We have opportunities to affect our ground water in a positive or negative way.
Wise use and management of our water will provide for our needs but overuse and
unwise use of our water can lead to very negative consequences for our water
system.
General Threats to Our Ground Water
- Saltwater Intrusion
- Lowered Ground Water Level
- Contamination
Saltwater Intrusion
Intrusion of
saltwater into fresh ground water aquifers can be caused by:
1) wells that tap water too close to saltwater
2) wells too close to the shore
3) wells that pump at an excessive rate
4) or some combination of the above
Due to the characteristics of
the Yorktown-Eastover Aquifer system, saltwater intrusion is more of a concern in these
aquifers than the Columbia Aquifer.
Lowered Ground Water Level
All wells cause some loss of ground water level around them. This area is called
the cone of depression. If pumping rates are too high or wells are too close
together, ground water level can drop so low that the water that comes from the well
is reduced. In extreme cases, the water level can fall so low that the material
around the well can be dewatered. Without water to hold the pores in this material
apart, pores will compact and a permanent loss of water results. This will in turn
affect the well and how much water it can yield.
The major source of fresh water
on the Eastern Shore is the Yorktown-Eastover Aquifers and since more industrial,
municipal and private systems use this water these aquifers have more potential
to be damaged by lowered ground water levels.
Preliminary Results of the Eastern Shore of Virginia Ground Water Model showing
change in water levels in the Upper Yorktown-Eastover Aquifer over the last 80 years.
Contamination
The Columbia Aquifer is the most at risk for contamination. The Columbia is the
water table aquifer and is generally found within 20 feet of the surface in the
middle of the Shore and less than 6 feet near the edges of the Shore. Much of the
earth in this aquifer is sand which allows water and contaminants
to rapidly soak into the ground. Some private residences use this aquifer for
drinking water but this aquifer is highly vulnerable to contamination. Major potential
sources of ground water contamination on the Eastern Shore include fertilizer,
pesticides, petroleum (gasoline, diesel, and oil), and wastewater from improperly
constructed or maintained septic systems.
