Storage coefficient revisited: is purely vertical strain a good assumption?

The storage coefficient that is used ubiquitously today was first defined by the analytical work of Theis and Jacob over a half-century ago. Inherent within this definition is the restriction of purely vertical compression of the aquifer during a reduction in pressure. The assumption is revisited and quantitatively evaluated by comparing numerical results using both one- and three-dimensional strain models in the presence of three-dimensional flow. Results indicate that (1) calculated hydraulic head values are nearly identical for both models; (2) the release of water from storage in terms of volume strain is nearly identical for both models and that the location of maximum production moves outward from the well as a function of time; (3) the vertical strain components are markedly different with at least 50% of the total volume of water pumped originating from horizontal strain (and increasing to as much as 70%); and (4) for the one-dimensional strain model to yield the necessary quantity of water to the pumped well, the resulting vertical compaction (land subsidence) is as much as four times greater and vertical strain is as much as 60% greater than the three-dimensional strain model. Results indicate that small changes in porosity resulting from horizontal strain can yield extremely large quantities of water to the pumping well. This study suggests that the assumption of purely vertical strain used in the definition of the storage coefficient is not valid.     

Watershed science:Bridging new advances in hydrological science with good management of river basins

<正>Watershed science traditionally refers to the themes of hydrology and water resource management.Watershed science has been experiencing a rapid evolution that thrives on a forceful superimposition of multi-discipline and innovative earth observing and information techniques.The water and its interactions with other systems in a watershed is increasingly becoming a focus in scientific communities,and several new disciplines such as ecohydrology,ecoeconomics,environmental hy-     

Is the connectivity function a good indicator of soil infiltrability distribution and runoff flow dimension?

Among the studies on runoff connectivity of soils with heterogeneous properties, the need to understand the relationships between soil heterogeneity and the associated runoff organization and amount is frequently mentioned. In this study, we simulate the stationary runoff–runon process on bi‐dimensional (2D) flat slopes for five infiltrability distributions, one of them correlated, as a function of rainfall intensity and flow dimension. We define flow dimension by 1 + ε, where ε is the outflow fraction transferred from one pixel to each of the two lateral downslope pixels. Our aim is to assess the effect of ε and soil heterogeneity on the connectivity function compared to the mean runoff flow rate, the wet area and the number of runoff patterns. The analysis of connectivity is carried within the percolation framework. The results show that the integral connectivity scale is more sensitive to the flow dimension and soil heterogeneity compared to the other variables. The wet area fraction does not depend on ε. Unlike previous studies, we find that increased runoff production is not necessarily related to increased connectivity. The use of the connectivity function within the percolation framework appears to be a valuable method for assessing the impact of soil heterogeneity and flow dimension on the runoff organization during a rainfall event. Copyright © 2014 John Wiley & Sons, Ltd.