GWP Consultants

Evaluation, Design, Delivery & Management of Earth & Water Resource Projects

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Silt lagoons


What is Pondsizer?

PondSizer is a software application for calculating the optimum size of attenuation ponds, settlement lagoons and sumps designed to ensure surface water discharges comply with regulatory requirements. GWP Consultants has used PondSizer successfully for some time in designing ponds and lagoons for controlling surface water runoff from quarries, storage mounds, landfill caps, roads and other developments. MIRO, under the ALS (MIST) programme, funded the development of PondSizer to promote its wider use through incorporating modifications that will facilitate its use by non-specialists.

Who is it for?

PondSizer will be useful for all with an interest in the environmental impacts of quarries, including quarry operators and managers, consultants, regulatory bodies, and other environmental organisations; but particularly by those with responsibility for designing management systems for quarry water. To encourage its use, the application is freely available. Training in its background and use, and support will be available from GWP Consultants on a commercial basis.

What does it do?

PondSizer incorporates calculation of the greenfield runoff rate. A user-friendly interface makes it easy for non-specialists to select appropriate runoff functions, catchment data and parameter values through drop-down menus, buttons and forms with prompts. Checks are in place to prevent the user selecting incompatible parameter values and Help screens are also provided. PondSizer uses rainfall parameters produced by the Flood Estimation Handbook Web Service which is developed and supported by Wallingford HydroSolutions on behalf of the Centre for Ecology & Hydrology and can be obtained through

PondSizer is now freely available for download in two versions that are compatible with the two versions of the FEH Data. Please ensure that you download the appropriate version.


PondSizer for FEH v1: Download                      PondSizer for FEH v2: Download


PondSizer has been developed under funding from MIRO, under the ALS (MIST) programme.

Capability Statements

To download our Capability Statements please refer to the Downloads page.

If you would like Project Description Sheets which give examples of our work or further information regarding GWP’s experience, please do not hesitate to contact us.