Well Drawdown and Specific Capacity

Drawdown, specific capacity (GPM per ft), and recommended pump-setting depth.

Run the calculator

Example

You enter

Static water level (ft below ground) 50
Pumping water level (ft below ground) 80
Discharge rate (GPM) 30
Pump-setting offset below pumping level (ft) 20

You get

Drawdown 30
Specific capacity 1
Recommended pump setting 100 ft below ground

Details, formula, and sources

With a marginal-well flag below 0.5 GPM/ft. Per AWWA A100 and USGS OFR 02-197.

Drawdown (ft) = pumping water level - static water level. Specific capacity (GPM/ft) = discharge / drawdown. Recommended pump setting (ft) = pumping level + offset (default 20 ft below the pumping level).

AWWA A100 (Water Wells) standard; USGS well-testing methods (USGS Open-File Report 02-197).

awwa.org for the A100 TOC; pubs.usgs.gov for the USGS report.

Estimate. Operator of record and primacy agency govern.

Field names used by the API: static_level_ft, pumping_level_ft, discharge_gpm, pump_offset_ft, drawdown_ft, specific_capacity_gpm_ft, pump_setting_ft

Specific-capacity floor < 0.5 GPM/ft flagged as a marginal wellAWWA A100 / USGS field practice
Pump-setting offset 20 ft below the pumping level (default; user overrides)well-pump field practice