Eco-hydrological alternation of Wei River in China

Altered flow regime due to river regulation and water development projects has been identified as a major factor in the deterioration of riverine ecosystem. The moving average method and Mann-Kendall statistical test are used to assess the trends of the annual flow. Four methods of Orderly cluster analysis, Pettitt statistical test, Rank sum test and Mann-Whitney statistical test are used to determine the significant change point which divided flows into two sequences of pre-influence and post-influence. Indicator of Hydrologic Alteration (IHA) and the Range of Variability Approach (RVA) method are used to calculate the eco-hydrologic target and study the eco-hydrological characteristics of post-influence. The results of Wei River show that annual flow at Linjiacun, Xianyang and Huaxian stations have decreased significantly. The significant change points are in 1990, 1990 and 1993 respectively. Indicators of July average flow, the average annual minimum flows, date of maximum, high pulse count, fall rate show significant increase and the overall degree of hydrological alteration for the three stations are 70.61%, 74.25%, 73.05% respectively, indicating a high degree of alteration. According to the regulation of eco-hydrologic alternations, it is considered that the key to protect river ecosystem is to meet the base flow and maintain flows within the eco-hydrology target range.