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This paper presents the results of an exploratory study on scour occurring around submerged spur-dike. The effect of flow depth and spur-dike dimensions was studied with the help of the experimental data. It was found that the overtopping ratio and the opening ratio are significantly affected on the maximum scour depth. The larger opening ratios (a) caused relatively small scour area and the bank erosion downstream the spur-dike hardly can occur. The longer spur-dike length & the lower flow depth produced scour area wider than the shorter spur-dike length & the higher flow depth. The data collected in this investigation would be useful for the development of numerical models of scour around submerged dikes.

Achieving accurate parameter calibration is a relatively difficult problem in development and application of physically based distributed hydrological models. In the current research, Morris' screening method (one factor at a time [OAT]) and an error evaluation calibration were jointly adopted for parameter sensitivity analysis (PSA) for a distributed hydrological model developed for a single mountainous terrain. The results indicated that (1) the order of sensitivity of the parameters for rainfall−runoff calculation is thickness of the first soil layer, coefficient of permeability, infiltration velocity, porosity, and coefficient of roughness; (2) the order of the parameters for snowmelt calculation is bulk transfer coefficient, temperature correction factor, and albedo of snow cover layer surface; and (3) the value change of each parameter of the first layer in the soil vertical profile mainly impacts the numerical value of discharge of the surface flow, while the value change of each parameter of the second layer impacts the numerical value of discharge of the surface flow less, but results in the peak misplacement to some extent. The results are expected to provide methodology references for PSA and calibration for the physically based distributed hydrological model which developed for mountainous or otherwise single terrain. K E Y W O R D Sbasin, hydrological modelling, Morris' screening method (OAT), physical parameter, sensitivity analysis, surface water

Shallow groundwater in unconsolidated sediments represents a substantial water resource in the Chinese Loess Plateau. However, prior to development of the water supply for agriculture, annual and seasonal fluctuation of the recharge mechanism should be clarified. Since the region is arid, the effect of plant water uptake on groundwater fluctuation must also be assessed. A study was therefore undertaken to clarify groundwater recharge together with interaction between the plant ecosystem and shallow groundwater at a field site in the Loess Plateau of China. Observations showed that recharge response of the groundwater level (GWL) was limited except for intensive rainfall during the rainy season. The main recharge to the groundwater occurred from horizontai inflow from focused recharge at the upstream end of the site. Fluctuation of the GWL produced by piant water uptake was monitored during the growing season. For seasonal fiuctuation of GWL, temperature was most important, while for diurnal fluctuation of GWL during the growing season, solar radiation was most important. During the growing season, the GWL declined during the daylight hours and recovered during the night. The diurnal fluctuation was well synchronized with the solar radiation, consistent with plant-water uptake by shrubs surrounding one of the observation wells.