Today we are initiating CO-OP Drought Operations, per the Water Supply Coordination Agreement (WSCA) of 1982. According to the WSCA, Drought Operations is triggered when flow in the Potomac River at Little Falls, plus Washington metropolitan area Potomac withdrawals, “is projected to be less than twice the projected withdrawals for any of the next five days.”
During Drought Operations, CO-OP staff provide twice daily reports of flows, withdrawal, and reservoir storage levels. Staff reviews forecasted flows and withdrawals to determine if releases from upstream reservoirs or other operational changes are required. We ask that water suppliers submit data twice daily: by 7:30 AM each morning, with an update by 1 PM.
Modest amounts of rainfall fell across much of the basin over the past 24 hours, ranging from trace amounts near the DC metro area to 0.75 inches in the western portion of the basin. 1/10 to 1/4 inches of rain is expected over the next 3 days according to the Middle Atlantic River Forecast Center, with highest amounts in the northern and western portions of the basin. The significant drop in Potomac River flow at the Point of Rocks gage is a temporary fluctuation due to upstream hydroelectric operations at Dams 4 and 5.
Please send any questions or comments to coop@icprb.org.
Thank you for your continued support!
CO-OP Drought Team
Daily flows:
Little Falls gage flow 2023-08-24: 513 MGD (794 cfs)
Little Falls gage flow 2023-08-25: 535 MGD (est., based on recently available real-time data) (828 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2023-08-24: 937 MGD (1450 cfs)
Point of Rocks flow 2023-08-25: 556 MGD (est., based on recently available real-time data) (860 cfs)
Yesterday's Washington metropolitan area Potomac River withdrawals and discharges (2023-08-24):
Fairfax Water Corbalis withdrawal (Potomac): 109 MGD
WSSC Water Potomac withdrawal: 145 MGD
Washington Aqueduct withdrawal: 143 MGD
Loudoun Water withdrawal: 5 MGD
Loudoun Water Broad Run discharge: 6 MGD
Total Potomac withdrawal: 402 MGD
Total net Potomac withdrawal: 397 MGD
Yesterday's Patuxent, Occoquan, and Net Total System Withdrawal (2023-08-24):
FW Occoquan withdrawal:72 MGD
WSSC Patuxent withdrawal:42 MGD
Yesterday's total system withdrawal (2023-08-24): 511 MGD
Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 1450 cfs
QPR, obs: 1450 cfs
QPR, WS: 0 cfs
Note to Loudoun Water: See NWS ensemble flow forecasts (HEFS, GEFS, NAEFS) for Point of Rocks flow for the next 7 days – see https://www.weather.gov/erh/mmefs_marfc?id=PORM2&model=NAEFS.
Recommended operations for today (2023-08-25 A.M.):
None at this time.
Reservoirs - Usable storage (1969-12-31 A.M., BG):
Facility, %Full, Current, Capacity*
WSSC’s Patuxent reservoirs, 55%, 5.6, 10.2
Fairfax Water’s Occoquan reservoir, 98% - provisional, NA, 8.05
Little Seneca Reservoir, 97%, 3.8, 3.9
Jennings Randolph Total Reservoir, 82%, 24.18, 29.4
Jennings Randolph water supply**, 100%, 13.1, 13.1
Jennings Randolph water quality**, 68%, 11.1, 16.3
Savage Reservoir, 63%, 3.96, 6.3
*Storage and capacities for Occoquan, Patuxent and Little Seneca reservoirs are provided by Washington metropolitan area water utilities, and based on best available information. Storage and capacities for Jennings Randolph and Savage reservoirs are based on observed water levels and available US ACE water level/storage tables from 1998. ICPRB estimates that sedimentation has resulted in a loss of total available storage in Jennings Randolph Reservoir of 1.6 BG in recent years, and this loss is not reflected in the numbers above.
** ICPRB's initial estimate. Final accounting of Jennings Randolph water supply versus water quality storage will be provided at a later date by the US ACE.
Note: Potomac River flow at Little Falls has dropped below the threshold for CO-OP drought operations. When this occurs, per the Water Supply Coordination Agreement of 1982, CO-OP begins twice daily monitoring and reporting of Potomac flows and withdrawals on behalf of the CO-OP suppliers, Fairfax Water, Washington Aqueduct, and WSSC Water. Suppliers can review data at CO-OP's Data Portal at www.icprbcoop.org. Reports formatted in approved templates should be submitted by email to coop@icprb.org by 7:30 am and 1:00 pm for automated processing. Published monitoring reports are at http://icprbcoop.org/products/monitoring-reports.