Rainwater harvesting


Polytunnels and glasshouses are used extensively within the soft fruit and ornamental horticulture sectors and they rely entirely on irrigation. In recent years there has been a growing interest in the potential for rainwater harvesting (RWH) systems to be used in polytunnel and glasshouse production to help businesses reduce their dependence on public mains water supplies, to reduce the need to treat surface water for irrigation and to reduce runoff risks.


Working with growers and key stakeholders, and building on earlier work with Kent County Council, researchers from Cranfield University have designed and developed a simple Microsoft Excel tool to help growers and farm business advisors evaluate the potential hydrological performance and water storage effectiveness of RWH systems to support investment decision making – the tool can be downloaded below. This nationally applicable tool is designed to be simple and intuitive to use and requires only a limited set of information.

Download Excel RWH tool

N.B. the RWH Excel file contains macros. Once downloaded, you will need to “Enable Editing” (if the file opens in Protected View) and also “Enable Content” (if macros have been disabled) in Excel to use it.

User guidance

The RWH tool user guidance manual briefly describes how to set-up and use the tool and interpret its outputs.


Rainwater Harvesting Tool- entering your site data:


Rainwater Harvesting Tool- interpreting the outputs:

Case studies

Glasshouse Glasshouse

Wyevale Nurseries are a leading supplier of wholesale plants to the amenity and retail sectors. The case study shows how the RWH tool was used to understand how their current rainwater harvesting system at Kings Acre will perform with their planned increase in reservoir storage capacity and to inform needs for modifying their glasshouse and horticultural polytunnel structures to improve system performance and reduce groundwater (and mains water) use.


Woburn Forest Growers

Woburn Forest Growers is a recently established wholesale plant nursey. The case study shows how the RWH tool was used to support Woburn Forest Growers in understanding the reliability of their rainwater harvesting system and the potential of increased storage capacity to reduce mains water use.