Wednesday, December 28, 2022

Power, War and CO2 Emissions

 2022 will prove to be a year when the world as we knew it shifted and changed. Putin’s unprovoked invasion of Ukraine was in part responsible for our changed views. As Putin has turned the war in Ukraine to mass civilian attacks using missiles and drones armed with high explosives targeting cities and the power infrastructure it appears he has pulled out the old playbook:  to terrorize the population so they would lose the will to fight and surrender. Instead, this war has strengthened our NATO alliance. It has become clear that our NATO partners are our friends. China, Russia and Iran are not.

Ukraine’s air defenses are weak, and Ukraine cannot retaliate in kind. Putin thinks strategic air attacks are his winning card. Ukrainian President Volodymyr Zelenskyy arrived in the United States this month with the goal to improve Ukraine’s air defenses. The United States needs to stop worrying about provoking Putin and worry about helping Ukraine stop him.

We have also learned over and over that China is not our friend and is eying expansion through invasion and proving they are the rightful first among nations.  We must rebuild our waning military and not allow it to suffer the same decay as Russia’s. Stand with our friends, arming and training them ahead of invasion is a good plan, too. The surveillance state and thought police are bad. We need to hear all voices or be caught unaware.

The war in Ukraine has also changed how we look at power, dependence on other nations, infrastructure and power generation portfolio.  Though the United States, the European Union and others have imposed economic sanctions on Russia and have announced plans to wean themselves off that country’s fossil fuels; Russia still supplies 40% of the natural gas for the European Union. As energy prices soared worldwide the United States went begging to other nations to produce more oil and gas. The only nation we did not encourage to produce more oil and gas was our own.

As Alaska Senator Dan Sullivan tweeted “This is national security suicide. shuts down energy production in America—particularly in Alaska—then goes on bended knee to dictators in countries like Iran, Saudi Arabia & Venezuela, begging them to produce more energy.”

Our leaders discussed windfall profits tax on energy companies and drew down 180 million barrels of our strategic oil reserve.  We need to look at our own energy portfolio and power use. Sustainability and reliability are as important as decarbonizing the electric generation in the United States. Extreme temperatures and prolonged severe weather conditions are increasingly impacting our power systems.

Extreme weather impacts increases electricity demand and forcing generation and other resources off-line. At the same time preference is given to the use of natural gas for heating rather than electricity generation. While the PJM has sufficient capacity to meet resource adequacy requirements, it may not have sufficient availability of resources during extreme and prolonged weather events as we almost discovered Christmas weekend. Peak electricity demand is increasing, and forecasting demand and its response to extreme temperatures and abnormal weather is increasingly uncertain. Specifically, electrification of residential heating requires the system to serve especially high demand on especially cold days.

Over Christmas weekend PJM and Dominion Power requested the public in its region to conserve electricity. Suggesting that electricity customers take simple electricity conservation steps such as:

  •  Setting thermostats lower than usual, if health permits.
  • Postponing use of major electric appliances such as stoves, dishwashers and clothes dryers until other times, and
  • Turning off non-essential electric lights, equipment and appliances.

The call for conservation was prompted by the inadequacy of our power supply to meet the demands of region wide frigid weather. We are a nation blessed with a plethora of natural resources. If we cannot heat and power our homes and ovens on a very frigid Christmas Eve, we are a declining nation.

Here at home the energy needs of the Commonwealth, its businesses and its families are changing – and growing. Virginia is already the data center capital of the world, and the industry is exploding along with the demand of 24 hours a day 7 days a week power needed to run them. At the same time Virginia has been on a short timeline to decarbonize the grid and electrify transportation and heating. When the wind does not blow or the sun does not shine, or the polar vortex arrives our grid needs to power our lives. 

Virginia has been outsourcing reliable baseload capacity to other states within the PJM, and increasing Virginia’s dependence on electricity imports from West Virginia and Pennsylvania. As a result, supply and transmission of energy to Virginia homes and businesses has the potential to become less reliable than today and could end up with rolling blackouts during both heat spells and cold snaps if we do not plan better.

According to Governor Glenn Youngkin, a growing Virginia must have reliable, affordable and clean energy for Virginia’s families and businesses. The Virginia Energy Plan must meet the power demands of a growing economy and ensures Virginia has that reliable, affordable, clean and growing supply of power by embracing an all-of-the-above energy plan that includes natural gas, nuclear, renewables and the exploration of emerging sources to satisfy the growing needs of Commonwealth residents and businesses.

Sunday, December 25, 2022

Freshwater Salinization Syndrome

Freshwater contains natural salts and minerals. However, dramatic increases in salt concentrations are occurring due to human activities including road salt application, water softening, mining and oil production, commercial and industrial processes, weathering of concrete, sea level rise, and fertilizer application. Over the last several decades, scientists have measured increases in salt concentration in several rivers around urban areas including the Potomac River and the Occoquan Reservoir. The salinity in the reservoir has been rising over time and may be reaching a critical stage. 

Many different types of salts contribute to freshwater salinization including sodium, chloride, potassium, calcium, and magnesium. Too much salt in freshwater can harm aquatic life, but there's more to the problem than that. Increased salt concentrations lead to a phenomenon called freshwater salinization syndrome (FSS). This syndrome is due to direct and indirect effects of salts that cause other pollutants in soil, groundwater, surface water, and water pipes to become more concentrated and mobile.

With rising salt levels comes rising chloride concentrations, all salts contain chloride which forms a solution in water with available free chloride. One example of these effects is that salts can increase the rate of metals reacting and  mobilizing from soils and pipes and can cause the breakdown of infrastructure. This process is called galvanic corrosion. The rising salinity is also associated in some areas with changing water chemistry. Sulfate levels are decreasing and alkalinity is rising. These are other factors that influence corrosion  in our infrastructure.  

Excess nutrients in the soil like nitrate-nitrogen can also be mobilized by high salinity, thereby exacerbating nutrient pollution, which contributes to the increasing presence of dead zones and/or harmful algal booms. Radioactive materials such as radium uranium naturally occurring in soils in Virginia can also be mobilized and become more concentrated in groundwater and surface water. Excess salts can make water undrinkable, increase the cost of treating water, and harm freshwater fish and wildlife.

The Occoquan Reservoir is an important part of our region’s drinking water supply, providing about 40% of the clean drinking water for around 2 million people. Though sodium mass loading to the reservoir is primarily from watershed runoff during wet weather and reclaimed water during dry weather, sodium concentration in the reclaimed provided by the Upper Occoquan Service Authority wastewater treatment plant water is higher than in outflow from the two watersheds at the present. However, the new Comprehensive Plane recently approved by the Board of County Supervisors will accelerated industrial, commercial and residential development in the Bull Run and Occoquan river watersheds. History has told us that development increases salinity. The massive development on currently open and forested land in Prince William will accelerate the rate of rising salinity. The solutions will not be cheap. – Desalination for the drinking water supply, new shortened life cycle for water, wastewater and distributions systems, nitrogen removal to meet the requirements of the Chesapeake Bay TMDL and so much more.

Wednesday, December 21, 2022

EPA Announces Bipartisan Infrastructure Grants

Over the past couple of weeks there have been a series of announcements by the U.S. Environmental Protection Agency of the selection of dozens organizations to receive a total of more than $26.7 million in grants funded through President Biden’s Bipartisan Infrastructure Law. These grants were all for environmental job training programs across the country under the Brownfield program. The grants will be dispersed through EPA’s Brownfields Jobs Training Program will recruit, train, and place workers for community revitalization and cleanup projects at brownfield sites. 

In the various press releases EPA Deputy Administrator Janet McCabe said “President Biden’s Bipartisan Infrastructure Law is supercharging EPA’s Brownfields Program, which is transforming blighted sites, protecting public health, and creating economic opportunities in more overburdened communities than ever before.”  

This is apparently all being done by Job Training. The Bipartisan Infrastructure Law, allocated more than $1.5 billion to EPA’s Brownfields Program which seeks to redevelop former industrial and contaminated sites. This historic investment enables EPA to fund the advancement of the environmental curriculum in job training programs that support job creation and community revitalization.

The Brownfields Jobs Training Program also advances President Biden’s Justice40 Initiative, which aims to deliver at least 40% of the benefits of certain government programs to disadvantaged communities. Based on data from the Climate and Economic Justice Screening Tool, approximately 97% of the communities selected to receive funding have proposed projects in historically underserved areas.

Brownfields Job Training  grants are made to nonprofits, local governments, and other organizations to recruit, train, and place unemployed and under-employed residents of areas affected by the presence of brownfield sites. Their graduates develop the skills needed to secure full-time, sustainable employment in various aspects of hazardous and solid waste management. All good, but not what I imagined infrastructure to be. I had thought that infrastructure money would go to infrastructure-  pipes and equipment- all the things that make up our infrastructure. Not job training programs.

Our nation’s drinking water infrastructure system is made up of 2.2 million miles of underground pipes that deliver drinking water to millions of people. There are more than 148,000 active drinking water systems in the nation, thought just 9% of all community water systems serve 78% of the population- over 257 million people. The rest of the nation is served by small water systems (about 8%) and private wells (about 14% of the population). There is a water main break every two minutes and an estimated 6 billion gallons of treated water is lost each day to leaks and water main breaks.

Funding for drinking water infrastructure has not kept pace with the growing need to address the aging infrastructure. Despite the growing need for drinking water infrastructure, the federal government’s share of capital spending in the water sector fell from 63% in 1977 to 9% of total capital spending in 2017. This is just on tiny corner of the Bipartisan Infrastructure Law Bipartisan Infrastructure Law, but an example of how money moves around the government into favored programs. I was hoping more of the infrastructure money would go to renewing our long neglected physical water infrastructure for future generations.

Monday, December 19, 2022

Reducing PWC Carbon Footprint


On November 17, 2020, the Prince William County Board of Supervisors adopted Climate Mitigation and Resiliency goals and authorized the creation of a Sustainability Commission.  The Commission is charged with advising on potential enhancements to the Community Energy and Sustainability Master Plan (CESMP), which will provide the map for how the county will reach its climate goals that includes Prince William County achieving 50% of 2005 CO2 emissions by 2030 and net-zero by 2050; but also include plans for adaption to climate change.

At the close of the COP-27 meeting the UN Secretary-General, Mr. Guterres, decried greenwashing – misleading the public to believe that a company or entity is doing more to protect the environment than it is.  He called for bring integrity to net-zero commitments by industry, financial institutions, cities and regions and to support a global, equitable transition to a sustainable future.

“Using bogus ‘net-zero’ pledges to cover up massive fossil fuel expansion is reprehensible. It is rank deception. This toxic cover-up could push our world over the climate cliff. The sham must end.” Mr. Guterres said that net-zero pledges should be accompanied by a plan for how the transition is being made. PW County is engaged in developing such a plan. The Sustainability Commission will provide the feed back on the plan for Prince William County.


Early in 2020, the General Assembly passed the Virginia Clean Economy Act (VCEA), which mandated a goal of 100% zero-carbon energy generation by 2050. This was to provide the major tool in achieving the County goals. Since 2010 Virginia electricity use has grown by about 40% while carbon intensity has decreased by almost 30%. This has been due to changing from coal to natural gas generation for a significant portion of electric power generation. 

Under the VCEA, Virginia is legally required to retire all baseload generation, except for the existing nuclear power plants, in favor of intermittent renewable generation. The VCEA as of 2020 would require additional solar panels enough to cover an area the size of Fairfax County (according to Dominion); and certainly requires technological advancement in power generation and storage. This is not realistic- it is the equivalent of a plan with a line that says "insert miracle here.".

  •  In 2020, natural gas accounted for 61% of Virginia's utility-scale electricity net generation, nuclear supplied 29%, renewables, mostly biomass, provided 6%, and coal fueled less than 4%.
  • Virginia’s Bath County Pumped Storage Station, with a net generating capacity of 3,003 megawatts, is the largest hydroelectric pumped storage facility in the world.
  • 21% of the power used in Virginia was generated in other PJM locations (West Virginia and Pennsylvania)

 The VCEA is facing challenges that may prevent it from achieving its goals in the stated time frame. According to VA Energy VCEA requires the Commonwealth to retire its natural gas power plants by 2045 (Dominion) and 2050 (Appalachian Power). These facilities currently comprise 67% of the current baseload generation as well as 100% of the power plants that meet peak demand. This switch mandated by VCEA has not been successfully accomplished anywhere in the world, yet. Advances in technology were always necessary to achieve the goals and those advances have not come fast enough.

According to Virginia Energy, during the foreseeable future, intermittent energy generation cannot meet all of Virginia's energy needs. At this time, solar and wind generation are affordable in many locations, but battery storage systems required to turn these generation sources into dispatchable energy are cost prohibitive. At the same time the extraordinary growth in electricity demand by the exploding number of data centers under development in Virginia requires that the Commonwealth increase the effective base load to meet what is forecast to be a 30% increase in electricity usage by 2040 (estimated by UVA Cooper Center).

To meet Virginians’ round-the-clock energy needs, full compliance with VCEA will require a reliance on other PJM states to produce the baseload generation capacity for the Commonwealth. However, that is not possible. The PJM has required that Dominion provide more generation into the system to meet the growing demand from data centers now and not wait for future technology.

It appears that electrifying the transportation sector which faces hurdles in accessibility for all, and the heating systems county wide will not meet the stated goals and timing of the resolution with the growth in power demand and land use changes approved in CPAs and the updated Comprehensive plan. However, there is hope that Prince William will be able to “bend the curve” if smart decision are made. The Community Energy and Sustainability Master Plan is being developed and includes adapting the county to impacts from climate changes.  You will have an opportunity to attend Townhalls meetings this spring to voice your concerns, ideas and provide feedback in the development of the Community Energy and Sustainability Master Plan. Please participate in the process and help us build a sustainable future for our children. 



Wednesday, December 14, 2022

Air Source Heat Pumps


from DOE

Heat pumps transfer the heat from a heat source to a heat sink using mechanical power. Different sources such as water, air and earth can be utilized as heat source for heat pump cycles. Air source heat pumps have been widely used in the south and mid-Atlantic states for decades. Warmer air leads to improving the performance of the heat pump cycle on air source heat pumps.  One of the main challenges using air source heat pumps is the effects of variations in climate and weather conditions on the operation of the heat pump cycles.

Air-source heat pumps take heat from the outside air, run it through a refrigeration cycle to step up the temperature, and deliver warm air to a building in winter and use the reverse cycle to cool the building in summer. One benefit of air source heat pumps in less extreme climates is that they can provide both heating and cooling, with the simple switch of a valve. Though, my friend insists that the air blown into the room is too cold. Though you do not get the hot blast of a gas furnace, I don’t experience cold air and think she needs to insulate her ducts.

Though the optimal operating point at maximum efficiency depends on geometric, thermodynamic and physical properties of the system components like the ducting and working fluids; in general. the colder it is outside the less efficient the heating cycle is. For years heat pump design has undergone improvements and changes to improve their performance in more extreme weather. Today, there are air source heat pumps available that will operate in more extreme conditions using less energy than the air source heat pumps of the past. 

Improvements continue. Research is on going is Alaska, Montana and Washington state to look at how the efficiency of a heat pump drops in colder temperatures, and how to appropriately size a heat pump for a home. The air-source heat pumps available today can keep your home warm even amid bone-chilling cold, using less energy than other types of heating systems. Or so the researchers say. One of the options to address heat loss in a duct system or avoid the cost of installing ducting is to utilize ductless min-split heat pumps in a home or addition.  

Ten years ago when I replace the failed air source heat pump in my house, I altered the size, changed the ducting configuration and materials, insulated the ducts, and bought a much more efficient heat pump with a variable speed. I ended up with a more comfortable home and a lower electric bill. I have been really happy with my current system, but heat pumps last only 8-12 years (in general) so I have been looking at the options on the market today.

There’s no official “cold climate” standard for heat pumps yet, but next month the U.S. Department of Energy, Energy Star program will introduce a cold-climate standard for air-source heat pumps. These heat pump will include a certification for air source heat pumps with an “acceptable” level of low-temperature performance and efficiency. 

For now, you will have to depend on the Energy Guide label which displays the heat pump's heating and cooling efficiency performance rating. Every residential heat pump sold in the United States has an Energy Guide label, look for it.

Heating efficiency for air-source electric heat pumps is indicated by the heating season performance factor (HSPF), which is a measure over an average heating season of the total heat provided to the conditioned space, expressed in Btu, divided by the total electrical energy consumed by the heat pump system, expressed in watt-hours. This is measured in set environmental conditions which is not going to occur outside your house on a regular basis. It is only a measurement for comparison like miles per gallon. Understand it as a measurement tool.

Cooling efficiency is measured by the seasonal energy efficiency ratio (SEER), which is a measure over an average cooling season of the total heat removed from the conditioned space, expressed in Btu, divided by the total electrical energy consumed by the heat pump, expressed in watt-hours. Once more this is measured in set environmental conditions.

The higher the HSPF the more effective the heat pump is on cold days at heating and the higher the SEER, the more effective the heat pump is at cooling on hot days. In general, the higher the HSPF and SEER, the higher the cost of the unit. However, the energy savings can return the higher initial investment during the heat pump's life. As I found when I replaced my first heat pump the new heat pump used less energy, substantially reducing air-conditioning and heating costs, but was also able to cool my house on the hottest of days and keep it warm in the winter. In our 4-season climate, getting the highest SEER and HSPF really paid off in overall satisfaction and operating cost savings.

Sunday, December 11, 2022

Gainesville West Data Center

 The Atlantic Research Corporation former Superfund Site (VAD023741705) at 5945 Wellington Road, Gainesville, VA is being redeveloped into a series of Data Centers by Amazon Corporation. The site is 117 acres in the Data Center Overlay District. They have applied for a Special Use Permit to increase the height of the buildings to 100 feet from the 75 allowed by right. Currently, the site is being graded for construction.

 As part of the redevelopment plan the on-site stream is being reconfigured and moved. In the planning package there are no permits for moving the stream or studies if the site development and stream relocation will impact the stability of the site institutional controls or create a pathway of exposure for the contaminants known to remain in the groundwater. In addition, the Environmental Constraints Analysis has been waived by the county along with the Perennial Flow Analysis for the on-site stream.

In a June 14, 2018 the U.S. EPA indicated that ARC had satisfactorily completed corrective actions pursuant to the CMI Order, Sections VI. H7 and I8.  In addition, Atlantic Research Corporation had taken Interim Measures to address perchlorate and other constituents of concern in soils.  However, EPA approved leaving contaminants in soil at the site above residential risk management levels, and at concentrations above risk-based standards in groundwater.  To ensure that the contaminants left on site would not injure the public or leave the site,  the regulators required that the Final Facility-wide remedy include ongoing groundwater monitoring and Institutional Controls (IC) Including:

  • Groundwater use restriction on the entire Facility
  • Soil is restricted on certain areas of the western parcel and included as part of the IC plan.
  • Vapor Intrusion controls are required for a specific area shown on a figure of the IC plan representing groundwater exceeding VISL.

According to the U.S. EPA website Atlantic Research Corporation continues to operate and manage a groundwater extraction and treatment system (Northern Deep Treatment System) with performance monitoring at on-site monitoring wells locations, including monitoring wells located at the downgradient property boundary. The groundwater extraction system includes approximately 53 monitoring wells that are sampled semi-annually or annually.

Constituents of concern (COCs) currently meet risk-based cleanup standards at the downgradient property boundary and there has been no off-site groundwater or surface water contaminant migration detected.

Pollution of surface water can cause degradation of ground-water quality and conversely pollution of ground water can degrade surface water. Thus, effective land and water management requires a clear understanding of the linkages between ground water and surface water as it applies to any given hydrologic setting. Within Prince William County Virginia there are four distinct geologic provinces: (1) the Blue Ridge, (2) the Culpeper Basin, (3) the Piedmont, and (4) the Coastal Plain. The U.S. Geological Survey divides the four geologic provinces of the county into seven hydrogeologic groups based on the presence and movement of the ground water calling them groups: A, B, B1, C, D, E and F.

It appears that in the area of this particular site, hydrogeologic group B and C are present.

Hydrogeologic group B underlies the western part of Prince William County and consists of sedimentary rocks of the Culpeper Basin. The predominant rock types are conglomerates, sandstones, siltstones, shales, and argillaceous limestones. Rocks within hydrogeologic group B tend to have moderate to excellent water-bearing potential because it is a fractured rock system with very little overburden. The highest reported yields in the county are from wells located in this hydrogeologic group, but this hydrogeologic group is susceptible to contamination- the fractures that carry water can easily spread a contaminant and without adequate overburden spills could flow to depth through a fracture.

Hydrogeologic group C, which is interspersed throughout the area of groups B and Bl, in the western part of the County, consists of igneous rocks (basalt and diabase) of the Culpeper Basin. The rocks of group C are Early Jurassic in age. The predominant rock types are basalt, sandstone, siltstone, diabase, hornfels, and granofels. 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.

I am concerned that development of the site and relocation and reconfiguration of the stream could potentially mobilize the chemical constituents of concern known to remain on-site:

Tetrachloroethylene (PCE), 1,1-Dichloroethene (1,1-DCE), Methylene Chloride, 1,1,1-Trichloroethane, 1,1,2-Trichloroethane, 1,1-Dichloroethane (1,1-DCA), 1,2,3-Trichloropropane, 1,2-Dichloroethane (1,2-DCA), Benzene, Carbon Tetrachloride,  Chloroethane, cis-1,2-Dichloroethene, Trichloroethene (TCE), Vinyl Chloride (VC), Perchlorate and 1,4-Dioxane.  The following COCs exceed vapor intrusion screening levels: PCE, TCE, VC, Benzene, 1,1-DCA, 1,2-DCA, and 1,1-DCE.

The U.S. EPA, VA DEQ maintain responsibility for the site. The specific address/Parcel ID from the special use approval does not have a joint permit application in process or an active VWPP permit. Any surface water impacts from the eventual data center would likely require a Virginia Water Protection Permit (VWPP) and a permit from US Army Corps of Engineers.

Though it is likely that such an application is being developed, because surface water impacts are ultimately proposed; however, the applications for the required permits have not been submitted to DEQ/USACE and the site is being graded without regard for the soil restrictions in the institutional controls and to all appearances the perennial stream and RPA has been wiped out.  No RPA  hearing was held. This should not happen. The environmental regulations and institutional controls exist to protect the community and essential water resources from exposure.

It is important that the U.S. EPA, VA DEQ  and USACE (who maintain responsibility for the site) approve the planed changes to the site that may impact the institutional controls and hydrology and determine if additional monitoring is necessary to ensure that the COCs are not mobilized to leave the site, before excavation and site work begin. Not after construction. The regulations are to protect us. The  county has failed in its duty and is not protecting the interests of the pubic in waiving the Environmental Constraints Analysis, RPA disturbance hearing, and granting the excavation permit ahead of the VWP permit.

Wednesday, December 7, 2022

2022 Dead Zone Update

Overall, the total volume of the 2022 Dead Zone in the Chesapeake Bay was the second lowest since 1985. The “Dead Zone” of the Chesapeake Bay is the common name given to the  volume of hypoxic amount of water with dissolved oxygen concentrations less than 2 mg/L- too low for aquatic organisms such as fish and blue crabs to thrive.

Hypoxia in 2022 started relatively late in the season. Around the beginning of June, the Dead Zone started to spread through the mainstem of the Bay. Although the size of the Dead Zone increased from June through July, the volume of hypoxic water stayed relatively low compared to the historical volumes and the mid-summer peak for the Dead Zone was slightly less than the historical average. The Dead Zone quickly decreased following the mid-summer peak and was effectively ended by the passing of the remnants of Hurricane Ian around the beginning of October. Overall, 2022 was a relatively good (low amount) year for hypoxia in Chesapeake Bay.

In the end the duration of hypoxia in summer 2022 was short and the total annual amount of hypoxia was relatively low, This was a relatively good year for hypoxic conditions in the Bay. On years like this it feels as if the Chesapeake Bay Clean Water Blueprint is making progress

Anchor QES and VIMS

Sunday, December 4, 2022

Beavers Improve Water Quality

As climate change worsens water quality and threatens ecosystems, the wooden dams of beavers may help lessen the damage.  This was the finding of a recent study by Stanford University researchers. Published November 8th 2022 in Nature Communications the study found that the wooden dams built by beavers raise water levels upstream, diverting water into surrounding soils and secondary waterways, the riparian zone. These zones act like filters, straining out excess nutrients and contaminants before water re-enters the main channel downstream.

The hotter, arid conditions that are expected to be brought by climate change will lessen water quality. However, these same conditions are favorable to the American beaver, and may have also contributed to a resurgence of the population and an explosion of dam building in the western United States.

The discovery of the profound impact of beaver dams came about serendipitously. When he was a  PhD student in 2017, lead study author Christian Dewey had started doing field work along the East River, a main tributary of the Colorado River near Crested Butte in central Colorado. Initially, Dewey had set out to track seasonal changes in hydrology, and riparian zone impacts on nutrients and contaminants in a mountainous watershed.

“Completely by luck, a beaver decided to build a dam at our study site,” said Dewey, who is now a postdoctoral scholar at Oregon State University. “The construction of this beaver dam afforded us the opportunity to run a great natural experiment.”

Beavers are semiaquatic mammals partial to freshwater environments.   They have the ability to create their own ecological niche by building dams.  Dam construction has the potential to alter the hydrology, biogeochemistry, and ecosystems of river corridors. Beavers build dams to help engineer their habitat for food supply (riparian and wetland vegetation), to create water bodies sufficiently deep that do not completely freeze during winter in  colder locations, and as a protection from potential predators. The dams and their ponds create riparian discontinuities baht allow a river to cleanse its waters and allow the created wetlands to absorb excess precipitation preventing catastrophic flooding.

To understand how beaver dams may affect water quality in a future where global warming produces more frequent droughts and extreme swings in rainfall, the Stanford researchers compared water quality along a stretch of the East River during a historically dry year, 2018, to water quality the following year, when water levels were unusually high. They also compared these yearlong datasets to water quality during the nearly three-month period, starting in late July 2018, when the beaver dam blocked the river.

Water quality is a measure of the suitability of water for a particular purpose – ecosystem health or human consumption, for instance. During periods of drought, as less water flows through rivers and streams, the concentrations of contaminants and excess nutrients, such as nitrogen, rise. Major downpours and seasonal snowmelt are then needed to flush out contaminants and restore water quality.

The researchers found that the beaver dam dramatically increased removal of nitrate, a form of nitrogen, by creating a surprisingly steep drop between the water levels above and below the dam.The larger the gradient, the greater the flow of water and nitrate into soils, where microbes transform nitrate into an innocuous gas.

For Further reading see:

Dewey, C., Fox, P.M., Bouskill, N.J. et al. Beaver dams overshadow climate extremes in controlling riparian hydrology and water quality. Nat Commun 13, 6509 (2022).

Dam builders and their works: Beaver influences on the structure and function of river corridor hydrology, geomorphology, biogeochemistry and ecosystems - ScienceDirect