Introduction

The plain of the Tuoshigan-Kumalake River is a oasis with vast evaporation. It is located northwest of the Tarim Basin and south of the Tianshan Mountain, in the upper Tarimu River Basin. This land has a long irrigation history and its ecological integrity is tightly linked to both natural hydrology and human impact. The local population uses the river water and spring water for free or at a very low cost. From 1980 to 2002, the irrigation area grew by a factor four (Fig. 1). Recently, environmental disturbances such as excessive reclamation due to the expansion of the agro-industry and consequent downstream drying up have increased. To counter these problems, a new regulation of water use for the Tarim River, has been developed. The regulation, which started operating at the end of 2001, was enacted to limit water use in the upper reaches of the Tarim River and rehabilitate the fragile ecosystem of lower reaches. The Tuoshigan and Kumalake River that converge at the Akesu River, the largest source of the Tarim River, are supposed to save water for the downstream areas. Civil works such as lining of irrigation ditches are planned or ongoing to help the area save water. In spite of the environmental impact studies that were performed before the civil works construction, the knowledge concerning the hydrological processes and water balance inside the Tuoshigan-Kumalake River plain is still limited. Some studies generally presented one special part of the hydrological characteristics, such as Li et al. (1997), Liang et al. (2003). However most studies only focused on the irrigation area, there is still no description of how the native plants are supplied with water and how the agricultural ecosystem affects the environment.

This study provides an integrated assessment of sources and quantities of discharge from the Tuoshigan-Kumalake River plain, offering recent records of agricultural water diversion entering the irrigation area, as well as calculated evapotranspiration from the irrigation area, native plants land and waste land inside the plain. The water supply to non-irrigation area and the groundwater exchange between irrigation area and non-irrigation area are focused to investigate how the agricultural ecosystem affects the environment in hyper-arid area. Due to data constrains, the study is limited to the period 1999-2002.