Which reports an agricultural reservoir needs

A farm irrigation reservoir is one of those projects where the agricultural reservoir planning reports you need are decided by earthworks and water, not by floor area. There is no building to measure, so the usual householder and floorspace thresholds do nothing. What drives the document list is the size of the excavation, the height and visibility of the embankments, where the water comes from, and what happens downstream if the structure fails. Expect a landscape and visual appraisal, a flood risk and hydrology case, an ecology baseline and a soils position as the core of the submission.

Whether the works are permitted development

Start with the agricultural permitted development rights in Part 6 of Schedule 2 to the Town and Country Planning (General Permitted Development) (England) Order 2015. Excavations and engineering operations reasonably necessary for the purposes of agriculture on a unit of five hectares or more can fall within Class A, and a reservoir to irrigate crops grown on the same holding is capable of qualifying.

Three limits usually bite. Prior notification to the local planning authority is required where the excavation or deposit of waste material covers more than 0.5 hectares, which almost any usable reservoir does. The works must serve agriculture on that unit, so a reservoir built to sell water, to supply a neighbouring holding or to serve a fishery is outside Part 6. And an Article 4 direction, a National Park designation or a scheduled monument on the land can remove the right altogether.

Even where Part 6 applies, two other regimes run in parallel. The Reservoirs Act 1975 brings structures that hold more than 25,000 cubic metres of water above the natural ground level into a supervision and inspection regime administered by the Environment Agency. And the Town and Country Planning (Environmental Impact Assessment) Regulations 2017 list water management projects for agriculture in Schedule 2, so screening is needed once the area of the works passes the Schedule 2 threshold. A screening opinion costs a letter and removes the biggest programme risk on the project.

Landscape and visual effects of embankments

A 4 m high clay embankment around five hectares reads as a new landform. In flat arable country it is visible for miles, and the mitigation planting takes a decade to do anything. This is the issue that decides most reservoir applications outside designated land.

The council will want a Landscape and Visual Impact Assessment prepared to the third edition of the Guidelines for Landscape and Visual Impact Assessment, with viewpoints agreed with the officer before the fieldwork rather than after. Inside or next to a National Landscape or National Park, the assessment carries more weight and the embankment profile usually has to change: shallower batters, a varied crest line, and soil placed to tie the toe into existing ground rather than meeting it at a hard angle.

A landscape strategy then sets out what is planted, how it is managed and for how long. Hedgerow and woodland planting that screens the structure from public rights of way is the single most useful thing to offer.

Flood risk, hydrology and downstream effects

Reservoirs change where water sits and where it goes. Two separate questions follow.

The first is flood risk to and from the site. If any part of the works falls in Flood Zone 2 or 3, or the site is one hectare or more, a Flood Risk Assessment is needed. Because the earthworks raise ground and intercept overland flow, the assessment has to address off-site effects: loss of floodplain storage, diversion of surface water onto neighbouring land, and the behaviour of the embankment in an extreme event.

The second is the water balance. Where does the fill water come from, at what rate, and what does taking it do to the river or aquifer in a dry summer. Winter abstraction into storage is the usual answer, and the Environment Agency assesses that through the abstraction licensing regime rather than through planning. A drainage strategy covering the inlet, the spillway, the draw-off and the discharge arrangements ties the two together.

And reservoir failure is the residual risk nobody wants in the report, and it is the one the lead local flood authority will ask about. Where a Reservoirs Act structure is proposed, a flood plan prepared by a qualified civil engineer forms part of the statutory regime and should be referenced in the planning submission rather than duplicated in it.

Abstraction licensing alongside planning

Abstraction and impoundment are consented separately by the Environment Agency, and the two consents are not sequenced for you. Applying for planning permission without a view on the abstraction position is how schemes end up with permission for a reservoir that cannot be filled lawfully.

Three points to settle early:

1. Whether the catchment is already fully licensed, which determines if a new winter abstraction licence is realistic or whether a licence trade is the only route.
2. Whether an impoundment licence is needed because the works dam or divert a watercourse, as opposed to a bunded reservoir filled by pumping.
3. Whether any existing licence can be varied, which is often faster than a new application.

Planning officers will not refuse permission because a licence has not been granted, but they will condition the development and they will expect the application to explain the intended source honestly.

Ecology, wintering birds and habitat creation

The ecology scope depends on what the land is now. Arable reversion has limited interest, but ditches, field margins, ponds and hedgerows all carry value, and a large open water body attracts wintering waterfowl, which matters if the site sits near a designated site.

A Preliminary Ecological Appraisal is the starting point, with great crested newt eDNA sampling between 15 April and 30 June if ponds lie within the zone of influence, and a reptile presence survey between April and October where rough grassland is affected. Where a protected species is likely, survey work and any licence require a suitably licensed ecologist under the Wildlife and Countryside Act 1981 and the Conservation of Habitats and Species Regulations 2017, and an AI-assisted draft is only the framing document for that specialist.

Biodiversity net gain under the Environment Act 2021 applies to most planning applications. The statutory metric must be completed by a competent person and the biodiversity gain plan approved by the authority before development starts. A reservoir can perform well on the metric where margins, reedbed and species-rich grassland are created on the embankment faces, so run the Biodiversity Net Gain Assessment early enough to influence the design rather than after the levels are fixed.

Agricultural land classification and soil handling

Excavating five hectares takes land out of cultivation permanently and moves a great deal of soil. Where best and most versatile land is involved, expect the authority to ask for an Agricultural Land Classification survey by a soil scientist, with sampling carried out when the ground is neither frozen nor waterlogged.

Pair it with a soil resource and handling plan: topsoil and subsoil stripped separately, stored in bunds of limited height, moved in dry conditions and reinstated on the embankment faces. That plan is also the answer to the question of where the excavated material goes, because importing or exporting soil brings waste controls into play.

The document list and its sequence

A workable order for a 2 to 6 hectare irrigation reservoir on a lowland arable holding, treated as illustrative rather than prescriptive:

• Pre-application advice and an EIA screening request, together, at the start.
• Preliminary Ecological Appraisal, so that survey seasons can be booked before they close.
• Topographic survey, then outline embankment design and levels.
• Landscape and Visual Impact Assessment with agreed viewpoints, informing the embankment profile.
• Flood Risk Assessment and drainage information, including spillway and overflow route.
• Agricultural Land Classification and the soil handling plan.
• Biodiversity net gain metric and gain plan.
• Planning Statement and supporting plans, submitted with the abstraction position explained.

Illustrative example: a 320 hectare arable holding proposes a 150,000 cubic metre winter-fill reservoir on grade 3a land, 1.2 km from a village. Part 6 prior notification is given for the excavation, but the authority confirms a full application is required because the stored water will also supply a neighbouring holding. Schedule 2 screening follows, the embankment is lowered by 800 mm after the viewpoint work, and the reservoir falls within the Reservoirs Act regime.

PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it. To see the likely document list for a specific holding, enter the postcode on PlanScope.