Articles
Validation of rainwater harvesting efficiency for irrigation of a heritage landscape
Article number
1429_29
Pages
243 – 250
Language
English
Abstract
Rainwater harvesting (RWH) is an essential strategy to cope with water scarcity and climate change impacts on landscapes and public gardens where irrigation is required, as well as supporting the wider hydro-ecological environment.
Previously, we modelled the rainwater harvesting potential for all Royal Horticultural Society garden sites.
At RHS Gardens Wisley, a lake was then built to hold rainwater harvested from a large roof to support the irrigation of a heritage woodland landscape.
The site was previously almost wholly dependent on river abstraction.
This study reports the real-world performance of rainwater harvesting to meet irrigation demand using a combination of modelling and field data, for the period October 2022 until September 2023. We found that approximately 70% of irrigation demand for the woodland landscape (10 ha) was satisfied from rainwater sources, saving 4976 m3 of river water abstraction.
This initial investigation provides improvements to rainwater harvesting modelling by combining modelled lake water storage volume and losses to evaporation with actual irrigation volumes abstracted from the lake and provides better insight into the volume of rainwater remaining available for use.
Additionally, the model allows an assessment of the ability of rainwater harvesting to meet the irrigation demand forecast under future climate change scenarios.
We compare the expected water availability for rainwater to water demand for simulated 1990-2000, 2030-2040 and 2070-2080 scenarios and note how shifts in the timing of rainfall and peak irrigation demand will impact the sufficiency of the lake water storage to supply future water requirements.
Previously, we modelled the rainwater harvesting potential for all Royal Horticultural Society garden sites.
At RHS Gardens Wisley, a lake was then built to hold rainwater harvested from a large roof to support the irrigation of a heritage woodland landscape.
The site was previously almost wholly dependent on river abstraction.
This study reports the real-world performance of rainwater harvesting to meet irrigation demand using a combination of modelling and field data, for the period October 2022 until September 2023. We found that approximately 70% of irrigation demand for the woodland landscape (10 ha) was satisfied from rainwater sources, saving 4976 m3 of river water abstraction.
This initial investigation provides improvements to rainwater harvesting modelling by combining modelled lake water storage volume and losses to evaporation with actual irrigation volumes abstracted from the lake and provides better insight into the volume of rainwater remaining available for use.
Additionally, the model allows an assessment of the ability of rainwater harvesting to meet the irrigation demand forecast under future climate change scenarios.
We compare the expected water availability for rainwater to water demand for simulated 1990-2000, 2030-2040 and 2070-2080 scenarios and note how shifts in the timing of rainfall and peak irrigation demand will impact the sufficiency of the lake water storage to supply future water requirements.
Authors
N.C. Cryer, J. Manning, P. Mealey, M.B. Gush
Keywords
rainwater harvesting, RWH, irrigation, water neutral
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