KHP Impacts on Water Quality


Klamath Hydroelectric Project reservoirs have a deleterious effect on downstream water quality, impacting stream temperatures, depressing dissolved oxygen (D.O.), and elevating pH levels (Kier Associates, 1991, QVIR, 2006). The most apparent problem is the blue-green algae blooms, which develop in these slowed, warmed warm waters and, following their release from the reservoirs, create degraded conditions downstream (CDWR, 1986). Nitrogen levels were about 3.5 times higher below the lake than in the streams flowing into the lake. Aphanizomenon flos-aquae is a common algal species in Iron Gate and Copco reservoirs during the summer season, indicating the nitrogen fixing is likely occurring there as well.


The reservoirs are sinks for nitrogen and phosphorus. Nitrogen concentrations (and phosphorus concentrations to a lesser extent), are predicted to increase under a dam removal scenario. See the Free-flowing vs. Lake page for information on how nutrient retention in KHP reservoirs compares to free-flowing reaches of the Klamath River.


Another way that the reservoirs affect Klamath River water quality is by increasing concentrations of ammonia. Ammonia is a nitrogen-containing compound that is toxic to fish. It is also a nutrient for aquatic plants and algae. The data clearly show that ammonia concentrations are often substantially higher below Iron Gate Dam than they are upstream, above Copco Reservoir (QVIC 2006). These higher ammonia concentrations represent a substantial zone of toxicity risk to the fish in the river below Iron Gate.

Ammonia's toxicity to fish depends on its concentration, stream temperature, pH level, and the duration of exposure (U.S. EPA 1999). As pH and temperature increase, ammonia converts from ammonium ions to dissolved ("unionized") ammonia that is lethal to salmonids at very low levels. For example, at 25 degrees C and at a pH of 9.0, 38% of the ammonia would be dissolved (Goldman and Horne 1983). Temperatures frequently exceed 25 degrees C and pH 9.0 in the Klamath River during summer. Unionized ammonia is highly stressful to salmonids (see Fish Health)

North Coast Regional Water Quality Control Board staff measured pulses of unionized ammonia coming out of Iron Gate Reservoir in 1997. A massive death of fish at a government fish trap downstream at Orleans (Big Bar) was attributed to poor water quality (Halstead, 1997). It coincided with the highest concentrations of unionized ammonia pulses from Iron Gate listed in the NCRWQCB staff report.

nutrient increase unionized ammonia graph
Ammonia levels above and below Copco and Iron Gate reservoirs in 2002 and 2003. Data from PacifiCorp chart by QVIR (2004) Unionized ammonia levels at the outfall of Iron Gate Dam in 1997. Data from NCRWQCB 104 B and chart from QVIR (2004).

Recovery Zone

Downstream of Iron Gate Reservoir is an area referred to as a "recovery zone" having prolific growths of rooted aquatic plants (macrophytes) and attached algae. These organisms thrive on the river's warm water and high nutrient concentrations here. Nutrients are removed from the water column (retained) and assimilated into the growing algae and macrophytes. Due to extreme algal activity in the recovery zone, daily fluctuations in water quality parameters like dissolved oxygen (D.O.) and pH can be adverse for salmonids, but the nutrient retention here lowers the downstream nutrient concentrations. Therefore, while water quality is degraded in the recovery zone, itself, the nutrient uptake in the river there improves the quality of the water downstream of it.

If dams were removed from the river, this recovery zone would expand upstream and water quality would be improved around Iron Gate, where salmon and steelhead concentrate.

Chlorophyl-a per square meter graph pH levels chart
Samples of periphyton from the bed of the Klamath River have been analyzed and the results reported as the amount of Chlorophyll-a per square meter. The US EPA regards values over 150 mg/sq meter indications of pollution. The Klamath River values in September 2004, by river mile, show that EPA's recognized pollution levels were exceeded not only below Iron Gate Dam (river mile 190), but from Sommes Bar down to Weitchpec (river miles 100 down to rm 40), as well. From HVTEPA (2008). Klamath River pH level data from 2000-2004 show high values (>9.0) just below Iron Gate Reservoir (RM 190), but then values consistently over 8.5 all the way to the river's estuary. Such pHs are highly stressful to juvenile salmon and steelhead. Chart from QVIR, 2006). [120 Kb]

Nutrient Spiraling

While the ability of the attached algae and macrophytes to assimilate nutrients in the recovery zone is substantial, and while it does benefit water quality downstream, this ability is not unlimited (Asarian and Kann 2006a). Thus, a substantial amount of nutrient escapes to travel far downstream, fueling algal and macrophyte growth that continues to degrade pH and D.O. conditions in the lower reaches of the Klamath River.

This condition of algae and macrophytes dying, decaying, and their still-living segments floating downstream to cause still more nutrient pollution late into the summer, and over long reaches of the Klamath River, is part of a process known as "nutrient spiraling".

Dissolved Oxygen

Dissolved oxygen (D.O.) levels can sag at night when photosynthetic activity ceases and algae consumes oxygen through respiration. Salmon and steelhead swimming ability drops when D.O. is less than 7 ppm.

The U.S. Fish and Wildlife Service measured D.O. levels lethal for salmonids at the Big Bar downstream migrant trap (at left) in the early morning of August 10, 1997 (Halstead, 1997). Service scientists suspected severe water quality problems because even warm water fish like suckers and dace were dying, not just salmonids. The 1997 event appears to have been anomalous (perhaps even erroneous data) because continuous water quality probes deployed at many mainstem stations from 2001 to present have not detected similarly low D.O.

Dissolved Oxygen chart


Hourly dissolved oxygen levels of the Klamath River at the Big Bar fish trap on August 9-10, 1997. Data from USFWS, Arcata. Chart from KRIS Version 3.0  

Water Temperature

Another important and well-recognized problem with the Klamath Hydroelectric Project is its deleterious effects on the river's water temperatures. The U.S. EPA (2003) recommends that temperatures for salmon spawning and egg incubation not exceed 13 C, measured as a "floating maximum weekly average". During the fall chinook salmon spawning season Klamath River temperatures exceed this goal for weeks because of a "thermal lag" created by the sheer temperature mass represented by the water in Iron Gate Reservoir (at right). This lag can delay chinook salmon spawning activity, decrease fertility, lower the number of eggs and, ultimately, the reproductive success of the salmon (McCullough, 1999).

Just as the Iron Gate thermal lag can harm the spawning of adult salmon in the fall, it also causes water temperatures to remain too low for good growth by young salmon (anything less than 4 degrees C) for several weeks in spring. This slows the growth of fry-sized salmon, decreases their feeding, and more than likely reduces their survival (QVIR, 2006). The Yurok Tribe (2006) expressed concern that KHP-driven temperature shifts create select pressure that is moving fall chinook runs later and later in the season.

Temperature graph .
Modeled water temperature below Iron Gate Reservoir with and without Project show that spawning temperatures required by adult chinook salmon would be available weeks earlier, and that temperatures to support proper juvenile salmon growth would be available if Iron Gate Dam were removed (QVIR, 2006)  



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