2022 WMA Drought Exercise - Day 1: Morning Potomac flow and demand update (Tuesday, 2022-11-15)

Submitted by admin1 on Tue, 11/15/2022 - 14:26

Welcome to the first day of the 2022 WMA Drought Exercise. The simulation day is Thursday, August 25, 2022, and the basin conditions have reached the threshold of the "Warning" stage of the MWCOG drought regional plan. An actual practice Drought Coordination Technical Committee (DCTC) MS Teams meeting is scheduled for today (Tuesday, November 15, 2022) from 4:00 PM to 5:00 PM, in response to simulated combined storage in Jennings Randolph and Little Seneca reservoirs dropping to 9.9 billion gallons (BG), or 60 percent of the combined capacity. The weather was unseasonably warm during the past winter, with year-to-date precipitation departures from average equaling 3.5 inches below normal. On June 1, all system reservoirs exceeded CO-OP's target of 90 percent capacity. But in late July, simulated flow in the Potomac River fell to a level requiring water supply releases from the system's upstream reservoirs. Since then, periodic releases from Jennings Randolph and Little Seneca reservoirs have augmented simulated river flow. Because operations have been ongoing over the summer period, the Washington Aqueduct shifted their river water withdrawals from Great Falls to Little Falls on August 16, 2022, when simulated flow at Great Falls above the Washington Aqueduct intakes dropped to 500 million gallons per day (MGD). This withdrawal shift is to maintain “at least 100 MGD plus Washington Aqueducts allocation up to 200 MGD between Great Falls and Little Falls dam” per the Potomac River Environmental Flow-By Study (MD DNR, 1981).

ACTUAL conditions, SIMULATED operations, and SIMULATED storages are reported below.

Best regards, 
The ICPRB CO-OP Drought Team

ACTUAL Recent basin-wide average precipitation (above Little Falls):
(based on CO-OP's Low Flow Forecast System analysis of Middle Atlantic River Forecast Center (MARFC) gridded multisensor precipitation estimates)
Yesterday's area-weighted average basin precipitation: 0 (inches)
Past 3-day cumulative area-weighted average basin precipitation: 0.7 (inches)
Past 7-day cumulative area-weighted average basin precipitation: 2.06 (inches)

ACTUAL Daily flows:
Little Falls gage flow 2022-11-14: 8725 MGD (13500 cfs)
Little Falls gage flow 2022-11-15: 9436 MGD (est., based on recently available real-time data) (14600 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2022-11-14: 10276 MGD (15900 cfs)
Point of Rocks flow 2022-11-15: 8467 MGD (est., based on recently available real-time data) (13100 cfs)

ACTUAL Yesterday's Washington metropolitan area Potomac River withdrawals and discharges (2022-11-14):
Fairfax Water Corbalis withdrawal (Potomac): 83 MGD
WSSC Water Potomac withdrawal: 114 MGD
Washington Aqueduct withdrawal: 117 MGD
Loudoun Water withdrawal: 4 MGD
Loudoun Water Broad Run discharge: 6 MGD
Total Potomac withdrawal: 319 MGD
Total net Potomac withdrawal: 312 MGD

ACTUAL Yesterday's Patuxent, Occoquan, and Net Total System Withdrawal (2022-11-14):
FW Occoquan withdrawal: 61 MGD
WSSC Patuxent withdrawal: 37 MGD

ACTUAL Yesterday's total system withdrawal (2022-11-14): 413 MGD

ACTUAL Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 15900 cfs
QPR, obs: 15900 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.

ACTUAL Today's estimated production* (2022-11-15):
FW estimated production: 117 MGD
WSSC estimated production: 145 MGD
Washington Aqueduct estimated production: 120 MGD
LW total estimated consumption: 20 MGD
Total estimated production: 382 MGD
*Based on CO-OP daily demand forecasting models. FW includes the LW purchase and excludes Falls Church. Washington Aqueduct includes Falls Church

ACTUAL Tomorrow's estimated production* (2022-11-16):
FW estimated production:125 MGD
WSSC estimated production:146 MGD
Washington Aqueduct estimated production:119 MGD
LW Total estimated consumption:21 MGD
Total estimated production:390 MGD
*Based on CO-OP daily demand forecasting models. FW includes the LW purchase and excludes Falls Church. Washington Aqueduct includes Falls Church

SIMULATED Recommended operations for today (DREX Day 1 A.M.):

SIMULATED Fairfax Water:
Reduce Potomac withdrawals by 5 MGD, keeping Potomac withdrawals steady. 
Griffith production per operational preference.

Per operational preference, keeping Potomac withdrawals steady. 

SIMULATED Little Seneca (release date, time, amount in MGD):
Begin Little Seneca release of 19 MGD as soon as possible.

SIMULATED Washington Aqueduct:
Meet all demands from Little Falls in order to maintain the Great Falls flowby.

SIMULATED North Branch Reservoirs A.M. Summary:
No North Branch releases at the moment.

SIMULATED Reservoirs - Usable storage (DREX Day 1 A.M., BG):
Facility, %Full, Current, Capacity
WSSC’s Patuxent reservoirs, 63%, 6.39, 10.2
Fairfax Water’s Occoquan reservoir, 70%, 5.65, 8.05
Little Seneca Reservoir, 56%, 2.2, 3.9
Jennings Randolph Total Reservoir, 65%, 18.97, 29.4
Jennings Randolph water supply**, 59%, 7.7, 13.1
Jennings Randolph water quality**, 69%, 11.27, 16.3
Savage Reservoir, 35%, 2.21, 6.3
** 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: Flow levels have dropped to a level that has triggered enhanced monitoring (SIMULATED), per the drought operations manual of the Water Supply Coordination Agreement. When adjusted flow at Little Falls (adjusted flow is gage flow plus upstream withdrawals) less the environmental flow is less than twice the Washington metropolitan area withdrawals, the water suppliers will begin reporting yesterday's and today's withdrawals and this morning's reservoir storage volumes. ICPRB asks that communications be sent by 7:30 am and updates sent by 1:00 pm. Reporting can be submitted through www.icprbcoop.org, by email to coop@icprb.org, or by telephone by leaving a message with the CO-OP operations number at 301-274-8132. Monitoring emails can be viewed at http://icprbcoop.org/products/monitoring-reports. Thank you for your contribution to the monitoring efforts.

AM Report
Enhanced Operations
Drought Exercise
Reservoir Release Made
Operational Change