With a $3.4 million grant from the Virginia Department of Environmental Quality, researchers from the College of Agriculture and Life Sciences will lead a comprehensive six-year study to determine how utility-scale solar farms impact stormwater runoff and local soil and water quality throughout the state.
"Solar is probably going to be the No. 1 land use change that will occur over the next decade in many parts of Virginia, particularly in existing agricultural and forested areas," said Ryan Stewart, associate professor in the School of Plant and Environmental Sciences and lead investigator of the project. "Even if it's not your neighbor's property, these sites will be somewhere nearby. We're collecting the data we need to do solar right."
Virginia ranks ninth in the nation for solar production, according to the Solar Industries Association, with 52 active utility-scale solar facilities generating upwards of 4,296 megawatts - enough to power 476,000 homes. Since Virginia passed the Clean Economy Act in 2020, mandating a transition to 100 percent renewable energy by 2050, the Virginia Department of Environmental Quality (DEQ) has received 50 active notices of intent from companies planning to build utility-scale solar installations. To meet Virginia's 2050 renewable energy goal of 16,100 megawatts, as many as 161,000 acres - or about 10 acres per megawatt - would be needed.
"The research question we are addressing here is: Is there a change in the soil and hydrology?" Stewart said. "The DEQ wants to know if and how these solar installations should be regulated and how they should be siting infrastructure. There's just not a lot of data out there and what is available is either not really applicable to this type of project or it's outdated."
In addition to helping inform DEQ regulatory policy, the study will offer guidance to localities considering solar farm proposals. Industry partners, including Dominion Energy, AES Corporation, Energix, and Urban Grid, have stepped forward to participate in the study by offering their solar facilities as research sites as well as providing commitments of cash and in-kind support for this research totaling over $500,000 to date.
"The industry, in general, is supportive of this research because our approach is we are going to go out to these sites and actually measure to see which models work and which don't," said co-investigator W. Lee Daniels, the Thomas B. Hutcheson Jr. Emeritus Professor of Environmental Science. "Even though it's a six-year project, that feedback loop to our cooperators will start occurring as soon as we have data and we can validate it."
The team will select six sites throughout Virginia to study - three fully developed, revegetated solar sites and three that will be monitored from pre-development through installation, revegetation, and their full operating phase. Each solar farm will be outfitted with multiple monitoring locations, instrumented to collect data on rainfall, surface water level, air temperature, and specific conductance. Flow-weighted composite samples taken from storm events will be analyzed for pH, sediment, nitrogen, phosphorous, and other potential contaminants.
The study will represent one of the largest collections of actual runoff data in Virginia since several localities contributed to the Environmental Protection Agency's Nationwide Urban Runoff Program completed in the 1980s, which still underpins many of the current runoff and watershed modeling applications in the Chesapeake Bay region. These models are extremely important in measuring progress toward achieving environmental goals such as the Total Maximum Daily Load for the Chesapeake Bay.
"In terms of modeling applications and validating and improving models, this data will be really useful and valuable to a lot of people," Daniels said. "This work is going to generate data that would also be applicable to construction sites, mixed-use sites, and pasture sites, for example. We'll have actual numbers to update all these 30- and 40-year-old assumed values that are underlying our models right now."
The research team integrates expertise from Virginia Tech and Virginia State University. Stewart, the lead principal investigator, is an expert in soil hydrology and stormwater infiltration. Daniels is an authority in the rehabilitation of disturbed lands who will assist with soil disturbance studies and work directly with the industry and DEQ. David Sample, professor of biological systems engineering and Extension specialist based at the Hampton Roads Agricultural Research and Extension Center, will lead efforts to model stormwater flows and local water quality impacts.
Sample recently conducted two similar stormwater monitoring studies in the cities of Virginia Beach and Fredericksburg.
"Each of these efforts will help expand our knowledge of runoff water quality and will help guide the design of mitigation measures and stormwater treatment," Sample said.
Advanced Extension Specialist John Ignosh with Virginia Cooperative Extension will facilitate stakeholder communication and provide field equipment support.
Co-investigators Vitalis Temu and Maru Kering, both associate professors at Virginia State University's Agricultural Research Station, will monitor how site vegetation reacts with solar panels and storm events.
"As society tries to confront climate change and look for sources of renewable energy, solar will be part of our energy portfolio for a while," Stewart said. "The chance to collect this kind of runoff data in the field and at this scale is rare, so we are very excited for that."
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