The e-mail report below concludes the 2011 CO-OP Drought Exercise. The exercise focused on use of our daily flow forecast tool and the newly updated OASIS model to inform decisions concerning reservoir releases. This fall we will be testing a variety of new operation procedures using our planning tools, PRRISM and OASIS, in conjunction with Hydrologic's WRF project on climate change. A brief after action report on this year's drought exercise will be forthcoming.
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The following (SIMULATED) releases have been requested today: a Little Seneca water supply release of 30 MGD (total target of 66 cfs); a Jennings Randolph release with a Luke target flow of 350 cfs (226 MGD).
(SIMULATED) Daily Flows:
Little Falls gage flow 09/20/15: 162 MGD (250 cfs)
Little Falls gage flow 09/21/15: 154 MGD (est., based on most recently available real time data) (238 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 09/20/15: 500 MGD (780 cfs)
Point of Rocks flow 09/21/15: 660 MGD (est., based on recently available real time data) (1020 cfs)
(ACTUAL) Today's estimated demand (09/21/11) P.M.:
WSSC P.M. estimated demand: 170 MGD
FW P.M. estimated demand: 150 MGD
Aqueduct P.M. estimated demand: 145 MGD
Total P.M. estimated demand: 465 MGD
(ACTUAL) Tomorrow's estimated demand (09/22/11):
WSSC estimated demand: 170 MGD
FW estimated demand: 155 MGD
Aqueduct estimated demand: 145 MGD
Total estimated demand: 470 MGD
SIMULATED operations for today (09/21/15):
Fairfax Water (SIMULATED):
Priority 1: keep Occoquan withdrawals as close to 90 MGD as possible.
Priority 2: maintain Potomac withdrawal as steady as possible.
Up to a 20 MGD load shift may be requested in the next day or two.
WSSC (SIMULATED):
Priority 1: keep Patuxent withdrawals as close to 30 MGD as possible.
Priority 2: keep Potomac withdrawals as steady as possible.
A load shift may be requested for a short period if absolutely necessary.
Seneca (SIMULATED release date, time, amount in MGD):
Continue the 30 MGD water supply release from Little Seneca as requested, for a target flow of 66 cfs.
Aqueduct (SIMULATED):
Little Falls: continue use of 50 and 100 MGD pumps (assuming 185 MGD withdrawal).
Great Falls: per operational preference, but keep gate settings as steady as possible.
North Branch Reservoirs (SIMULATED):
The water supply release with a Luke target of 350 cfs (226 MGD) continues.
(SIMULATED) Reservoirs - Usable Storage (BG)
Facility %Full Current* 2015 Estimated Capacity*
WSSC’s Patuxent reservoirs: 23% 2.32 9.9
Fairfax Water’s Occoquan reservoir: 60% 4.57 7.6
Little Seneca Reservoir: 87% 3.13 3.6
Jennings Randolph water supply**: 66% 7.82 11.8
Jennings Randolph water quality**: 70% 10.36 14.7
Savage Reservoir: 53% 3.24 6.1
*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.