Source Water and Well Operations
Groundwater and wells
Know the difference between static water level (no pumping) and pumping water level. Drawdown is the difference. Specific capacity = pumping rate ÷ drawdown, in gpm/ft; it falls as a well fouls or the aquifer declines. Well construction matters: casing, grout seal, screen, and gravel pack keep out surface contamination and sand. Sanitary seals and wellhead protection are first barriers. Pump setting, column pipe, and controls affect yield and water hammer.
Source water quality
Surface water varies with season, runoff, and algae; groundwater is more stable but can carry iron, manganese, hardness, arsenic, and nitrate. Source water assessments identify potential contaminant sources and susceptibility. Intakes and wells need protection from flooding, spills, and backflow.
Traps
Questions mix up static and pumping levels, or ask for specific capacity in the wrong units. A well that pumps sand is not simply “high yield” - it may signal screen damage or over-pumping. Do not assume groundwater needs no disinfection; groundwater under the influence of surface water often requires treatment.
Worked example
A well pumps 500 gpm with a drawdown of 25 ft. Specific capacity = 500 ÷ 25 = 20 gpm/ft. If drawdown doubles to 50 ft at the same pumping rate, specific capacity falls to 10 gpm/ft - a signal of fouling or declining aquifer performance.