Creating a farm reservoir for irrigation
Volume and fill source decide everything. Agricultural permitted development, the raised reservoir threshold, winter abstraction licensing and the survey seasons that set the programme.
Farm reservoir consent is three consents wearing one name. You need a planning position for the excavation and the embankments, an abstraction licence for the water you intend to put in it, and, above a volume threshold, registration and supervision under reservoir safety legislation. The abstraction licence is usually the one that decides whether the scheme happens at all, because a reservoir you cannot legally fill is an expensive hole.
Work out the volume and the fill source before anything else. Those two figures set which regimes apply and in what order.
Excavation and embankments as engineering operations
Digging a reservoir and forming banks around it are engineering operations, which are development under section 55 of the Town and Country Planning Act 1990. Whether you need an express permission depends on the agricultural permitted development rights.
Part 6 of Schedule 2 to the Town and Country Planning (General Permitted Development) (England) Order 2015 allows works reasonably necessary for the purposes of agriculture on an agricultural unit of five hectares or more, including excavations and engineering operations, subject to the conditions and limits the Order sets. For the operations it lists, you must apply to the authority for a determination as to whether its prior approval is required for the siting, design and external appearance of the works, and wait for the answer. The Order also restricts works near a classified road and works connected with certain uses, so read the current text rather than a summary.
The test that gets contested is whether the works are reasonably necessary for agriculture on that unit. A reservoir sized for the holding's own irrigation demand meets it comfortably. One sized to supply a neighbouring enterprise, or partly for a fishery or a water sports use, does not, and the fallback is a full planning application.
Where the site is in a National Landscape, a National Park, a conservation area or the Green Belt, the permitted development position narrows and the landscape evidence carries more weight. A reservoir is a big earthwork, and openness matters in Green Belt terms.
The raised reservoir threshold and its regime
The Reservoirs Act 1975, as amended, regulates raised reservoirs by the volume they are capable of holding above the natural level of any part of the adjoining land. In England the threshold was lowered so that structures above 10,000 cubic metres come within the registration regime, with the Environment Agency as enforcement authority and a risk designation determining the level of supervision required. Verify the current thresholds, registration duties and designation process with the Environment Agency before you settle on a design, because the figures and the commencement of particular provisions have moved.
The word "raised" is where designs get changed. A reservoir formed wholly by excavation below existing ground level, with spoil taken away rather than banked up, may fall outside the raised reservoir definition entirely. One of the same capacity formed by ringing a shallow dig with embankments may not. The supervision obligations, the panel engineer inspections and the emergency planning that follow are ongoing costs, so it is worth testing whether a lower profile design avoids them.
Say in the planning submission which side of the threshold the reservoir falls, and how the volume was calculated. Officers rarely know this legislation and will ask.
Winter abstraction and the licence application
Filling a reservoir from a watercourse or a borehole is abstraction, and abstraction of more than 20 cubic metres a day needs a licence from the Environment Agency under the Water Resources Act 1991.
For irrigation reservoirs the licence sought is normally a winter or high-flow one. The logic is that water is taken when river flows are high and stored for use in the growing season, which is why winter storage reservoirs are encouraged in catchments where summer abstraction is fully committed. Expect conditions setting a hands-off flow below which abstraction must stop, an annual volume limit, a daily rate limit, and a season during which abstraction is permitted.
Two practical points. In heavily abstracted catchments a new licence may not be available at all, and the answer to that question should be obtained from the Environment Agency before you spend on design. And a time-limited licence affects the business case, because a 12-year licence against a 40-year asset is a different investment from a permanent one.
The full guide to planning permission for a farm reservoir or irrigation pond covers the application route in more detail, and the licensing sequence above sits in front of it.
Spoil, levels and the waste position
A reservoir generates a lot of excavated material. Where it is used to form the embankments on the same site, there is no waste question and the earthworks are part of the engineering operation. Where it is spread on adjoining land to raise levels, or taken off site, the position changes.
Raising the level of land is itself an engineering operation needing a planning position, and depositing material can engage waste controls unless the material is being used in accordance with a recognised code of practice for reusing excavated material on site. Describe the earthworks balance in the application: volumes excavated, volumes used in banks, volumes spread and where, with existing and proposed levels shown on a section.
The clay lining question belongs here too. Where suitable clay exists on site, using it avoids a synthetic liner and the visual problem of an exposed liner edge. Where it does not, a geomembrane liner needs an anchor trench and a protective cover, and the detail matters to the appearance of the finished bank.
Landscape effects of banks and liners
A reservoir reads in the landscape as a long horizontal bank, often on a skyline, with a hard geometric edge that nothing else in a field pattern shares. That is what a landscape officer objects to, rather than the water.
The design moves that work are unfussy. Keep the bank height down by taking more of the volume below ground. Batter the outer face at a shallower angle than the minimum and grade it into existing contours rather than stopping at a toe. Vary the bank crest level slightly so it does not read as a ruled line. Plant the outer face with species from the local hedgerow palette, and avoid a continuous belt that becomes its own linear feature. Where the reservoir is visible from public rights of way, a Landscape and Visual Impact Assessment prepared to the recognised guidelines with viewpoints agreed in advance will carry the case better than photographs taken from the farm gate.
Ecology, archaeology and the survey programme
Large-scale excavation on farmland brings two survey requirements that applicants often discover late.
Ecology first. A walkover and habitat assessment through a Preliminary Ecological Appraisal identifies whether protected species surveys are needed, and reservoirs sit in exactly the habitats where they often are: ditches with water vole, ponds with great crested newts, hedgerows with nesting birds. Survey seasons are unforgiving. Newt work is tied to a spring window and breeding bird survey visits run across the spring and summer, so a project that decides to apply in September may be waiting until the following year. Where a protected species licence is needed, that work must be carried out by a suitably licensed ecologist, and a drafted report is a starting point for that professional rather than a substitute.
Archaeology second. A reservoir strips and disturbs a large area to depth, which is the profile county archaeologists treat as high risk. An Archaeological Desk-Based Assessment drawing on the Historic Environment Record is the usual first step, and on a site with known cropmarks or an alignment of interest expect a request for geophysical survey and trial trenching before determination rather than by condition.
Reports the application should carry
- A planning statement with the agricultural justification, the volume calculation and the reservoir safety position.
- Existing and proposed levels, sections through the banks, and an earthworks balance.
- Landscape and visual work proportionate to the site's exposure and designations.
- Ecology appraisal, with any protected species surveys programmed to the right season.
- Archaeological desk-based assessment, and field evaluation where the record justifies it.
- Geotechnical information on the founding conditions for the banks and the suitability of site-won material, since a Geotechnical Assessment also supports the safety case.
- A construction traffic note where material is imported or exported.
Start the abstraction licence conversation first, the survey programme second, and the planning application last. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. For specialist technical reports, qualified professional input may be required.
Frequently asked questions
Does a farm reservoir need planning permission?
Excavation and embankments are engineering operations and therefore development. On an agricultural unit of five hectares or more, Part 6 of Schedule 2 to the GPDO 2015 may cover works reasonably necessary for agriculture, subject to its limits and to a prior notification of siting, design and external appearance. A reservoir sized beyond the holding's own needs falls outside that and requires a full application.
When does the Reservoirs Act apply?
It regulates raised reservoirs by the volume they can hold above the natural level of adjoining land. In England the threshold was lowered so that structures above 10,000 cubic metres come within the registration regime, with the Environment Agency as enforcement authority and a risk designation setting the supervision required. Verify the current thresholds and duties with the Environment Agency before fixing a design.
Can a reservoir design avoid the raised reservoir regime?
Sometimes. A reservoir formed wholly by excavation below existing ground level, with spoil removed rather than banked, may fall outside the raised reservoir definition, while one of the same capacity ringed by embankments may not. Because panel engineer inspections and emergency planning are ongoing costs, it is worth testing a lower profile design.
What sort of abstraction licence do irrigation reservoirs need?
Usually a winter or high-flow licence, taking water when river flows are high and storing it for the growing season. Expect a hands-off flow below which abstraction must stop, an annual volume limit, a daily rate limit and a permitted season. In heavily abstracted catchments a new licence may not be available, so ask the Environment Agency before spending on design.
Which surveys hold up a reservoir application?
Ecology and archaeology. Newt work is tied to a spring window and breeding bird visits span spring and summer, so a scheme that starts in September can wait a year. A large stripped area to depth is the profile county archaeologists treat as high risk, so expect a desk-based assessment and possibly geophysics and trial trenching before determination.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.