A Natural Resource Management Guide for the County of Morris A ...

water table.
The world below the land’s surface is described, hydrologically,
in terms of zones, each specific in physical structure and role as
a vehicle for infiltrating water. First is the unsaturated zone, or
zone of aeration. Most of the pore space is filled with air, but
water occurs in the smaller openings as soil moisture and in a
capillary fringe (“zone above the water table in which water is
1
held by surface tension” ) that extends upward from the water
table. After a heavy rain the zone of aeration may become
almost saturated; in a long, dry spell it is nearly dry. With the
onset of rain, moisture taken up by plants is replaced;
subsequent percolating rainfall extends beyond the zone of
aeration to the
Traveling With Water
The water table marks the top of the saturated zone where all the openings are saturated. Having reached this
zone, rainwater's identity changes to ground water. An understanding of the water table and the thickness,
permeability, and composition of the overlying unsaturated zone is instrumental in estimating ground water
migration, whether in terms of recharge or movement of contaminant plumes.
All the land area transmitting water beyond the plant root zone, to the ground water, is considered to be the
ground water recharge area. The water table generally follows the topography although ground water divides
do not necessarily mirror surface water divides.
Ground water can recharge aquifers or provide base flow for surface waters. Where ground water meets the
surface it discharges into marshes, lakes, springs, or streams where it resumes its journey through the
hydrologic cycle via evaporation. Surface water bodies can either gain from or lose to ground water sources.
During dry periods, ground water can provide almost sole support to stream flow. Because of ground water's
interrelationship with surface water, stream flow data can enhance our understanding of regional recharge
rates, aquifer characteristics, and ground water quality and quantity.
Water table, and ground water levels are dynamic, reflecting seasonal and human
imposed influences impacting recharge and discharge. Normally, recharge occurs
during and immediately following precipitation. During early spring, frequent
rainfalls coupled with snowmelt result in rapid increases in ground water storage,
and a rise in the water table. Significant recharge also occurs during late fall, and
winter (unless the ground is frozen) when plants are dormant and evaporation is
minimal. In late spring, summer, and early fall, much potential recharge is lost to
evapotranspiration. Discharge on the other hand occurs continually, although at
varied rates. In addition to normal seasonal fluctuation, long term trends of either
above or below normal precipitation are manifested by a rise or fall in ground water
and water table levels, respectively.
Water Lobelia
1
U.S. Environmental Protection Agency, Wellhead Protection: A Guide For Small Communities, 1993.
A Natural Resource Management Guide
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