Hydro · Water rights and permits
Three separate bodies of law can govern a household micro-hydro project: who may use the water, whether the federal government regulates the power, and what may be built in a streambed. They are administered by different agencies who will not coordinate on your behalf.
Read this first, build last
Everything in the preceding seven guides assumes you are permitted to take water from your stream and generate power with it. That assumption is doing a great deal of work, and it is the one most likely to end a project after money has been spent.
This page sits at the end of the reading order only because the earlier guides tell you what you are asking permission for. Read it before you buy anything.
State law. Whether you may divert, how much, and when. This is the layer that has nothing to do with electricity and everything to do with whether the project exists.
The Federal Power Act, administered by FERC. Whether your project needs a federal license, qualifies for an exemption, or falls outside federal jurisdiction entirely.
The Clean Water Act, fish and wildlife agencies, and state dam safety where an impoundment is involved. What may physically be built in and near the water.
Layer one
American surface water law divides into two traditions, shaped by how much water each part of the country had when its rules were written. Which one governs your creek changes the question you are asking.
Landowners along a watercourse hold a right to make reasonable use of the water, so long as that use does not unreasonably harm other riparian owners. The right comes with the land and is not lost by not using it.
Most eastern states have layered a permit system on top of the common-law doctrine, so reasonable use is now often something a state agency determines rather than something neighbors argue about. Missouri's extension service, for instance, describes a combination of riparian rights and reasonable use, with any work diverting a stream from its normal flow requiring a federal Section 404 permitMicro-hydropower for the Home, Farm or Ranch, regulatory considerations">[1].
Rights are allocated by seniority of first use rather than by land ownership. First in time, first in right. A senior holder downstream is entitled to their full allocation before a junior holder upstream takes any, which can mean a stream on your land is spoken for.
Rights are also tied to beneficial use and can be lost through non-use. Whether generating power counts as a beneficial use, and whether a non-consumptive diversion that returns the water needs its own right, are state-specific questions with real answers you can obtain.
First: do I need a water right or permit to divert water for a non-consumptive hydroelectric use, given that the water returns to the same stream a short distance downstream? The answer is not obvious and varies considerably.
Second: what minimum flow must remain in the channel, and in which seasons? That figure is your real design flow, and the measuring guide's arithmetic should be rerun against it rather than against what the creek carries.
Layer two
People assume a small system is too small for federal attention. Size is not the test. Under section 23(b)(1) of the Federal Power Act, a hydropower project must be licensed or granted an exemption if it meets any of four conditions[2]:
The fourth condition is the one that catches people, and connecting to the interstate grid is a recognized way of affecting interstate commerce. A purely off-grid system on a small non-navigable stream crossing private land, touching no federal land, sits differently from a grid-connected one, but this is a determination rather than a conclusion you reach yourself.
Which is why the useful part of FERC's own guidance is the last line. If you are developing a new site and are unsure whether your project meets any of the criteria, contact FERC staff assigned to your region, or file a Declaration of Intention and the Commission will determine whether your project must be authorized. For an existing project or dam, request a Declaratory Order[2].
That matters more than any summary a website can give you. The agency with jurisdiction publishes a process for finding out whether it has jurisdiction over your specific project, and using it produces an answer you can rely on. Guessing does not.
If FERC does have jurisdiction
FERC issues three types of development authorization for small projects: conduit exemptions, 10-megawatt exemptions, and licenses[2]. A fourth category sits outside the licensing requirement altogether.
Facilities on non-federally owned conduits with installed capacity up to 40 megawatts are not required to be licensed or exempted, provided the conduit is not operated primarily for the generation of electricity and was not licensed or exempted on or before August 9, 2013. The developer files a Notice of Intent with the Commission[2].
A conduit is a man-made channel. Irrigation ditches, municipal water lines and industrial supply pipes qualify. A natural stream does not.
For a small conduit hydroelectric facility up to 40 megawatts using a man-made conduit operated primarily for non-hydroelectric purposes. The route for conduit projects that do not meet the qualifying conduit criteria above.
For projects of 10 megawatts or less built at an existing dam, or using a natural water feature for head, or an existing project of that size proposing to add capacity. The applicant must propose to install or add capacity at a non-federal pre-2005 dam or at a natural water feature, may be on federal lands but not at a federal dam, and must hold the real property interests or an option on them[2].
The natural water feature language is the provision most relevant to a run-of-river household project, and it is worth raising specifically when you contact regional staff.
The full process, required where no exemption applies. A license conveys the power of eminent domain to obtain lands or rights needed to construct, operate and maintain the project. It is also a considerably longer and more demanding undertaking than anything a household project should expect to need.
Exemptions are issued in perpetuity, which is a genuine advantage over a license that must eventually be renewed. They exempt the project from Part I of the Federal Power Act, and the process is more straightforward than licensing[2].
They do not convey eminent domain, and an exempted project remains subject to mandatory terms and conditions set by federal and state fish and wildlife agencies and by the Commission. Those conditions are where minimum flows and screening requirements usually appear, and they are not negotiable in the way a permit application sometimes is.
Layer three
Separate from who owns the water and who regulates the power is the question of what may be constructed in a streambed. This layer applies whether or not FERC has jurisdiction.
A permit from the Army Corps of Engineers is required to discharge dredged or fill material into waters of the United States. Building a weir, setting an intake structure or placing fill in a channel is that. The program allows both individual permits issued project by project and general permits, including nationwide permits, which authorize common activities with minimal impacts and are the faster route where a project fits one.
The governing test is demanding: no discharge may be permitted if a practicable alternative exists that is less damaging to the aquatic environment, or if the nation's waters would be significantly degraded. Applicants must show impacts were avoided, then minimized, then compensated for what remains.
Where a federal license or permit may result in a discharge into waters of the United States, the state or authorized tribe must certify that the discharge will comply with water quality requirements. The certifying authority may grant certification, grant it with conditions, deny it, or waive it, and it has a reasonable period of up to one year to act[3].
The consequential detail is that any conditions attached to a Section 401 certification become conditions of the federal permit itself. This is where a state exercises real influence over a federally permitted project, and it is why the state agency conversation matters even when the permit is federal.
State and federal fish and wildlife agencies set mandatory conditions on FERC exemptions and licenses, and separately administer requirements on screening, passage and instream flow. Where a listed species is present, the Endangered Species Act adds a further layer. These agencies are usually the source of the specific numbers that shape an intake design, so reach them early rather than after the screen is bought.
Any structure holding water back brings the state dam safety program in, with requirements keyed to height, storage volume and hazard classification. The impoundments guide covers what that involves and why it is a different order of undertaking from a diversion.
Where to start
None of them cost anything, all of them are routine for the person answering, and together they will tell you within a few weeks whether your project is possible.
Ask whether a non-consumptive hydroelectric diversion needs a water right or permit in your state, and what minimum instream flow applies to your reach. This call determines whether there is a project at all.
Describe the site and ask whether it is jurisdictional. If the answer is unclear, ask about filing a Declaration of Intention. Mention the natural water feature provision of the 10-megawatt exemption if a diversion is contemplated.
Describe the physical work in the channel and ask whether it needs an individual permit or fits a nationwide permit. They handle this question constantly and will tell you quickly.
Ask what screening and passage requirements apply on your stream, and whether any listed species are present. Their answer sets slot size and approach velocity at your intake, which is a design input rather than a formality.
Follow every useful phone call with a short email summarizing what you were told and asking the person to correct anything you have misunderstood. Agencies reorganize, staff change, and a project takes years. The file you build now is what protects you later, and it costs ten minutes each time.
Common mistakes
Federal jurisdiction turns on where the project is and what it connects to, not on how many watts it makes. An 800 watt system and an 800 kilowatt system face the same jurisdictional test.
Owning both banks does not mean owning the water. In prior appropriation states a senior holder downstream may have a superior claim to the flow crossing your land.
Every calculation in this section should be rerun once the minimum instream flow is known. The permitted diversion is the design flow, and it is often well below what the creek carries.
Water rights, energy jurisdiction and construction permits are separate tracks with separate timelines. Clearing one says nothing about the others, and none of them will tell you about the rest.
Unpermitted work in a streambed can require removal and restoration at the owner's expense, on top of whatever the installation cost. This is the most expensive mistake available on this page.
Rules change. Section 401 certification regulations, for example, have been revised more than once in recent years and were under further revision in 2026. Confirm current requirements with the agencies rather than with a page.
The section, complete
Eight guides, one creek. Sixty feet of gross head measured with a garden hose and a pressure gauge. Three hundred and twenty gallons a minute in the driest month, of which 150 might lawfully be diverted. Four inch pipe rather than three, because friction was worth fifteen feet of head. A small Pelton runner turning fast enough to drive a generator without a gearbox. A diversion load that keeps the machine from running away. Roughly 810 watts, continuously, through every hour of every February night.
That is more energy than the fifteen panel solar array in the adjoining section produces on an average December day, from equipment that fits on a workbench. Water is the best resource on this site, and this section exists because the few properties that have it deserve to know what it is worth.
Measuring head and flow, with a hose and an afternoon. Rerun it against your permitted flow.
Read the guideWater rights, zoning and property due diligence, carried state by state.
Read the sectionThe other five areas, for properties whose best resource is something other than water.
Read the sectionSources
This page is a general orientation and is not legal advice. Water law is state-specific and the descriptions of riparian and prior appropriation doctrines above are broad generalizations with many state-level variations. Federal regulations change: Section 401 certification rules have been revised repeatedly in recent years and were under further revision during 2026. Jurisdictional determinations are made by the agencies, not by summaries. Contact your state water agency, FERC regional staff, your Army Corps district and your state fish and wildlife agency before committing to a project.