Permit for a dam?


Active member
Feb 14, 2024
Do you believe I'd need a permit to dam up the stream that runs through my property? I'm not sure where the stream originates; I also don't know where it ends exactly. I'd like to use it to irrigate my garden, but the stream bed gets pretty dry during July and August when we receive less rain. A dam would fix that issue.
United States
This is in my wheelhouse so I'm happy to respond here :). In terms of federal regulation, you might need a Clean Water Act Section 404 permit from the U.S. Army Corps of Engineers (i.e., my shop) if the stream flows perennially or intermittently. If you have an ephemeral stream, and you can document it as such, then you won't need a Corps permit. The Corps considers a stream to be ephemeral ("non-relatively permanent" in current regulatory terms) if it only flows in direct response to rain events. If the stream carries some base flow (i.e., flows in the absence of rainfall at least a couple days per year), then it's at least intermittent and is probably Corps-regulated.

This distinction between intermittent and ephemeral flow became important following last year's Sackett decision, in which the Supreme Court put limitations on what qualifies as a regulated stream or wetland (aka "waters of the U.S.") under the Clean Water Act. Relevant to your dam project, the Supreme Court found that "waters of the U.S." like streams must be "relatively permanent waters" (RPWs) that would, "in ordinary parlance," be described as "streams, oceans, rivers, and lakes." The Biden administration issued its 2023 amended rule, which codified the unregulated status of non-RPWs but didn't provide any real direction in terms of how RPWs vs. non-RPWs should be classified the field. We recently discussed the latest tools and guidance for making RPW/non-RPW determinations over in this thread, if you're interested.

If you know for a fact your stream is intermittent, then you should reach out to Corps regulators to discuss next steps. You can use this online map to find contact info for the Corps Regulatory District operating in your area. There may also be other state/local agencies that regulate waterways similarly to the Corps that you'll need to obtain permits from. You can often start by talking to someone at one agency, like the Corps, and through that conversation learn about other agencies and staff you should reach out to for information on additional federal/state/local permitting requirements.
Building a dam on a stream has a potential environmental and legal implications. Therefore, you need a permit to build a dam even when the flows through property. Since you are altering water flow can that can impact ecosystems, water quality, and neighboring properties, you need a permit.
I think it's safe to say that a permit is likely required in this type of scenario. Especially when it has to do with any public water sources. I wonder if building said dam would also require a building permit? Other than that, I'd reach out to local permitting offices and ask around. @Eric seems to have ya covered though. :)
I'm coming at this from a farmer's perspective. Since you'd like to use the stream for irrigation, it also stands to reason that your downstream neighbors rely on that water source as well. If you block that source of water, you'll have unhappy neighbors who might complain and attempt to get the permit revoked. It might not be worth the hassle. Plus, if the permit goes through, don't be surprised if your upstream neighbors do the same to you.
I see; it doesn't look as simple as I originally thought it would be, and it's probably not worth the hassle nor upsetting my neighbors. I'll have to weigh this decision some more before making a decision.