Section 16 · Design & Build
Permits, water rights & environmental flow
A ram is a benign machine, but it still takes water, alters a stream, and stands on someone's land. The rules differ enormously between countries and even between neighbouring catchments — the questions you have to answer do not.
Water law is local, it changes, and the penalties for ignoring it are usually imposed on the person who installed the pump. Use this page to know what to ask about, then ask the authority that actually regulates your stream.
Water rights & abstraction
In most jurisdictions water in a stream is not owned by the landowner. It is held by the state, the crown or the community, and the right to take it is allocated by licence. Where that is the case, installing a pump and taking water without one is not a technicality — it is the offence that gets schemes shut down.
A ram's net take is unusually small
This is the fact most worth knowing, because it changes the conversation with a regulator. A ram does not consume the flow it runs on; it diverts most of it and returns it to the channel a few metres later. Only the delivered fraction leaves the stream for good — and that fraction is governed by the lift ratio.
At a 10:1 lift ratio, with a 60% energy efficiency, about 6% of the drive flow is delivered uphill and the other 94% returns to the channel. The licence conversation is about that 6%, not about the flow you take. See the two efficiencies.
- What a licence usually controls: the maximum rate you may divert, the daily or annual volume, the season or months in which you may take it, the point of abstraction, and the minimum flow that must remain in the channel.
- Priority and drought. Licences are commonly ranked, and in a dry year the low-priority holders are told to stop first. A ram designed for the dry season can be throttled or stopped without damage — see winter & drought — but a scheme sized on wet-season flow will breach its licence every summer.
- Domestic or small-use exemptions exist in some places and are narrower than people assume, and often attach to a dwelling rather than to a field or a herd.
- The return flow is not always free. Some regimes treat a diversion-and-return as an abstraction anyway, and care about the intake and the reach between the intake and the outfall.
Environmental flow & fish
The flow you leave behind matters as much as the flow you take. Environmental (or minimum) flow is partly an ethic and increasingly a condition of the licence: the reach between your intake and the waste outfall has to stay a stream rather than a damp channel.
Design for the dry season, not the wet one
The measurement discipline is on the source assessment page; the point here is that it is also a compliance issue. A design that works only above a wet-season flow is a design that breaks its conditions every year, whatever the pump can physically do.
- Gauge the low-flow month — the season your flow is at its lowest (often summarised as a low-flow statistic such as Q95, the flow exceeded 95% of the time) is the one that decides how much you can take.
- Leave a residual flow by design. A forebay with a spillway that passes a set flow is a simple way to guarantee the channel keeps water, and to show a regulator that it does.
- Mind the cumulative effect. One ram returning 94% of its flow is trivial; twenty upstream of each other, each with an intake screen and a diversion, are a series of small barriers and losses in the same reach.
Fish and other stream life
The drive pipe is a trap. Water is drawn through a screen and accelerated down a pipe to a valve that slams roughly once a second, and anything small enough to pass the mesh travels the whole way. Intake screening has two jobs: keep debris out of the drive pipe, and keep animals out of it.
- Keep the approach velocity across the screen low. Fast flow pins small fish to the mesh; a generous screen area for the flow, with the screen set at an angle rather than square to the current, lets them swim away and sheds debris downstream to be cleaned.
- Keep the waste outfall in the channel and well clear of the bank, so the spent flow returns where it came from rather than eroding a bank or silting a spawning reach. The outfall design in cold climates matters here too.
- A void is sometimes needed. Where a diversion weir or a small dam is part of the design, some regimes require a passable notch or ramp so the structure does not become a barrier. Ask before you pour concrete.
Everything argued here about fish applies to grit and leaves. A screened, generous intake keeps the valve seat clean and the beat steady — the same design that protects the stream protects the machine. See intake & forebay.
Land, structures & records
Beyond the water itself there is the ground it crosses and the things you build on it.
| What | The question to settle first |
|---|---|
| Land tenure and access | Whose land does the drive pipe cross, and whose does the delivery line cross? A verbal agreement with the neighbour who is friendly today is not a scheme that survives a sale. |
| Riparian and bank works | Are you allowed to excavate in the bank, place a forebay, or run a pipe across the bed? |
| Weirs, dams and headworks | Anything that raises or holds back water is usually a regulated structure, even a low diversion weir built for gauging (gauging methods). Temporary structures count while they are in the water. |
| Protected and heritage sites | Conservation areas, listed structures and archaeological sites all carry their own consents — the 1890 Idaho ram that is now on a national register would have been a listed structure to work around, not through (case studies). |
| Discharge and waste | Your spent water is going back to the channel, but its point and condition of return may still be conditioned. |
| Community agreement | Where more than one household depends on the supply, the arrangement that keeps it running is a social document, not a hydraulic one (who keeps it running). |
Keep the paperwork with the pump
A licence is only useful if the people operating the scheme know what it requires. Put the conditions, the abstraction limits and any monitoring obligation on the same sheet as the as-built record, and let the log carry the readings that show you are inside them — the as-built record & handover. When an inspector or a funding body asks, the answer is already written down.
Find out who allocates water in your catchment and what they require. Measure the low-flow season. Leave a residual flow you can point to. Screen the intake generously. Get the landowner's agreement in writing. Keep the conditions with the machine.
With the site legal and the water allocated, the engineering starts: Design & Sizing.