Antelope Flat Reservoir (Crook)

Reachcode: 17070304003841 | Area: 199.6 acres | Shoreline: 3.6 mi | View on Interactive Map

(From Atlas of Oregon Lakes, Johnson et al. 1985). Antelope Flat Reservoir is an irrigation impoundment on the south side of the Maury Mountains in Central Oregon. It is situated near the headwaters of Bear Creek, a tributary of the Crooked River, and was formed by a 33-foot high earthfill dam at the west end of Antelope Flat. Antelope Flat is the name given the dish-shaped valley that supports an exceptional variety of vegetation, from grassy sagebrush on the lower slopes to sparse juniper stands and pine forest at the higher elevations. The reservoir has a storage capacity of nearly 2000 acre-feet and a surface area of 170 acres when full; but it is often drawn down to less than half that size by late summer to satisfy downstream irrigation needs. Rainbow trout are found in the reservoir and there have been reports of a high growth rate and good success by anglers. Recreation facilites have been provided near the dam, including a good paved boat ramp. There is no campground at the reservoir, but a good one nearby.

The maximum depth of the reservoir is 28 feet at full pool and the average depth is only 11 feet. The water is frequently turbid because of the growth of phytoplankton and because of bank erosion caused by surface waves, thus decreasing water transparency. The concentration of ions is fairly high, characteristic of the semi-arid Crooked River drainage. Alkalinity and conductivity are above average for eastern Oregon reservoirs. The concentration of phosphorus is very high, and chlorophyl is above average. Macrophytes grow in all of the littoral zone, especially at the swampy area near the inflow at the east end of the reservoir. Because of the combination of shallow water and a significant supply of nutrients from the drainage basin, Antelope Flat Reservoir is distinctly eutrophic.

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No mussel data available.

The list of plants below includes results of aquatic plant surveys conducted by the Center for Lakes and Reservoirs as well as aquatic invasive plant species detections that have been reported to iMap Invasives: an online, GIS-based invasive species reporting and querying tool.

Plants listed in the table below are categorized as native to Oregon, on the Oregon Department of Agriculture’s (ODA’s) Noxious Weed List, on the Federal Noxious Weed List, or non-native but not listed as noxious. Federal Noxious Weed List plants are plants determined by USDA to be serious threats to U.S. agriculture, irrigation, navigation, public health or the environment (7 C.F.R. 360.200). The ODA Noxious Weed categories are:

ODA Class A - weeds either unknown or with small enough infestations to make eradication or containment possible; targeted for eradication or intensive control.

ODA Class B - regionally abundant weeds (may have limited distribution in some counties); targeted for local/regional control on case-by-case basis.

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Date Species Status Source
Aug. 8, 2013 Limosella sp. (mudwort) Native CLR
Aug. 8, 2013 Alisma gramineum (narrowleaf water plantain) Native CLR
Aug. 8, 2013 Eleocharis acicularis (needle spikerush) Native CLR
Aug. 8, 2013 Myriophyllum sibiricum (northern watermilfoil) Native CLR
Aug. 8, 2013 Callitriche hermaphroditica (northern water-starwort) Native CLR
Aug. 8, 2013 Potamogeton richardsonii (Richardson's pondweed) Native CLR
Aug. 8, 2013 Stuckenia pectinata (sago pondweed) Native CLR
Aug. 8, 2013 Potamogeton pusillus (slender pondweed) Native CLR
Aug. 8, 2013 Nitella sp. (stonewort) Native CLR
Aug. 8, 2013 Ranunculus aquatilis (water-buttercup) Native CLR