Study on vegetation ecological water requirement in Ejina Oasis

Abstract

The Ecological Water Requirement (EWR) of desert oasis is the amount of water required to maintain a normal growth of vegetation in the special ecosystems. In this study EWR of the Ejina desert oasis is estimated through the relational equation between normalized difference vegetation index (NDVI), productivity and transpiration coefficient, which was established by a combination of the RS, GIS, GPS techniques with the field measurements of productivity. The results show that about 1.53×10 8 m 3 water would be needed to maintain the present state of the Ejina Oasis, and the ecological water requirement would amount to 3.49×10 8 m 3 if the existing vegetation was restored to the highest productivity level at present. Considering the domestic water requirement, river delivery loss, oasis vegetation water consumption, farmland water demand, precipitation recharge, etc., the draw-off discharge of the Heihe River (at Longxin Mount) should be 1.93×10 8 ―2.23 ×10 8 3 to maintain the present state of the Ejina Oasis, and 4.28×10 8 ―5.17×10 8 m 3 to make the existing vegetation be re-stored to the highest productivity level at present.