Virginia Coastal Plain Groundwater Issues David K. Paylor March 27, 2015.

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Virginia Coastal Plain Groundwater Issues David K. Paylor March 27, 2015

Transcript of Virginia Coastal Plain Groundwater Issues David K. Paylor March 27, 2015.

Page 1: Virginia Coastal Plain Groundwater Issues David K. Paylor March 27, 2015.

Virginia Coastal PlainGroundwater Issues

 

David K. Paylor

March 27, 2015

Page 2: Virginia Coastal Plain Groundwater Issues David K. Paylor March 27, 2015.

Geology 101

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Virginia Physiographic Provinces

COASTAL

PLAIN

PIEDMONT

BLUE RIDGEVALLEY A

ND RID

GE

APP. PLATEAU

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CONFININGUNITS

CONFINED AQUIFERS

UNCONFINEDAQUIFER

IMPACT

CRATER

BED

RO

CK

Coastal PlainAquifer System

WEST

EAST

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AQUIFERS• YORKTOWN-EASTOVER

• PINEY POINT

• AQUIA

BASEMENT BEDROCK

FLUVIAL SEDIMENTS

MARINE SEDIMENTSPOTOMAC AQUIFER

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VA Coastal Plain Aquifer Cross-Section

McFarland & Bruce, 2006

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Groundwater Terms and Concepts

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Well Water Levels IndicateDirection of Flow

AQUIFER

HIGH WATERLEVEL

LOW WATERLEVELFLOW

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Well Water Levels IndicateDirection of Flow

AQUIFER

LOW

HIGH

FLOW

AQUIFER

FLOW

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CONFINING UNIT

Well Water Levels IndicateDirection of Flow

AQUIFER

LOW

HIGH

AQUIFER

HIGH

LOW

LEAKAGEDOWN

LEAKAGEUP

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Cone of Depression

Confined Aquifer

Not a bathtub drain–actually a

drop in pressure

The pressure in the aquifer changes with distance from the well.

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Potentiometric Surface

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Groundwater Management in Virginia

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Long-term Scientific Study

1913

19451988

1999

2006

2010

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Scientific Milestones• Regional studies (late 1970s –early 1980s)• Hydrologic Framework I (1988)• Coastal Plain Groundwater Flow Model I (1990)• Coastal Plain Groundwater Flow Model II (1998)• Chesapeake Bay Impact Crater (1999)• Land Subsidence Study (2002)• Hydrologic Framework II (2006)• Coastal Plain Groundwater Flow Model III (2009)• Eastern Shore Model I (2009)• Groundwater Quality Trend Study (2010)• Program Peer Review (2011)• Potomac Aquifer Study (2013, pending publication)

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Virginia Groundwater Withdrawals by Aquifer

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Legislative History of GW Management

• Virginia Well Capping Law (1956)• Groundwater Management Act of 1973• 1986 Amendments to Act of 1973• Ground Water Management Act of 1992

• Private Wells (32.1-176.4, VDH-1986)

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GW Management Areas

Management Area 6/17/13 Management Area

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Management Issues

• Reversal of the hydraulic gradient (groundwater flow) leads to salt water intrusion

• Declining water levels• Subsidence and loss of storage

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Reversal of Hydraulic Gradient and Saltwater Intrusion

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Groundwater Pumping and Reversal of Hydraulic Gradient

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Salt Water Intrusion - Upconing

Pumping draws the salt water upwards into the well.

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Salinity Within the Aquifer System

Heywood and Pope, 2009

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Groundwater Level Declines

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Artesian Characteristics Lost Over Time

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Long Term Water Level Decline

LONG-TERM DECLINE

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Decline from Pre-Pumping Levels

-250

+100

-180

+150

100%

77%

POTOMAC AQUIFER

WEST EAST

+140

+50

PRE-PUMPING LEVEL

PRESENT-DAY LEVEL

+30

FRANKLIN80%

LAND SURFACE

FLOW

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Simulated Change in Storage of Water in the Potomac Aquifer from Pre-development to 2008

Values >1 indicate head is below the 80% criterion

Legend

Available Storage Used

PCT_USED

0.00 - 0.10

0.11 - 0.25

0.26 - 0.50

0.51 - 0.75

0.76 - 1.00

1.01 - 72.50

Head Below Unit Top

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Land Subsidence and Loss of Storage

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Land Subsidence

-1.6

-2.4

-2.8

-4

-3.6

-1.2

-0.8

-4.4

-2

-1.2

-2

-2

-1.6

-2

-3.2

-3.2

0 25Miles

0 25Miles

West Point

Franklin

Suffolk

Chesa

peake

Bay

Franklin ExtensometerOct. 1979 – Dec. 1995Depth = 255 m

Suffolk ExtensometerJune 1982 – Dec. 1995Depth = 484 m

Rates of Elevation Change (1940-1971) mm/yearHoldahl and Morrison, 1974

Measurement of Compaction and Subsidence

Major Pumping Centers

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5 0

4 0

3 0

2 0

1 0

0

CU

MU

LAT

IVE

CO

MP

AC

TIO

N (

mm

)

1980 1985 1990 1995

5 0

4 0

3 0

2 0

1 0

0

CU

MU

LAT

IVE

CO

MP

AC

TIO

N (

mm

)

SUFFOLK3.7 mm/yr

FRANKLIN1.6 mm/yr

Subsidence Record

MONITORING DISCONTINUED

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Conclusions

• Water levels continue to decline in the primary aquifers.

• Land is subsiding.• Salt water intrusion is occurring.• Primary aquifers are not being pumped sustainably for the long-term.

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Other States’ Responses

• Maryland – No irrigation withdrawals from the Potomac Aquifer. No new permits in areas where water levels have reached 80% of pre-development head.

• North Carolina – Reduce all existing withdrawals from the Potomac Aquifer by 30-75% over 15 years. Began 2006. State provided funds to convert to other sources. No new withdrawals from Potomac Aquifer.

• Georgia–South Carolina – Designated areas where no additional withdrawals are allowed and other areas where only incremental withdrawals are allowed. Mandatory conservation to reduce existing max withdrawals and GW monitoring.

• Savannah-Hilton Head Regional Management Area – Pumping limited based on areas reaching 500 mg/l Chloride in less than 113 years.

• Florida – Regional pumping caps on all withdrawals. All withdrawals including agr. are metered and conservation/efficiency mandated. 

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Options Resulting From Peer Review

• Regulatory options include:– Reduce pumping– Spread out pumping– Modify management goals– Issue permits in regional or aquifer groupings– Implementation of greater water conservation

• Program recommendations include:– More data collection:

• water levels• water quality• land subsidence

– Implement new generation modeling tool– Increase program resources

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Short-term Actions

• Amend GWMA regulations to:– Expand the management area– Determine regulatory compliance using full area of impact– Use land surface instead of pre-pumping head– Add greater clarity on expectations for use of alternative sources and water 

conservation• Implement use of new (2009) model• Collaborate with other agencies:

– Specific data on well location and construction– Un-captured withdrawals

• Reinstate GW quality sampling within chloride network starting with 20-25 samples/year

• Allow for drought contingencies in permits

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Short-term Actions Under Review

• Begin moving existing pumps above the top of the Potomac Aquifer 

• Improvements to groundwater withdrawal reporting

• Continue to increase GW quality samples to 50 per year

• Work with VEDP and local governments regarding availability of GW in recruitment locations

• Review program and funding resources

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Other Longer-term Policy Options

• Optimize the new model to spread out withdrawals and evaluate impact

• Add subsidence package to the model • Evaluate drawdown criteria for subsidence/salt water intrusion

• Continue to increase annual GW quality samples 

Page 39: Virginia Coastal Plain Groundwater Issues David K. Paylor March 27, 2015.

Other Longer-term Policy Options(cont.)

• Facilitate greater use of alternatives such as wastewater reuse, surface water conjunctive use, and water recycling

• Consider additional regulatory changes• Evaluate need for an across the board reduction target and implementation schedule

Page 40: Virginia Coastal Plain Groundwater Issues David K. Paylor March 27, 2015.

Questions?