1. Diana L. Duckworth Rustburg High School Campbell County Schools
Groundwater
Diana L. Duckworth
Rustburg High School
Campbell County Schools

2. Key Concepts Porosity: percentage of the rock that is empty space
Depends on grain size, shape, & sorting
Permeability: ability of a rock to yield water
Depends on grain size (larger grains have larger pores), grain shape, & sorting
Large pores, less impact of friction
Rounded grains, larger pores
Poor sorting, small grains fill in pores & reduce permeability

3. Distribution of Water Underground
Zone of Aeration
Pores filled with air
Water Table
Surface of Zone of
Saturation
Pore space filled
With water
Water infiltrates ground when it rains. Percolates down
under the force of gravity.

4. Water table reaches surface at springs, rivers, & lakes
Water table follows the shape of the land.
Water flows downhill underground.
Lakes
River
Side View
Water flows from high ground into
streams, lakes & marshes.

5. Man’s Usage of Groundwater
Two kinds of wells:
Ordinary well that requires pumping
Artesian well where water rises to surface without pumping
Recharge Area
Aquaclude
Artesian Aquifer

6. Two water levels Ordinary Wells Static water level Pumping water level
Drawdown
Cone of
depression
Side View

7. Problems with Overexploitation
Withdrawals in excess of recharge rates:
Artesian wells lose pressure, must be pumped
Ordinary wells can produce overlapping cones of depression
Lead to dewatering of aquifer
Lower stream levels in drought
Salt water intrusion in coastal areas
island
ocean
lagoon
Salt water table
Fresh water
floats on salt water

8. Hillside Springs Perched water table Spring Aquaclude
Roaring Springs, North Rim
Grand Canyon

9. Groundwater Budget Income = precipitation
Outgo = runoff + evapotranspiration
Surplus: precipitation is greater than evapo-transpiration & runoff
Water table rises
Deficit: precipitation is less than evapo-
transpiration & runoff
Water table falls
Steady state: precipitation = evapotranspiration & runoff
Water table stays steady
Water Balance Equation P = E + R + G
Where G = change in water table

10. Caves CO2 dissolves in groundwater Dry caves Becomes acidic
Dissolves limestone
Joints enlarged into caves
Dry caves
Dripping water evaporates
Creates stalactites & stalagmites

11. Sinkholes Roof of cave collapses Leaves circular depression
May fill with water
Map view
sinkhole
cave
SIDE VIEW

12. Groundwater Topography
Karst topography
Sinkholes
Caverns
Disappearing streams
Ponds with no surface outlet
Limestone terrain