Groundwater Recharge and Groundwater Quality IssuesVincent W. Uhl, PH, PGVincent Uhl Associates, Inc.Lambertville, NJ

Slides 1 to 10

Presentation Summary

Assess Groundwater Resources from a Growth – Management Perspective

Look at Limitations and Opportunities Local Planning to Protect Water

Resources Tools needed to accomplish this planning

Hunterdon Aquifers

Piedmont (Brunswick, Lockatong, Stockton)

Highlands (PreCambrian and Limestone)

Sourlands and Cushetunk Mountain (diabase)

Water Budget Overview P = R + I + ET P = Precipitation R = Runoff I = Infiltration

(Recharge) ET = Evapo-

transpiration Annual Averages

usually used

Infiltration ≈ Baseflow

Recharge to ground water eventually flows to streams unless taken out through wells

GW Recharge

Soils, precipitation, land cover

Part moves “quickly” to streams

Part moves to aquifers and then “slowly” to streams or wells

Groundwater Recharge – Ways to Estimate Sophisticated Water Balance (See Van Abs

Slide 4) NJGS Method Recharge as a fixed percentage of precipitation Baseflow Analysis

Very Conservative – e.g. 7day 10 year low flow Average Baseflow DRBC Approach in SE PA Watersheds which is 75%

of the 25-year recurrence baseflow.

Recharge Estimates – The Math

Recharge is often expressed as gallons per day per square mile (gpd/mi2)

Examples for the Highlands Precambrian Rock aquifers:7 day 10 year low flow – 85,000gpd/mi2

Average annual base flow – 525,000 gpd/mi2

75% of 25-year baseflow recurrence interval – 225,000 gpd/mi2

Translating Recharge to:Gallons per day per acre 640 acres in a square

mile. 85,000 gpd/mi2

525,000 gpd/mi2

225,000 gpd/mi2

130 gpd/acre 820 gpd/acre 350 gpd/acre

Translating Gallons per day per acre of recharge to lot sizes Using 400

gpd/household 130 gpd/acre 820 gpd/acre 315 gpd/acre

3 acre lots 0.5 acre lots 1.25 acre lots

Go to Slides 11 to 23