Using Lidar to Measure Reservoir Storage

Elevation-Area-Capacity Relationships of LakePowell in 2018 and Estimated Loss of Storage Capacity Since 1963

Scientific Investigations Report 2022-5017
Water Resources Mission Area
Prepared in cooperation with the Bureau of Reclamation

For a while now, we’ve been waiting for LIDAR, light detection and ranging technology, to bring us the elusive self-driving car. Unfortunately, it always seem to be 5 years out. However, I read with amazement about a team of scientists from South America and the United Kingdom who used helicopter-mounted lidar to peer below the rainforest foliage and get a view of the remains of structures below the trees discovering villages that are hundreds of years old and had been swallowed by the jungle.

Now, scientists are finding many other uses for Lidar. The U.S. Geological Survey (USGS) , in cooperation with the Bureau of Reclamation (Reclamation), surveyed Lake Powell between fall 2017 and spring 2018 topographic light detection and ranging (lidar) data (land elevation) and multibeam bathymetry (bed elevation of a water body to calculate the capacity of Lake Powell, the second largest reservoir in the nation.

Lake Powell is located on the Colorado River across the Utah– Arizona border and was created in 1963 by the completion of the Glen Canyon Dam. Nearly 200 miles of the Colorado River was flooded upstream from the dam creating the reservoir/lake. In the United States only Lake Mead, which is approximately 300 miles downstream on the Colorado River is larger.

Though the instrumental record of the Upper Colorado River Basin is robust, with daily stream gage monitoring going back decades, only two studies have estimated the Lake Powell storage capacity. The original, pre-Glen Canyon Dam elevation-area-capacity tables (Bureau of Reclamation, 1963) that were calculated from contour maps and a reservoir-wide, range-line bathymetric survey that was completed 25 years post-impoundment in 1986 (Ferrari, 1988). Both studies utilized the best-available technology at the time but lacked the precision of current surveying methods.

Lake Powell has continuously trapped sediment from the sediment-laden Colorado and San Juan Rivers at the river deltas, diminishing the storage capacity at the highest elevations of the reservoir. During the most recent survey of Lake Powell, USGS scientists used high-resolution multibeam bathymetry and lidar to create the equivalent of an underwater topographic map of the reservoir. The data were then combined to create a topobathymetric digital elevation model (TBDEM), a continuous representation of submerged bathymetry and subaerial topography.

Just as the land above the water has its highs and lows, so too does the land beneath the water’s surface. Those features are known as bathymetry. In a reservoir the build-up of sediment slowly over time reduces the capacity of to the reservoir – how much water it can hold.

The lidar topographic data were acquired during a 2-day airborne survey on April 2 and April 3, 2018, and completed by The Atlantic Group, LLC they found that the total storage capacity of Lake Powell is now 25,160,000 acre-feet. This is a decrease of 1,833,000 acre-feet or 6.79% of storage capacity from 1963 to 2018. The average annual loss in storage capacity was approximately 33,270 acre-feet per year between 1963 and 2018.

Locally, the Occoquan Reservoir in an urbanized area has suffered a 15% loss of capacity associated with accelerated siltation over a shorter period of time.

Governor Youngkin Begins withdrawal from RGGI

Last week Governor Glenn Youngkin signed Executive Order 9 to direct DEQ to examine the impact of RGGI and start the process of ending Virginia's participation in the program. This occurred with the released the Regional Greenhouse Gas Initiative (RGGI) report.

At the time of the announcement the Governor comment that “costs are soaring for Virginia families … and that RGGI is in reality a carbon tax passed on to families, individuals and businesses throughout the Commonwealth--it’s a bad deal for Virginians. Hardworking Virginians are having to do more with less as inflation steals a historic amount from their paychecks and the failed Biden Administration energy policies are costing Virginians more at the pump and in their homes. We're working every day to cut energy taxes and reduce costs--like the RGGI carbon tax--and make Virginia the best place to live, work and do business." 

The following conclusions and findings were made in the Regional Greenhouse Gas Initiative (RGGI) report: 

• Prior to RGGI, electricity generation in Virginia has increased while CO2 per MWh has almost been cut in half over the last ten years. This was primarily due to changes in the types of generation as seen below.
• Because of the captive nature of their ratepayers, the ability for power-generators to fully pass on costs to consumers, and the fact that the Code of Virginia dedicates RGGI proceeds to grants programs, participation in RGGI is in effect a direct carbon tax on all households and businesses; 
• In addition, consumers are unable to avoid the pass through of these costs because they do not have the opportunity to switch electric providers – Dominion and other providers are monopolies in most regions of Virginia.
• The imposition of the RGGI “carbon tax” fails to achieve its goal as a carbon “cap-and-trade” system because it lacks any incentive for power-generators to actually reduce emissions, due to the ability to pass through costs to consumers.
• The costs of compliance with the trading rule and participation in RGGI have begun to materialized in higher electricity rates as identified in the filings before the State Corporation Commission by Dominion Energy. 
• Emission allowance prices have increased over time, and are expected to continue increasing which will increase the tax on ratepayers. 

 On July 10, 2020, Virginia formally adopted the CO2 Budget Trading Program (Part VII of 9VAC5-140) for the power sector to implement a carbon emissions trading and reduction program as authorized by the Clean Energy and Community Flood Preparedness Act (Article 4 of Chapter 1219 of the 2020 Acts of Assembly). The rule allowed for full participation in the Regional Greenhouse Gas Initiative (RGGI) to reduce carbon dioxide (CO2) emissions and make emissions allowances available for sale through an auction program that power producers use for compliance purposes. Proceeds from allowance sales are returned to Virginia to fund climate mitigation and resilience programs. Virginia began full participation in RGGI on January 1, 2021, and participated in five quarterly auctions to date. On January 15, 2022, Governor Youngkin issued Executive Order 9 (2022) (EO-9) to re-evaluate the program.

The review found that prior to the implementation of the RGGI: That a major shift has occurred in the Virginia power sector where electricity generation from coal has been replaced by cleaner generation sources of natural gas and more recently renewable energy generation sources. Also, during the same time, in-state electricity generation had increased by about 30%, which has led to the mass emissions levels remaining relatively constant. Over this time period, Virginia has become the world's data center capital which might have accounted for the growth in electricity demand.

The review also found that:

Because of the captive nature of their ratepayers, the ability for power-generators to fully pass on costs to consumers, and the fact that the Code of Virginia dedicates RGGI proceeds to grants programs, participation in RGGI is in effect a direct carbon tax on all households and businesses.  RGGI fails to achieve its goal as a carbon “cap-and-trade” system because it lacks any incentive for power-generators to actually reduce carbon emissions.  

Other states participating in the RGGI program designed their systems to provide rebates to their ratepayers, in Virginia the program operates as a hidden tax on consumers in which the funds are disbursed through grant programs. Virginia consumers were originally told that the program would not increase their energy bills, and given the rate increases approved, this is untrue. This is an inefficient method to tax and distribute funds for the benefit of Virginians without achieving the intended greenhouse gas emission goal.

The compliance costs of RGGI program participation have submitted by Dominion Energy and approved by the SCC, and have begun to impact electricity rates.  These costs are and will continue to be directly related to the cost of allowances, along with other charges allowed under current law and regulations.  Allowance prices have varied significantly in the past, and future prices will continue to vary.  Four other RGGI participating states (and prospectively a fifth) provide electric bill assistance to customers using some of their auction proceeds which Virginia does not. 

Spring- Time to Flush the Pipes

 As part of the annual maintenance program for the regional water distribution systems in Virginia and Washington DC, on March 21st , 2022 Fairfax Water, the Washington Aqueduct, Loudoun Water and the City of Manassas will switch from chloramine to chlorine to disinfect their water. During this time, Arlington Department of Environmental Services, DC Water, the Prince William Service Authority, Loudoun Water and Fairfax Water will begin flushing their water distribution systems. Each spring these water distribution companies flush their water mains by opening fire hydrants and allowing them to flow freely for a short period of time.

Fairfax Water will disinfect with chlorine from March 21st  to June 13th and the water systems the flushing of the water mains in Fairfax and Prince William will occur during that time. Crews from the Service Authority and Fairfax Water will open hydrants throughout their service area in brief intervals in order to draw water more forcefully through the distribution system and scrub out the pipes. This helps to dislodge sediment that may have collected in water mains over the past year. In DC, Arlington and  Falls Church, the flushing will occur from March 23 through May 9th , 2022. Those jurisdictions purchase treated drinking water from the Washington Aqueduct. Loudoun Water also announced they will be starting their program on March 21st.

For most of the year, chloramines, also known as combined chlorine, is added to the water as the primary disinfectant. During the spring the water treatment plants for Fairfax Water, Loudoun Water and the Washington Aqueduct switch back to chlorine in an uncombined state, commonly referred to as free chlorine. This free chlorine reacts with sediments suspended during flushing and kills bacteria that may be in the bio-film that forms on the pipe walls. Many water chemistry experts believe this short exposure to a different type of disinfectant maintains a low microbial growth in the bio-film and improves the quality and safety of the water.

This change in disinfection is an annual program to clean the water distribution pipes and maintain high water quality throughout the year. The U.S. Army Corps of Engineers Washington Aqueduct provides water to the District of Columbia, Arlington County, and other areas in Virginia. Fairfax Water provides water to Fairfax County and parts of both Loudoun and Prince William County. WSSC does not switch their disinfectant.

You may notice a slight chlorine taste and smell in your drinking water during this time, this is not harmful and the water remains safe to drink. Depending on your location within the distribution system, it could take up to a week for your drinking water to transition from combined to free chlorine at the beginning of the flushing program, or from free chlorine to combined chlorine at the conclusion of the flushing program. You may want to use filtered water to drink or leave an open container of water in the refrigerator for a couple of hours to allow the smell to dissipate. Refrigerator filters remove chlorine so you do not have to worry about ice. Water customers who normally take special precautions to remove chloramine from tap water, such as dialysis centers, medical facilities and aquarium owners, should continue to take the same precautions during the temporary switch to chlorine. Most methods for removing chloramine from tap water are effective in removing chlorine. The annual chlorination is important step to remove residue from the water distribution system. Free chlorine is better suited to remove residue that may have collected in the pipes than chloramine and a coordinated opening of fire hydrants serves to flush the system and scrub the pipes.

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.

Do you know what’s in your well water?

Prince William County Extension will be having a test your well water clinic in April.  The kit pick-up and drop off with be a drive by at the Extension Office in Manassas. Introduction and sampling instructions will be presented by an online video and results and interpretation will be by Zoom meeting.

Water samples will be tested for: iron, manganese, nitrate, lead, arsenic, fluoride, sulfate, pH, total dissolved solids, hardness, sodium, copper, total coliform bacteria and E. Coli bacteria. Sample kits will be $65  this year. Registration and pre-payment must be online by going to https://tinyurl.com/VCE-PW-VAHWQP before April 4th 2022.  I had no trouble following the link and prepaying. Be aware they will send multiple email confirmations- a receipt and confirmation of registration from  the VCEPrograms email and a payment receipt from the Bursar at Va Tech.


The Prince William Drinking Water Clinic has 4 parts:

1. Watch Kick-Off Meeting PowerPoint & How to Collect Water Sample using links below:

Kickoff Meeting PowerPoint and How to Collect Water Sample

2. Sample Kit Pickup- on Saturday, April 9th from 9:00am-12:00pm (noon) at the VCE Office, 8033 Ashton Ave, Manassas 20109. This is a drive-through pick up (remain in your car. There will be a VCE tent and signs with directions in the parking lot.)

3. The Sample Drop Off on Wednesday, April 13th  from 6:30am-10am ONLY at the VCE Office, 8033 Ashton Ave., Manassas 20109. Just walk up to the VCE canopy and hand them your samples with the paperwork. 

4. Results Interpretation Meeting (Zoom)-on Tuesday, May 17th, 7:00pm-9:00pm, there will be a live Zoom interpretation meeting which will explain the report, include a discussion, and answer questions on dealing with water problems. Zoom link and details will be emailed to everyone who registers.

Household water quality is driven by geology, well construction and condition, nearby sources of groundwater contamination, and any water treatment devices and the condition and materials of construction of the household plumbing. To ensure safe drinking water it is important to maintain your well, test it regularly and understand your system and geology. If you have water treatment equipment in your home you might want to get two test kits to test the water before and after the treatment equipment to make sure you have the right equipment for your water and that it is working properly.

The chart below shows what was found in the the testing conducted last year.

Restoring the Woodland

My house sits on a bit over 10 acres, about three of them lawn and ornamental gardens. The remaining seven acres is woodland, and much of the woodland is part of the “resource protected area,” RPA, as you can see on the green overlay below. Over the past decade invasive species seemed to takeover the woodland after dozens of trees were lost to Emerald Ash Borer.  

Until a few years ago I felt we did not have to worry about dead trees, as it was all part of the natural process of renewal. However, the number of dead and dying trees had increased dramatically and it was obvious that the invasive vines were choking out the renewal process. So with guidance from the Forest Service and the Chesapeake Bay Act guidelines I began a project to restore the woodland.

RPA’s as defined in the Chesapeake Bay Preservation Act are vegetated areas along water bodies, such as lakes, streams, rivers, marshes or shoreline. RPAs are the last line of defense for the protection of water quality. These buffers stabilize shorelines and stream banks, filter pollutants, reduce the volume of stormwater runoff and provide critical habitat for aquatic species and wildlife. Trees and shrubs in riparian buffers reduce erosion, improve air quality, and provide shade in the summer, windbreaks in the winter and adventures all year for little boys.

A healthy forest has living trees functioning as part of a balanced and self replacing ecosystem that is a complex mix of trees, understory shrubs and groundcover. In a healthy woodland the process of natural succession occurs over time. Small saplings develop and will become the next generation of trees as the older ones die out. Though benign neglect had been my rule for managing the RPA, it seemed clear the woodland needed some help to renew itself. We contacted the Virginia Department of Forestry for assistance and guidance in this effort.

Assistance came in the form of Kinner Ingram, an Urban and Community Forestry Specialist from the Virginia Department of Forestry. He came out and inspected the woodland and made some recommendations.  He felt that with removal of the invasive vines and the hanging dead trees the wood might begin to renew itself. He put his recommendations in a report for me to submit to Clay Morris, Natural Resources Section Chief, Environmental Services Division of Prince William County Public Works. Though there has been some questions about the Chesapeake Bay Advisory Board role in exceptions. I was strictly by the book in what is allowed in an RPA.

Though the RPA covers just 2/3 of the woodland, I am treating all the wooded area in the same way.  I applied for a Permitted Buffer Modifications under (9VAC25-830-140.5) to do the RPA. After the Mr. Morris reviewed the second year of work he granted us permission to complete the project as outlined in the roadmap for restoring the woodland health provided by the Forest Service and implemented by Wetland Studies and Solutions. General woodlot management for the removal of the invasive vines and some of the dead trees to facilitate regrowth and regeneration of the woodland. In the area where we just removed the invasive Autumn Olive, we are planning of seeding a wildflower mix this spring. It is hoped that the surviving trees will spread their seeds in the open areas and that the piles we created will serve as habitat for wildlife.

Horrible tangled mass of invasive vines above and below is the after picture

I am not a landscape designer, but I dream someday of having a “niceish sort of woodland” with a pathway to wander that Jane Austin herself would approve of- an ode to Kings Point Park where I spend much of my teen years wandering the woods and picnicking with Jane Austin’s books. Right now my budget every year goes to the hand removal (with clippers and chain saw) of the invasive vines and plants and creating habitat piles of the cut up dead trees. A small portion of the budget each year is used to paint the stumps of the vines with herbicide to extinguish them and keep my foot path clear. Someday a garden folly will mark the entrance to the woodland.  

This is an image I loved from the Haddonstone catalogue. 

Right now I am enchanted with the Haddonstone Folly

Bi-County Parkway is Stopped Again

At last Tuesday’s Board of County Supervisors meeting the Supervisors voted unanimously supported a resolution to remove the Bi-County Parkway from the County's Mobility Plan at this time. In 2016, the Board of County Supervisors at the time had voted to remove the project from its Comprehensive Plan. The proposal was then resurrected as part of the current Comprehensive Plan update, potentially to serve as a widening of Pageland Lane to serve the proposed PW Digital Gateway.

The Bi-County highway corridor in its last incarnation is approximately 45 miles in length, and is essentially a more direct route for north/south commuters, and cargo and truck traffic connecting I-95 to Dulles Airport and Route 7. The key elements of the Bi-County Parkway as outlined by VDOT in 2013 were:

• “Construction of a continuous high-occupancy vehicle (HOV) facility between I-95 and the area west of Washington Dulles International Airport, which would operate during peak periods in the morning and evening.”
• “Establishment of a high-occupancy toll (HOT) system for the Corridor between the intersection of VA 234 and Country Club Drive and the Washington Dulles International Airport area. Vehicles carrying three or more persons (HOV 3+) would be able to access the system at no cost, and other vehicles would pay a toll to access the HOV/HOT lanes during peak periods.”
• “Construction of a new roadway connection between the North-South Corridor and the Washington Dulles International Airport area, providing connections to VA 606 and improving regional and statewide access to the airport, surrounding freight facilities, and the Metrorail Silver Line.”
• “Provision of new and expanded transit services operating throughout the Corridor... They will provide north-south mobility as well as connections for individuals destined toward the east and west via transfers at convenient locations such as park-and-rides and rail stations. Construction of a continuous multi use trail along the Corridor for the use of bicyclists and pedestrians, allowing them to access activity centers throughout the north-south corridor seamlessly.”
• “Improvements to transportation demand management programs (TDM) within the Corridor, focused on marketing and promotion of the expanded transit services and the HOV network.”

The Commonwealth of Virginia still carries the Bi-County Parkway within their overall transportation plan. This mean that Prince William County will never be rid of the possibility of the Bi-County Parkway popping up. Prince William County community objections to this planned parkway have focused on several issues that are still of concern to the community:

• The Bi-County Parkway will drive all the east-west traffic to I-66 increasing traffic on that road.

• The Bi-County Parkway is intended to be a 4 lane and 6 lane highway that will provide direct access to Dulles Airport, but would have limited access to the Prince William community.
• The planned road will require that Virginia invoke eminent domain to take more than a dozen homes.
• Route 234 through the Battlefield that provides road access to several businesses and Sudley Methodist Church (that predates the Civil War) will be eliminated, and effectively land lock and isolate the Church within the park to a slow death. In addition, the planned  designations of “Village Mixed Use” for Catharpen would be nullified.
• Construction of a continuous high-occupancy vehicle (HOV) facility between I-95 and the area west of Washington Dulles International Airport would effectively sever northwestern Prince William County from the rest of the county and Manassas.
• The Bi-County Parkway does nothing to improve east-west traffic, instead it provides connectivity to the airport that Prince William residents do not want, divides the county and eliminates connections within our county and only benefits the Loudoun County developments.
•  The route through Prince William County’s Rural Crescent potentially damages our watershed and water resources. The Rural Crescent as long as it still exists provides a significant portion of our green infrastructure to our community connecting  the still intact habitat areas through a network of corridors that provide for wildlife movement and trails as well as pathways for pollinators. Maintaining intact, connected natural landscapes is essential for basic ecosystem and watershed preservation to ensure that there will always be clean air and water in Northern Virginia. The Northern Virginia Regional Commission (NVRC) has called the corridor one of three priority conservation area for the region.

Though there has been confusion on who requested the Bi-County Parkway reintroduced as part of the Comprehensive Plan, once again, Supervisor Candland has fought to stop it and was able to join with Supervisor Baily to convince the other Supervisors that this roadway was not in the best interests of Prince William County.