干旱区生态环境知识资源中心

The Tuoshigan-Kumalake River alluvial plain is a vast evaporation oasis (annual rainfall of less than 100 mm) located in the upper Tarim River, a large inland river in central Asia. Regulations have been enacted recently to limit water use in the plain because large water consumption reduces the discharge to downstream and jeopardizes the ecosystem of the lower reaches of the Tarim River. Engineering works are planned, or are under construction, to save water but without consideration for the hydrological connections within the plain. The objective of this paper is to investigate the hydrological cycle inside the plain, which is impacted by intensive cultivation, and to highlight the interactions between the cultivation system and the natural ecosystem. A conceptual water balance methodology was used for evaluating the water transformations between the river channel irrigation ditches, irrigation area and non-irrigation area based on the records of water diversion, spring flow studies, and monitoring of precipitation, temperature and other hydrological parameters. Water budgets for the mainstem of the Tuoshigan-Kumalake and the Wushi and Wensu sub-areas were calculated for the alluvial plain for the period 1999-2002. Results show that the irrigation system is inefficient in using earth ditches on sandy soil and that groundwater exchange between the irrigation and non-irrigation areas accounts for nearly half of the water supply to the non-irrigation area, which suggests that any human disturbance to the irrigation system might rapidly influence the surrounding natural ecosystem.