Water Wells and Groundwater Fundamentals
This domain tests the groundwater and well-construction knowledge a pump installer needs before choosing equipment: aquifer behavior, water levels, well yield, and sanitary protection.
Core rules and concepts
- An unconfined aquifer has a water table; a confined aquifer is under pressure and has a potentiometric surface. Pump-setting decisions depend on the pumping water level, not just the static level.
- Specific capacity = pumping rate ÷ drawdown. It describes how much water level drop a well produces per unit of flow; it is not a guarantee of long-term yield.
- Well construction includes casing, screen or open borehole, gravel pack, grout, and a sanitary well seal. The seal keeps surface water and debris out.
- Well yield must be established by a yield test. The pump should be selected for the sustainable yield, not the highest short-term test rate.
- Protect the wellhead from flooding, backflow, and contamination. Disinfect with chlorine after construction or repair, then flush and test as required.
Worked example
A well pumps 150 gpm and the water level falls 30 ft from static. Specific capacity = 150 ÷ 30 = 5 gpm per ft. If the target is 200 gpm and specific capacity is assumed constant, expected drawdown = 200 ÷ 5 = 40 ft. If the static level is 50 ft, expected pumping level is 50 + 40 = 90 ft. A 10-ft safety margin gives at least 100 ft. Reason: pumping level is static level plus drawdown.
Traps
Using static level as pumping level, assuming specific capacity stays constant at high flow, confusing well yield with pump capacity, and ignoring seasonal decline all cost marks.