Thursday, March 28, 2013

Sustainable Groundwater in Virginia

USGS groundwater monitoring well Prince William County, VA

It’s almost spring here on the edge of rural Virginia and time to think about the water supply. Last year was a dry summer over much of the continental United States and groundwater levels in Virginia were negatively impacted. The snow, sleet, and rain we’ve had in the past two months have soaked the ground ending the drought conditions lingering from last year. If your water like mine is supplied by a well, you need to be aware of the factors that impact your water supply and practice household water conservation in times of drought or low supply to live within your annual water resources. There are dry years and wet years and water availability will vary, though it is not always obvious. The groundwater aquifer you tap for water is not seen and has no supply gauge, but still you have to be aware of your water budget and live within it, something that transplants from the suburbs and city are not always aware of. No water supply is unlimited and a well is limited by the aquifer and age and condition of the well and you need to be aware of your water use. 

The good news for us in Virginia is that according the U.S. Drought Monitor, Virginia is no longer in drought conditions, but the U. S. Geological Survey, USGS, is still showing 20% of the groundwater monitoring wells in Virginia at below average water levels for this time of year. A deluge of heavy rains could change that in a hurry since the soil in our region is no longer dry.  I feel quite lucky that the monitoring well up the road from my house is showing a higher than average water level for the 39 years of monitoring data the USGS has. Nonetheless, unless my neighbors and I use the groundwater sustainably, we could all run out of water during the dog days of summer.
This low spot off Logmill Road took 36 hours to soak in after the last rain.

The water level in a groundwater well usually fluctuates naturally during the year. Groundwater levels tend to be highest in the spring in response to winter snowmelt and spring rainfall when the groundwater is recharged. Groundwater levels begin to fall in May and typically continue to decline during summer as plants and trees use the available shallow groundwater to grow and streams draw water to supplement their flow. Natural groundwater levels usually reach their lowest point in late September or October when fall rains begin to recharge the groundwater again.

The natural fluctuations of groundwater levels are most pronounced in shallow wells that are most susceptible to drought. Older wells in areas near springs and rivers tend also to be shallow, because they were installed before modern equipment in the shallow first aquifer that is immediately impacted in drought. Most modern wells are drilled wells that penetrate about 100-400 feet into the bedrock.  However, deeper wells may be impacted by an extended drought and take longer to recover. In addition, water production in a well tends to decrease over time because sediment builds up in a well. To provide a reliable supply of water, a drilled well must intersect bedrock fractures containing ground water and the natural occurring sediment, minerals and slime producing bacteria can clog those fractures over time. Without a geological event like an earthquake, groundwater changes tend to happen slowly as water use grows with increased population or irrigation and recharge is impacted by adding paved roads, driveways, houses and other impervious surfaces diminishing the water supply over time.

Groundwater and surface water are interconnected, yet the law in Virginia and most of the east coast treats surface water rights differently from groundwater rights. The rights to surface water in Virginia, as well as inmost Eastern states, are allocated based on the riparian doctrine. This rule gives an owner of land bordering on water the right to use that water so long as the use does not unreasonably affect the water available to other riparian land owners. Rights to groundwater, on the other hand, are governed by the American Rule. This permits an unlimited use of groundwater beneath one’s land so long as it is not wasteful and is used in a manner consistent with the use of the land lying above the water even if your water use impairs your neighbor’s well. This potentially leaves groundwater in the eastern states subject to unsustainable use and as our water resource are needed to serve more and more people we need to develop sustainable methods of managing groundwater and the rights to the water.    

No comments:

Post a Comment