Off-grid living · US
Living by a stream
How to use a stream for water and power safely: flood risk, water rights, treating surface water and sizing micro-hydro.
Before
- Look up the parcel on FEMA's official flood map at the Flood Map Service Center, and ask the local floodplain official. Build anything you can't afford to lose out of the floodplain. 6
- FEMA's National Risk Index gives wider community risk by county and census tract, not for a single building site. 1
- Owning streamside land doesn't always mean you can use the water. Western states generally use prior appropriation, which separates water rights from land. 2
- For power, you may need a separate water right even if you already hold one for another use. Start with your county engineer. 3
During
Choose the spot, not just the stream
A stream gives you water, irrigation and possibly power, but streams flood. Before you buy, look up the parcel’s address on FEMA’s Flood Map Service Center, the official source for flood maps, 6 and ask the county’s floodplain official whether your building site is in a mapped flood zone. FEMA’s National Risk Index is useful for wider context, but it rates risk by county and census tract, not for a single building site. 1 Put your house, food stores and batteries on high ground.
Water rights come first
In most Western states, water is allocated under the prior appropriation doctrine: the right to use water is separate from the land, and older rights are served first in a dry year. 2 Eastern states generally follow the riparian doctrine instead, which gives use rights to owners of land bordering the water. California uses both systems, and every state has its own variations. 2 Ask the state water agency what you can take, for what use, and how much, before you rely on it.
Using water to make power can need its own water right, even if you already hold one for household or irrigation use. 3
Make stream water safe to drink
Surface water can carry germs from animals and people upstream, so never drink it untreated. CDC’s steps: 4
- If the water is cloudy, filter it through a clean cloth, paper towel or coffee filter, or let it settle and draw off the clear water.
- Bring it to a rolling boil for 1 minute. Above 6,500 feet, boil for 3 minutes.
- If you can’t boil, use unscented household bleach at the dose on CDC’s chart for your bleach strength, and let it stand at least 30 minutes. Our water guide has the full table.
Boiling and bleach don’t remove fuel or chemical contamination. If the stream runs past roads, mines or farms, get a lab test.
Micro-hydro: power around the clock
A small hydro system runs day and night, which makes it a strong partner for solar. DOE gives a quick estimate for a system running at 50 to 70% efficiency: 3
Watts ≈ net head (feet) × flow (gallons per minute) ÷ 10
Head is the vertical drop from intake to turbine. Net head subtracts pipe friction, which DOE says you can estimate at 5 to 10% for planning. 3
For example, 50 feet of gross head less 10% losses is 45 feet. With 40 gallons a minute of flow, that’s 45 × 40 ÷ 10 = 180 watts, or about 4.3 kWh a day if it runs all day.
Measure your site
- Head: a professional survey is most accurate. For a rough number, run a hose or tube down the slope in sections and measure the drop of each. 3
- Flow: ask USGS, the Army Corps of Engineers, USDA or local water authorities for data first. Otherwise time how long the stream takes to fill a bucket, or use the float method. 3
- Design flow: use the lowest average annual flow so the system still works in a dry season. 3
- Too little drop: DOE says a drop under 2 feet will probably make small hydro unfeasible. 3
Permits
Start with your county engineer and state energy office. You’ll also need to contact FERC and the U.S. Army Corps of Engineers. Permits are usually simpler when the system has little environmental impact and you aren’t selling power to a utility. 3
Use the energy and solar calculator to see how much of your daily use hydro could cover.