Groundwater Recharge Design: Pits, Trenches, Shafts, and Percolation Tanks
Groundwater recharge structure selection depends on catchment area, soil infiltration rate, depth to water table, and land availability. Rain GEO SAT's Expert engine evaluates all four common structures — pit, trench, shaft, and percolation tank — and ranks them for the site.
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Structure selection matrix
Recharge pits suit small catchments (<300 m²) with sandy or loamy soil. Trenches handle linear catchments (compound walls, driveways). Recharge shafts are needed when the vadose zone is deep (>15 m) or the top layers are impermeable. Percolation tanks are appropriate for community-scale recharge (>2 ha catchment) in undulating terrain.
- Recharge pit — 1.5 m × 1.5 m × 3 m, filled with graded filter media
- Recharge trench — 0.6 m wide, 1.5 m deep, length = catchment area × 0.05
- Recharge shaft — 0.5 m diameter, bored to permeable strata, cased top 3 m
- Percolation tank — earthen bund across natural drainage line, storage 10,000–100,000 m³
Sizing formula
Recharge structure volume V (m³) ≥ Peak Design Rainfall (m) × Catchment Area (m²) ÷ (Infiltration Rate (m/hr) × Design Duration (hr)). Rain GEO SAT uses 1-in-10-year 1-hour rainfall intensity from IMD IDF curves as the peak design event.
Frequently asked questions
- How often should recharge structures be cleaned?
- Filter media should be raked or replaced annually before monsoon. Silt trap should be desilted after every major rain event. Rain GEO SAT generates a maintenance schedule with each report.
- What is the lifespan?
- Well-maintained recharge pits and trenches last 15–20 years. Recharge shafts and borewell recharge systems typically need major refurbishment after 8–10 years.
Ready to apply this on your site?
Rain GEO SAT calculators use IMD, NASA POWER, Open-Meteo, and CGWB data to deliver engineer-grade rainwater harvesting and groundwater recharge designs.
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