Annis is an earth dam located in Natrona County, Wyoming, built in 1948. It carries a Low hazard potential classification and has a fair condition assessment.
Dam profile
NID height · 25 ft25 ft tall and 130 ft long, taller than 50% of U.S. dams with a recorded height. Height is drawn to scale against a two-story house, about 25 ft; the profile is a generic embankment section and the water level is illustrative.
About Annis
The primary purpose of Annis is irrigation. The dam stores and diverts water for agricultural irrigation, supporting farming operations in the surrounding area. The dam is owned by Annis Ranch Trust (private). It impounds the Arkansas Creek near Alcova.
The dam stands 25 feet tall and stretches 130 feet across, creates a reservoir covering 26 acres, and has a maximum storage capacity of 332 acre-feet. Completed in 1948, the structure is well-established, with more than 75 years of service.
This dam has a low hazard potential classification, meaning that failure would cause minimal damage, limited primarily to the dam owner's property, with no expected loss of life. Its condition is rated fair — the dam has minor deficiencies that are being addressed or do not pose an immediate safety threat. The most recent inspection on record was 09/23/2021.
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Location
| State | Wyoming |
| County | Natrona |
| Nearest City | Alcova |
| River/Stream | Arkansas Creek |
| Coordinates | 42.45830, -107.01740 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 25 ft |
| Dam Height | 25 ft |
| Dam Length | 130 ft |
| Year Completed | 1948 (78 years old) |
Storage & Hydraulics
| NID Storage | 332 acre-ft |
| Max Storage | 332 acre-ft |
| Normal Storage | 166 acre-ft |
| Surface Area | 26 acres |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Irrigation |
| Owner | Annis Ranch Trust |
| Owner Type | Private |
| Hazard Classification | Low |
| Condition Assessment | Fair |
| Last Inspection | 09/23/2021 |
| Emergency Action Plan | Not Required |
Identifiers
| NID ID | WY00405 |
| Federal ID | WY00405 |
| More Info | State Dam Safety Program |