Spatial variability plays an important role in nonlinear hydrologic processes. Due to the limitation of computational efficiency and data resolution, subgrid variability is usually assumed to be uniform for most grid-based rainfall-runoff models, which leads to the scale-dependence of model performances. In this paper, the scale effect on the Grid-Xinanjiang model was examined. The bias of the estimation of precipitation, runoff, evapotranspiration and soil moisture at the different grid scales, along with the scale-dependence of the effective parameters, highlights the importance of well representing the subgrid variability. This paper presents a subgrid parameterization method to incorporate the subgrid variability of the soil storage capacity, which is a key variable that controls runoff generation and partitioning in the Grid-Xinanjiang model. In light of the similar spatial pattern and physical basis, the soil storage capacity is correlated with the topographic index, whose spatial distribution can more readily be measured. A beta distribution is introduced to represent the spatial distribution of the soil storage capacity within the grid. The results derived from the Yanduhe Basin show that the proposed subgrid parameterization method can effectively correct the watershed soil storage capacity curve. Compared to the original Grid-Xinanjiang model, the model performances are quite consistent at the different grid scales when the subgrid variability is incorporated. This subgrid parameterization method reduces the recalibration necessity when the Digital Elevation Model (DEM) resolution is changed. Moreover, it improves the potential for the application of the distributed model in the ungauged basin.
OPEN ACCESSWater 2015, 7 2692
The solidification technology can meet the requirements of landfill by enhancing the sewage sludge strength. The solidified sludge strength would be decreased by landfill leachate action because the acid could dissolve the hydrated materials. Chemical kinetics equation was obtained by reaction order α, β and rate constant k, which reflected the acid effect on hydrated materials by Ca2+ and were got based on the laboratory experiments. The research results showed that the strength loss could be neglected in engineering because pH value of leachate possessed less impaction on solidified sludge strength. Moreover, after adding clay minerals, the strength loss is smaller and the buffering capacity is stronger.
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