Borehole Calculator

Borehole Calculator — measure your borehole impact. Evidence-based formula with reduction tips.

Borehole Calculator estimates whether a tested groundwater source can meet a stated household demand. It combines sustainable yield, pumping hours, and demand rather than assuming that a drilled hole can provide unlimited water. The central result is a supply balance, followed by the annual abstraction volume that helps you understand the scale of the proposed use. Rainwater Harvest Calculator and Water Use Calculator answer adjacent questions, but they use different boundaries and should not be substituted for this estimate.

Water planning works best when a measured flow, a dated rainfall record, a supplier rate, or a site test replaces a broad national average. Keep the unit and time period visible next to every result, and run a conservative scenario before making a purchase or changing a water system.

Use the result to compare choices rather than to promise an outcome. A dry-season scenario, a lower pump yield, a blocked filter, a changed household size, or a different soil can materially change the useful volume. Write down which parts of the result are measured and which are assumptions, then revisit the estimate after maintenance, weather, equipment, or local restrictions change. This makes the calculation useful to a household, installer, grower, or regulator without confusing a transparent planning model with a site survey or operating approval.

Enter a sustainable yield from a recovery or pumping test, not the short-term maximum reported when the borehole was first drilled.
Enter the number of hours the pump is expected to run each day and the household's measured or estimated daily demand.
Read the surplus or deficit first. A surplus on paper does not replace storage, filtration, pressure, or drought resilience checks.
Compare the annual abstraction result with the current regulatory information for your area and source.
Save the result with the date, site, equipment, and assumptions so the estimate can be reviewed when conditions change.

borehole yield formula and assumptions

Daily available supply = sustainable yield (litres/hour) × pumping hours per day; supply balance = available supply − household demand; annual abstraction = daily supply × 365.

The formula is deliberately transparent: it multiplies the activity quantity by the relevant rate or efficiency and keeps the main uncertainty in an editable input. Real performance can differ because of leakage, weather, pressure, soil, storage, seasonal demand, maintenance, and the quality of the original measurement.

Use litres and cubic metres consistently. One cubic metre is 1,000 litres, and one millimetre of rainfall over one square metre represents one litre before collection losses. Annual figures are useful for planning, but they do not imply that supply arrives evenly each day.

Interpreting your borehole yield result

Use the result as a planning range

A positive balance means the stated daily demand fits within the simplified pumping scenario. A negative balance means the pump schedule, tested yield, storage, or demand must change; it does not prove that the aquifer is unusable. Seasonal groundwater levels can fall, and a yield test is only representative of its test conditions.

A result that looks precise can still be uncertain. Test the answer with lower and higher flow, rainfall, demand, efficiency, or reuse assumptions. Compare scenarios over the same period and keep capital equipment, treatment, pumping energy, maintenance, and installation costs separate from the water-volume result.

Ecology tips and best practices

Measure household demand from a meter or a representative diary where possible.
Ask for the tested sustainable yield, drawdown, recovery time, and water-quality results before choosing equipment.
Include a pressure vessel or storage tank in a full design if demand peaks exceed the pump's preferred continuous rate.
Check iron, manganese, hardness, bacteria, nitrate, and other parameters relevant to the local geology.
Keep a drought scenario with lower yield and higher outdoor demand.
Record the source and date of local rainfall, water prices, flow tests, or environmental measurements.
Use storage and overflow calculations alongside annual yield; a large annual total may still provide little water during a long dry spell.

One litre per day becomes 365 litres per year, so small changes in a daily routine can matter when annualised.
Efficiency is a fraction of applied water, not a guarantee that every plant, household, or storage tank receives the same amount.
Scenario ranges are more honest than extra decimal places when the input is an estimate.

Common mistakes to avoid

Using the initial drilling yield as a permanent sustainable yield.
Ignoring pump recovery time or assuming the pump can run continuously.
Comparing litres per hour with annual demand without converting the time basis.
Treating a volume calculation as proof that water is safe to drink.
Assuming a borehole replaces mains backup during a power cut or dry period.
Mixing a daily demand with a weekly or annual supply without converting the time period.
Counting the same captured or reused water twice in a household offset.
Treating an educational result as a permit, engineering design, water-quality certificate, or guarantee of supply.

In England, abstraction above 20 cubic metres per day may require an environmental permit, but exemptions and rules depend on the source, purpose, location, and current regulations. Scotland, Wales, and Northern Ireland have different regulatory arrangements. This page provides educational planning guidance only. Confirm current requirements with the relevant water company, environmental regulator, local authority, installer, or qualified water professional before construction or abstraction.