Morgan Lake (Union)

Reachcode: 17060104001358 | Area: 59.6 acres | Shoreline: 1.3 mi | View on Interactive Map

(From Atlas of Oregon Lakes, Johnson et al. 1985)  Morgan Lake is a small reservoir in the Powder River Valley near the city of LaGrande. It was built early in the century with the construction of a 22-foot high dam on Deal Creek, and it served originally as a private water supply. It has since been acquired for public fishing under a cooperative agreement among the city of LaGrande, the Oregon Department of Fish and Wildlife, and the Isaak Walton League. The lake is stocked regularly with rainbow trout, and the fish grow rapidly in the productive water; most anglers catch their limits. No motorboats are allowed on the lake. There are sanitary and picnic facilities available for visitors, but no campgrounds. However, there are several undeveloped campsites located on the shoreline. The natural drainage basin to Morgan Lake is very small, and the major inflow is water diverted through a canal from Sheep Creek. Outflow is into Deal Creek, with much of it returned immediately back to Sheep Creek. The terrain surrounding the lake is relatively flat and rocky and much of it is covered by a sparse pine forest. It is, for the most part, private land, although the lake itself is owned by the city of LaGrande.

The concentrations of major ions, alkalinity and conductivity in Morgan Lake are above average for lakes in northeastern Oregon. Water transparency is moderate (7.8 feet; 2.4 meters) and the chlorophyl concentrations are low. The concentration of phosphorus is surprisingly high and indicates that the lake should be classified as eutrophic. The environs are managed as a wildlife refuge, and there is a substantial population of ducks and other waterfowl on the lake. There is also some cattle grazing in the drainage basin, and both of these activities contribute to the elevated concentrations of phosphorus. Much of the lake is shallower than 10 feet, thus making nutrients available to the surface water. The lake develops a strong thermal stratification, and by late summer is sometimes anoxic below 15 feet depth. This clinograde oxygen curve is further evidence that the lake should be classified as eutrophic. The reducing conditions in the hypolimnion also accelerate the recycling of phosphorus from bottom sediments, further contributing to the elevated phosphorus in the surface water. Cattails, skunk cabbage, water lilies and other macrophytes develop in shallow areas.


Printable Lake Map
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
Sept. 5, 2013 Elodea canadensis (common elodea, Canadian waterweed) Native CLR
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