TEMPORAL AND SPATIAL VARIABILITY OF HYDRAULIC CONDUCTIVITY OF A STREAMBED IN A TYPICAL CONTINENTAL RIVER, CHINA

The hydraulic conductivity (K) of streambed sediment is a basic parameter in studying the exchange of water between surface sources and ground sources, the transport of solutes, etc. Inadequate understanding of K upper stream of the Tarim River makes it difficult to allocate water optimally. Particle sizes of streambed sediment upstream and midstream of the Tarim River were analysed and, coupled with data on water temperature and run-off, the spatial and temporal variation in K was studied. The results of the study were as follows. (1) In 132 sediment samples, the particle size was less than 5 mm; the sediment was predominantly sandy; and the Sauerbrei's formula proved to be the most reliable empirical formula. (2) At any given water temperature, K increased along the course of the river at locations upstream whereas K at midstream locations showed no obvious regularity. Changes in K with depth showed no consistent pattern. (3) At 20 degrees C, the mean value of K across all the locations was 44.29 m/d, that in the upper reaches was 64.53 m/d, and that in the middle reaches was 37.82 m/d; the difference was largely due to the differences in the process of sediment deposition.