Study On Seepage Water Loss In Lower Reaches Of The Yellow River

The lower reaches of the Yellow River is a "suspended" river. Stream water recharges shallow groundwater throughout the year and contributes a significant part to stream natural water loss. In this study, basing on analysis of physical geographical, geological, and hydrogeological conditions, the streambed hydraulic conductivities (K) of the lower reaches of the Yellow River have been determined by using in-situ standpipe test and laboratory grain size analysis test. In-situ standpipe tests from Huayuankou, Gaocun, Sunkou, Aishan and Luokou, give streambed vertical hydraulic conductivities (K_v) of 0.71, 0.29, 0.34, 0.19 and 0.24 m/d respectively. Streambedhorizontal hydraulic conductivity (K_h) at Huayuankou is 1.81 m/d and the ratio of K_h to K_v is about 2.6, implying anisotropic streambed sediment. Compared withlaboratory grain size analysis test, in-situ standpipe test represents in-situ condition better, gives reliable results, easily to operate and consumes short time. Besides, the modified Rosin-Rammler model developed in this study presents the best-fit of a grain size distributional model curve to experimental points.By use of groundwater dynamics method to estimate stream water seepage loss in different time scales, where the observed stream water level, runoff, and maximum water depth are chosen as variables to obtain regression equations for seepage water loss in different sections of the stream. Within the study time period, seepage water loss is maximum (9.67×10~8m~3) in the year 2004 and minimum (6.21×10~8m~3) in 1997, with an annual average being8.01×10~8m~3. Seepage water loss is mainly influenced by runoff and withdrawal for agricultural and industrial purposes. Annual seepage water loss per channel length decreases as flow path extends to the lower reach and it is maximum value in the section between Huayuankou and Jiahetan.For the last part, cumulative average deviation and parameters for non-uniformity, concentration and amplitude of variation are introduced to analyze inter-annual and annual distribution laws of seepage water loss among the recent 15 years (1991 ～ 2005). Annual distribution of seepage water loss in the year 1996 and 2001 are respectively the most uniform and non-uniform. Average annual seepage water loss during concentration period (in August) accounts for 10% of the annual value, and monthly seepage water loss comes to the minimum value in February. The above...