WWRC 94-09
Analysis of Rainfall-Infiltration Recharge to Groundwater
Abstract
Understanding the recharge process and its relationship with rainfall is
of critical importance to the management of groundwater systems. In
this research, in-situ lysimeter experiments, statistical methods, and
numerical simulations were used to study the process of rainfall-infiltration
recharge to the groundwater. With a shallow groundwater
table, each recharge process corresponds to an individual rainfall event.
Therefore, the infiltration-recharge can be predicted directly from rainfall
events through a statistical correlation. The advantage to use the
statistical correlation for estimating the recharge is a minimal
requirement of input data and computation effort, compared with
numerical simulations. As the depth to groundwater increases, the
degree of correspondence between rainfall and recharge processes
decreases. Below a certain depth, only the correspondence between
relatively large rainfall events and peaks in the recharge processes may
be observed. A technique was developed to separate the recharge
process corresponding to rainfall events, and a concept of effective
rainfall events was introduced to analyze the rainfall-recharge
relationship. If the water table is further deep, there will be only one
peak in the annual recharge process, and the processes of different
years may overlap. Only a correlation between the annual precipitation
and infiltration-recharge can be obtained. For a very deep water table,
the variation of the infiltration-recharge rate becomes quite small, which
can be approximated as a constant. The recharge rate may be
determined using an annual or multi-year water balance.
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