Sunday, January 7, 2024

Tracking Water Use in Virginia

The Commonwealth of Virginia is a water rich state, but water is not unlimited. After the statewide drought of 1999-2002 Virginia has been required to look at water use to sustainably use our available water resources most effectively. This reporting is still developing but allows us to see and begin to understand our water use, identify trends and to try to keep the Commonwealth on a sustainable water path.

The Water Supply Planning (WSP) program was created after the 1999-2002 drought and requires all localities in Virginia to submit a water supply plan, either individually, or as part of a regional planning unit that was amended in 2020 and now requires that a locality report as part of 26 regional planning units. Information reported is what are the water sources and how much water they currently use. This planning includes both surface water and groundwater. However, the categories of water use are limited.

DEQ compiles the information included in each Plan, as well as the water reported water withdrawals collected through the Annual Withdrawal Reporting from Water Withdrawal Permitting Programs to create a model used to evaluate the sustainability of our water resources.  The results of this collective analysis are published in the State Water Resources Plan. The most recent completed plan was published in late 2022 using the data from the previous year and much of the comments below are paraphrased from the report.

In calendar year 2021 total reported water withdrawals were approximately 5.66 billion gallons per day (BGD), including the cooling water withdrawals at nuclear and fossil fuel power generation facilities, which were 77% of water used. Excluding power generation, 2021 reported withdrawals totaled 1.27 BGD, a 2.9% increase compared to the five-year average and an 8% increase over 2020- a year impacted by the pandemic. I had not realized how much public water use was impacted by the first year of the pandemic and look forward to seeing the data in the next few years. The 2021 total is the highest within the last five years and the curve (excluding 2020) seems steeper. 

from DEQ

This increase in water withdrawals over the last five years is largely driven by increased volume from public water supply facilities. Deliveries of water from public supply to specific users are not reported to DEQ; therefore, the reported withdrawals for public water supply do not differentiate between the categories of end users. There is no way to see what accounts for that growth (or for that matter the sharp fall in 2020), though it seems unlikely that in a period of decreasing personal water use that increase is just a reflection of population growth since Virginia’s population grew less than ½% over the five year period. In 2021 public water supply withdrawals increased by 3.8% (from the 5 year average) to 803 million gallons per day (MGD). Despite reductions in per capita water use, reported public water supply withdrawals have steadily increased.

Other drivers of increased reported withdrawals in 2021 were increases in agricultural irrigation and manufacturing, which were 17.6% (3.4 MGD by volume) and 1.1% (3.9 MGD by volume) higher than the five year average respectively. Both 2020 and 2021 featured periods of the growing season of drier than normal conditions which may be contributing to the increase in irrigation compared to the average.

The DEQ identifies new, continuing, and future priorities, challenges, or other topics important to water resources management and notes that in 2021, Commissioners of the Interstate Commission on the Potomac River Basin (ICPRB) passed a Resolution on Enhancing Water Supply Resilience for the Washington Metropolitan Area and the major water companies in Northern Virginia. This is the first step in updating the Low Flow Allocation Agreement (LFAA) of 1978 and the Water Supply Coordination Agreement (WSCA) of 1982 both are the foundational agreements of the ICPRB. DEQ presented data indicating that water supply withdrawals may reduce mean monthly flow of the Potomac River and tributaries by as much as 40% during moderate and extreme drought flows. This is significant since research literature indicates that species impacts can be seen with a 20% reduction in river flow. Drought response may have to change to protect the native species.

To forecast the potential for climate change to impact streamflow, DEQ developed a series of climate change scenarios that simulate how streamflow during a drought may change using the best available global climate models. These scenarios represent the initial effort by DEQ to address climate uncertainty and surface water resources within the Commonwealth. While the models suggest an overall increase in precipitation, they also identified the potential for more severe periods of drought.

The ability to provide a predictable and reliable water supply under any climatic condition is critical to Virginia’s economic well-being. Therefore, developing a process for incorporating the evaluation of climate change into water withdrawal permitting and water supply planning and review, is an important element of resiliency planning.

Annual water withdrawal reporting is one of the most important data sources for DEQ. Reporting of water withdrawals allows for informed modeling and planning decisions related to the Commonwealth’s future water demands and availability. However, addressing impacts from water users that are exempt from the requirement to obtain a VWP surface water or groundwater withdrawal permit, or otherwise are unpermitted, is a challenge in managing both surface water and groundwater to provide certainty that this water will be available for future growth over the long term under all conditions. Only 21% of surface water withdrawals are subject to permitting requirements. A process to incorporate the users who are exempt from permits into the reporting needs to be developed to assure the sustainability of our water resources.

The proportion of groundwater use that is exempt from permitting, or otherwise unpermitted, although smaller in absolute terms than exempt surface water demands, is more difficult to estimate since much of it comes from domestic or private wells with no requirement to report withdrawals or parts of the state that are not part of a groundwater management area. In a groundwater management area there are few exemptions from the requirement to obtain a permit for groundwater withdrawals, but in the rest of the Commonwealth, the monitoring of groundwater use is limited. Information is essential to planning for a sustainable Virginia.

Water withdrawals that are reported to DEQ are then linked into the surface water model, which enables DEQ to prepare up-to-date and accurate water budgets and conduct cumulative impact analyses in f permit decisions and water supply planning efforts. Withdrawal data is also used by other programs within DEQ, other agencies, counties and the public. The effectiveness of the Commonwealth’s water resource management depends on the comprehensiveness and accuracy of this self-reported withdrawal information.

In Virginia the Water Withdrawal Reporting Regulation requires the annual reporting of monthly water withdrawals (surface water and groundwater) of volumes greater than an average of 10,000 gallons per day (GPD) during any month, or one million gallons per month for crop irrigation. The regulation allows the submission of metered and estimated water withdrawal information. DEQ maintains withdrawal data as far back as 1982, but there has been limited work to determine what is the supply of water available to the Commonwealth. We are coming to the point where we need to know that.

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