21 – Open Water — Lakes, Rivers, Ponds and Reservoirs
Eva L. Greda, David H. Johnson, & Thomas A. O’Neil
Lakes, Ponds, and Reservoirs
Geographic Distribution. Lakes in Oregon and Washington
occur statewide and are found from near sea level to about 10,200
ft (3,110 m) above sea level. There are 3,887 lakes and reservoirs
in western Washington and they total 176,920 acres (71,628 ha)226.
In contrast, there are 4,073 lakes and reservoirs in eastern Washington
that total 436,843 acres (176,860 ha).227
There are 6,000 lakes, ponds, and reservoirs in Oregon including
almost 1,800 named lakes and over 3,800 named reservoirs, all amounting
to 270,641 acres (109,571 ha). Oregon has the deepest lake in the
nation, Crater Lake, at 1,932 ft (589 m).23
Physical Setting. Continental
glaciers melted and left depressions, where water accumulated and formed many
lakes in the region. These kinds of lakes are predominantly found in Lower Puget
Sound. Landslides that blocked natural valleys also allowed water to fill in
behind them to form lakes, like Crescent Lake, Washington. The lakes in the
Cascades and Olympic ranges were formed through glaciation and range in
elevation from 2,500 to 5,000 ft (762 to 1,524 m). Beavers create many ponds and
marshes in Oregon and Washington. Craters created by extinct volcanoes, like
Battleground Lake, Washington, also formed lakes. Human-made reservoirs created
by dams impound water that creates lakes behind them, like Bonneville Dam on the
main stem of the Columbia River. In the lower Columbia Basin, many lakes formed
in depressions and rocky coulees through the process of seepage from irrigation
waters.226 Structure. There are four
distinct zones within this aquatic system: (1) the littoral zone at the edge of
lakes is the most productive with diverse aquatic beds and emergent wetlands
(part of Herbaceous Wetlands habitat); (2) the limnetic zone is deep open water,
dominated by phytoplankton and freshwater fish, and extends down to the limits
of light penetration; (3) the profundal zone below the limnetic zone, devoid of
plant life and dominated with detritivores; (4) and the benthic zone reflecting
bottom soil and sediments. Nutrients from the profundal zone are recycled back
to upper layers by the spring and fall turnover of the water. Water in temperate
climates stratifies because of the changes in water density. The uppermost
layer, the epilimnion, is where water is warmer (less dense). Next, the
metalimnion or thermocline, is a narrow layer that prevents the mixing of the
upper and lowermost layers. The lowest layer is the hypolimnion, with colder and
most dense waters. During the fall turnover, the cooled upper layers are mixed
with other layers through wind action.
Back to Top
Rivers and Streams
Geographic Distribution. Streams and rivers are distributed
statewide in Oregon and Washington, forming a continuous network connecting high
mountain areas to lowlands and the Pacific coast. There are >12,000 named
rivers and streams in Oregon, totalling 112,640 miles (181,238 km) 23 in length.
Oregon’s longest stretch of river is the Columbia (309 miles [497 km]) that
borders Oregon and Washington. The longest river in Oregon is the John Day (284
miles [457 km]) and the shortest river is the D River (440 ft [134 m]) that is
the world’s second shortest river. Washington has more streams than
any other state except Alaska. In Washington, the coastal region has 3,783
rivers and streams totaling 8,176 miles (13,155
km)174. The Puget Sound Region has 10,217 rivers and
streams, which add to 16,600 miles (26,709 km) in
length.223 The rivers and streams range from cold,
fast-moving high-elevation streams to warmer lowland valley
rivers.223 In all, there are 13,955 rivers and streams
that add up to 24,774 miles (39,861 km).174 There are
many more streams in Washington yet to be catalogued.174
Streams reflect flowing water [.greaterequal]6 feet (2 m) wied;
narrower water bodies are considered within their respective habitats.
Physical Setting. Climate of the area’s coastal region is very wet.
The northern region in Washington is volcanic and bordered to the east by the
Olympic Mountain Range, on the north by the Strait of Juan de Fuca, and on the
west by the Pacific Ocean. In contrast, the southern portion in Washington is
characterized by low-lying, rolling hills.174 The
Puget Sound Region has a wet climate. Most of the streams entering Puget Sound
have originated in glacier fields high in the mountains. Water from melting
snowpacks and glaciers provide flow during the spring and winter. Annual
rainfall in the lowlands ranges from 35 to 50 inches (89-127 cm), from 75 to 100
inches (191 to 254 cm) in the foothills, and from 100 to >200 inches (254 to
508 cm) in the mountains (mostly in the form of snow).174
Rivers and streams in southwestern Oregon are fed by rain and
are located in an area composed of sheared bedrock and thus an unstable terrain.
Streams in that area have high suspended-sediment loads. Beds composed of gravel
and sand are easily transported during floods. The western Cascades in
Washington and Oregon are composed of volcanically derived rocks and are more
stable. They have low sediment-transport rates and stable beds composed largely
of cobbles and boulders, which move only during extreme events.81
Velocities of river flow ranges from as little as 0.2 to 12 mph
(0.3 to19.3 km/hr) while large streams have an average annual flow of 10 cubic
feet (0.3 m3) per second or greater.23, 169 Rivers and
streams in the Willamette Valley are warm, productive, turbid, and have high
ionic strength. They are characterized by deep pools, and highly embedded stream
bottoms with claypan and muddy substrates, and the greatest fish species
diversity. High desert streams of the interior are similar to those of the
Willamette Valley but are shallower, with fewer pools, and more runs, glides,
cobbles, boulders, and sand. The Cascades and Blue mountains are similar in that
they have more runs and glides and fewer pools, similar fish assemblages, and
similar water quality.218 Lakes, Rivers
and Streams
Landscape setting. This habitat occurs
throughout Washington and Oregon. Ponds, lakes, and reservoirs are typically
adjacent to Herbaceous Wetlands, while rivers and streams typicaslly adjoin the
Westside Riparian- Wetlands, Eastside Riparian-Wetlands, Herbaceous Wetlands,
and Bays and Estuaries habitats. Other Classifications and
Key References. This habitat is called riverine and lacustrine in Anderson
et al.,10 Cowardin et al.,53
Washington Gap Analysis Project,37 Mayer and
Laudenslayer,150 and
Wetzel.217 However, this habitat is referred to as
Open Water in the Oregon Gap II Project126 and Oregon
Vegetation Landscape-Level Cover Types.127
Back to Top
Natural Disturbance Regime. There are seasonal and decadal variations in
the patterns of precipitation. In the Coast Range, there is usually 1 month of
drought per year (usually July or August) and 2 months of drought once in a
decade. The Willamette Valley and the Cascades experience 1 month with no rain
every year and a 2-month dry period every third year. In eastern Oregon, dry
periods last 2 or 3 months every year, with dry spells as long as 4- 6 months
occurring once every 4 years. Dry years, with <33% of normal precipitation,
occur once every 30 years along the coast, every 20 years in the Willamette
Valley, every 30 years in the Cascades, and every 15 years in most of eastern
Oregon.23
Floods occur in Oregon and
Washington every year. Flooding season west of the Cascades occurs from October
through April, with more than half of the floods occurring during December and
January. Floods are the result of precipitation and snow melts. Floods west of
the Cascades are influenced by precipitation mostly and thus are short- lived,
while east of the Cascades floods are caused by melting snow, and the amount of
flooding depends on how fast the snow melts. High water levels frequently last
up to 60 days. In 1984, heavy precipitation flooded Malheur and Harney lakes to
the point where the two lakes were joined together for several years. The worst
floods have resulted from cloudbursts caused by thunderstorms, like Heppner,
Oregon’s 1903 flood. Other “flash floods” in the region were
among the largest floods in the U.S. and occurred in the John Day Basin’s
Meyers Canyon in 1956 and the Umatilla Basin’s Lane Canyon in
1965.23 Effects of Management and
Anthropogenic Impacts. Sewage effluents caused eutrophication of
Lake Washington in Seattle, where plants increased in biomass and caused
decreased light transmission. The situation was corrected, however, before it
became serious as a result of a campaign of public education, and timely cleanup
of the lake.146 Irrigation projects aimed at watering
drier portions of the landscape may pose flooding dangers, as was the case with
Soap Lake and Lake Leonore in eastern Washington. Finally, natural salinity of
lakes can decrease as a result of irrigation withdrawal and can change the biota
associated with them.92 Removal of gravel
results in reduction of spawning areas for anadromous fish. Overgrazing, and
loss of vegetation caused by logging produces increased water temperatures and
excessive siltation, harming the invertebrate communities such as that reported
in the John Day River Basin, Oregon.146 Incorrectly
installed culverts may act as barriers to migrating fish and may contribute to
erosion and siltation downstream.174 Construction of
dams is associated with changes in water quality, fish passage, competition
between species, loss of spawning areas because of flooding, and declines in
native fish populations.146 Historically, the
region’s rivers contained more braided multi-channels. Flood control
measures such as channel straightening, diking, or removal of streambed material
along with urban and agriculture development have all contributed to a loss of
oxbows, river meanders, and flood plains. Unauthorized or over-appropriated
withdrawals of water from the natural drainages also has caused a loss of open
water habitat that has been detrimental to fish and wildlife production,
particularly in the summer.174 Agricultural,
industrial, and sewage runoff such as salts, sediments, fertilizers, pesticides,
and bacteria harm aquatic species.146 Sludge and heavy
waste buildup in estuaries is harmful to fish and shellfish. Unregulated aerial
spraying of pesticides over agricultural areas also poses a threat to aquatic
and terrestrial life.174 Direct loss of habitat and
water quality occurs through irrigation.130 The Oregon
Department of Environmental Quality, after a study of water quality of the
Willamette River, determined that up to 80% of water pollution enters the river
from nonpoint sources and especially agricultural activity.23
Very large floods (e.g., Oregon Flood of 1964) may change the
channels permanently through the settling of large amounts of sediments from
hillslopes, through debris flow, and through movement of large boulders,
particularly in the montane areas. The width of the channel along the main
middle fork of the Willamette increased over a period of 8 years. Clearcutting
creates excessive intermittent runoff conditions and increases erosion and
siltation of streams as well as diminishes shade, and therefore causes higher
water temperatures, fewer terrestrial and aquatic food organisms, and increased
predation. Landslides, which contributed to the widening of the channel, were a
direct result of clearcutting. Clearcut logging can alter snow accumulation and
increase the size of peak flows during times of
snowmelt.197 Clearcutting and vegetation removal
affects the temperatures of streams, increasing them in the summer and
decreasing in winter, especially in eastern parts of the Oregon and
Washington.24 Building of roads, especially those of
poor quality, can be a major contributor to sedimentation in the
streams.82 Status and Trends. The
principal trend has been in relationship to dam building or channelization for
hydroelectric power, flood control, or irrigation purposes. As an example, in
1994, there were >900 dams in Washington alone. The dams vary according to
size, primary purpose, and ownership (state, federal, private,
local).214 The first dam and reservoir in Washington
was the Monroe Street Dam and Reservoir, built in 1890 at Spokane Falls. Since
then the engineering and equipment necessary for dam building developed
substantially, culminating in such projects as the Grand Coulee Dam on the
Columbia River.214 In response to the damaging effects
of dams on the indigenous biota and alteration and destruction of freshwater
aquatic habitats, Oregon and Washington state governments questioned the
benefits of dams, especially in light of the federal listing of several
salmon species. There are now talks of possibly removing small dams, like the
Savage Rapids Dam in Oregon, to removing large federal dams like those on the
lower Snake River.23 Back to Top
|
|
