Recognition the Spatio-temporal Patterns of Low-flow Changes in the Yellow River over the Last Half Century

Low flow is widely regarded as the primary flow conditions for the anthropogenic and aquatic communities in most rivers, particularly in such an arid and semi-arid area as the Yellow River. In this study, a procedure combining Mann-Kendall trend test, wavelet transform analysis and spatial mapping techniques is presented to identify the spatio-temporal patterns of low-flow changes in the Yellow River (1955-2005). The results indicate that: 1) no trends can be detected in the major low-flow conditions in the upper Yellow River, while downward trends can be observed in the middle and lower Yellow River; 2) similar patterns of periodicity are detected in the 7-day min (AM7Q) in the upper and middle Yellow River, while different patterns are found in the lower Yellow River; 3) the increasing coefficients of variance of primary low-flow conditions suggest the variability of the low flow is increasing from the upper to lower stream; 4) climate changes and uneven temporal-spatial patterns of precipitation, jointly with highly intensive water resource utilization, are recognized as major factors led to the decreasing of low-flow in the lower Yellow River in recent decades. The current investigation will be beneficial to regional water resources management for the Yellow River basin, characterized by serious water shortage.