Groundwater Awareness Week

It’s National Groundwater Awareness Week (March 10-16, 2014). According to George Harlow at the US Geological Survey (USGS) in Richmond, VA about 34% of all drinking water in Virginia is supplied by groundwater and there are 1.7 million Virginians whose drinking water is sourced from groundwater and supplied by their own private wells. Well ownership comes with the responsibility of keeping the water well in good working order and managing your own water supply. Ensuring that your water is safe to drink, of good quality is your responsibility and should be done annually. Managing your water use is an on-going challenge.

The groundwater aquifer you tap for water is not seen so 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. Many who are on public water on the east coast are very accustomed to thinking of water supply as unlimited. Your well is not unlimited and living with a well you need to be aware of your water use and water budget. A diminished water supply can be caused by drop in water level in the well due to drought or over pumping of the aquifer, or the well could be failing (though equipment problems are the most common cause of well failure). Groundwater supply and quality can and do change because groundwater systems are dynamic.

The National Ground Water Association (NGWA) and most health departments recommend that private well owners test their water annually for at a minimum bacteria and nitrate. When you bought your house in all probability you only tested your water for was bacteria, that is not adequate to ensure your water supply is safe. There are many other contaminants that might be of local concern that you could test for and there are common contaminants that can be health hazard or water quality issue; however, not every contaminant needs to be tested for each year. The quality of your water will be determined by the source of the groundwater, the ability of your local geology to protect or impact your aquifer and the absence or presence of a potential local source of contamination. According to the US EPA actual events of groundwater contamination have historically been rare; however, as population density increases and we use more and more chemicals, pesticides and drugs, there are more opportunities to contaminate our groundwater. The most common sources of pollution to groundwater supplies come from two categories; naturally occurring ones and those caused by human activities. Naturally occurring contamination are produced from the underlying soil and rock geology.

Human activities can also contaminate groundwater. Improperly constructed and sealed wells can allow surface contamination to enter the well. Improperly maintained septic systems containing human waste and any chemical you flush down the drain, horses, and backyard poultry can contaminate the groundwater. Leaks from underground storage tanks, excessive use of fertilizers and pesticides, surface disposal of solvents, motor oil, paint, fuel, or nearby landfills or industrial operations can contaminate groundwater. While a confining geological layer can protect groundwater from surface contaminants, there is very limited natural protection in karst terrain and fractured rock systems that are very common in Virginia. So while we have rich supplies of groundwater our aquifers can be very susceptible to contamination.

The Virginia Household Water Quality Program out of Virginia Tech recommends that wells be tested for 14 chemical and bacteriological contaminants: iron, manganese, nitrate, lead, arsenic, fluoride, sulfate, pH, total dissolved solids, hardness, sodium, copper, total coliform bacteria and E. Coli bacteria. The Virginia Cooperative Extension (VCE) Office will be holding a drinking water clinic for well owners on March 31, 2014 in Prince William County and will perform the 14 analysis listed above analysis for just $49. (The water clinics are subsidized by a grant to the Virginia Household Water Quality Program.) That is enough information to address most water problems and ensure that your water is safe for your family to drink. To sign up for the program please call 703-792-7747 or email master_gardener@pwcgov.org.

If your water is supplied by a well, you also need to be aware of the factors that impact your water supply and respond to them, making sure to live within your water budget. There are dry years and wet years and you need to know which you are in. Direct determination of the groundwater level in your well requires a water level meter which can cost hundreds of dollars, but the condition of the aquifer can be obtained from a proxy well. The U.S. Geological Survey, USGS, maintains a group of 20 groundwater monitoring wells in Virginia that measure groundwater conditions daily and can be viewed online. One of the Virginia wells is just up the road from me in the same groundwater basin and is currently measuring at normal groundwater levels. As a matter of fact, all twenty of the Virginia monitoring wells are currently at or above normal groundwater levels, so if you are in Virginia it doesn’t look like there are going to be any problems with water supply this year.

groundwater conditions in Virginia

The water level in a groundwater well usually fluctuates naturally during the year. Groundwater levels tend to be highest in the early 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 streamflow draws water. 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. However, deeper wells may be impacted by an extended drought and take longer to recover.

In the fractured rock systems of the Piedmont where I live, most wells draw groundwater from vertical fractures in the bedding plane. Fractures can run dry or become clogged with sediment over the years. In unconsolidated sediments of the coastal plain ground water is pulled from the saturated zone. Prince William County is divided between these two areas. To provide a reliable supply of water, a drilled well must intersect bedrock fractures containing ground water and recharge at a rate greater than the typical domestic demand of 5 gallons per minute during periods of water use or have adequate storage within the well itself. In the typical 6 inch diameter well each foot of depth equals about a gallon and a half. So a 200 foot deep well that recharges at 1 gallon a minute could easily serve a family if the water demand were spread out throughout the day.

Failure of the well itself is rarely sudden, but happens especially in drought. A drought caused well failure may be restored when the drought ends. All problems with private wells break down into equipment failure, depletion of the aquifer or other groundwater problems and failing well design and construction. Though not as common as equipment failure, there are times that the problem is the well and the water supply. If the well cannot recharge at the same rate at which water is being pumped out of the well, you will experience intermittent episodes of severe water pressure loss or possibly loss of water entirely. If you have water first thing in the morning and again when you get home from work, but the supply seems to run out especially when doing laundry or taking a shower. Then you may have a groundwater problem or a well problem. Knowing the condition of the local aquifer will allow you to know which.

Water, Water Everywhere, How Much is there to Drink?

All the water that ever was or will be on earth is here right now. More than 97% of the Earth’s water is within the in oceans. The remaining 2.8% is the water within the land masses. The land masses contain all the fresh water on the planet. Of the land surface water, 77% is contained in icecaps and glaciers and for all practical purposes is inaccessible in the short run. The remaining fresh water is stored primarily in the subsurface as ground water with a tiny fraction of a percent of water is stored as rivers and lakes.

The water on earth never rests, it is constantly moving within the hydrologic cycle along various complex pathways and over a wide variety of time scales. Water moves quickly through some pathways -rain falling in summer may return to the atmosphere in a matter of hours or days by evaporation. Water may travel through other pathways for years, decades, centuries, or more—the groundwater stored in the Wasia aquifer in Saudi Arabia fell from the atmosphere as rain thousands of years ago.

Water enters the atmosphere through evaporation and exits as precipitation -rain or snow. Typically, water remains in the atmosphere as vapor for about 10 days and it is this time that allows water to move from the oceans to the land mass. Then condenses and becomes rain, snow, or mist. The pattern of precipitation changes over time and causing or responding to changes in the climate of the planet. A falling raindrop might evaporate, or perhaps be taken up by a blade of grass or other plant. The rain drop might fall on the ground and form a puddle or run off across hard packed soil or pavement. This water will likely evaporate, infiltrate the soil or travel to a stream and ultimately flow to an ocean; at any point along this journey water can evaporate and start again. The average time for water to go from rain to stream flow to oceans ranges between 16 and 26 days. Mankind has interrupted the flow of streams and rivers to the oceans by diverting water for irrigation and building reservoirs, thus slowing or interrupting its flow to the ocean. http://pubs.usgs.gov/circ/2007/1308/pdf/C1308_508.pdf

Not all surface water flows to oceans. Some lakes and wetlands have no surface drainage. They lose water to evaporation and to groundwater. Water moves much more slowly in the subsurface than in the atmosphere or on land surface. Water that infiltrates the soil can remain in the unsaturated zone where it is returned to the atmosphere by evaporation or plant transpiration or the water it can discharge to the surface in a channel becoming surface flow; or it can begin the longer journey- traverse the unsaturated zone and recharge an underlying aquifer. The water that remains in the unsaturated zone typically remains in the subsurface less than a year. Infiltrated water that travels to the saturated zone, and becomes recharge for the aquifer spends much more time in the subsurface. The time that it takes for water to travel through the entire thickness of the unsaturated zone varies tremendously. It can take mere hours to travel through thin unsaturated zones in humid regions to millennia, for thick unsaturated zones in arid regions. The types of soil and rock, the amount of overburden and ground cover and the thickness of the unsaturated zone determines the travel time.

The available supply of fresh water is limited to that naturally renewed by the hydrologic cycle or artificially replenished by the activities of mankind. The recharge rate, the amount of natural replenishment, varies with weather and can exceed water demands during unusually wet periods or fall far below demands during drought periods. Despite conservation the need for water continues to grow planet wide with the growth of human population and the development of emerging economies.