Borehole Specific Capacity

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Evaluate Well Performance in Seconds

When a borehole is drilled, one of the first questions everyone asks is: how much water can it produce? The Borehole Specific Capacity Tool answers that question by computing the ratio of pumping rate to drawdown, giving you a single number that characterizes well productivity. It's the quickest way to compare well performance across sites, screen potential water sources, and flag underperforming boreholes before investing in permanent pumping infrastructure.

Specific capacity is defined as the yield of a well per unit of drawdown, typically expressed in liters per second per meter (L/s/m) or gallons per minute per foot (gpm/ft). A high specific capacity means the aquifer delivers water generously relative to the water level drop caused by pumping. A low value signals either a tight formation, a poorly developed well, or both. This borehole specific capacity calculator handles the computation instantly once you enter your pumping test data.

How to Use This Tool Effectively

Enter the steady-state pumping rate from your borehole test and the corresponding drawdown measured in the pumped well. The tool divides the rate by the drawdown to give you the specific capacity. If you have data from multiple pumping rates (a step-drawdown test), enter each step separately to see how specific capacity changes with increasing extraction. A declining specific capacity at higher rates indicates well losses or aquifer dewatering that could limit sustainable yield.

For best results, use data from a pumping test that has reached approximate equilibrium. If the water level is still dropping when you record the drawdown, the calculated specific capacity will overestimate the well's true long-term performance. Tests of at least 24 hours at constant rate provide the most reliable data, though shorter tests can still offer useful preliminary screening values.

Who Needs Borehole Specific Capacity Data

Drilling contractors use specific capacity as a quick metric to assess whether a new borehole meets the client's yield requirements. If the target is 2 L/s and the available drawdown before the pump intake is exposed is 15 meters, then the borehole needs a specific capacity of at least 0.13 L/s/m to be viable. Running this check on site with the borehole specific capacity tool takes seconds and can inform immediate decisions about whether to deepen the hole, attempt further development, or move to a new location.

Hydrogeologists compile specific capacity databases across regions to map aquifer productivity. These datasets inform groundwater development strategies at district and national scales. Water utilities use specific capacity trends over time to monitor well aging. A gradual decline in specific capacity suggests screen encrustation, biofouling, or aquifer compaction, all issues that targeted rehabilitation can address if caught early.

Real-World Use Cases

A rural water supply project in a crystalline basement terrain has drilled 30 boreholes. Pumping test data is available for each. Using the specific capacity tool, the project hydrogeologist ranks all 30 wells by productivity in minutes, identifies the top 10 candidates for motorized pump installation, and flags 5 wells with suspiciously low specific capacity for additional development (surging, jetting, or acidization).

An industrial facility drawing groundwater for process cooling notices its borehole can no longer sustain the required 5 L/s without excessive drawdown. Comparing current specific capacity to the original test data reveals a 40 percent decline over eight years. This quantified decline justifies the capital expenditure for a well rehabilitation program to the facility's management.

Pro Tips for Reliable Calculations

Always record the duration of pumping alongside rate and drawdown. Specific capacity at one hour of pumping is not the same as at 24 hours, because aquifer boundaries and storage effects take time to manifest. When comparing wells, ensure you're comparing specific capacities measured at similar durations and rates.

If your borehole penetrates multiple aquifer zones, consider whether the drawdown you measured represents the composite response. Partially penetrating wells in thick aquifers may show lower specific capacity than fully penetrating ones, even in the same formation. Normalizing for penetration depth helps make fair comparisons.

The Borehole Specific Capacity Tool processes everything locally in your browser with zero data uploads. It's fast, private, and always available when you need a quick well performance check in the field or office.