Land Use and Land Cover Changes Impact on Groundwater

Kumari Yadav S (2023) Land Cover Change and Its Impact on Groundwater Resources: Findings and Recommendations. Groundwater - New Advances and Challenges. IntechOpen. Available at: http://dx.doi.org/10.5772/intechopen.110311.

This is a book to read. The editor of the book cited above examined many of the  groundwater studies recently completed that assess the impact of Land Use and Land Cover (LULC) changes on groundwater. As you can imagine many of the impacts vary and there are tremendous gaps in our current knowledge. Below I have excerpted some of the introduction highlights. You can order a copy of the book from Amazon.

Groundwater is an essential. It serves as a buffer against short- and long-term fluctuations in surface water availability brought on by climatic variability. Approximately 2 billion people on earth depend primarily on groundwater for domestic and agricultural.  Groundwater is crucial for irrigated agriculture and for ensuring the safety of the world’s food security. Feeding mankind is the largest use of water. It accounts for 90% of freshwater consumption. The annual groundwater use for irrigation is 545 km³ of which 43% of the water used annually comes from groundwater.

In many areas, groundwater may be the sole supply of water that is always present. The use of groundwater is influenced by variables, including accessibility, transportability, cost-effectiveness, and availability. The main reasons why people choose to use groundwater water are reliable supplies and reasonable prices 

Groundwater recharge is the vertical flow of water that reaches the water table and increases groundwater storage. Rates of recharge vary by orders of magnitude over space and time, depending on the interaction of climate, soil, geology, surface hydrology, vegetation, and land use. Groundwater recharge, which occurs primarily through rainfall-recharge and surface water and groundwater interaction processes, replenishes groundwater aquifer systems. The change in LULC impacts groundwater recharge processes by modifying the earth’s hydrological system and balance.

Scientists are finding that the quantity, locations, and timing of groundwater recharge and discharge are increasingly altered due to rising population, agricultural growth, and urban land area. For groundwater development and sustainable groundwater resource management, groundwater recharge determines the groundwater withdrawal rates in a region

Land use change is a complex, dynamic process, which has direct impacts on soil, water, and the atmosphere. The most urgent problem of the twenty-first century in terms of groundwater monitoring and accurate projections is the rapidly changing Land Use and Land Cover (LULC). LULC change is becoming a major ecological concern influencing the groundwater recharge significantly. Understanding groundwater recharge in turn is necessary to determine what is a sustainable use rates and analyze aquifer sensitivity to pollution.

Groundwater quality is declining due to rising water demand, urbanization, changing land use and land cover, and climate change. Changes in LULC are among the most significant anthropogenic interventions.  LULC impacts the surface of the Earth by changing vegetation in forests, water bodies, and adding human structures.

While groundwater is an essential and significant portion of the freshwater supply for household, agricultural, and commercial applications, the effects of LULC change on groundwater recharge are not adequately understood, which leads to groundwater depletion. Therefore, understanding the impacts of LULC change on the groundwater is needed for the optimal management of natural resources.

Changes in land cover in the USA caused a rise in both the minimum and maximum temperatures. Additionally, groundwater condition (both quality and quantity) and its recharge are negatively impacted by urbanization of previous agricultural and open spaces. The hydrology of the region has been shown to have changed as a result of the conversion of natural, agricultural, and other low-population density sites into urban/suburban populations. Evidence shows that when urbanization is excessive, more than half of the precipitation drains off and just a small portion is infiltrated deeply.

The change in land cover has a significant impact on the change in groundwater recharge. Estimating groundwater recharge is crucial in managing water resources including surface water resources. It has become widely accepted that changes in LULC have an impact on groundwater. Numerous factors influence LULC change and its impact on recharge. Understanding of these processes and monitoring their impact is required to manage groundwater resources to be sustainable.

The Prince William County Board of Supervisors has once again issued a directive to staff for a groundwater study. The PW County Department of Public Works has submitted a proposal to the Prince William County Board of Supervisors for Groundwater Study to address concerns with the impact of future developments and the sustainability of groundwater as a water supply.

Last time the Department of Public Works proposed only to have the U.S. Geological Survey (USGS) create a Soil Water Balance Model and that it was not necessary or cost effective to study the actual groundwater in the various soil types in the county. This was not followed up on and was inadequate to assure sustainable water for all our residents.  Approximately 15% of Prince William County depend on groundwater for their drinking water. This includes the about 16,000 private wells in the semi rural areas of the county and the Evergreen Water District is supplied by groundwater wells.

We do know that groundwater availability varies by location even within Prince William County (Nelms and Richardson, 1990). Precipitation and soil types determines how much the shallower groundwater is recharged annually. The volume of water that can be stored is controlled by the reservoir characteristics of the subsurface rocks. We need monitoring wells spread in the areas of the county where groundwater is depended on in each of the soil types. In addition, we need the groundwater wells of commercial users to track usage. We need to ensure the sustainability of the groundwater in Prince William County. The water supply is not unlimited.

 

Drought Continues

 

I am sitting inside today hoping for rain with a minor eye injury preventing me from doing any significant reading hanging out in bright lights. So, I’m revisiting drought conditions in Virginia. Virginia generally receives about 44 inches of precipitation per year in Prince William County and over 40 inches in all of the Commonwealth, and is historically considered “water rich" area. However, droughts are not uncommon, and Virginia has a history of multi-year droughts. The graph below shows the frequency of drought years (yellow to red colors) to wet years (blue shades) from 1895 to the present in Virginia.

 

Virginia | Drought.gov

The Virginia Department of Environmental Quality (DEQ), in coordination with the Virginia Drought Monitoring Task Force, has expanded the drought warning advisory to now include 60 counties and cities, and has maintained a drought watch advisory for 32 counties and cities. Due to improving conditions related to recent precipitation in Southeast Virginia, the drought watch advisory previously issued for the Chowan and Southeast Virginia has been lifted. All other regions within the Commonwealth remain affected by drought. Continued precipitation shortfalls in combination with sustained high temperatures have resulted in rapid intensification of drought throughout the majority of the Commonwealth.

Drought conditions can also develop rapidly, especially when the lack of rain and high temperatures combine to quickly increase the loss of water from the landscape via evapotranspiration. There is increased regional awareness of how these rapid-onset droughts, sometimes referred to as "flash droughts." Virginia experienced a high-impact drought during the late summer and fall of 2023 that was a primary factor in several community water restrictions and several major wildfires, including the Matts Creek Fire in the Jefferson National Forest. Wildfires are not common in Virginia.

This map shows precipitation for the past 60 days as a percentage of the historical average (1991–2020) for the same time period in Northern Virginia. The counties are outlined with their familiar shapes. Green/blue shades indicate above-normal precipitation, while brown shades indicate below-normal precipitation. (Because climate is always changing, all historical averages reflect the most recent past 30 years.)

 

 

This map shows the average maximum daily temperature for the past 30 days compared to the historical average (1991–2020) for the same 30 days. Negative values (blue hues) indicate colder than normal temperatures, and positive values (red hues) indicate warmer than normal temperatures.

Groundwater and the Slow Death of a Watershed

This has been a dry summer so far.  The water year which runs from October 1- September 30 is running about around 30 inches in Prince William County. The average would be about 36 inches of rain by July 30^th.   After a wet decade, this is our second dry summer. The U.S. Drought Monitor map by the NOAA Climate Prediction Center indicates that 86% of Virginia is experiencing drought conditions, with 35% is experiencing severe drought conditions.  

According to the ICPRB the rain deficit for the Potomac Basin was about 2 inches in June. The U.S. Drought Monitor indicates that about 52% of the Potomac River Basin is experiencing moderate drought conditions, while 38% is experiencing severe drought conditions. The Climate Prediction Center’s U.S. Seasonal Drought Outlook, as of June 30, 2024, indicates drought is likely to persist in the Potomac Basin over the coming months. 

The reason that ICPRB tracks the drought condition of the Potomac River basin and the flow of the river is because the Potomac River, its tributaries, reservoirs and the associated groundwater resources are the source of drinking water for the over 6,000,000 people in the Washington Metropolitan area. Although hidden in the subsurface, groundwater is the most important freshwater compartment in the hydrological cycle by quantity. Groundwater exists below all land with varying distance to the surface, but only in  20-30% of the land area is groundwater close to the land surface. The conditions of the surface streams and the rainfall provide some hints of what may be happening underneath the ground.

Groundwater is intricately linked to the other components of the hydrological cycle (Sophocleous, 2002). Groundwater releases water to streams sustaining the base flow of streams and rivers (Hare et al., 2021). Groundwater is the primary source of springs and many wetlands (e.g. marshes, peat bogs) (Bertrand et al., 2011; Havril et al., 2018; Gleeson et al., 2020a). Finally, the groundwater saturated subsurface, the hydroporic  constitutes the largest continental biome contributing to the health and purity of our water resource. The small changes in the springs, seeps and streams is telling us that our watershed is changing, and not in a good way.

Ground water flow and storage is often viewed as static reservoirs that serves as the savings account for surface water flow. Through the hyporheic zone groundwater feeds streams between rain storms, but groundwater is dynamic and continually changing in response to human and climatic stress [Alley et al., 2002; Gleeson et al., 2010]. Changes in precipitation patterns, the amount of precipitation and the changes in land use impacts available groundwater and surface water.

from the groundwater project

Mankind’s hand in changing the land surface impacts water resources. Land use changes that increase impervious cover, add more suburban lawns, roadways, buildings, pavement and eliminates woodlands does two things. It reduces the open area for rain and snow to seep into the ground and percolate into the water table and on into groundwater and the impervious surfaces cause stormwater velocity to increase preventing water from having enough time to percolate into the earth, increasing storm flooding and preventing recharge of groundwater from occurring. Land use changes also potentially increases the use of groundwater by adding more homes and businesses (like Amazon who reports drawing millions of gallons of groundwater in the Manassas area).

Slowly, the changes in land use change the ecology of the watershed and can reduce the water supply over time. As groundwater levels fall, perennial steams that feed the rivers become intermittent during dry periods like this past month and last July and August. I believe this is what is happening in the area of the Bull Run Mountain Conservancy where for the second summer in a row, what where perennial streams have stopped flowing in the summer.

It appears that with the current level of development, the depth to groundwater is increasing enough to disconnect some streams from the groundwater during summer months. The ecology begins to die and streams become intermittent and eventually become ephemeral- flowing only during rainstorms. It is believed that this begins to happen at 5-10% impervious cover, but whatever level we are at, we are seeing the beginning of the changes. The groundwater is becoming disconnected from Little Bull Run and Catlett’s Creek in the area of the headwaters of those streams. Once the hydrology and ecological biome is destroyed by development, it cannot be easily restored, if at all. Though there have been a few attempts we have not succeeded in restoring a watershed. We need to stop this now to save our drinking water supply. A network of continuous monitoring well is necessary to monitor the situation and take necessary actions to ensure that we have sustainable drinking water for all our residents.  

Protecting the Occoquan Reservoir requires protecting all the water resources in a region because all water in the watershed is connected. Precipitation moves into the water table (the hyporheic zone) down to groundwater or into rivers and streams. Disrupting the balance of water flow can have dire consequences. The available supply of fresh water is continually renewed by the hydrologic cycle and in the case of the Occoquan Reservoir the actions of mankind when we add the flow from the Upper Occoquan Service Authority wastewater treatment plant. During low flows the fraction of treated wastewater could exceed the amount of natural water.

The quantity and quality of ground water in Prince William County varies across the county depending on the geologic and hydrogeologic group and we must look at them all. Generally speaking, the groundwater in the county is recharged in elevated areas and discharges to streams and estuaries. However, the paths and duration of groundwater flow are different between consolidated rocks and unconsolidated material, between the Culpeper Basin and the Piedmont and the area within the Potomac Aquifer.

Changing land use and climate are impacting the Occoquan Reservoir. High wastewater effluent additions to rivers under low flow conditions can introduce pharmaceutical, personal care and cleaning chemicals into the drinking water supply at higher concentrations. Due to declining water potentials in groundwater aquifers and the infiltration of surface water into the subsurface, contamination by these chemicals poses a serious risk for groundwater quality (Bradley et al., 2014; Karakurt et al., 2019; Kubicz et al., 2021). A multitude of micropollutants are already being found in groundwater in the United States and worldwide at increasing concentrations (Lapworth et al., 2012). Moreover, the rising number of persistent micropollutants passing sewage treatment plants leads to a complex mix of contaminants in surface waters. 

We need more information before we destroy our precious Occoquan Watershed. We are paving over the watershed with roads, data centers, parking lots houses and infrastructure reducing the groundwater recharge, our stream flow and increasing the water demand. The Virginia Water Withdrawal Reporting Regulation only requires the registration and annual reporting of surface water and groundwater withdrawals of any entity withdrawing more than 300,000 gallons per month (that is equivalent to the combined daily use of about 140 people). Though there is no control or management of the water withdrawals except in the Groundwater Management areas of Virginia, essentially the Tidewater and adjacent areas. Of course, the way around the reporting requirements is to have several wells, none of which exceed the limit. Much the way its done with back up generators whose combined power equals a rather large on demand power plant that would never be allowed to operate on diesel as a combined entity is just fine as dozens upon of dozens of back up generators at the ever expanding fleet of data centers. We need to begin now to ensure that our future has water for all.

This article includes ideas and comments from:

Anke Uhl, Hans Jürgen Hahn, Anne Jäger, Teresa Luftensteiner, Tobias Siemensmeyer, Petra Döll, Markus Noack, Klaus Schwenk, Sven Berkhoff, Markus Weiler, Clemens Karwautz, Christian Griebler,
Making waves: Pulling the plug—Climate change effects will turn gaining into losing streams with detrimental effects on groundwater quality,
Water Research, Volume 220, 2022, 118649, ISSN 0043-1354,
https://doi.org/10.1016/j.watres.2022.118649

and

Julia Zill, Christian Siebert, Tino Rödiger, Axel Schmidt, Benjamin S. Gilfedder, Sven Frei, Michael Schubert, Markus Weitere, Ulf Mallast,

A way to determine groundwater contributions to large river systems: The Elbe River during drought conditions, Journal of Hydrology: Regional Studies, Volume 50, 2023, 101595, ISSN 2214-5818,

https://doi.org/10.1016/j.ejrh.2023.101595.

(https://www.sciencedirect.com/science/article/pii/S2214581823002823)

Water Quality in the Bull Run and Evergreen System

 As of July 1, 2024 Prince William Service Authority was rebranded as Prince William Water to more clearly convey what it is that they do and also to stop confusing them in internet searches with Pittsburgh Water and Sewer Authority who was also using PWSA.

Prince William Water has posted their 2024 Water Quality Report that covers the testing that took place during the 2023 year. PW Water met or exceeded all federal and state water quality requirements for calendar year 2023. It is to be noted that most of the water that PW Water delivers to customers is purchased from Fairfax Water (15   million gallons a day from the Occoquan Reservoir and 9 million gallons a day from the Potomac) and Manassas ( 5 million gallons a day). However, the Bull Run Mountain and Evergreen System  gets its water from six groundwater wells located throughout the Bull Run Mountain and Evergreen Water System, and  provides an average of 92,000 gallons of water per day for their customers. The Service Authority has operated the groundwater well system since 1990.

The water quality data from the Bull Run Mountain and Evergreen System caused me  pause. The water quality is only treated for corrosiveness, and meets all state and federal Safe Drinking Water Act standards. However, the testing under the Lead and Copper Rule found the presence of lead in the first draw samples. The Lead and Copper Rule requires community water systems to monitor lead and copper levels at the consumers' taps. If action levels are exceeded, installation of corrosion control treatment is required. If the action level for lead is exceeded, public notification is required.

from PW Water

Compliance with the lead and copper action levels is based on the 90th percentile lead and copper levels. This means that the concentration of lead and copper must be less than or equal to the action level in at least 90% of the samples collected. The regulations tell you exactly how to calculate that result based on the number of samples taken and how many samples need to be collected. Prince William Water, though only required to collect 10 samples collected 14 due to good response rates. With 13-17 samples the EPA states that you should average the second and third highest sample results to get the 90th percentile level. The level of lead in the drinking water calculated in this way was 4.6 parts per billion. This is below the 15 μg/L μg/L or parts per billion action level. However, the U.S. Environmental Protection Agency (USEPA) Lead and Copper Rule lead action level of 15 μg/L is not a health-based standard, rather it is used to identify system-wide contamination. There is no safe level of lead exposure. Water lead levels as below 5 μg/L can increase a child’s blood lead level and cause permanent damage to biological and developmental processes.

The Lead and Copper Rule requires systems to monitor drinking water at customer taps. If lead concentrations exceed an action level of 15 μg/L the system must undertake a number of additional actions to control corrosion. The good news is that the Bull Run and Evergreen Water System is already controlling for pH because some of the wells produce slightly acidic water that would over time tend to damage pipes and plumbing fixtures.  We do not know where in the system the lead is coming from. Future testing under the revisions to the Lead and Copper Rule may give use some answers. Under the newist revisions testing for lead would require a first draw and a flushed sample (technically the 5^th sample). This would tell us if the lead is coming from the home or from the well or distribution system and entering the home in the water delivered to the home.

The presence of lead in drinking water in homes supplied by both municipal service and private wells has been linked to the corrosion of lead-bearing plumbing components. In older homes the water service lines delivering water from the water main in the street into each home were once commonly made of lead. This practice began to fade by the 1950’s but was legal until 1988. Lead was also used to solder copper pipes together before 1988 (when the 1986 ban on lead in paint and solder went into effect). Also, until very recently, (2011 Reduction of Lead in Drinking Water Act) almost all drinking water fixtures were made from brass containing up to 8% lead, even if they carry a plated veneer of chrome, nickel or brushed aluminum and were sold as "lead-free." So even homes built with PVC piping in the 2000’s may have some lead in most of the faucets.

Galvanized iron is still commonly used for well casings and fittings and drop pipes in well deeper than 600 feet. Before 2014 Prime Western grade “lead free” galvanized steel zinc coating was required to contain between 0.5%-1.4% lead. After 2014, “lead free” galvanized steel have less than 0.25% lead in the surface coatings. Nonetheless, under corrosive conditions, any lead used in coatings can be easily released to the water and pumped to the household tap or accumulate in scale layers on the pipe surface or well bottom where scale can accumulate and be released or picked up and pumped with the water.

Corrosive water is the primary risk for lead in well water. However, over time water with a neutral pH could dissolve the coating on galvanized iron and in brass well components. The well completion reports do not document materials used for well components in Virginia or anywhere else to my knowledge. Once installed a well casing cannot be removed. It is possible to line the casing with a plastic pipe a technique used to seal a well where the grouting has failed. All the other components of the well can be replaced, though excavation would be required to replace the exterior portions of the pitless adaptor. However, scale that has accumulated on the bottom of the well might remain a source of lead if it is not mechanically removed.

Fortunately, addressing lead in water is very easy. Install an end-of-tap water filter. Look for filters certified by the National Sanitation Foundation (NSF) for lead removal and reduction. Install this filter on the tap you use most often for cooking or for water to drink. You probably already have on your refrigerator. Be aware that these small units are limited in the amount of time that the filter is effective in removing lead.  There are also whole house filters that have the NSF certification that are more expensive, but might be a better solution.

Electricity Demand and Heat

A heat advisory has been in effect all week as sweltering, humid heat has blanked the Washington Metropolitan area. In these last few days I have been most grateful to have air conditioning (something I did not have until 2007 when we moved to Virginia, so it still seems like a wonder). 

Cooling takes energy. The heat has impacted the demand for electricity, not only for cooling all our homes, but also for keeping the data centers throughout the region cool enough to prevent damage to their computer equipment. The electricity that powers our lives- charges our phones, powers the internet, equipment, lights, homes, office, air conditioning and soon everything else is there when we need it because of the power grid, an interconnected system that keeps electricity flowing to our homes and businesses every moment of every day.

from PJM

PJM Interconnection, a regional transmission grid operator, works behind the scenes to ensure the reliability of the power grid and to keep the lights on. PJM is our regional transmission organization that takes responsibility for grid operations, reliability, and transmission service within 13 states and the District of Columbia: Delaware, Illinois, Indiana, Kentucky, Maryland, Michigan, New Jersey, North Carolina, Ohio, Pennsylvania, Tennessee, Virginia, and West Virginia. As part of that mission PJM forecasts the demand and makes sure the power generation is available to meet that need. 

PJM has issued (another) Hot Weather Alert for today July 10, 2024 the weather is forecast to let up somewhat in the next few days. PJM served a peak demand of of 146,947 MW (which matched last summer's peak demand) on July 8, 2024 and a peak of 144,400 MW on July 9th 2024.Overall, PJM is projecting a higher peak demand for electricity this summer of approximately 151,000 MW compared with the 2023 summer peak load of 147,000 MW. 

During Hot Weather Alerts PJM members are expected to review plans to determine if any maintenance/testing, scheduled/being performed, on any monitoring, control, transmission/generating equipment can be deferred/canceled to ensure that the grid keep operating. We have power today because Pennsylvania, Illinois, Indiana, Michigan and West Virginia are net generators of power these days.

from PJM

From the Energy Information Administration (EIA):

Though consumption of electricity in the U.S. commercial sector has recovered from pandemic levels, that recovery has not been uniform. Annual U.S. sales of electricity to commercial customers in 2023 reached 14 billion kilowatthours (BkWh), or 1%, more than in 2019. However, electricity demand growth has been concentrated in a handful of states experiencing rapid development of large-scale  data centers.

Electricity demand has grown the most in Virginia. Virginia has become a major hub for data centers, with 94 new facilities connected since 2019 given the access to a densely packed fiber backbone and to four subsea fiber cables. Electricity demand also grew substantially in Texas which has attracted a high concentration of data centers and cryptocurrency mining operations. Electricity demand has grown  by 14 BkWh in Virginia and 13 BkWh in Texas. 

from EIA

Commercial electricity demand in the 10 states with the most electricity demand growth increased by a combined 42 BkWh between 2019 and 2023, representing growth of 10% in those states over that four-year period. All this growth is attributed to demand of large scale computing facilities. By contrast, demand in the forty other states decreased by 28 BkWh over the same period, a 3% decline.

DEQ Issues Drought Warning for Northern VA

Last week, the Virginia Department of Environmental Quality issued a drought warning advisory for our area. A drought warning advisory indicates a significant drought is imminent for the Northern Virginia Region which includes Fauquier, Loudoun, Prince William, Arlington, and Fairfax counties and for the Shenandoah region, which includes Augusta, Rockingham, Shenandoah, Frederick, Page, Warren, and Clarke counties. Fauquier County WSA water systems have already implemented Mandatory Outdoor Water Usage Restrictions for their customers.

from DEQ 

Virginia generally receives 44 inches of precipitation each year and is historically considered “water rich." However, droughts are not uncommon, and Virginia has a history of multi-year droughts, including the record-breaking droughts of 1999–2002, 2007–2008, and 2010–2012. Virginia also experienced a short, high-impact drought during the late summer and fall of 2023 that was a primary factor in several major wildfires, including the Matts Creek Fire in the Jefferson National Forest; and the seasonal drying out of what had been perennial streams.

Droughts in Virginia can have far-reaching impacts on agriculture, water availability, and wildfires. Drought conditions can also develop rapidly, especially when the lack of rain and high temperatures combine to quickly increase the loss of water from the landscape via evapotranspiration. There is increased regional awareness of how these rapid-onset droughts, sometimes referred to as "flash droughts," can cause significant agricultural economic impacts and supply concerns to other water users-residential, commercial and industrial.

Flash drought is simply the rapid onset or intensification of drought. It is set in motion by lower-than-normal rainfall , accompanied by abnormally high temperatures, winds, and radiation. Together, these changes in weather can rapidly alter the local climate. Higher temperature increases evapotranspiration—the process by which water is transferred from the land to the atmosphere by evaporation from the soil and by transpiration from plants—and further lowers soil moisture, which decreases rapidly as drought conditions continue.

If not predicted and discovered early enough, changes in soil moisture that accompany flash drought can cause extensive damage to agriculture, economies, and ecosystem goods and services. Though Virginia now has a Water Resource Plan that is compiled every 5 years, it is still early in the process. Virginia is projecting an 18% increase in water use There is no forecast of a growing need for water to cool data centers. Dominion Power and PJM were caught flat footed by the surge in demand for electric power. While data centers use relatively less cooling water than power, the water use the Washington Post reports that a large data center uses between 1 million and 5 million gallons of water a day for cooling. That is as much water as a town of 10,000 to 50,000 people. That water use does not appear to be counted in the water use projections. In addition, that water use cannot be reduced during drought. 

Data centers that obtain their water from Public Supply may have back up groundwater wells. In Virginia there are not regulations on that outside the Potomac Aquifer Groundwater Management Area. The Virginia Water Withdrawal Reporting Regulation only requires the registration and annual reporting of surface water and groundwater withdrawals of any entity withdrawing more than 300,000 gallons per month. A backup well might not trip the reporting requirement. There is no control or management of the water withdrawals except in the Groundwater Management areas of Virginia. This may impact our ability to respond to drought in the future. The data center need for cooling water will become part of the “base” need that we will need to have adequate water storage to supply.

Following the guidance in the Virginia Drought Assessment and Response Plan, the Virginia Drought Monitoring Task Force (DMTF) monitors and evaluates hydrologic and water supply conditions for DEQ .  The DMTF is also responsible for making recommendations for Drought Stage declarations.  These declarations are intended to facilitate communities’  preparation for a drought. Drought warning responses are called for when the onset of a significant drought event is imminent.

DEQ uses the indicators listed below to gauge the presence and severity of hydrologic drought across the 13 Drought Evaluation Regions.  According to the Virginia DMTF, a work group of state and federal agencies coordinated by DEQ, the primary factors contributing to the advisory are low precipitation across the state over the past 90 days, low stream flows and low groundwater levels compared to previous levels for this time of year.

Each day, DEQ compares groundwater levels and streamflow records from “real-time” continuous recording wells and gaging stations across Virginia to long-term records (at least 10 years) for the current month.  For groundwater, daily records are compared; for streamflows, the average of the previous seven days’ flow records are compared.

A drought warning indicates that a drought is imminent. So local governments and and water utilities are advised to implement restrictions on water use- both voluntary and mandatory.  Rainfall deficits, high temperatures and high outdoor water use have contributed to the increasing drought warning signs. Drought Indicators tracked by DEQ (and key to Drought Map) are:

• Precipitation (Prcp)
• Groundwater Levels (GW)
• Streamflow (Flow)
• Reservoir Levels (Res)

DEQ 

According to the DEQ drought indicator map for July 7th 2024 the USGS Groundwater monitoring well 49V 1 is at emergency state. The water level is a few feet below last July and the lowest level in years.  

Time to Expand the Groundwater Management Area

Last week when Brad White of DEQ gave a talk at the Prince William Conservation Alliance, one of his slides struck a memory of a previous conversation I had with DEQ. Before the Covid pandemic shut down Virginia I had a conversation with DEQ about groundwater use in Fauquier and Prince William.  I said, that these days after the abandonment of the groundwater supply wells in Manassas  groundwater in that area wasn’t really used. I was corrected and told, no, Amazon has a reporting well in Manassas and IBM is leasing the PWSA well for a pump and treat for the groundwater contamination.

DEQ knew this because the Virginia Water Withdrawal Reporting Regulation requires the registration and annual reporting of surface water and groundwater withdrawals by January 31 of each year of any entity withdrawing more than 300,000 gallons per month (that is equivalent to the combined daily use of about 140 people). Though there is no control or management of the water withdrawals except in the Groundwater Management areas of Virginia, the information is collected, summarized and included in the Annual Water Resources Report and in the Virginia State Water Resources Plan. Of course, the way around the reporting requirements is to have several wells, none of which exceed the limit. It works the same way as multiple back up generators whose combined power equals a rather large on demand power plant that would never be allowed to operate on diesel as a combined entity is just fine as dozens upon of dozens of back up generators at the ever expanding fleet of data centers.

So, that when Mr. White showed the slide below, he commented that 40,000,000-70,000,000 gallons of groundwater a year was being used for a pump and treatment system (the old IBM site) and 30,000,000-35,000,000 gallons of groundwater a year was being used by an industrial user (who I believe to be that Amazon data center previously mentioned by DEQ) . Should Virginia be managing the amount of groundwater that is used and will be used in the future for datacenters?

from DEQ

The USGS recently published The Soil-Water-Balance Model to Estimate Recharge to Blue Ridge, Piedmont, and Mesozoic Basin Fractured-Rock Aquifers, Fauquier County, Virginia, 1996 through 2015 by By Kurt J. McCoy and David E. Ladd. That study found that the 20-year average recharge in Fauquier County from the SWB model ranged from 8.1 inches per year (in/yr) in Blue Ridge aquifers to 5.3 in/yr in Mesozoic basin aquifers. The authors noted that “although mean annual precipitation volumes vary slightly across the County, the contrast in recharge among the Blue Ridge and western Piedmont aquifers with that of the Mesozoic basin aquifers is largely a result of differences in soil infiltration capacity. Precipitation totals 20 percent below mean annual precipitation from 1996–2015 produced drought recharge rates that were less than 50 percent of mean annual recharge.”

the recharge in 2001 was less than 50% of the 20 year average

Also noted  is that “recharge is highest and most variable in deciduous forest areas overlying crystalline rock aquifers in the Blue Ridge geologic province. Annual recharge to aquifers in the Blue Ridge geologic province was strongly influenced by annual differences in precipitation. The lowest and least variable rates of recharge for the period of simulation were computed for pasture/hay or developed areas overlying sedimentary rock aquifers in the Mesozoic basin.” In Fauquier County if proliferation of data centers were to reduce areas of recharge where forests and pastures were removed and paved over with roadways, parking lots, data centers and substations and water use increased for cooling and other uses, they could overtax the groundwater aquifers that are the primary source of water supply for the county in a dry year and possibly not meet demand during an extended drought.

This is what happened in the Tidewater that is entirely dependent on the Potomac groundwater aquifer. At one time the water resources seemed unlimited, but they were not and resulted in the Groundwater Management Act. Under the Ground Water Management Act of 1992 and the Groundwater Withdrawal Regulations, Virginia manages groundwater in the two Groundwater Management Areas in the state. The Eastern Virginia Groundwater Management Area and the Eastern Shore Groundwater Management Area.  The Eastern Virginia Groundwater Management Area encompasses the counties of Charles City, Essex, Gloucester, Isle of Wight, James City, King George, King and Queen, King William, Lancaster, Mathews, Middlesex, New Kent, Northumberland, Prince George, Richmond, Southampton, Surry, Sussex, Westmoreland, and York; and  areas of Caroline, Chesterfield, Fairfax, Hanover, Henrico, Prince William, Spotsylvania, and Stafford counties east of Interstate 95; and the cities of Chesapeake, Franklin, Hampton, Hopewell, Newport News, Norfolk, Poquoson, Portsmouth, Suffolk, Virginia Beach, and Williamsburg. The Eastern Shore Groundwater Management Area encompasses the counties of Accomack and Northampton.  Any person or entity located within a declared GWMA must obtain a permit to withdraw 300,000 gallons or more of groundwater in any one month.

Without water there can be no life, no economy. The allocation of water resources must be sustainable and fair. We cannot allow the richest corporations on earth to take water in quantities of their choosing without regard for other users. The commonwealth of Virginia needs to ensure that both surface and groundwater use remains sustainable for all. This can only be accomplished by monitoring  the availability of groundwater and surface water and and controlling the use of water. The richest corporations on earth do not get to decide if we have water.

Groundwater Monitoring Well 49V 1

 

Last week Sam Caldwell a Hydrologist from the United States Geological Survey (USGS) who generally specializes in the areas of the Potomac Aquifer spoke at a panel discussion about groundwater and geology. In his presentation Mr. Caldwell walked us through  groundwater level depth data to help us understand the information that can be collected. 

from USGS S. Cadwall presentation

from USGS

In Prince William County the USGS has only two continuous monitoring wells.  Well 49V in the northwest corner of the county has been in operation for over 50 years.

from USGS S.Cadwell presntation

location of well 40V 1 in google maps

According to Mr. Caldwell groundwater level data can be very useful. With 10 years of data we can be very confident of the trend at one particular well. For most of the last 50 years  the water level in well 49V has been fairly stable. However, if you just look at the last 16 years it does not look quite as stable.

from USGS

 A slight downward trend is observed  in the data. This is a single well. To create a pantographic map of the groundwater in Prince William County you would need several wells in each aquifer and geographic region of the county collecting data for at least a decade. This way the USGS could create a potentiometric map of the surface of the aquifer.

from USGS S.Caldwell Presentation

When you add to this data, the precipitation data for the same period you see that July 2017 was very dry, and the complete recovery of the groundwater level only happened after a 2.5 inch rainfall on the 27th of July. What is intriguing is the amount of recovery that occurred during the dry period. The second and third recoveries align with the rainfall that month. 

Rain data from summer 2017 in inches of rain

from CoCoRHS precipitation monitoring station PW-15

from USGS S.Caldwell presentation

Looking at the groundwater level against the historical averages also in informative. Combining groundwater level data, with surface water data and precipitation data would allow use to quantify the recharge of the groundwater over time and model the groundwater level. Once more you can see that the groundwater level in the past year has with the exception of January, been average or below average. Gathering this data and tracking groundwater levels is the first step in ensuring that all Prince William County residents have sustainable water. 

PWCA Tuesday Groundwater and Geology

On Tuesday evening the Prince William Conservation Alliance and Mid-county Civic Association presented a panel discussion: “Water, Water, Will There Be a Drop to Drink? The Science of Groundwater and Best Practices to Preserve Our Drinking Water Supply” with guest speakers Brad White and Sam Caldwell. Brad White is from the Department of Environmental Quality (DEQ) Groundwater Characterization Team and specializes in the Piedmont and Blue Ridge regions of Virginia. Sam Caldwell is a Hydrologist from the United States Geological Survey (USGS) who generally specializes in the areas of the Potomac Aquifer. The full recording of the panel discussion is available on the Prince William Conservation Alliance YouTube channel. Prince William Conservation Alliance - YouTube

I am only going to give you some highlights that I found interesting, though I’ve excluded an observed and fascinating  groundwater anomaly in Loudoun County, because it is in Loudoun County and requires more data and information. The only real takeaway is that groundwater often does not do what is expected by a simple understanding of a situation- geology and groundwater.

Prince William County is the county in Virginia with the most diverse geology. There are four major hydrogeologic groups: a small area of Blue Ridge Crystaline, Piedmont-Sedimentary and Volcanic, Piedmont Crystaline, and the Coastal Plain. Though all groundwater comes from precipitation, generally speaking, the groundwater in each of those hydrogeologic zones comes from different sources. The groundwater in the Blue Ridge is found in the crystalline rock fractures. In the Piedmont-Sedimentary and Volcanic geologies water come from the Culpeper Basin a large and productive aquifer that in years past had been tapped for public water supply. Now, there are only a few reported large users, but the buildout of western portion of the county has made it the sole source of water for a growing number of residents. The Piedmont Crystaline area is a far less productive groundwater area with a random fracture orientation as discovered by Nelms and Brockman. Finally, the Coastal Plain is within the confines of the Coastal Plain Aquifer.

The Coastal Plain is the only groundwater management area in Virginia. In all other areas of Virginia groundwater use is not managed or controlled. Users of more than 300,000 gallons of per month are asked to report their use to DEQ. There are no permits required on a state level and Prince William requires none.

Though it has been decades since David Nelms,  Donna Richardson and A.R. Brockman did their groundwater and geological work studying the extent of PCE contamination from the IBM spill from their former site on Goodwin Drive in Manassas, that work is the basis for all the knowledge that is available about the groundwater and geology of Prince William County. It is also, the reason that Prince William Service Authority abandoned use of the groundwater supply wells in the Manassas area (within the Culpeper Basin) for the Public Water Supply.

In 1978, IBM discovered a release of chlorinated solvent from a storage tank at their 660 acre facility in Manassas,  Virginia. They began groundwater monitoring and found chlorinated solvents specifically PCE, TCE, DCE and TCA in the groundwater. IBM installed 49 on- and 45 off-site wells. Groundwater treatment began on-site in 1985 and off-site in 1997. The PCE plume had migrated off-site towards a public well in the Prince William County Service Authority (PWCSA) system. IBM installed a treatment system at the public well in 1985, and in 2001, the PWCSA discontinued use of the well. So as you can see below the reduction in use of groundwater for pubic water supply after 1980's. 

IBM leases the well for use as part of the contaminated groundwater recovery system. This is known as a “pump and treat system” which consists of pumping contaminated groundwater from the three on-site and two off-site wells to carbon absorption tanks where the chlorinated VOCs are removed. The treated water is discharged to surface streams under a permit issued by the Commonwealth of Virginia. Since 2001, Manassas has not used  wells as a drinking water supply. However, IBM paid for the work of Nelms, Brockman and Richardson of the USGS and a settlement paid for a portion of the allocation agreement with Fairfax Water.

Currently, there are only a few reporting users of more than 300,000 gallons per month of groundwater: the IBM pump and treat on-going remediation, a user in Manassas reporting 35 million gallons per year (believed to be Amazon), and a quarry dewatering operation.  

Wells within the formations of the Culpeper Triassic Basin are the most productive in the county. The basin was formed several million years ago and is believed to have once been a closed basin. The fractured rock systems are extremely productive with limited overburden and almost direct recharge to the bedrock fractures from surface fractures. In the Piedmont Crystalline area in Mid-County, the bedrock fractures are the groundwater reserves, but the orientation varies and are not reliably present. The thick overburden can be a store of groundwater. Finally, the Coastal Plain in Prince William is a small area adjacent to the fall line where it recharges the aquifer. It is capped with a confining layer of clay that creates a pressurized system. Though an private wells are in the upper aquifer.

This final image shows the electrical conductivity of the groundwater. Generally, the higher the specific conductivity, the more ions in solutions. This is typical of more soluble rocks where the minerals are picked up by the groundwater and the water is “hard.” So a specific conductivity map is mapping hard water. 

Finally, Mr. White concluded with four points:

• When groundwater was used for public water supply in the 1980's and 1990's the reported use from those using more than 300,000 gallons a month was higher. 
• The historic use of groundwater for public water supply in the past has demonstrated the substantial capacity for groundwater withdrawals from the portion of the county within the Culpeper Triassic Basin.
• The Coastal Plain portion of Prince William County is actively managed through a permitted withdrawal system in the Groundwater Management Area of the state. No such management system is in place in the rest of the county. 
• Proactive monitoring of groundwater pressures in the Coastal Plain and Triassic Groundwater system may provide valuable baseline information. 

There are Groundwater Problems

 I recently received the following (edited) query. Michelle Trenum suggested I contact you regarding our neighborhood, Mackenzie Meadow in Nokesville. I wanted to see if you had any information on Nokesville‘s water table, or anything I could present to the residents at our HOA meeting. The neighbor right next to me is having well issues. Apparently he has the most shallow well in our neighborhood. I believe he said it was just under 300 feet in depth, and he seems to run out of water when the neighbor on the other side of him  uses a lot of water at once. Meanwhile, there are neighbors with irrigation systems to water their lawns daily encompassing around half of their 10 acre lot . A few years ago a neighboring farm told me that after Mackenzie Meadow was built, they could no longer water their fields without running out of water. Any information you can provide, I would greatly appreciate it.

Groundwater is the moisture and water that exists in the spaces between rocks, the pores in the soil and fractures in the geology-the invisible portion of the water cycle. Groundwater is renewed through precipitation infiltrating into the ground, though seasonal, but can be extracted year-round. Provided that there is adequate replenishment, and that the source is protected from pollution, groundwater can be extracted indefinitely and can be robust in the face of drought. However, groundwater is not unlimited.

Increase the amount of groundwater extracted beyond what is replenished, then slowly over time the aquifer is used up, the water level falls and wells go dry. Development adds people, businesses and industry. All need water- increasing the demand for water while adding roads and buildings that prevent the infiltration of precipitation into the ground.  Essentially, reducing the replenishing (recharge) of the aquifer while increasing the demand for water. This potentially unsustainable combination. Increase water use or reduce recharge by eliminating forested areas and replacing them with compacted soils (lawns that need to be watered), pavement, buildings and over time the aquifer will become exhausted.

Groundwater is both used for water supply and serves to support steam flow between rain storms. Groundwater comes from rainwater and snow melt percolating into the ground. Typically, the deeper the well (thousands versus hundreds of feet) the further away is the water origination and the older the water. The groundwater age is a function of local geology, the amount of precipitation and the rate that water is pumped out of the aquifer. Geology also determines the ease with which water and contaminants can travel through an aquifer and the amount of water the land can hold. The land surface through which groundwater is recharged must remain open and uncontaminated to maintain the quality and quantity of groundwater.

We do know that groundwater availability varies by location even within Prince William County (Nelms and Richardson, 1990) . Precipitation and soil type determines how much the shallower groundwater is recharged annually. The volume of water that can be stored is controlled by the reservoir characteristics of the subsurface rocks. A significant portion of Nokesville is Hydrogeologic group C . The rocks of group C are Early Jurassic in age and include: the Mount Zion Church, Hickory Grove, and Sander Basalts; an unnamed diabase; and thermally metamorphosed rocks.

Rocks within hydrogeologic group C tend to have generally poor water-bearing potential because of the wide spacing between fractures, mineralization of fractures, and random fracture orientations. Better yields have been obtained from wells finished in areas where the diabase is intersected by cross-strike lineaments (Nelms and Richardson, 1990, p. 25) and in areas underlain by basalt which also exist in Nokesville.

Water resources are sustainable when the water used on average does not exceed the recharge to the aquifer.  To use groundwater sustainability requires adequate measurements and observations over years. Though the U.S. Geological Survey, USGS, maintains a group of groundwater monitoring wells in Virginia that measure groundwater conditions daily, only two are in Prince William County. One in Prince William Forest Park and one of the within the former Rural Crescent in the siltstone Hydrogeologic group B.

The water level in a groundwater well usually fluctuates naturally during the year. Groundwater levels tend to be highest in the early spring (my most recent reading) in response to winter snow melt 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.

However, groundwater levels can be affected by how many other wells draw from the aquifer, how much groundwater is being used in the surrounding area for residential, agricultural, industrial or commercial use, or how development has impacted groundwater recharge. Development typically increases impervious cover from roads, pavement and buildings.  This reduces the open area for rain and snow to seep into the ground and percolate into the groundwater and the impervious surfaces cause stormwater velocity to increase preventing water from having enough time to percolate into the earth, increasing storm flooding and preventing recharge of groundwater from occurring. Slowly, over time, this can reduce groundwater supply and the water table falls.

The well below is the one located in the northwest portion of the Rural Area just west or Route 15 in the Culpeper groundwater basin it is about 18 miles from Mackenzie Court, and in a different Hydrogeologic group and would not be representative of the groundwater in Nokesville.  Daily monitoring data available from that well go back decades and the groundwater level was fairly stable until around 2004. What can be seen in the graph below is the slow decline in the water level despite not experiencing any significant droughts since 2008 and having the wettest year on record in 2018. The decline is modest over this period but, will continue and get worse over time especially if demand for groundwater and impervious is not managed. This area of Prince William County appears to have a slowly growing problem.

USGS Well 49V

The monitoring well in Prince William Forrest Park is in an overburden aquifer and tends to reflect precipitation since the area around the well has not increased use or development during the data period. Prince William County needs more information about groundwater.

Potential problems are still at a manageable stage. Groundwater models and data from more monitoring wells can help develop a picture of the volume of the water within the groundwater basin and at what rate it is being used and at what rate it is being recharged. We need to know if the current and planned use of our groundwater is sustainable even in drought years. We need to understand how ground cover by roads, parking lots and buildings will impact groundwater recharge and what level of groundwater withdrawals are sustainable on site to ensure all residents of Prince William County will continue to have water. 

It is unreasonable to think that the approximate16,000 wells supplying households and the Evergreen Water System could somehow all connect to public water supplies from the Potomac River or Occoquan Reservoir many miles away. The tens of millions of dollars it cost to do this would have to be borne by the private well owners. The PW Board of Supervisors to fund the groundwater study as quickly as possible to ensure the continued availability of water for all our residents.

 

Water Pressure Problem in one Part of the House

Not too long ago, a beloved member of my household complained to me that there was a loss of water pressure in the bathroom of his man-cave. Since he supported me through graduate school he has a lifetime right to have me manage all equipment or groundwater issues. So, I applied my common sense and engineering degrees to the problem.

Typically, a reduction in pressure from the well can have several causes:

1. the well going dry,
2. a leak or blockage in a pipe in or from the well
3. a pump problem
4. a pressure tank or pressure switch problem
5. an electrical problem (pump is running on 120 instead of 240)

However, the loss of pressure in only one section of the house is likely to be a plumbing problem. The man-cave bathroom is right behind the utility closet where the pressure tank is. First, when you have a pressure problem take a look at your pressure tank. Looked good at around 50 psi.

The pressure tank is only 4 years old

Next, I went upstairs to the master bedroom to judge how the water pressure looked in our sink and bathtub. Then I wandered around checking water pressure at all the faucets and showers. In the end it seemed to me that only the wet bar sink, the mancave bathroom and the refrigerator water line were impacted.

All these items are on the west side of the house where the well and pressure tank are located, but they are not in the same plumbing line. Didn’t sound like a blockage. I pulled the aerator from one of the impacted sinks. It was filled with little black granules. I looked in the toilet tank and saw black  and brown granules at the bottom of the tank. This was clearly iron and/or manganese.

What came out of the aerator looked black

In the toilet tank it looked like rust-iron

Iron and manganese are naturally occurring elements commonly found in groundwater in many parts of the country including here. Under the Safe Drinking Water Act the standard Secondary Maximum Contaminant Level (SMCL) for iron is 0.3 milligrams per liter (mg/L or ppm) and 0.05 mg/L for manganese. This level of iron and manganese are easily detected by taste, smell or appearance. My naturally occurring levels are a fraction of those levels and so present no taste or staining issues, and at levels naturally present in groundwater iron and manganese do not present a health hazard. However, their presence in well water can cause accumulation of mineral solids over time that can clog water treatment equipment and plumbing. 

Iron and manganese deposits build up in pipelines, pressure tanks, water heater and water softening equipment. These deposits restrict the flow of water and reduce water pressure. My very problem. I actually exacerbated the problem by chlorinating my well. Iron and manganese exist in many different chemical forms. The presence of a given form of iron or manganese in geologic materials or water depends on many different environmental factors. Dissolved iron and manganese are easily oxidized to a solid form by mixing with air or an oxidizing agent.

Groundwater tends to be an oxygen poor environment; typically, the deeper the aquifer the less dissolved oxygen is present. Iron and manganese carbonates in an oxygen poor environment are relatively soluble and can cause high levels of dissolved iron and manganese to be carried from a deep well. When the iron and manganese are oxidized reddish brown or black particles form and settle out as water stands. These particles are often found trapped in washing machine filters, water treatment equipment, and in plumbing fixtures. Chlorine or hydrogen peroxide is an excellent chemical oxidizing agent. Thus, their presence in the aerators and toilet tanks.

I called Chris Jones from Chantilly Plumbing to help me remove, clean and where needed replace all my aerators and shower heads. I’ll let the toilet tanks go for now and replace the filter cartridge in the refrigerator.