IPCC Sixth Assessment Report- Mitigation and Planning

 In case you missed it, the Intergovernmental Panel on ClimateChange, IPCC, released their sixth report. The scientists find that:

• Climate Change is already affecting ecosystems globally
• The planet is being impacted unevenly
• There is already a 1.5 degree Celsius of warming baked into the future by past greenhouse gas emissions no matter how much countries cut emissions now.
• Despite pledges made in Glasgow at the COP 26 meeting the world is still on track for a 2-2.9 degree Celsius warming
• China and India are not our friends and their emissions will continue to grow significantly.
• Adaption to climate change is what we as a planet will have to do.

Increases in frequency and severity of extreme weather events such as heatwaves and heavy rain are occurring across all continents and all oceans. Climate change is affecting nature, people’s lives and infrastructure everywhere.  Our world is warming, the climate changing and extreme events are increasingly impacting nature and people's lives. According to the IPCC, about half of the world’s population currently experiences severe water shortages at some point during the year, in part due to climate change and extreme events such as flooding and droughts. Drought conditions have become more frequent in many regions, caused lengthening wildfire season and increasing the areas burned in the western U.S. and other parts of the world.

“Healthy ecosystems and rich biodiversity underpin human survival. They provide countless services that make our Earth a habitable place. However, climate change and increases in extreme weather events are drastically and progressively impacting nature, weakening the structure, functioning and resilience of ecosystems.”

“The world’s ecosystems on land, in freshwater and in the ocean provide a wide array of essential services to humans. They produce the food we eat and the oxygen we breathe. They filter our water, recycle nutrients and help to limit global warming by storing large amounts of carbon. Furthermore, they cool the air and offer “green” or “blue” spaces such as parks and lakes for fun, adventure and relaxation, thus improving our health and mental well-being. In short, healthy ecosystems are essential for human survival and make our Earth livable.”

“Climate change – with its slow-onset events like sea level rise and ocean acidification and increases in extreme weather – is drastically and progressively affecting our world’s biodiversity and ecosystems. “

Although there have been some positive impacts on agricultural productivity in some high-latitude regions, as the planet warms some of the current agricultural land  will become increasingly unsuitable. Impacts will continue to increase, weakening the structure, functioning and resilience of ecosystems and their ability to regulate our world’s climate. Right now, ecosystems are removing and storing more carbon from the atmosphere than they emit, helping to balance global warming.

“Nature offers a lot of untapped potential, not only to reduce climate risks, and deal with the causes of climate change, but also to improve people’s lives. By restoring and safeguarding ecosystems on land and in the ocean, we help plants and animals to build climate resilience. Nature, in turn, can help us regulate the climate, give us clean, safe water, control pests and diseases and pollinate our crops. However, investing in nature alone won’t be enough. To secure a healthy, livable planet for everyone, we need to transform our way of life fundamentally, especially key elements such as our industry and energy sector as well as how cities and infrastructures are planned and built. Taking action now gives us the best chance of success.”

We need to preserve our ecosystems and cohesively plan our growth, development, infrastructure, energy use and protect our water resources. This begins here, at home with the Rural Crescent.

ICPRB Needs to Model Toxic Algae Blooms

Each summer for the past few years, toxic blue green algae has been found in in our region. The problem appears to be growing worse. This past summer the Virginia Department of Health issued a Harmful Algae Bloom (HAB) Advisory for a 53-mile stretch of the North Fork of the Shenandoah River in August. Samples taken from algal mats on the river bottom contained harmful levels of toxins produced by cyanobacteria. Other areas of Virginia reported non-toxic algae blooms and there were several crowd sourced reports of algae in August.

Algae blooms also called harmful algal bloom (HAB) or dead zones form in summers when higher temperatures reduce the oxygen holding capacity of the water, the air is still and especially in years of heavy rains that carry excess nutrient pollution from cities, suburban lawns and farms. The excess nutrient pollution combined with mild weather encourages the explosive growth of algae fed by excessive nutrient pollution. However, toxic algal blooms are relatively new.

Not all algal blooms are toxic or hazardous. Only the certain species of blue-green algae form the toxin, for reasons that aren't fully understood. Toxic bacteria were not a problem until the 21st century, though algae blooms have been a problem on Lake Erie, the Gulf of Mexico, the Chesapeake Bay and other areas for over half a century. Only algae that contains microcystine or cyanobacteria, a toxin produced by microcystis, a type of blue-green algae that spreads in the summer are hazardous. In 2014 routine water testing in Toledo, Ohio found two samples that tested positive for microcystin at concentrations higher than the VDH advisory level of 1 microgram per liter for potable water. This shut down their water supply for days.

In the 21st century toxic or hazardous algal blooms have become a concern in our region. They occur when algae grow out of control when there are favorable environmental conditions. Hazardous algal blooms, the ones that contain the toxins, can lead to the poisoning of fish, shellfish, birds, livestock, domestic pets and other aquatic organisms that can lead to human health impact from eating fish or shellfish exposed to toxins as well as drinking water contaminated by toxins. Our existing water treatment plants do not remove the toxins and toxic algal blooms could disrupt water supply in our region.

This past summer in mid-July the Virginia Department of Environmental Quality (DEQ) found extensive multi-species benthic algal mats in the North Fork Shenandoah River. Analysis found that the mats contained several cyanobacteria and high levels of cyanotoxins. Tropical Storm Ida came through the North Fork Shenandoah River watershed on September 2, 2021, with severe winds and dumping almost 4 inches of rain on parts of the watershed sharply raising river flow rates.

Anticipating the storm’s potential to scour the algal mats from the river and wash them downstream, the Interstate Commission on the Potomac River (ICPRB) ran its emergency spill model to attempt to track the algae as it was carried downstream by storm flows. The ICPRB then implemented sampling to determine if measurable algal toxin levels reached the Potomac River mainstem after the storm. Samples were collected near the mouth of the Shenandoah River when their models indicated the scoured North Fork algal material would be passing.

The North Fork Shenandoah River is the raw water source for several towns including Woodstock, Strasburg, and Winchester, VA. Two toxins were detected in raw and/or finished water samples at Strasburg on August 3rd, 9th , and 12th but not detected in subsequent samples. Cylindrospermopsin was detected in one finished water sample at Strasburg on August 3rd (0.062 µg/L).

Neither toxin exceeded VDH’s advisory thresholds. Microcystin, nodularin and saxitoxin were not detected in any samples. The relatively low cyanotoxin levels in the water column and water supply intake samples suggested to the scientists at the ICPRB that the algal mats were still intact for the most part and were not releasing measurable toxins to the water column.

The Scientists believe that the North Fork algae bloom was washed out by Tropical Storm Ida before the die-off of the bacteria and release of the toxins and that the rainfall associated with the storm served to dilute the concentration of toxic bacteria. Tropical Storm Ida’s very high flows diluted the cyanotoxins in the scoured algal mats to non-detectable levels before they reached the Potomac mainstem.

However, the scientists suggest that “this might not be the case when streamflows are lower, as is more typical of late summer and early autumn, and cyanobacteria blooms are senescing. Further investigation of the downstream transport of cyanotoxins in the Potomac River and its tributaries could be done with river flow models that are more advanced than the spill model used.” While the spill model was adequate for the purposes of this rapid response sampling, the spill model is a relatively simple with built-in assumptions that cannot be changed to reflect actual river conditions. “Additional field observations and algal bloom sampling would also provide a better understanding of how rapidly cyanotoxins decompose once they are released into the water column and exposed to different river conditions.”

A new model needs to be built to reflect the behavior of the river and the cyanotixins to help prepare all the local water agencies for future toxic or hazardous algal events. With the increase in these events in our region we must be prepared for toxic bacteria impacting our regional water availability. Sadly, we need to be able to predict when toxic bacteria may force the Washington Aqueduct, WSSC, Fairfax Water and Loudoun Water to close their Potomac River intakes. Our water companies will need to be prepared with enough water storage to ride out a potential annual toxic bacteria event. Welcome to our new world.

The Potomac River May Run Out of Water

 This is a summary of the ICPRB report published September 2020:

The Washington, DC, metropolitan area (WMA) with over three million workers many of whom serve or support the federal government  is also home to almost five million residents. The region’s water suppliers have an important responsibility beyond supplying the needs or the residents: to provide 24/7 water that ensures the federal government, including Congress, the Pentagon, and key agencies can function.  

The water suppliers share the Potomac River as the major regional water resource, and so 35 years ago and came together to form the Interstate Commission on the Potomac River Basin (ICPRB) and a cooperative agreement (Co-Op)  of funding and using the water resources available regionally. One of the requirements of the agreement is that every five years a study be conducted to evaluate whether available resources will be able to meet forecasted water demands. The seventh in the series of such studies has just been released.  This time the ICPRB found that if droughts become much more severe as predicted in the climate forecast, even with the addition of the Vulcan Quarry, Milston Quarry, Travilah Quarry and Luck Stone Quarry B as reservoirs (adding over 13 billion gallons of water storage) and using water restrictions and demand management the WMA water supply may be unable to meet combined water supply needs and the environmental flow-by at Little Falls. In other words according to the forecast by 2050 we run out of water for periods under more than one third of the forecast scenarios. It is to be noted that without the addition of the 7.8 billion gallon Travilah Quarry as additional storage the WMA water systems experience failures by 2040 in the forecasts.

The new ICPRB study forecasts of water demands for the WMA through, 2050, taking into account projected demographic and societal changes that may affect future water use,  forecasts of water availability, considering the potential impact of changes in climate and upstream water use on system resources, and  an evaluation of the ability of current and planned system resources to meet the forecasted demands. Using various scenarios the  current study also assesses the effectiveness of several options for enhancing the current regional water supply system that were recommended in a special study conducted in 2017 (Schultz et al., 2017). This special study evaluated and compared the ability of 10 proposed changes and additions to the WMA water supply system to meet the challenges of growing regional demand for water with a supply that does not grow and the potential impacts of climate change when the region expects to have more intense wet years and longer droughts.

The Potomac River supplies, on average, just over three quarters of the WMA’s surface water needs. The rest of the water supply comes from Occoquan River, the Patuxent River and regional groundwater supplies an estimated 27% of end use demand. The Co-Op members provided the funding for three upstream reservoirs: Jennings Randolph, Little Seneca, and Savage. Water in these reservoirs is released during drought to augment natural river flow. In addition, Fairfax Water and WSSC Water rely daily on reservoirs outside of the drainage area of the Potomac River, on the Occoquan River (7.85 billion gallons) and the Patuxent River (10.4 billion gallons), respectively. Two additional reservoirs are planned to be in place within the next 20 years: Loudoun Water’s Milestone Reservoir(1.25 billion gallons)  , scheduled for completion in 2024, and Fairfax Water’s Vulcan Quarry Phase 1 (1.7 billion gallons), planned to be in place by 2040 to augment their Occoquan supply.

Due to continuing improvements in efficiencies of household water fixtures and appliances and consumer behavior, water use in the WMA has remained remarkably steady for almost three decades despite continuing population growth. Water demand averaged 453 million gallons per day (MGD) for the CO-OP suppliers during the most recent period for which data is available (2014-2018). This does not count the water use from groundwater nor the water use by smaller water supply utilities that have their own water supply. Forecasts of average annual water demand were developed using average per person and household use and a forecast that population in the WMA in 2050 will be 6.1 million, a 27% increase from 2018 levels. The ICPRB projects that average annual  water demand will increase to 501 MGD (10%) by 2040 and to 528 MGD (16%) by 2050. The estimated uncertainties (one standard error) in 2040 and 2050 are ±9.7% and ±10.4%, respectively.

While the demand for water increases, the climate projections indicate that the mid-Atlantic states, on average, are becoming and will continue to get “wetter.” Climate scientists also warn; however,  that extreme conditions, that is, floods and droughts, will become more severe.  Our water infrastructure will have to include more water storage to meet a larger demand during longer droughts.

The ICPRB used nine scenarios to represent ranges of uncertainties in the impact of climate change on water availability in the Potomac basin and in future WMA water demand. For each scenario, Potomac Reservoir and River Simulation Model (PRRISM) simulations were done in  four different configurations of the WMA system: a system with current and planned resources, and a system that has been enhanced with  operation controls using water restrictions,  the current system with operating controls and the Travilah Quarry and finally the current system with operation controls the Travilah Quarry and Luck Stone Quarry B added storage.

On average, precipitation in the Potomac River watershed in 2040 and 2050 is projected to increase by 8% and 10%, respectively, and temperature is projected to increase by 2.16 °C (3.9 °F) and 2.5 °C (4.5 °F), respectively. There is tremendous uncertainty about how climate change will affect streamflows. This study relies on a simple climate response function, based on a least squares multiple regression analysis, to predict mean annual natural Potomac River flow from mean annual precipitation, mean annual temperature, and the previous year’s mean flow.

Four summary statistics are used as key performance metrics are listed in the colored boxes below:

• Percent years with no Potomac flow deficits: the percentage of years in the simulation period in which flow in the Potomac River at Little Falls is above 100 MGD (the Little Falls flow-by) on every day of the year, that is, in which combined WMA Potomac water supply needs and the environmental flow-by at Little Falls is always met.
• Percent years with emergency restrictions: the percentage of years over the simulation period in which emergency water use restrictions are implemented on one or more days of the year. In this study, emergency restrictions are assumed to be implemented when combined water supply storage in Jennings Randolph and Little Seneca reservoirs is below 5% of the combined capacity.
• Maximum 1-day Potomac flow deficit (MGD): the maximum shortfall in meeting combined WMA Potomac water supply needs and the Little Falls environmental flow-by on any single day of the simulation period.
• Minimum Travilah Quarry storage (BG): the minimum storage in Travilah experienced over the course of the simulation period.

The last statistic, minimum Travilah Quarry storage, is of interest because of the dual role that Travilah is expected to play in the WMA water supply system: as a backup supply in case of an emergency spill and as a resource to mitigate drought. Reductions in Travilah storage during drought reduce or eliminate this reservoir’s ability to serve as a backup supply in case of a spill. Results of the study indicate that if droughts become much more severe as climate models forecast, the WMA system may be unable to meet combined water supply needs and the environmental flow-by at Little Falls even if all of the recommended options of the 2017 alternatives study are implemented, including Travilah Quarry and Luck Stone Quarry B. 

The Charts show: Percent years with no Potomac River deficits, Percent years with emergency restrictions, Maximum 1-day Potomac River flow deficit, Minimum Travilah Quarry storage top to bottom in each box.

Chesapeake Bay Watershed has Plenty of Water this Year

The lead editorial in Science magazine last month began “The Western Hemisphere is experiencing a drought of crisis proportions. In Central America crops are failing, millions are in danger of starvation...” Editor Marcia McNutt goes on to illustrate the extent and severity of the drought and then to talk about the advances being made in measuring water availability using the Gravity Recovery And Climate Experiment (GRACE) satellites to measure large scale changes in groundwater and moisture from space and a new method for measuring groundwater extraction by measuring regional land uplift (Borsa et al., Ongoing drought-induced uplift in the western United States, Science vol. 345 issue 6204 page 1587). These new methods are allowing scientists to begin to measure the amount of groundwater extracted from an aquifer and the remaining water. This is a first step in managing surface and groundwater together. Both surface and groundwater are part of one connected system responding on different timescales to precipitation based on specific geology. The availability of water resources are not constant and certainly not unlimited.

We chose to live in this little corner of Virginia for the water (on my part) and proximity to my husband’s home or origin. While several counties of Virginia were abnormally dry this past September (according to the Drought Monitor), the dry area was south of us. Groundwater levels in the monitoring well down the road have been normal for most of the year. We seem to be doing just fine this year sitting as we do between the Potomac River and Bull Run and have plenty of water. The National Weather Service’s Middle Atlantic River Forecast Center (MARFC) reports a Potomac basin total precipitation of 28.3 inches of precipitation so far this year thought that is 2.3 inches below normal- 2.2 inches of that shortfall, was in September. Both MARFC and the NOAA are prediction a wet fall along the Potomac watershed and the south in general. Texas is finally seeing relief and recovery from their drought. The drought is California is expected to continue north of the Colorado River. 

from the climate prediction center

The Potomac River is the fourth largest river along the Atlantic seaboard and the lifeblood of our region. The Potomac River starts life as a spring at the Fairfax Stone in West Virginia. The river flows approximately 385 miles to the Chesapeake Bay increasing in size and flow from its tributary streams and rivers in West Virginia, Maryland, Pennsylvania, Virginia, and the District of Columbia growing to become the Bay's second largest Tributary. The River provides more than 500 million gallons of freshwater daily to those living in its watershed, in addition to irrigation water, and the more than 2 billion gallons of water a day for power plants.

The Potomac River is one of the least dammed large river systems in the Eastern United States. The combined storage capacity of all major reservoirs upstream of Washington, DC makes up less than 7% of median flow. Nonetheless, the Potomac River’s flow needs to be managed to assure the 500 million gallons per day the river supplies for drinking water to the region and the approximately 100 million gallons necessary for essential environmental services. The Interstate Commission on the Potomac River Basin (ICPRB) was created to manage and allocate the flow of the Potomac River. They reported last week, that despite a dry September recent rains have ensured that there is sufficient flow in the Potomac River to meet the Washington metropolitan area’s water supply demand without the need for water releases from the upstream reservoirs- Little Seneca and Jennings Randolph to keep the river at adequate flow.

The ICPRB manages the water withdrawals from the Potomac River by having Fairfax Water utilize their Occoquan Reservoir water treatment plant to maintain adequate flow to the Chesapeake Bay and having the other water utilities utilize their storage. The ICPRB reports it’s very unlikely (1-3% likelihood) that river flow will have to be augmented with water released from either the Little Seneca or Jennings Randolph reservoirs this year. Our region is well‐protected from a water supply shortage because of carefully designed drought‐contingency plans and continued strong precipitation. In addition to help maintain a consistent water supply, WSSC (the Maryland water utility) has their Patuxent reservoirs with a capacity of more than 10 billion gallons that is currently over 80% full and more reservoirs are planned for the entire system to ensure the water supply for the region can endure a prolonged drought. Back in the 1960’s during a severe and extended drought, when the population was only a fraction of what it is now, water withdrawals to supply drinking water to the three water utilities in the region from only the Potomac River reduced flows in the Potomac to such an extent that the River practically ran dry, leaving only mud between Great Falls and the tidal river.
Each fall when the Potomac is at its lowest flow the ICPRB maintains daily monitoring of the flow at Point of Rocks and Little Falls to always be prepared for the possibility that more serious drought conditions may develop in the upcoming weeks. At present, there is sufficient flow in the Potomac River to meet the Washington metropolitan area’s water demands, but the ICPRB remains diligent and watchful because weather as we know is changeable. 

from ICPRB

The U.S. Geological Survey (USGS) reports that groundwater levels are generally near normal for the region with both above and below normal levels scattered throughout the area. If your water is supplied by a well, you need to be aware of the factors that impact your water supply and regularly practice household water conservation to live within your water resources when necessary. Unfortunately, we do not have the ICPRB to help us manage our water resources and use. There are dry years and wet years and water will vary, though it is not always obvious. 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. 

My groundwater is very young, basically the groundwater levels in my well and the nearby USGS monitoring wells respond within a day to a rain storm despite being more than 100 feet deep. In many groundwater systems are not as directly tied to precipitation and so that is not true. Many well owners think of their water supply as unlimited until the well fails. Your well is not unlimited and you need to be aware of your water use. You need to be aware of the relationship between groundwater and surface water and how your well responds to drought and rainfall. During dry periods when my garden is in most need, my well is most vulnerable. I will only water my herbs and new plantings. Everything else in my garden has got to make it on what our climate provides (though I would probably try to save the cherry and plum trees in a drought- but not at the risk of my water supply).

USGS monitoring well 49V 1 shows a response to rainfall

The Potomac River Flow

At the last meeting of the Potomac Watershed Roundtable, Curtis Dalpra, Communications Manager for the Interstate Commission on the Potomac River Basin (ICPRB) presented the results of a study to examine what the impacts of various senarios on the flow of the Potomac River which supplies much of the drinking water in the Washington Metropolitan Area. At one point in his presentation he stated that the flow of the Potomac has fallen, but did not have the data on hand to specify over what period. The region had only recently emerged from an extended drought and so I went back to the study that the ICPRB performed to examine adequacy of the Potomac River flow with projected land use and population growth without climate change to see if I could find the data. What I found did not indicate a reduction so much as a change in flow to the river.

Both Images from ICPRB

As shown in the two charts above taken from the ICPRB, there appears to be an increase in both precipitation and runoff (surface flow to the rivers) over the past century rather than a decrease. Mr. Dalpra might have been referring to the recent drought and changes in flow patterns. Low flows have been lower, and high flows higher, in the past than they are now. These flow changes are the result of some combination of changes in land use, consumptive water use, augmentation of low flows using reservoir water and possibly changes in the climate or to the extensive drought that hit this region several years ago and expanded to a multi-year drought.

The region seems to have recovered from that drought according to the Drought Monitor. However, in reviewing the data I did discover that about 70% of the Potomac is used in power generation, though it is not clear what proportion of that use is consumptive. In the United States over 90% of all power is generated by using the power source (coal, gas, nuclear and even solar) to heat water to create steam that drives the turbines and generates electricity. Nationally, less than half of the fresh water is used in power generation, but that is because irrigation water usage is much lower in the Potomac River basin where agriculture is much less dependent on irrigation.

The Potomac is the fourth largest river along the Atlantic seaboard. The Potomac River starts life as a spring at the Fairfax Stone in West Virginia. The river flows approximately 385 miles to the Chesapeake Bay increasing in size and flow from its tributary streams and rivers in West Virginia, Maryland, Pennsylvania, Virginia, and the District of Columbia. The Potomac River grows to become the Chesapeake Bay's second largest Tributary. The River provides more than 500 million gallons of freshwater daily to those living in its watershed, as well as irrigation water , and the more than 2 billion gallons of water a day for power plants.

The Potomac River is one of the least dammed large river systems in the Eastern United States. The combined storage capacity of all major reservoirs upstream of Washington, DC makes up less than 7% of median flow. Nonetheless, the Potomac River’s flow needs to be managed to assure the 500 million gallons per day the river supplies for drinking water to the region and the essential environmental services. The ICPRB was born out of the severe and extended drought in the 1960's when water withdrawls to supply drinking water to the region from the River reduced flows to such an extent that the River practically ran dry, leaving only mud between Great Falls and the tidal river.

Ultimately (after more than a decade) the ICPRB was created to manage the water withdrawls from the Potomac to ensure that essential services like wastewater assimilation and habitat maintenance. The ICPRB monitors river flows and withdrawls to ensure the 100 million gallons per day minimum flow- at Little Falls and the 300 million gallons per day from Great Falls to Little Falls. These minimum flow levels have been observed since the early 1980's, but during that time flows have rarely been that low.

It is possible that River median flows at the measuring points of Little Falls and Great Falls is changing and may be decreasing due to population growth and associated land use changes that have taken place in the past 15 years. Population growth accelerates loss of forest and farmland, hardens surfaces, increases demand for water. Urbanization can significantly alter a river’s flow. Impervious surfaces of roadways, sidewalks, parking lots and building foundations increase stormflow peaks, frequency, and duration, impart greater erosive power to the water by increasing velocity, and reshaping stream contours. Rivers are sustained by groundwater between in drier periods, but urban and suburban development reduces recharge of the groundwater. Deforestation increases the proportions of rainfall running off the landscape instead of seeping into the ground where it can be taken up by plants or enter the groundwater.

The original old growth forests of the region were largely destroyed by slash-and-burn agriculture and by logging to build the region. After destroying 60%-70% of the original forest cover by the 1890’s the trend reversed. Marginal agricultural lands were abandoned and young forest began to reestablish. The new forests that grew up in the 20th century helped restore ecological and hydrological functions. Increases in forest acreage continued until the late 1900s, when expanding urbanization began to reverse that trend and the wooded lands at the suburban edge began to be developed in increasing numbers.

Increased development reduces groundwater infiltration, increases the demand for drinking water and the demand for power. Even without climate change impact, human uses of land and water can interrupt or break many of the natural connections between river flow and precipitation. Analysis by the ICPRB found that land use change is a greater source of hydrologic alteration than dams, impoundments or water withdrawals.

Potomac Watershed Roundtable- Reliability of Drinking Water Supply

On Friday, October 4th 2013 the Potomac Watershed Roundtable met at the offices of Loudoun Water in Ashburn, Virginia. Curtis Dalpra, Communications Manager for the Interstate Commission on the Potomac River Basin (ICPRB) presented the results of a study to examine what the impacts of Climate Change might be on Drinking Water Supplies in the Washington Metropolitan Area. Let’s back up to understand why and how this study was done.

Turn a tap in most places of the Washington Metropolitan region, and water, primarily from the Potomac River, flows. The system that today provides ample water to the area does not provide unlimited water. The water supply for the region will become less reliable in coming decades, especially during droughts, as the population continues to grow and as surface flow to the Potomac River decreases by changes in the land use of the watershed and changes in climate impact the river.

The Washington Metropolitan region population and development has reached the point that during times of drought, natural flows on the Potomac are not always sufficient to allow water withdrawals by the utilities (including power generation which takes an awesome amount of water) while still maintaining a minimum flow in the river for sustaining aquatic resources. ICPRB allocates and manages water resources of the river through the management of the jointly owned Jennings Randolph Reservoir (built in 1981), Potomac River Low Flow Allocation Agreement (1978) and the Water Supply Coordination Agreement in 1982 which designated a section of the ICPRB as responsible for allocating water resources during times of low flow. These steps improved reliability of the water supply and ensured maintenance of in-stream flows to meet minimum aquatic habitat requirements. The section of ICPRB responsible for all this is known as the Section for Cooperative Water Supply Operations on the Potomac (CO-OP.

An important aspect of the Water Supply Coordination Agreement of 1982 is periodically forecasting the region’s future needs for water and assessing the current water supply system’s ability to meet those needs. This analysis is conducted every five years to look 30 years in the future to incorporate new data and ideas and allow time for the water utilities to develop new supply or operating parameters in time to meet demand. Careful future planning has ensured and uninterrupted water supply though several significant droughts.

The 2010 Washington Metropolitan Area Water Supply Reliability Study -Demand and Resource Availability for the Year 2040 was done as two studies. The 2010 study estimates that water demand in the Washington Metropolitan region will rise from its current level of approximately 500 million gallons per day to between 610 and 665 million gallons a day by the year 2040. Over this same period, population in this area is projected to increase from 4.2 million to 5.3 million.

According to that portion of the study, the Washington Metropolitan Area’s current water supply system will likely meet demands through the year 2030, under a range of hydrologic conditions similar to those experienced during the past 78-year period of historical record. However by the year 2040, the current system may have difficulty meeting the region’s demands during periods of severe drought without emergency water use restrictions, and/or the development of additional supply resources.

The key assumption for that report was that the future flow of the Potomac River will mirror the hydraulic conditions for the past 78 years. If hydraulic conditions are changing or a 78 year period is inadequate to predict the possible extent of droughts, this could impact the availability of water. So the ICPRB engaged a study for various climate scenarios of water supply availability from Potomac Watershed to determine if the water supply would be adequate to serve the population. The National Research Program of the U.S. Geological Survey (USGS) actually performed the study using six of the global climate models and three atmospheric CO2 scenarios to create 18 separate possible scenarios. The USGS then “downscaled” the 18 global climate predictions to the Potomac River basin and to other areas as part of a separate project on climate change being conducted by the Chesapeake Bay Program Office and the USGS’s Virginia Water Science Center (your tax dollars at work). In addition, the Chesapeake Bay Program’s Phase 5 Watershed Model was used to estimate the impact of changing temperatures and precipitation on Potomac basin stream flows.

There is tremendous uncertainty in projecting the future climate of the earth, especially at the regional scale. Though global climate models are continually being refined and improved, they do not capture complexity of the interrelations of earth’s land, water, and atmospheric systems that we do not yet fully understand. Local nuisances can be lost in the broad sweeps of mathematical modeling of a living system. Scientific confidence in global model projections is higher for temperature than for precipitation, higher for global scales rather than small regional scales, and higher for longer time frames than shorter ones.

Though the modelers have always claimed greater accuracy for temperature forecasts than precipitation, they have not done a good job of forecasting surface temperature for the past decade. The average surface temperature of earth has actually not increased in the past decade and none of the climate models have been able to adequately explain that anomaly. For the period of 1970 to 2000 the median surface temperature as recorded by measurements increased 0.3 ± 0.04°F per year. However, there has been little further warming of the surface of the planet, particularly over the oceans in the most recent 10 to 15 years. Nonetheless, with all those disclaimers, the USGS did get some predictions out of their 18 scenarios.

Results for the 18 climate scenarios fell into three categories: minor impact, moderate impact, and major impact. The biggest impact is the ability of the regional water utilities to continue to supply water on demand during droughts as the climate changes (or not). Six of the scenarios are predicted to have little impact on the system during a moderate drought and the projected population of the region can be supplied with drinking water from the Potomac River and current systems and operations. Six of the climate change scenarios fall into the “moderate impact” category. Under these scenarios the region is predicted to experience more frequent and stricter water use restrictions, but no water supply shortages during a moderate drought. Reservoir levels are predicted to fall to significantly lower levels during a drought than would occur in the absence of climate change with the projected and assumed increase in population.

Prince William County the Retirement Mecca that will Survive Climate Change

The climate of the earth is constantly changing. Scientific studies have indicated that over the past century the earth has warmed 1.3 degrees Fahrenheit. This warming is not particularly alarming in itself given our planetary history, but the speed of this temperature increase and the fact that the warming is projected to continue at an accelerated pace is worrisome. The planetary warming is forecast to cause sea levels to rise due to melting of sea ice in parts of the world, and changes in weather and patterns and precipitation. If carbon dioxide (CO2) concentrations in the atmosphere are the driving force in earth’s temperature that many scientists believe, then these trends are likely to continue. On a whole earth basis the climate models show at this point there is nothing that we can do to stop global warming and climate change.

As the concentrations of CO2 in the atmosphere increase, the warming produced by the greenhouse gas effect is strengthened. Computer modeling of the climate predicts that there will be feedbacks that significantly increase the impact from the increasing CO2. Even if the concentration of CO2 in the earth’s atmosphere were to stabilize at this level, the changes in the climate of the earth in response to the atmospheric CO2 levels would continue for hundreds of years. In reality, the global emissions of CO2 will not stabilize or decrease any time soon and will continue to rise for at least a generation. What is going to happen will happen, so we need to plan for change and make decisions for the next 30-50 years based on likely outcomes.

It is my plan to live for another 40 years. My relatives do pretty well and I am an optimist and a “real food” and exercise devotee. So when it came time to select a place to live in retirement, climate change was one of the factors taken into consideration- water availability, distance from the coast, elevation, along with proximity to family, medical service and an airport and several other factors. Now, I find myself in northwest Prince William County a place that the Washington Post recently described as becoming “a regional retirement mecca, a small-scale version of Florida on the outskirts of Washington.” I made my choices based to a large extent on general projections of climate released by various groups, not having the tools or resources to do much more.

Now, however, the Interstate Commission on the Potomac River Basin (ICPRB) has completed a study in water supply availability and the health of the Potomac Watershed for various climate scenarios. The focus of their study was the Potomac River, which supplies water to the Washington Aqueduct, Washington Suburban Sanitary Commission (WSSC), and Fairfax Water who all funded the study. The Potomac River supplies 78% of the regions drinking water and the water utilities of the region must plan for the future. In addition, there must be adequate flow of the Potomac below Little Falls to ensure that the balance of saline and fresh water for the health of the Chesapeake Bay estuary. So, on the water rate payer’s nickel I get to see what the future might look like here in in Prince William County.

The National Research Program of the U.S. Geological Survey (USGS) actually performed the study using six of the global climate models and three atmospheric CO2 scenarios to create 18 separate possible scenarios. The USGS then “downscaled” the 18 global climate predictions to the Potomac River basin and to other areas as part of a separate project on climate change being conducted by the Chesapeake Bay Program Office and the USGS’s Virginia Water Science Center (your tax dollars at work). In addition, the Chesapeake Bay Program’s Phase 5 Watershed Model was used to estimate the impact of changing temperatures and precipitation on Potomac basin stream flows.

The most advanced types of models currently being used to project future global climate are general circulation models (GCMs). A GCM is a numerical model which represents the important physical, chemical, and biological processes on the Earth’s surface, in the atmosphere, and/or in oceanic systems that affect climate. The USGS used models from the National Center for Atmospheric Research (USA), Norway, Australia, Russia and Japan as listed in the chart below.

From ICPRB publication

In addition, the three CO2 emissions scenarios were based on IPCC’s Climate Change 2007: Synthesis Report (IPCC, 2007c). The USGS used relatively low emissions (B1), medium emissions (A1B), and high emissions (A2) temperature forecasts for each model to create the 18 scenarios.

IPCC Climate Change 2007

There is tremendous uncertainty in projecting the future climate of the earth, especially at the regional scale. Though global climate models are continually being refined and improved, they do not capture complexity of the interrelations of earth’s land, water, and atmospheric systems that we do not yet fully understand. Local nuisances can be lost in the broad sweeps of mathematical modeling of a living system. Scientific confidence in global model projections is higher for temperature than for precipitation, higher for global scales rather than small regional scales, and higher for longer time frames than shorter ones. Nonetheless, with all those disclaimers, the USGS did get some predictions out of their 18 scenarios.

Though it is predicted by the climate models that precipitation will increase on a global scale, when dealing with only the Potomac River basin, the models differed on whether precipitation will increase or decrease. The models project that the total annual precipitation varies from plus 9% to minus 9% or that the rainfall/ snowmelt that averaged 42.2 inches during the reference period (1988-1999) may stay within 4 inches of that average. Though, it is to be noted, that year to year weather variations in rainfall in the region are large, precipitation has varied from over 80 inches to below 20 inches in the past. Also, in the 18 climate scenarios, the increase in annual average temperature by 2040 increases for the area from 1.3 to 4.1 degrees Fahrenheit when compared with the reference period of 1988 to 1999. The average increase, over all scenarios is 2.7 degrees Fahrenheit. (These temperature predictions were the basis of the energy savings and water savings projects for my home that were geared for a slightly warmer, drier climate, though I am still hoping for wetter.)

Though annual rainfall increases in half of the climate change scenarios, flow in the Potomac River falls in most scenarios. Changes in both temperature and precipitation affect stream flows. Changes in rain or snow affect the amount of water that runs off the land surface and enters streams during rainfall. Precipitation also affects the amount of water recharging groundwater aquifers, which are the primary source of stream flow during dry weather periods. Increasing temperatures will cause more rain to be lost to evaporation from the soil, streams, and will increase transpiration, the water released to the atmosphere by plants. These increases in evaporation and transpiration will tend to reduce flow in streams which in turn reduces flow in the Potomac. With rising population, this could require changes in water use and supply for the area and reduce groundwater availability for private well owners like me.

Average annual basin-wide evaporation and transpiration is predicted to increase by 6-8%. Groundwater recharge decreases under all but three of the climate scenarios, and as I watch the statistically low water level in the monitoring well up the road, I worry about my well water supply. According to study results, the seasonal pattern of groundwater recharge does not change significantly under climate change, with January, February, and March remaining the months of greatest recharge. However, the average annual amount of groundwater that provides base flow to streams and the water in my well, is predicted to decrease in 16 out of the 18 scenarios by as much as 34% in one case.

Results for the 18 climate scenarios fell into three categories: minor impact, moderate impact, and major impact. The biggest impact is the ability of the regional water utilities to continue to supply water on demand during droughts as the climate changes. Six of the scenarios are predicted to have little impact on the system during a moderate drought and the projected population of the region can be supplied with drinking water from the Potomac River and current systems and operations. Six of the climate change scenarios fall into the “moderate impact” category. Under these scenarios the region is predicted to experience more frequent and stricter water use restrictions, but no water supply shortages during a moderate drought. Reservoir levels are predicted to fall to significantly lower levels during a drought than would occur in the absence of climate change with the projected and assumed increase in population.

However, the remaining six climate change scenarios are scary. Under these dreadful six scenarios, unless we make changes in the water supply systems we run out of water. These scenarios predict that both mandatory and emergency water use restrictions would be imposed and most system reservoirs would become empty or close to empty during a moderate drought. In addition, these six scenarios predict on some days of the drought the Potomac River would fail to provide sufficient water to meet demand and environmental needs. Our regional water utilities: The Washington Aqueduct, Washington Suburban Sanitary Commission (WSSC), and Fairfax Water working together with the ICPRB can make changes to the structure and operation of the water supply system to make it more robust. The Potomac River will continue to supply water to the region, we will have to use it more wisely to ensure adequate water supply in the future, but there will be water.  Clearly though, development in the groundwater recharge zones (mostly the Rural Crescent in Prince William County) and open areas needs to be limited to protect the groundwater and stream base flow that supplies our water.

Less Rain Means a Cleaner Bay

Rainfall has been below normal. In the Washington Metropolitan area Virginia, Maryland and the District of Columbia are dependent on the flows of the Potomac River and the Occoquan for their water supply. Potomac River basin has been abnormally dry this year with the eastern shore of Maryland in a moderate drought and river flows below normal. Although the recent rainfall has eased drought in some areas, not enough rain has fallen to raise watershed stream flow to normal levels. Temperatures have been abnormally high and there appears little chance for precipitation in the near term.  But for now, the Interstate Commission on the Potomac River Basin, ICPRB, reports that from a water supply perspective, there is sufficient flow in the Potomac River to meet both the Washington metropolitan area’s water needs and the environmental water flow needs without augmenting river flows by releasing water from the upstream reservoirs. So we can enjoy the clearer flows of the river with little worry or need to conserve water for now.

The ICPRB allocates and manages the water resources of the Potomac River through the management of the jointly owned Jennings Randolph and Little Seneca reservoirs, the Potomac River Low Flow Allocation Agreement and the Water Supply Coordination Agreement adopted in 1982 which designated the ICPRB as responsible for allocating water resources during times of low flow and assist in managing water withdrawals at other times. The ICPRB limits water withdrawals by the local water utilities coordinating Fairfax Water’s utilization of the Occoquan and Potomac and limiting total withdrawals from the Potomac if necessary. In the event that the Potomac River flow at Little Falls is below 700‐million gallons per day the ICPRB releases water from Jennings Randolph and Little Seneca reservoirs to make up the flow and ensure that the saline and freshwater balance necessary to maintain the oxygen levels for oysters, clams and crab populations is maintained. The reservoirs ensure in-stream flows to meet minimum aquatic habitat requirements and the drinking water needs of the region.  

The July 5th Water Supply Outlook from the ICPRB reports that both groundwater and stream flow remain adequate for the short term, but are below normal as rainfall has been below normal for much of the early spring and June. Jennings Randolph (the big reservoir) is full and we are not going to run out of water this year. The good news is that nitrogen and phosphorus contamination in the Chesapeake Bay could fall to the lowest levels since the droughts of a decade ago. The nitrogen and phosphorus contamination in the Bay is correlated with rainfall as seen below and we can enjoy this little preview of what a cleaner Bay might look like.

From the Chesapeake Bay Program 2012

Since the 1970’s large algae blooms have formed in both the Potomac and Upper Bay portions of the Chesapeake Bay watershed each summer. Larger than normal blooms occurred in the upper Chesapeake Bay and its tributaries during August and September 2000 and 2011. These blooms were probably the result of greater than normal amounts of freshwater and nutrients entering the Bay in those years, but there are still factors that need to be studied.  The dead zones form in summers when higher temperatures reduce the oxygen holding capacity of the water, the air is still and especially in years of heavy rains that carry excess nutrient pollution from cities and farms. The excess nutrient pollution combined with mild weather encourages the explosive growth of phytoplankton, which is a group of single-celled algae. While the phytoplankton produces oxygen during photosynthesis, when there is excessive growth of algae the light is chocked out and the algae die and fall below the interface between the warmer fresh water and fall into the colder sea water. The phytoplankton is decomposed by bacteria, which consumes the already depleted oxygen in the lower salt level, leaving dead oysters, clams, fish and crabs in their wake. Thus, the name- dead zone.

In a wedge estuary such as Chesapeake Bay the layers of fresh and salt water are not typically well mixed, there are still several sources of dissolved oxygen. The most important is the atmosphere. At sea level, air contains about 21% oxygen, while the Bay’s waters contain only a small fraction of a percent. This large difference between the amount of oxygen results in oxygen naturally dissolving into the water. This process is further enhanced by the wind, which mixes the surface of the water. Recent heavy wind storms may have increased oxygen levels in various water layers. ICPRB staff scientists will be working with Maryland and West Virginia natural resources scientists to survey algae blooms in the upper Potomac watershed. Researchers will visit numerous sites along the Potomac, its South Branch up to Moorefield, W.Va., the Cacapon River, and the lower Shenandoah River. The summer-long assessment will document the types and extent of algal blooms in this section of the watershed.

While the recent storm brought much damage, the powerful winds that took down trees also served to mix the waters of the Potomac. The waters of the Bay appear clearer than they have in recent years. While drought does improve nitrogen, phosphorus and sediment levels in the Bay in the short run, the cost of drought can be high (agricultural losses and water restrictions) and ultimately droughts end and the rains will come.  The Chesapeake Bay Foundation still judges the Bay to be “dangerously out of balance” despite progress made in the health of the Bay in the past 30 years and this year’s clear waters and healthy shad run. As the Washington Post Reported recently, the District’s 45 miles of Potomac watershed streams and rivers is so tainted with bacteria from the combined sewer overflows that the city prohibits swimming. The waters of the Potomac are the primary drinking water supply for the region they should be clean enough to be safe for swimming and recreation.  The Watershed Implementation Plans from the six states and Washington DC and the $2.6 billion sewage treatment plant upgrade for Washington DC under the Chesapeake Bay TMDL will further improve the waters of the Potomac and the Bay in the next decades. The Maryland, Virginia and the District estimates that it will cost more than $30 billion for them to meet the mandates of the Chesapeake Bay TMDL pollution diet over the next 13 years. Water is not free, it’s just we do not often see many of the costs associated with it. We need to see and understand all the cost of guaranteeing 24/7 access to clean abundant water.  

The Rural Crescent, the Occoquan and the Water Supply

The Board of Supervisors of Prince William County have allocated $60,000 to engage a study to examine if the goals desired from the creation of the Rural Area of the county have been met through the implementation and management of the Rural Crescent. In addition, the study is to identify other rural preservation tools that would allow the elimination of the Rural Crescent restrictions on development density. This is a direct result of a motion by Supervisor Martin Nohe at the regular March meeting of the Prince William County Board of Supervisors.

The Rural Crescent was created in 1998 and originally intended as an urban growth boundary for the county designed to preserve the agricultural heritage and force redevelopment along the Route 1 corridor rather than development in the remaining rural areas. This was to be accomplished by limiting development to one home per 10 acres with no access to public sewers. The Rural Crescent has been chipped away at for years, but still contains 80,000-acres; however, active farming in Prince William continues to decrease.  To adequately judge the utility of the Rural Crescent the study must consider its impact on water resources and water ecology. While the Rural Crescent may have been the wrong policy to preserve our agricultural heritage, it has been a success at preserving water resources, protecting our groundwater and supporting the ecosystem of our estuary. In addition, continued redevelopment of areas with preexisting infrastructure will allow Prince William County to improve storm water management in those areas and score nutrient points for the EPA mandated TMDL as well as revitalize older areas of the county and support of sustainable development. The Rural Crescent is about water, specifically groundwater.

The Rural Crescent in Prince William aligns roughly with the Culpeper groundwater basin, one of the more important watersheds in Virginia and essential to the health of the Occoquan Reservoir which in turn is an essential element in the drinking water supply of Fairfax Water - Prince William Service Authority, PWSA, obtains most of the drinking water they distribute in the county wholesale from Fairfax Water. Besides purchased water from Fairfax Water, PWSA operates the Evergreen water wells that draw water directly from the Culpeper Basin and thousands of home owners have private wells that also draw from the aquifer. The Virginia-American Water Company also distributes water purchased from Fairfax Water. Any changes in land use have the potential to negatively impact groundwater, the watershed and the Occoquan Reservoir and should be considered in the study of “other preservation tools.”  

The Rural Crescent is located within the northeast quadrant and eastern quadrant of the Culpeper basin and consists of an interbedded sequence of sedimentary and basaltic that is highly fractured and overlain by a thin cover of overburden. While ground water flows generally speaking west to east, the fractures within the rock run predominately north south. Contaminants can enter the groundwater at these fractures and zigzag through the aquifer, but these fractures also serve as recharge areas. Groundwater is typically protected against contamination from the surface by the soils and rock layers covering the aquifer, but there is inadequate overburden in much of the Rural Crescent. Once contaminated, groundwater is very difficult to clean and in a fractured rock system there is limited if any natural attenuation and the aquifer could be polluted beyond our ability to remediate.

Generally, groundwater in the Culpeper Basin is replenished each year through precipitation. Groundwater recharge through precipitation requires adequate area for infiltration of rainwater, control of sheet flow created by roads and paved areas, as well as protecting the most geologically favorable infiltration points. Precipitation and snow melt flows over the ground as surface runoff. Not all runoff flows into rivers, much of it soaks into the ground as infiltration. Some water infiltrates deep into the ground and replenishes the saturated subsurface rock of the aquifer, which store huge amounts of freshwater for long periods of time. Some infiltration stays close to the land surface and can seep back into rivers, creeks, and ponds as base flow for the rivers, and some ground water finds openings in the land surface and emerges as fresh water springs.

According to the U.S. Environmental Protection Agency, impervious cover levels of 10% can significantly impact watershed health increasing stormwater runoff. When runoff volume increases, runoff velocity increases, and peak storm flows causes flooding and erosion.  Increased stormwater velocity increase soil erosion, increases nutrient contamination and reduces water infiltration into groundwater. The groundwater is essential as the base flow to the streams and rivers that feed the Occoquan Reservoir during the dry months. The groundwater stored in the watershed can supply adequate water to maintain river flow during droughts. Maintaining open areas provides areas of groundwater recharge and controls runoff. Decisions about the fate and management of the Rural Crescent will impact groundwater quantity and quality and in turn will impact water flows to the Occoquan Reservoir during dry periods.  Flow to the Occoquan Reservoir is essential in managing the drinking water withdrawals from the Potomac River.  The Interstate Commission on the Potomac River Basin, ICPRB, manages the Potomac River drinking water allocations for the entire region by “suggesting” the quantity that Fairfax Water draw from the Occoquan and Potomac daily.  Prince William County’s decision on the fate of the Rural Crescent could impact drinking water supplies in Fairfax, Maryland, and DC as well as our own county.

 

The “rural preservation tools” to be investigated as part of the study are sustainable community concepts, high density communities utilizing the strategies of Low Impact Development, LID, which include dedicated open space. While high density communities built adjacent to dedicated open space of cute community farms as is being done in Loudoun might preserve our agricultural heritage, it will not guarantee the preservation of our ecosystem and water. When development disturbs more than 10% of the natural land by covering surfaces with roads, driveways, walkways, patios, and homes the natural hydrology of the land is disturbed, irreparably disturbed. These developments while much better than traditional developments still disturb more than half the land area by significantly increasing building density. 

The lack of overburden limits natural protection to the aquifer, but has allowed easy infiltration. The sedimentary rocks of the Rural Crescent are productive aquifers and feed not only the groundwater wells that provide drinking water to Evergreen and other communities, but also feeds the tributaries to Bull Run assuring the base flow to the rivers and streams that feed the Occoquan. Our freshwater resources need to be managed as a whole. Development that will impair the recharge of the aquifer can result in impacts to the entire region, including the decrease in water level and aquifer storage, reductions in stream base flow and lake levels, loss of wetland and riparian ecosystems, saltwater intrusion and changes in groundwater quality. Our future and our children’s future is our water. We can’t allow it to be destroyed  in paving roads and building houses for short term gain.

Sharing Our Water in the Potomac Watershed

The May 1st Potomac Basin Drought Monitor indicated that most (96.8%) of the Potomac River Basin was abnormally dry (D0). Stream flows measured at Point of Rocks and Little Falls were below median levels.  Precipitation levels in the Basin were below normal in April by 1.2 inches. Most of the groundwater monitoring wells were normal to low across the Basin.  I was not the only one wondering if this would be the beginning of a drought, and worried about my own water supply. Then the rains came.

For the past two weeks as thunder storms have rolled through the region, I checked the water level in the nearby U.S. Geological Survey (USGS) well 49 V1 almost daily and watched as the water level has risen. For two weeks the regular downpours have kept my 15 new trees well watered while the groundwater level has risen 3 feet in the USGS well 49 V1! My drinking water well is undoubtedly as flush as 49 V1 and I’m relieved. The water level has gone from the 10th percentile to the 90th in two fairly wet and stormy weeks. My garden is beautiful, and I can with a clear conscience plan to fill the “gator bags” on my new trees during the dry days of summer. I’ve seen first-hand how immediately rainfall and its percolation into the ground directly impact groundwater.

The groundwater and rain also feed the river at the bottom of my land. That water flows into Bull Run at Sudley Springs and onto the Occoquan River. The rain also feeds the tributaries to the Potomac River.  The Washington metropolitan area gets nearly 90% of its drinking water from the Potomac River. The remaining 10% of the region’s supply is from the Patuxent and Occoquan rivers, Goose Creek (a Potomac Tributary that runs through Loudoun County), Lake Manassas (which feeds the Occoquan), the Jennings Randolph and Little Seneca Reservoirs and groundwater resources that serve small community supplies and private wells like mine. Though I fixate on the water resources in my little corner of the region which I have no ability to supplement, the Potomac River is truly the lifeblood of the region. The Potomac is the region’s major source of drinking water, accepts the clean effluent from waste treatment plants, cools power generation plants, and with the C&O Canal, Lake Manassas, and the Occoquan Reservoir provides water recreation and breath taking scenery to our communities.

The Washington Aqueduct Division of the U.S. Army Corps of Engineers (WAD), the Fairfax County Water Authority (FCWA) and the Washington Suburban Sanitary Commission (WSSC) furnish about 95% of the metropolitan region's water. A number of distribution agencies like Prince William Service Authority purchase some or most all of their water wholesale from the big three and distribute that water in their communities. A number of smaller agencies and self-supply portions of distribution agencies supply the remaining 5% of the water.

For more than two centuries the waters of the Potomac seemed unlimited so that the region is not hampered and tied by water allocation agreements created centuries ago that bind many areas of the arid west to fixed and rigid allocations. Instead, the Interstate Commission on the Potomac River Basin, ICPRB, which was authorized by congress in 1940 to address the pollution of the river facilitated the creation of the Potomac River Low Flow Allocation Agreement in 1978 in response to the droughts of the 1960’s and 1970’s.  Back in the days when the ICPRB was formed, raw sewage flowed directly into Four Mile Run, Hunting Creek, Hooffs Run, and the Potomac River. The river tributaries were putrid and clogged, a foul mix of bubbling, decomposing human waste in brown waters. Shorelines were devoid of wildlife, and tests showed dozens of disease-causing pathogens. Water pollution was so bad that propeller airplane passengers from D.C. (filled with the members of congress) could look down and see the sludge. The extent of the problem was documented in 1949 by the Izaak Walton League, one of the first conservation organizations in the U.S., in a film showing water conditions in Alexandria.

The ICPRB was one of the first organizations with a congressional mandate to consider water resources on a watershed basis, rather than along political boundaries. However, now, the focus of the ICPRB has changed. Sewage is not released into the Potomac (unless the combined sewer systems in Baltimore or Washington overflow).  We have reached the point in population density and development that during times of drought, natural flows on the Potomac are not always sufficient to allow water withdrawals by the utilities (including power generation which takes an awesome amount of water) while still maintaining a minimum flow in the river for sustaining aquatic resources. ICPRB allocates and manages water resources of the river through the management of the jointly owned Jennings Randolph Reservoir (built in 1981), Potomac River Low Flow Allocation Agreement (1978) and the Water Supply Coordination Agreement in 1982 which designated a section of the ICPRB as responsible for allocating water resources during times of low flow. These steps improved reliability of the water supply and ensured maintenance of in-stream flows to meet minimum aquatic habitat requirements as defined by the Maryland Potomac River study in 1981. The section of ICPRB responsible for all this is known as the Section for Cooperative Water Supply Operations on the Potomac (CO-OP), and is formally empowered in its duty by the Water Supply Coordination Agreement of 1982.

This ICPRB is intended to coordinate all the political entities, Maryland, Virginia, Fairfax Water, Washington DC, the federal government and counties and cities within and dependent on the watershed to address the basin’s major challenges, including water quality impairments, water supply and restrictions, flooding, groundwater use, nonpoint source pollution and emerging contaminates. The ICPRB role has been somewhat overshadowed by the recent EPA mandated Chesapeake Bay TMDL, but the ICPRB remains primary in coordinating water supply management and spearheading coordination of effluent water quality issues as they impact drinking water supplies. In their most recent water supply update on June 4th ICPRB assures us that “there is sufficient flow in the Potomac River to meet Washington metropolitan area’s water demands without augmentation from upstream reservoirs.”  After the recent rains it appears unlikely that the Washington metropolitan area’s back up water supply- primarily the Jennings Randolph reservoir helped in by the smaller supply at Little Seneca reservoir will be needed during the summer of 2012.  ICPRB also brings you the Potomac River Watch.
Thanks to Curtis Dalpra Communications Manager at CO-OP for his help.