Over the years I have driven along the Columbia River dozens of times from Portland to 180 miles upstream where the river turns north into Washington State.
(Rie Miyazaki is co-author of the Columbia River material, here and on the Intro page).
I always had the impression that I was driving beside a wide river, with willows growing on sandbars, whitecap waves due to the strong gorge winds, and water gushing from the power plants of several dams.
Finally we made a series of collections and took river samples from several sites in the river- (near Multnomah Falls, at Bonneville Dam, at the Dalles, at Umatilla, all in Oregon, and west of Mesa, Wa. not far north of the Oregon border.)
p. 4- there are over 400 dams, reservoirs, and hydroelectric projects; on the Columbia and Snake rivers there re 18 major dams. Eleven large dams on the main Columbia River turn the river into a series of slow-moving reservoirs. The lowest is Bonneville Dam.
p. 6- Historically the system had an average to rich bottom fauna. This included Trichoptera and chironomid larvae, mayfly nymphs and mollusks (Roebeck et al. 1954 in Ebel et al 1989). "Today the main stem of the Columbia River is considered depauperate in species (Ebel et al 1989)".
The river at Richland is in fact the upper end of the lake formed by a dam at Umatilla, Oregon.
--- the dot in the middle of the above photo.
A real river seems to exist upstream, opposite the town of Mesa (map, above).
The Columbai River shore west of Mesa is gravel and stones.
The substrate between stones is covered with silt and living and decaying plant material.
As the cracked crusts of silt indicate on the rocks above, the river substrate is unsuitable for the original river benthic invertebrates, and no aquatic insects were found in August 2009. Shells of bivalves were abundant on the shore.
Below are historical records, extracted from publications by Meyer and McCafferty , 2007, Washington and Oregon Mayflies:
Almost all the the following species were shared by the Saskatchewan and Columbia Rivers. They are still present in the former (see discussion on Home), but apparently long gone from the latter.
Records from Washington--------------------------------------------------------------------------------------------------------
(Benton County, Washington, is often cited below. The Columbia River forms the east boundary of Benton County, and the river forms the west boundary of Franklin County.
Baetiscidae, Baetisca columbiana Edmunds, Franklin (County?) near Mesa, Washington, Columbia River. Reported by G. F. Edmunds. A similar species, Baetisca lacustris is found in the Sask. River.
Baetidae, Callibaetis fluctuans (Walsh), Benton County, Wa., Columbia River. A similar species, Callibaetis palidus, is found in the Sask Riv.
Ephemeridae, Ephemera simulans Walker, Benton County, Columbia River, Hexagenia limbata (Serville), Benton County. Both of these species are also presently found in the Saskatchewan River.
Heptageniidae, Heptagenia solitaria McDunnough, Benton County, Columbia River, Maccaffertium terminatum (Walsh), Columbia River. Both genera, plus the species M. terminatum are found in the Sask. River.
Leptohyphidae, Tricorythodes minutus Traver, Benton County, Columbia River. This species is found in the Saskatchewan River.
Leptophlebiidae, Traverella albertana (McDunnough), Benton County, Columbia River, This species is found in the Saskatchewan River.
Polymitarcidae, Ephoron album (Say), Benton County. This species is found in the Saskatchewan River.
(The Snake River is an eastern fork forming the Columbia River, and the John Day River enters the Columbia from the south in Oregon)
Baetidae, Camelobaetidius mexicana (Traver and Edmunds), Baker County Snake River and C. warreni (Traver and Edmunds) John Day River (both rivers are tributaries of the Columbia River). C, warreni is found in the Saskatchewan River.
Ephemeridae, Hexagenia limbata (Serville), Portland (Columbia River?) and Bonneville Dam. This species is found in the Saskatchewan River.
Heptageniidae,Maccaffertium terminatum (Walsh), Snake and John Day Rivers. This species is found in the Saskatchewan River.
Leptophlebiidae, Choroterpes albiannulataMcDunnough, John Day River. This species is found in the Saskatchewan River.
Polymitarcidae, Ephoron album (Say), Snake River (east tributary of the Columbia River. This species is found in the Saskatchwan River.
Missing from the Oregon/Washington Columbia River data are evidence of the "Southwest" presence- e.g. Ametropus and Lachlania, and "Eastern" representatives such as Pseudiron, Macdunnoa, and Raptoheptagenia.