Balance inflows, outflows, and storage across any system. Include rainfall, pumping, and evaporation seasonal losses. Get instant results, then download clean files for stakeholders.
The calculator applies a control-volume water budget. All terms are converted to a common volume basis (m³) over the selected period.
Tip: Use “Measured final storage” to assess meter/estimate consistency.
| Month | Area (km²) | P (mm) | ET (mm) | Qin (m³) | Qout (m³) | W (m³) | ΔS (m³) |
|---|---|---|---|---|---|---|---|
| Jan | 1.50 | 62 | 40 | 105,000 | 88,000 | 12,500 | +31,000 |
| Feb | 1.50 | 80 | 55 | 120,000 | 90,000 | 15,000 | +27,500 |
| Mar | 1.50 | 45 | 70 | 92,000 | 96,000 | 16,500 | −41,250 |
| Apr | 1.50 | 28 | 85 | 78,000 | 84,000 | 18,000 | −66,000 |
Example values illustrate seasonality; your site may differ.
This calculator supports water-budget checks for reservoirs, tanks, detention basins, irrigation command areas, and small catchments. It converts mixed inputs into a single volume basis over a defined period, helping engineers compare operational targets against available water. Use it for preliminary planning, monthly reporting, and quick QA on monitoring data before deeper modeling.
Depth-driven terms (precipitation and evapotranspiration) are entered as depth and converted using the selected area, enabling consistent storage accounting even when field measurements are reported in millimeters. Flow terms can be provided either as total period volumes or as average daily rates; daily values are multiplied by period days to obtain a comparable volume. This reduces unit mismatch and improves auditability.
A positive ΔS indicates net gain in storage, commonly associated with wet periods, high inflows, or reduced releases and withdrawals. A negative ΔS indicates drawdown, often driven by high evaporation, planned releases, pumping demand, or seepage losses. Compare predicted final storage with operational constraints to identify shortage risk, spill risk, or required release adjustments.
When a measured final storage is available, the calculator reports a closure error (measured minus predicted) and a normalized percentage. Large errors may indicate rating-curve drift, unmetered diversion, inaccurate area, underestimated seepage, or incorrect return-flow assumptions. Track closure by month to prioritize meter calibration, field surveys, and refined loss estimates.
Teams can export results to CSV for spreadsheets, dashboards, or regulatory submissions, and generate a PDF summary for reviews and sign-off. Typical deliverables include monthly inflow/outflow reconciliation, drought operations notes, and asset performance tracking for leakage programs. Keep assumptions consistent and document data sources to maintain comparability across periods and sites.
It is the control footprint used to convert depth terms into volume, such as reservoir surface area or catchment area contributing rainfall-runoff during the chosen period.
Use totals when you already have summed volumes for the period. Use daily rates when instruments report average per-day values; the calculator multiplies by period days automatically.
Many stations report rainfall in millimeters. Converting depth with area produces an equivalent volume that is compatible with storage and discharge accounting.
Use it for leakage, spills, unmetered losses, operational wastage, or any outflow that is not already represented by measured surface or groundwater terms.
Provide measured final storage to see the mismatch between predicted and observed storage. Persistent, large errors suggest data gaps or assumptions that need refinement.
Yes. Set surface inflow and outflow to zero, then use Gin and Gout with withdrawals, return flows, and losses to evaluate storage change for the defined control volume.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.