Some experimental results concerning rapid water table response to surface phenomena

The water balance of a 600 mz field site on a lateritic hillslope in Kerala, southwest India, has been studied during two southwest monsoon seasons. Surface runoff was of minor importance while infiltration and evapotranspiration were the major components amounting to approximately 2/3 and 1/3 of the rainfall, respectively. Groundwater response was rapid, involving fluctuations of several metres. Recharge mechanisms hypothesized are water movement via preferred pathways from the ground surface to the capillary fringe where rapid rise in groundwater level is brought about by a transmitted pressure pulse. Groundwater recharge was found normally to take place during the southwest monsoon season only. The field study demonstrates that seasonal shallow groundwater recharge representing the major portion of the rainfall may be observed in this lateritic terrain in the humid tropics. It indicates a good potential for further groundwater development. Moreover, conditions are conducive to a considerable contribution to possible recharge to deeper aquifers. The observed groundwater recharge is the result of a complex process on which further research will throw more light.

Section: Soil Moisturementioning

confidence: 99%

A water balance study in lateritic terrain

Langsholt

1992

“…In addition, rises in shallow water table could increase risk of temporary groundwater flooding because of rapid water table responses to storm events. Earlier studies have observed disproportionate rises in water table elevations after intense rainfall (Kayane and Kaihotsu, 1988;Waswa et al, 2013). Germann and Levy (1986) attributed the rapid rise in water table elevation in response to precipitation to capillary fringe groundwater ridging in which a small addition of water to the capillary fringe resulted in a rapid and large rise in water table elevation that drops immediately after the storm.…”

Section: Introductionmentioning

confidence: 99%

Modelling soil water dynamics considering measurement uncertainty

Kisekka

Migliaccio

Muñoz‐Carpena

et al. 2014

In shallow water table‐controlled environments, surface water management impacts groundwater table levels and soil water dynamics. The study goal was to simulate soil water dynamics in response to canal stage raises considering uncertainty in measured soil water content. Water and Agrochemicals in the soil, crop and Vadose Environment (WAVE) was applied to simulate unsaturated flow above a shallow aquifer. Global sensitivity analysis was performed to identify model input factors with the greatest influence on predicted soil water content. Nash–Sutcliffe increased and Root Mean Square Error reduced when uncertainties in measured data were considered in goodness‐of‐fit calculations using measurement probability distributions and probable asymmetric error boundaries, implying that appropriate model performance evaluation should be carried out using uncertainty ranges instead of single values. Although uncertainty in the experimental measured data limited evaluation of the absolute predictions by the model, WAVE was found a useful exploratory tool for estimating temporal variation in soil water content. Visual analysis of soil water content time series under proposed changes in canal stage management indicated that sites with land surface elevation of less than 2.0‐m NGVD29 were predicted to periodically experience saturated conditions in the root zone and shortening of the growing season if canal stage is raised more than 9 cm and maintained at this level. The models developed could be combined with high‐resolution digital elevation models in future studies to identify areas with the greatest risk of experiencing saturated root zone. The study also highlighted the need to incorporate measurement uncertainty when evaluating performance of unsaturated flow models. Copyright © 2014 John Wiley & Sons, Ltd.

A threshold condition for soil‐water transport

Torres

2002

The unsaturated flow equation is a robust tool for predicting water movement through fully characterized soils with well-defined sets of initial and boundary conditions. On the other hand, Beven (1989) and Germann (1990) for 50 min, stopped irrigating for 20 min, and then rained at 200 mm h −1 until the prism collapsed at 11 min. During the initial irrigation, the pressure heads increased to near-zero, and soil-water contents increased to ∼0·35 (porosity ∼0·50). These values changed