Assessment of the flow regime alterations in the Lower Yellow River, China

Flow regimes have become a fundamental part of ecological informatics to reveal the complex interactional mechanism lying between flow regimes and ecological system. In this study, the changes of flow regimes were investigated to obtain the suitable flow regimes for maintaining the ecological integrity in the Lower Yellow River, China. The temporal abrupt for annual streamflow was explored with Mann-Kendall method (M-K method), and alterations of flow regimes at daily scale were described in accordance with Indicators of Hydrologic Alteration (IHA) and Histogram Matching Approach (HMA). Results showed that: (i) the annual flow presented a downward abrupt in 1984, and after that year, the flow magnitude was smaller in general, and the frequency of low flow was much higher during all the twelve months: (ii) during the post-impact period, both of the maximum and minimum flow magnitudes for 1-day, 3-day, 7-day, 30-day and 90-day declined, and frequency distribution distances were larger than 70% except for 1-, 3-, 7- and 30-day minimum flows; (iii) the number and duration of low pulse extended for the post-impact period, whereas the number and duration of high pulse decreased: and (iv) suitable ranges of monthly magnitude as well as number and duration days for high/low pulses were obtained (e.g., 743 to 3979 m(3)/s for monthly flow magnitude in July, August, September, October and November with similar target ranges, from 94 to 1075 m(3)/s for the rest seven months). The results indicate that the flow magnitude of the Yellow River has a decreasing trend, and some critical hydrologic characteristics should be taken into account due to their importance for ecosystems health in the downstream Yellow River Basin. (c) 2011 Published by Elsevier B.V.