organic carbon content in desertified lands, it is calculated that the total emission of C into atmosphere in the last 30 years reached 112.2 Tg due to the hydrological degradation, of which 28.3% came from the surface layers, 0～1.0 m in depth. Among the factors contributing to these problems, human activities are foremost. Solving these problems will require raising the level of scientific and technological expertise in the monitoring, conservation, protection, and rehabilitation of water resources and associated habitats. Presently, the greatest priority is to expand and improve the conservation and optimal allocation of soil-water resources in the basin.