Pioneer Canal and Laramie River by Tony Bergantino
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In 1986, Wyoming enacted legislation defining "instream flow" as a beneficial use of water and stipulated how instream flow water rights would be filed, evaluated, granted or denied, and ultimately regulated (Wyoming Statutes Section 41-3-1001 to 1014).

The first filing was for a 5.8 mile segment of the Clark's Fork River in 1986. Since 1986, approximately six applications per year have been filed for instream flow water rights. Nearly all instream flow segments are through lands with some public ownership (Forest Service, Bureau of Land Management, State, public fishing easements). Instream flow filings have been focused on the State's most productive streams and on streams with sensitive, native game fish like Colorado River cutthroat trout.
 Allows an application for an instream flow water right in a similar manner as any other water right.  No public access through or across private land to instream flow segments.
 Protects all pre-existing water rights.  Prohibits abandonment or condemnation of existing water rights to secure water for instream flow.
 Maintains the State's ability to develop all the water allocated to Wyoming under our interstate compacts & Supreme Court decrees.  Disallows private individuals, organizations or other entities to hold an instream flow water right. Instream flow water rights may only be held by the state.
 Attaches an instream flow water right to a specific stream reach or segment.  Doesn't automatically reserve or designate any amount of water for instream flow in all streams. Each filing must be based on site-specific biological & hydrological studies & go through a review process.
 Allows other water rights to be sold or donated to the State for conversion to instream flow. The Game & Fish Department has the responsibility of seeking the change from other uses to instream rights prior to granting the change of use.  Denies issuance of an instream flow water right if Wyoming's use of water under an interstate compact or court decree will be impacted.
 Allows cities & towns to condemn an instream flow water right for municipal purposes.
 Asserts that only the State may hold instream flow water rights.


  1. WGFD identifies stream reaches where instream flows for fisheries are critical & unappropriated surface water appears available.
     -WGFD conducts field studies & prepares a biological report that identifies the minimum amount of water necessary to maintain or improve the existing fishery.
  2. WWDC prepares a water right application and submits it to the State Engineer's Office.
     -The priority date of the water right is the application acceptance date (just as it is with any other water right).
  3. WWDC completes a hydrology study on the availability of unappropriated water to meet the water rights application request.
  4. SEO conducts a public hearing to present WGFD & WWDC information & receive public comments.
     -Normally a 30 day comment period is allowed to provide written comments.
  5. SEO issues a decision.
  6. Board of Control adjudicates or finalizes the water right.
Q: How can an instream flow be provided on a stream when most or all of the summer flow is already appropriated for downstream uses?
A: The water of a stream is often reused many times on its way downstream by virtue of return flows from upstream diversions. An instream flow filing on a stream segment may make use of already appropriated water because the water is committed to a senior point of diversion downstream of the segment of interest. Because that water, by law, must reach the downstream diversion point, an instream flow permit assures the water's presence in the upstream channel, & thus creates an opportunity for "piggybacking" an instream flow water right, using the same water.
Q: Why is it necessary to file for instream flows in stream segments upstream from existing water users since the water must be delivered to those users anyway?
A: Existing water law protects downstream water rights but does not guarantee that those flows will remain in the upstream segment. Instream flow water rights are a way to keep needed amounts of water in the stream for fisheries while protecting senior water rights.
Q: When can the State request regulation to satisfy an instream flow water right?
A: Like any other water right not receiving its full permitted amount of water, the State may request regulation of the stream to satisfy the instream flow water right according to Wyoming water law.
Q: Does issuance of an instream flow water right reduce the amount of water available for other uses?
A: Yes and no. An instream flow water right has an established priority date. When that right is in priority, the State may call for water. A request for regulation to satisfy an instream flow water right may prevent an upstream junior user from reducing the stream flow and may limit the upstream senior users to their statutory water right amounts in order to meet the amount needed for the instream flow permit. However, the instream flow water right does not consume any water so once the water leaves the instream flow segment, it is available for downstream uses.
Q: Do instream flows tie up all the remaining water in a stream?
A: It depends on the amount of the instream flow right and where the segment lies within the basin. Instream flow water rights are based on specific studies that, according to the law, identify the minimum amount of water needed to maintain or improve an existing fishery. In almost all cases, these studies indicate that any reduction of natural flows during low flow periods will impact stream fisheries. However, the majority of the annual yield of most streams, that comes during spring runoff, should still be available for other uses. But during low flow periods, an instream flow right downstream in the basin could limit the amount of water available to later development upstream.
Q: Do instream flows prevent future water development?
A: Certainly not downstream of the instream flow segment. An instream flow water right, like a water right for any other use, can limit future water development upstream in the drainage. In some cases, State-approved instream flow water rights can facilitate the Federal permitting process for water development projects. The reality of many water development projects today is that they cannot be built without minimizing or avoiding environmental impacts, which often means providing instream flows. Knowing instream flow requirements early in the planning process allows developers to modify their projects accordingly, avoiding lengthy studies of instream flow needs and facilitating the permitting process.
Q: How can an instream flow water right provide fishery benefits if the requested amount isn't always present in the stream at the time of year it is requested?
A: Instream flows are determined by identifying the long-term productive potential of the stream and are intended to allow the fishery to benefit from naturally occurring stream flows up to the permitted flow levels. The existing fishery has adapted to natural variations in flow. There are fewer fish in streams during drought periods and more during times of abundant water. Thus, maintaining the existing fishery simply means maintaining existing flow patterns up to the identified amounts. An instream flow water right that protects only the low (drought) flows can lead to losses in the existing fishery.
Q: Isn't storage needed to provide instream flows?
A: The law limits the use of storage water to creating or maintaining fisheries - not improving them. There are few if any places in the state where construction of storage solely to create a fishery would be a cost-effective use of state money. Storage has been used in some cases to maintain fisheries as a mitigation component of some projects ad is an effective way to secure permit approval for new projects.
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