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Interstate Commission on the Potomac River Basin

(ICPRB)

• ICPRB represents 5 states.• Mission: enhance, protect and conserve

the water and associated land resources of the Potomac River basin and its tributaries through regional and interstate cooperation.

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ICPRB - Four major areas of interest

• Public information

• Water resources, quantity, and supply

• Water quality

• Living resources

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BASIN ISSUES - SOCIAL

Economy, Growth and DevelopmentBasin ImpactExpanded Commuting Expanded Development Expanded Demand for Water

Power DeregulationNew Plant ProposalsConsumptive Use Impacts

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BASIN ISSUES - ENVIRONMENTAL

Low Flow at Little FallsEnvironmental Needs PerceptionMD DNR

Improved Water Quality Blue Plains Return to EstuaryImproved Water Quality in Estuary BNR

670 0 70 140 Miles

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EW

S

Metro Washington service area supplied by CO-OP utilities in the Potomac Basin

Interstate Commission on the Potomac River Basin June 2000Source: WSSC, FCWA, USACE

Potomac River Basin and the portion of the Washington metropolitan area served (in part) by the Potomac River

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Washington area: three major water suppliers

• The three suppliers provide water to a total of 3.6 million people.

• These suppliers cooperate during droughts, pooling their resources to maximize water supply reliability.

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Overview of study area and resources

OccoquanRiver

PatuxentRiver

PotomacRiver

Fairfax CountyWater Authority

Washington Suburban Sanitary Commission

Rockville DPW

Washington Aqueduct COE

Major Source

CO-OP utility

Wholesale or independent utility

Key:

District of Columbia Water and Sewer Authority

Arlington County DPW

Falls Church DPW

Vienna DPW

Prince William Service Authority

Virginia American Water Co.

Loudoun County Sanitation Authority

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1070 0 70 140 Miles

N

EW

S

Metro Washington service area supplied by CO-OP utilities in the Potomac Basin

Interstate Commission on the Potomac River Basin June 2000Source: WSSC, FCWA, USACE

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Water supply intakes and portion of Potomac River protected by environmentalflow recommendation.

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1960-70’s forecast of Potomac shortages

• In times of low-flow, predicted demands are higher than flow.

• Implication: The COE, the most downstream water user, would run out of water if nothing were done.

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Proposed structural solutions

• Series of 16 reservoirs

• Interbasin transfers

• Pilot estuarine treatment plant

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LFAA - 1978

• No jurisdiction would suffer disproportionate shortages.

• Water rationed as a percentage of the normal wintertime water use.

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Water Supply Coordination Agreement (1981)

• Mandates that suppliers coordinate operation of all facilities.

• Minimizes chances of a shortfall.

• Payment formula for future water supplies based on incremental growth ratios.

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Little Seneca

Jennings Randolph

Potomac Basin and water supply reservoirs

Occoquan

Patuxent

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Jennings Randolph Reservoir

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Little Seneca Reservoir

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Patuxent (Duckett) Reservoir

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Occoquan Reservoir

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Little Falls intake

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Little Falls flow near Washington DC , summer 1999

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100

200

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1,0006/

23/9

9

6/30

/99

7/7/

99

7/14

/99

7/21

/99

7/28

/99

8/4/

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8/11

/99

8/18

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8/25

/99

Flo

w (

mil

lion

gal

lons

per

day

)

Jennings Randolph Release

Flow target

Flow that would have occurred without a release

Flow that would have occurred without a release

Jennings Randolph release

Target

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1,000

10,000

100,000

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1999 Potomac withdrawals plus environmental flow recommendation

Note: Little Falls 1929-1997 flow adjusted to represent that flow before metro Washington withdrawals and after Jennings Randolph and Savage reservoirs' water quality augmentation releases

Potomac flows and demands

Higher flows

Median flows

Minimum flows

Demands

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Drought Management Issues

• Public response plan

• Media outreach and communications

• Practiced drought operations

• Utility and regional cooperation

• Planning for future demands

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Drought website (http://www.potomacriver.org, follow link for “Drought Exercise 2000”)

• Water supply status and key operational data are updated each day during droughts and for drought exercises including:– Reservoir storage,

– River flow,

– Precipitation forecasts,

– Utility withdrawals, and

– Daily summaries.

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Today’s probability of meeting demand

• If the worst recorded drought were to occur this summer, the three major Washington metropolitan area suppliers would be able to meet water demands.

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Tomorrow’s probability of meeting demand

• ICPRB continues to assess the reliability of the current water supply system for the Washington metropolitan area. The most recent study was completed in 2000 and is available at: www.potomacriver.org/metrostudy.html

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Benefits of regional cooperation

• Smooth operations during drought.

• Systems based operating strategies minimize possibility of shortfall.

• Stronger management and a unified voice.

• Trust in the procedures and institutions in place.