Laymen's Summary of Water Quality Findings in the Clark Fork-Pend Oreille Watershed 1984-2002

Algae photos courtesy of Dr. Vicki Watson, University of Montana

This page summarizes the scientific findings in a report on nutrients, metals, and algae in the Clark Fork-Pend Oreille watershed  from 1984 to 2002. Water quality can be measured by a variety of scientific tests, so we have linked the highlighted scientific terms to definitions that you may find useful. Click on any of the highlighted terms to find its definition.

What is a watershed?    What do we monitor and why?

The BIG picture

Portions of states shown on map: Washington, Idaho, Montana. To view information specific to your state, just click on the links above or anywhere on the preferred state in the watershed map:

As you can see, the Clark Fork-Pend Oreille watershed is very large and covers three states, as well as part of British Columbia in Canada.  Scientists have been collecting data to help understand how water quality changes over time and at different places in the watershed. Included in the summary were findings from:

Using all this data, scientists have been able to determine that nutrient and metal-related    water quality in the watershed is slowly getting better in most areas, but a lot of work still needs to be done. 
 
Below is a general summary of trends in these water quality parameters:  nitrogen, phosphorus, metals (copper and zinc), and algae (periphyton and chorophyll-a). 
 
 

NITROGEN AND PHOSPHORUS

Over the period of 1984 to 2002 scientists have determined that total phosphorus and total nitrogen have generally decreased from the headwaters of the Clark Fork River to Lake Pend Oreille (with some exceptions). These types of nutrients have been identified as important indicators of potential algae growth in the Clark Fork River. Reducing their levels has been one of the main goals of the Council.

METALS

Scientists have also determined that the level of metals (copper and zinc) in the water generally decreased from the headwaters of the Clark Fork River to Lake Pend Oreille, as well. These metals have been found at high levels in the upper Clark Fork River and are associated primarily with mining operations in the headwaters that are part of an Environmental Protection Agency (EPA) Superfund clean-up site stretching from Butte to Missoula, Montana.

ALGAE

Scientists have set target levels for attached algae (chlorophyll-a and periphyton) in the Clark Fork River (in Montana) and monitoring reveals that target levels are still exceeded at most sites most of the time. From 1998 to 2002 some study sites showed a slight increase in algae, while others showed a slight decrease or no change at all. There are many factors that can effect algae growth and the hope is that each year we will learn more from data being collected and eventually be able to identify how to maintain acceptable levels. Click here to see photos of algae in the Clark Fork River. 

In Lake Pend Oreille, Idaho, three of the five sites sampled for attached algae (chlorophyll-a and periphyton) have an overall increasing trend, with one site showing no change, and one site showing a decreasing trend. Sometimes an increase in attached algae may point to a decline in overall water quality, but not always. Scientists are hoping to continue to collect data which should help provide answers to the questions being raised.

In the Pend Oreille River, Washington, two sites are monitored for nutrients. Data shows that nutrient levels are not changing significantly over time. Nutrient levels are generally low in the Pend Oreille River in Washington and scientists monitor two stations there to help understand the big picture of water quality as water flows through the watershed. 

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MONTANA

Summary of water quality in the Upper & Lower Clark Fork River - Montana

ALGAE

Attached algae (chlorophyll-a and periphyton) levels were monitored in the Clark Fork River from 1998 to 2002. Data shows that levels increase at some sites and decrease or show no change at others.

Click here to see pictures of algae in the Clark Fork River, Montana.

 

 

Upper Clark Fork River  (headwaters to Missoula)

NUTRIENTS

Viewing the series of graphs for nutrients, you see that higher concentrations of phosphorus are found in the upper Clark Fork River. Scientists believe this is caused by three factors: stream flow, point sources, and geology. Total phosphorus levels increase slightly downstream of Deer Lodge wastewater discharge but then continue to decrease to just above the city of Missoula. A lot of time, money and effort from everyone involved with the Council in Montana have been spent to try and decrease the amount of nutrients in the Clark Fork River--and IT'S WORKING!

Total nitrogen generally decreases from the headwaters downstream. Scientists believe the levels of total nitrogen are caused by four factors: streamflow, nonpoint sources, point sources, and geology. Nitrogen levels in the upper Clark Fork River are influenced by wastewater discharges and tributaries draining agricultural areas. 

Click on the numbered links below to view graphs for the Upper Clark Fork River. Most graphs also have an audio clip which explains the graph. To hear these clips (MP3), click on the link, and open your computer's media player (such as Windows Media Player if you have a PC). For a free download of Windows Media Player, click here.

NUTRIENT GRAPHS:

METALS

Copper concentrations were highest in the upper watershed near the Superfund site and remain elevated in the Clark Fork River above the Little Blackfoot River.

Zinc concentrations fluctuated throughout the upper and middle watershed and were highest at Silver Bow Creek at Opportunity. Zinc concentrations remain high until just above Missoula.

Lower Clark Fork River (Missoula to Lake Pend Oreille)

NUTRIENTS

Total phosphorus levels in the lower Clark Fork River increase downstream of Missoula but then continue to decrease to the last station monitored on the Clark Fork River in Idaho. Higher phosphorus levels just below Missoula are likely due to Missoula's wastewater treatment plant. The City of Missoula has spent approximately $16.2 million dollars to upgrade its treatment plant over the last five years in order to reduce the amount of phosphorus entering the Clark Fork River and the data shows that their work is beginning to pay off!

Like phosphorus, total nitrogen levels increase below Missoula then decrease to the confluence of Lake Pend Oreille in Idaho. Both phosphorus and nitrogen levels are relatively low due to larger volumes of water and the influence reservoirs.

Click on the numbered links below to view graphs for the Lower Clark Fork River. Each graph also has an audio clip which explains the graph. To hear these MP3 files, open a media player such as Windows Media Player if you have a PC. (For a free download of Windows Media Player,click here.)

METALS

Below the Little Blackfoot River, copper concentrations decrease steadily downstream and become so low at the three Clark Fork River sites below Thompson Falls that copper can no longer be detected using laboratory equipment.

Below Missoula, zinc levels begin to decrease as waters from the Blackfoot and Bitterroot Rivers flow into the Clark Fork River and dilute the overall zinc concentrations. In the Clark Fork River below the confluence of the Flathead River, zinc can no longer be detected using laboratory equipment.

Algae photos courtesy of Dr. Vicki Watson, University of Montana

IDAHO

Summary of water quality in Lake Pend Oreille - Idaho  

ALGAE

Five nearshore Lake Pend Oreille stations were monitored for attached algae (chlorophyll-a and periphyton) from 1998 to 2002.  Data shows that one of the five sites had an overall increasing trend in attached algae with two sites showing no change and two sites showing a decreasing trend.  Sometimes an increase in attached algae may point to a decline in overall water quality, but not always.  At this point there is only enough information to raise more questions than provide answers, and scientists are hoping to continue to collect data so that if a problem is identified, appropriate action can be taken. 

NUTRIENT LOADING

Using nutrient data collected as part of this study and a computer model developed by the US Army Corps of Engineers, scientists calculated the yearly nutrient load to Lake Pend Oreille from the Clark Fork River.  A border nutrient agreement signed between the states of Idaho and Montana in 2002 set target levels for total phosphorus entering Lake Pend Oreille from the Clark Fork River.  The loading calculations from this study show that those targets are being met.  

Click here to see a graph of total phosphorus loading to Lake Pend Oreille. Graphs also have audio clips. To hear these clips (MP3), click on the link, and open your computer's media player (such as Windows Media Player if you have a PC). For a free download of Windows Media Player,click here.

SECCHI DISK DEPTH

Secchi data has been collected in Lake Pend Oreille since 1952 and the data shows that there has been little change in the clarity of the open waters since that time. 

Click here to see a graph of Secchi disk readings in Lake Pend Oreille.

 

WASHINGTON

Summary of water quality in the Pend Oreille River – Washington

NUTRIENTS

The Pend Oreille River at Newport had decreasing trends for nitrogen while phosphorus remained the same. No trends were detected for the Metaline Falls sampling station. Here are links to Information about the two monitoring sites on the Pend Oreille River: Newport, Metaline Falls

The Washington State Department of Ecology has more  information about monitoring on its River and Stream Water Quality Monitoring web page.