Water tools

Flow equalization basin volume from an hourly flow profile

Paste a day of hourly flows. The basin must hold the largest cumulative excess of inflow over the constant outflow, which the cumulative curve shows directly.

Hourly flows, one per hourAny number of equal intervals works; 24 hourly values describe a day. Separate with spaces, commas or new lines.

Equalization volume (theoretical)

470m³

Add 10 to 20% for mixing, aeration and freeboard, and for the pump never quite matching the average.

Constant outflow (average)

112.3m³/h

Peak inflow

170.0m³/h

Minimum inflow

45.0m³/h

Peak factor removed

1.51

Hours of average flow stored

4.2h

How it works

With the basin pumped out at the average rate, the stored volume after each interval is the running sum of inflow minus outflow:

\bar{Q} = \frac{1}{n} \sum_{k = 1}^{n} Q_{k} S_{j} = \sum_{k = 1}^{j} (Q_{k} - \bar{Q}) Δ t

(1)

The basin must span the full swing of that curve, from its lowest point to its highest:

V = \max_{j} S_{j} - \min_{j} S_{j}

(2)

where

$Q_{k}$: inflow in interval k, m³/h
$\bar{Q}$: average inflow, the constant outflow, m³/h
$n$: number of intervals
$S_{j}$: volume stored after interval j, m³
$Δ t$: interval length, h
$V$: basin volume, m³

This is the classical cumulative-inflow construction. In-line basins equalize flow and dampen concentration; off-line basins take only the excess over a set rate and need less volume. Downstream units are then sized on the average flow instead of the peak, which is where the saving comes from.

Flow equalization basin volume from an hourly flow profile

How it works

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