Everything about Groundwater Recharge totally explained
Groundwater recharge or
deep drainage is a
hydrologic process where
water moves downward from
surface water to
groundwater. This process usually occurs in the
vadose zone below plant
roots, and is often expressed as a
flux to the
water table surface. Recharge occurs both naturally (through the
water cycle) and anthropologically (for example, "artificial groundwater recharge"), where rainwater and or
reclaimed water is routed to the subsurface.
Groundwater is normally recharged naturally by rain, though this may be impeded by human activity such as paving ground or cutting down forests, which result in the
water running off and flowing away down drains, creeks and rivers, after falling as rain. Use of groundwater, especially for farming, may also lower the water tables. Groundwater recharge is an important process for
sustainable groundwater management, since the volume-rate
abstracted from an
aquifer should be less than or equal to the volume-rate that's recharged.
Recharge can help move excess salts that accumulate in the root zone to deeper soil layers, or into the ground water system. This is evident through the
salinity of the upper soil layers, where at least 25,000 km² of Australia and 5% of current cultivated land has elevated salinities. Another environmental issue is the disposal of waste through the water flux such as dairy farms, industrial, and urban
runoff.
Estimation methods
Rates of groundwater recharge are difficult to quantify, since other related processes, such as
evaporation,
transpiration (or
evapotranspiration) and
infiltration processes must first be measured or estimated to determine the balance.
Physical
Physical methods use the principles of
soil physics to estimate recharge. The
direct physical methods are those that attempt to actually measure the volume of water passing below the root zone.
Indirect physical methods rely on the measurement or estimation of soil physical parameters, which along with soil physical principles, can be used to estimate the potential or actual recharge.
Chemical
Chemical methods utilize the presence of water-soluble substances, such as
isotopic tracer, moving through the soil, as deep drainage occurs.
Numerical models
Recharge can be estimated using
numerical methods, using such
codes as
HELP,
UNSAT-H,
SHAW, and
MIKE SHE. The 1D-program
HYDRUS1D is available online. These codes generally use
climate and
soil data to arrive at a recharge estimate, and use
Richards equation in some form to model groundwater flow in the
vadose zone.
Further Information
Get more info on 'Groundwater Recharge'.
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