Aquifer Recharge Calculator Formula

Understand the math behind the aquifer recharge calculator. Each variable explained with a worked example.

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Formulas Used

Annual Recharge

annual_recharge = recharge_acre_ft

Annual Recharge (Gallons)

recharge_gal = recharge_gallons

Daily Average

daily_avg = recharge_gallons / 365

Households Supplied

homes_served = recharge_gallons / 365 / 300

Variables

VariableDescriptionDefault
area_acresRecharge Area(acres)100
annual_rain_inAnnual Rainfall(inches)35
infiltration_pctInfiltration Rate(%)25
recharge_acre_ftDerived value= area_acres * annual_rain_in * infiltration_pct / 100 / 12calculated
recharge_gallonsDerived value= recharge_acre_ft * 325851calculated

How It Works

How to Calculate Aquifer Recharge

Aquifer recharge is the natural or managed process of water percolating into underground aquifers.

Formula

Recharge (acre-feet) = Area * Rainfall * Infiltration % / 12

1 acre-foot = 325,851 gallons

Typical Infiltration Rates

  • Sandy soil: 40-80%
  • Loam soil: 20-40%
  • Clay soil: 5-15%
  • Urban (impervious): 5-10%

    • Worked Example

    100 acres of loam soil receiving 35 inches rainfall with 25% infiltration.

    area_acres = 100annual_rain_in = 35infiltration_pct = 25
    1. 01Recharge: 100 * 35 * 0.25 / 12 = 72.9 acre-feet
    2. 02In gallons: 72.9 * 325,851 = 23,762,833 gallons
    3. 03Daily average: 23,762,833 / 365 = 65,103 gallons/day
    4. 04Homes served: 65,103 / 300 = 217 homes

    Ready to run the numbers?

    Open Aquifer Recharge Calculator