ALBERT

Description: Evaluation of stream-aquifer interaction and water balance for a catchment often requires specific information on streambed parameters, such as streambed hydraulic conductivity, seepage flux across the streambed etc. This paper describes a simple, inexpensive instrument that is used to measure these streambed parameters under the condition of a stream disconnected from groundwater. Our method includes a seepage cylinder for simulation of river water depth. The proposed method was applied to estimate the vertical hydraulic conductivity of a streambed and the changes in vertical seepage rate from stream to groundwater with varied stream water depth in the Manasi River of Xinjiang Uygur Autonomous Region, China. The vertical hydraulic conductivities of the streambed determined from twelve sites along the Manasi River vary from 1.01 to 29.m/day where the stream disconnects from the groundwater. The experimental results suggest that there are two kinds of relations between the vertical seepage rate and the simulated stream water depth. One is a linear relation between the two variables with low Reynolds numbers (less than 10); the other is a nonlinear relation (exponential relation) between the two variables with larger Reynolds numbers (greater than 10). This second relationship is quite different from the traditional model that usually calculates the vertical seepage rate from stream to groundwater under the condition of disconnection using a linear relation (Darcy's Law). Our results suggest that a linear relation can only be used for a limited range of river water depth. This method gives a convenient tool for rapidly estimating the streambed hydraulic conductivity and the changes in the vertical seepage rate across streambed with varied stream water depths for the case of a stream disconnected from groundwater. This article is protected by copyright. All rights reserved.

Description: This study examined the effects of different soil texture configurations on water movement and solute transport to provide a reliable scientific basis for the application of negative-pressure irrigation (NPI) technology. HYDRUS-2D was used to analyze water movement and solute transport under NPI. The main results are as follows. (1) HYDRUS-2D can be used to simulate water movement and solute transport under NPI, as there was good agreement between the simulated and measured values for water contents, NaCl concentrations, and wetting distances in the horizontal and vertical directions; the Nash–Sutcliffe efficiency coefficients were in the range of 0.94–0.97. (2) Layered soils have obvious effects on water movement under NPI. With the emitter position in the loam layer, when a coarse texture of loamy sand was present below the loam layer (namely, L-LS), irrigation water accumulated in the topsoil, and this led to an increase in evaporation compared with the homogeneous loam profile. However, fine texture silty loam or silty clay loam layers beneath the loam layer (namely, L-SiL or L-SiCL, respectively) was more conducive to water infiltration into the lower layer, and this increased the amount of water infiltration and simultaneously reduced the surface evaporation effectively. (3) Layered soils have obvious effects on solute transport under NPI, and salt accumulation will readily occur in the clay-rich soil layer at the interface. The maximum soil salt accumulation of L-LS occurred above the soil interface between the two soil layers with a value of 21.8 g kg -1 ; however, for L-SiCL and L-SiL, the maximum salt accumulation occurred below the soil interface between the two soil layers, with values of 23.8 g kg -1 and 20.08 g kg -1 , respectively. (4) Interlayered soils showed remarkable changes in the water infiltration characteristics and salt-leaching intensities under NPI, and the properties for the soil profile with a silty loam interlayer were better than those for the soil profile with a silty clay loam interlayer. The soil profile with a loamy sand interlayer had the lowest amount of water infiltration, which resulted in reductions of the salt-leaching intensities. Thus, NPI is clearly not suitable for loamy sand soil. Overall, the results demonstrated that soil texture configurations affected water movement and solute transport under NPI. Therefore, careful consideration should be given to the use of NPI to achieve target soil water and solution conditions and reduce water loss.

Description: Evaluation of stream-aquifer interaction and water balance for a catchment often requires specific information on streambed parameters, such as streambed hydraulic conductivity, seepage flux across the streambed and so on. This paper describes a simple, inexpensive instrument that is used to measure these streambed parameters under the condition of a stream disconnected from groundwater. Our method includes a seepage cylinder for simulation of river water depth. The proposed method was applied to estimate the vertical hydraulic conductivity of a streambed and the changes in vertical seepage rate from stream to groundwater with varied stream water depth in the Manasi River of Xinjiang Uygur Autonomous Region, China. The vertical hydraulic conductivities of the streambed determined from 12 sites along the Manasi River vary from 1.01 to 29.m/day where the stream disconnects from the groundwater. The experimental results suggest that there are two kinds of relations between the vertical seepage rate and the simulated stream water depth. One is a linear relation between the two variables with low Reynolds numbers (less than 10); the other is a nonlinear relation (exponential relation) between the two variables with larger Reynolds numbers (greater than 10). This second relationship is quite different from the traditional model that usually calculates the vertical seepage rate from stream to groundwater under the condition of disconnection using a linear relation (Darcy's Law). Our results suggest that a linear relation can only be used for a limited range of river water depth. This method gives a convenient tool for rapidly estimating the streambed hydraulic conductivity and the changes in the vertical seepage rate across streambed with varied stream water depths for the case of a stream disconnected from groundwater. © 2013 John Wiley & Sons, Ltd.