Aquifer Recharge Calculator Formula
Understand the math behind the aquifer recharge calculator. Each variable explained with a worked example.
Formulas Used
Annual Recharge
annual_recharge = recharge_acre_ftAnnual Recharge (Gallons)
recharge_gal = recharge_gallonsDaily Average
daily_avg = recharge_gallons / 365Households Supplied
homes_served = recharge_gallons / 365 / 300Variables
| Variable | Description | Default |
|---|---|---|
area_acres | Recharge Area(acres) | 100 |
annual_rain_in | Annual Rainfall(inches) | 35 |
infiltration_pct | Infiltration Rate(%) | 25 |
recharge_acre_ft | Derived value= area_acres * annual_rain_in * infiltration_pct / 100 / 12 | calculated |
recharge_gallons | Derived value= recharge_acre_ft * 325851 | calculated |
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
Worked Example
100 acres of loam soil receiving 35 inches rainfall with 25% infiltration.
- 01Recharge: 100 * 35 * 0.25 / 12 = 72.9 acre-feet
- 02In gallons: 72.9 * 325,851 = 23,762,833 gallons
- 03Daily average: 23,762,833 / 365 = 65,103 gallons/day
- 04Homes served: 65,103 / 300 = 217 homes
Frequently Asked Questions
What is aquifer recharge?
Aquifer recharge is the process by which water moves downward through soil and rock to replenish underground water stores. It can be natural (from rain) or managed (through injection wells or infiltration basins).
Why is recharge important?
Many aquifers are being depleted faster than they recharge, threatening drinking water supplies and agriculture. Managing recharge helps sustain water resources for the long term.
How does urbanization affect recharge?
Impervious surfaces (pavement, roofs) prevent infiltration, reducing recharge by 50-90% compared to natural land. Permeable paving, rain gardens, and green infrastructure help restore recharge.
Ready to run the numbers?
Open Aquifer Recharge Calculator