Britain is heading for an exceptionally poor potato harvest after the hot, dry summer, according to new reporting published on 9 October. Analysis cited by the industry estimates that drought and heat could reduce Great Britain’s crop by around 440,000 tonnes, with an estimated value impact of between £80 million and £169 million.
Those figures describe an industry-level estimate, not the loss on every farm. Yield, quality and financial impact will vary by region, variety, soil, irrigation access and contract. The wider warning is clear, however: dependable water has become a strategic production issue rather than a problem to address only when a dry spell arrives.
The government has announced up to £15 million for a new Water Management Grant round focused on on-farm reservoirs. Defra said the scheme was expected to open in autumn 2026, but the latest published announcement does not provide final eligibility rules or an application route. Farmers should therefore prepare evidence now without committing expenditure on the assumption that it will qualify.
Why planning cannot wait for the application form
England entered October with most monitored reservoirs classed as notably or exceptionally low. Overall storage was below half full when the seasonal expectation was almost three-quarters. The Environment Agency also said the country would need 120% of average rainfall over the following seven months to be entirely out of drought by spring.
Some farmers were allowed to begin filling storage reservoirs from 1 October rather than 1 November, subject to environmental restrictions and individual licence conditions. That change does not create a general right to abstract. The licence, catchment position and any Section 57 restriction still matter.
A reservoir project brings together water need, hydrology, abstraction, planning, engineering, electricity, safety and finance. The following checks will help turn a broad idea into information that can support a grant application and an investment decision.
Seven checks for an on-farm reservoir project
1. Quantify the production problem
Start with the crop plan and the water deficit it creates. Record irrigated area, crop and variety, soil type, expected application depth, timing, historic abstraction and the peak weekly requirement.
Use several seasons rather than designing around one unusually dry year. Include the cost of lost yield, reduced specification, rejected crop, interrupted planting and emergency water arrangements. This creates a business case based on production risk rather than a vague desire for more storage.
2. Confirm where the water can legally come from
A reservoir is only useful if it can be filled lawfully and reliably. Identify the proposed source: winter surface-water abstraction, borehole, roof-water harvesting, drainage water or a combination.
Check existing abstraction licences, hands-off-flow conditions, seasonal limits and permitted quantities. Speak to the Environment Agency early if a new licence or variation may be required. An earlier filling concession in one drought year should not be treated as a permanent change to the licence.
Compare the theoretical water available with what would actually have been captured in several recent winters. A large empty reservoir is not resilience.
3. Size the scheme around usable capacity
Headline capacity is not the same as usable irrigation water. Allow for dead storage, evaporation, sediment, freeboard, leakage risk and water reserved for environmental or operational requirements.
Model at least three seasons: an ordinary year, a dry year and a severe year with restricted abstraction. Then test how many hectares and irrigation cycles each volume supports.
Include the relationship between reservoir location and pumping energy. A cheaper earthworks site may cost more over its life if water must be moved a long distance or lifted substantially.
4. Establish planning and environmental constraints
Do not assume that “making reservoirs easier to build” removes the need for permission or assessment. Confirm the planning route with the local authority and obtain competent advice on ecology, landscape, archaeology, flood risk, public rights of way and proximity to watercourses or designated sites.
Consider excavated material, construction traffic, noise, fencing and the effect on neighbours. If habitat creation is part of the design, keep it compatible with the reservoir’s agricultural function and safety requirements.
5. Build a complete cost plan
Budget beyond excavation and lining. A credible estimate should cover design, surveys, planning, licence work, earthworks, liner or clay preparation, inlet and outlet structures, pumps, filters, pipework, electricity, controls, fencing, signage, commissioning and professional fees.
Add contingency and identify VAT and cash-flow treatment. Previous grant rounds had their own intervention rates, thresholds and eligible-cost rules; do not assume the new round will repeat them until the official guidance is published.
Request comparable written quotations and state whether prices include ground conditions, reinstatement, testing and connection work.
6. Plan safe operation and maintenance
Reservoirs introduce risks including drowning, unstable edges, vehicles near banks, electrical equipment, pressurised pipework and unauthorised access. Design access, fencing, rescue arrangements and inspection points from the outset rather than adding them after construction.
Define how water levels, banks, liners, valves, pumps and electrical systems will be inspected. Keep vegetation controlled without damaging structures. Anyone operating pumps, tractors or other machinery should have suitable information, training and a clear defect-reporting route.
Working cabs will also carry mud and moisture during irrigation and maintenance work. Farm Packs supplies heavy-duty seat covers for tractors, pickups and other working vehicles, but any cover must fit the exact seat and must not obstruct belts, controls, sensors or adjustment.
7. Prepare an evidence file before the window opens
Create one project folder containing:
- the water-need calculation and crop assumptions;
- abstraction correspondence and licence information;
- site plans, photographs and ownership or tenancy evidence;
- planning and environmental advice;
- design options and usable-capacity calculations;
- itemised quotations and funding plan;
- expected productivity and resilience benefits;
- project risks, permissions and delivery timetable.
Keep assumptions dated. When Defra publishes the new scheme rules, compare this file with the actual eligibility, scoring, procurement and start-date requirements before signing contracts or beginning work.
Treat funding as support, not the business case
The difficult 2026 season demonstrates why water resilience matters, but a reservoir is not automatically the right answer for every business. Soil management, irrigation scheduling, equipment efficiency, crop choice, shared infrastructure and alternative sources may deliver better value in some situations.
The strongest project should make operational and financial sense before grant support, with funding improving affordability rather than rescuing an unsuitable design. Quantify the need, prove the source, obtain permissions and understand the whole-life cost. That preparation will put a farm in a stronger position when the application window opens—and produce a better investment decision if the scheme or eligibility differs from expectations.
This article provides general information and does not replace advice from the Environment Agency, Rural Payments Agency, local planning authority, qualified engineers, accountants or safety professionals.
Sources
The Times: Hottest summer means smallest potatoes — 9 October 2026
Energy & Climate Intelligence Unit: Impact of the 2026 summer drought and heatwaves on the European potato harvest — 15 September 2026; updated 17 September 2026
Defra and Environment Agency: England’s reservoirs continue to feel drought strain — 2 October 2026
Defra Farming Blog: New drought support for farmers — 15 August 2026
