The effect of hydrologic process changes on NDVI in the desert-oasis ecotone of the Hexi Corridor

In the arid inland river basins of northwestern China, human activities control almost all the surface hydrologic processes. The potential effects of these altered hydrologic processes are gradually becoming clear, especially since the 2000 implementation of the integrated water resources management projects in the Shiyang River, the Heihe River, the Tarim River, and the Shuler River. While the appearance of these eco-hydrology changes and consequent environmental effects in the oasis has attracted broad attention, related research is still lacking. Eco-hydrological process changes in the desert-oasis ecotone were investigated in the Pingchuan irrigation district in the middle reaches of the Heihe River. The results showed that the annual average amount of surface water irrigation during the past 20 years has decreased by 1.498x10(7) m(3), while the annual average amount of well irrigation has increased by 1.457x10(7) m(3), since 2000, when the State Council of China approved the water diversion scheme for the Heihe River Basin. The groundwater depth before the water diversion scheme generally varied between 2.44-3.19 m (average 2.73 +/- 0.24 m), while that after the water diversion scheme has varied between 3.08-4.01 m (average 3.79 +/- 0.62 m). The distribution area of < 3 m groundwater depth decreased from 3612 to 394 hm(2); while the distribution area of > 3 m groundwater depth increased from 853 to 3843 hm(2). However, although the hydrologic processes changed dramatically, no significant effects on vegetation productivity in the desert-oasis ecotone were detected during the study period.