Introduction
to Basic Ground-Water Flow
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By
the earthDr!
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Describing
Ground-Water Flow using Equipotentials
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Looking
at the figure below, it is evident that ground-water flow is in the direction
of the red arrows which follow the steepest grade at the surface of the
water table. These arrows are at right angles to the ground-water
contour lines (equipotential lines). The construction of contour
lines is not limited to just
A 3-dimensional view of the water table is depicted in this figure using equipotential lines (equipotential lines are often referred to as water table contour lines when they are depicted at the surface of the water table). In a 3-dimensional view such as this, it is possible to display equipotential lines in both a cross-sectional view (side view) and in a plan view (downward view from overhead) for all water table elevations. Notice that the cross-sectional equipotential line of 88 foot also shares this contour line with the plan-view equipotential line of 88 foot. All of the cross-sectional equipotential lines are paired in like manner with one, and only one, plan-view equipotential line of similar magnitude. These paired equipotential lines when turned about their origin describe a plane (flat surface), unless these equipotential lines are describing some boundary of a curved equipotential surface. Equipotential surfaces assist in visualization of water-table flow, but from a 3-dimensional perspective. Remember: just as surface runoff flows as sheet flow over hilly terrain, at a right angle to imaginary contours of the surface grade, so too does ground water flow at a right angle to equipotential lines and normal to the equipotential surface. This sectional view of the water table is a 3-dimensional view. A 3-dimensional view is not a typical way to present ground-water flow. The presentation of a cross-sectional view (this last figure) of equipotential lines is not as common as a plan view presentation of equipotential lines. Development of cross-sectional equipotential lines requires |
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EMAIL:
earthDr@earthDRx.org |
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