Following in the footsteps of the Voluntary Nutrient Reduction Program (VNRP) for the Clark Fork River in Montana, the Council is moving its nutrient reduction effort downstream to Idaho's Pend Oreille Lake. Pend Oreille Lake, with a maximum depth of 1200 feet, is the fifth largest natural freshwater lake in the United States. Inflow from Montana's Clark Fork River heavily influences water quality in the deep, open waters of the lake, which have remained relatively clean and constant over the past 50 years. However, water quality in the shallow near-shore areas of the lake is beginning to decline due to development and human activities around the lake. Increased nutrient loading from residential development, septic tanks and stormwater runoff has caused increased and nuisance levels of algae and aquatic weed growth in these near-shore areas.

The Council began work with Region 10 of the U.S. EPA , the Idaho Department of Environmental Quality (IDEQ), and local governments, groups, industries and citizens to develop an overall nutrient management plan for the lake. The EPA has approved a TMDL (Total Maximum Daily Load) for Pend Oreille Lake. This sets a standard to prevent an increase in pollution levels. To view the summary of the 2002 TMDL for Nutrients for Nearshore Waters of Pend Oreille Lake, Idaho please click here.

A pro-active approach to preventing increased pollution in the nearshore waters was taken by combining the MT-ID Border Nutrient Load agreement with the Lake Management Plan. Working with the Tri-State Water Quality Council and the IDEQ, local agencies and community volunteers have developed such a plan, which includes specific pollution controls and management actions to reduce the amount of nutrients going into the lake from local sources. Representatives from the Council met with local governments and community organizations in the lake's watershed to discuss the plan, to seek feedback, and to solicit participation in the plan's implementation.

The plan consists of measures to reduce impacts from shoreline property, development, stormwater runoff, roads, forestry, agriculture, boating and recreation, and also includes education programs and water quality monitoring to ensure success of the plan.  In December of 2004 the Pend Oreille Lake Nearshore Nutrient TMDL Implementation Plan was released. Elements of this plan have already been implemented. One example is the Pend Oreille Lake*A*Syst Program sponsored by the Bonner Soil & Water Conservation District.  This Lakeshore Assessment System is a voluntary eduactional program designed ot assist shoreline property owners to make well informed decisions in the management of their waterfront property.  Another example is the 2007 Survey of Lakefront Property Owners and the accompanying outreach materials to fill in gaps in homeowner's knowledge of water quality.


To set the stage for this Lake Management Plan, a Border Agreement between the States of Idaho and Montana to protect the deeper, open water quality of the lake has already been facilitated by the Council. The Border Agreement sets nutrient targets to be met in the lake, and apportions responsibilities for meeting those targets between the two states. Please read below for futher information on this agreement.

Montana and Idaho Border Nutrient Load Agreement for Pend Oreille Lake (Open Water)

GOAL: Protect Pend Oreille Lake open water quality

WATERS AFFECTED: Pend Oreille Lake and Clark Fork River

TARGETS: · An area-weighted euphotic-zone average concentration of 7.3 ug/l total phosphorus for Pend Oreille Lake · Total loading to Pend Oreille Lake of 328,651 kg/yr total phosphorus · 259,500 kg/yr total phosphorus from Montana (Clark Fork River at Montana/Idaho state line) · 69,151 kg/yr total phosphorus from the Pend Oreille Lake watershed in Idaho · Greater than a 15:1 total nitrogen to total phosphorus ratio

AREA PROTECTED: Open waters of the lake (waters where the maximum depth is greater than 2.5 times water transparency as measured by Secchi depth) from the mouth of the Clark Fork River to the Long Bridge (Highway 95.)

Technical Guidance Summary. 

In September 1999, the Tri-State Water Quality Council (Council) created a Technical Team to develop technical guidance for an agreement between the states of Montana and Idaho for establishing nutrient targets and apportioning loads to Pend Oreille Lake. The impetus for developing the targets was concern over maintaining the water quality of the open waters of Pend Oreille Lake and the need to address potential impacts from the Clark Fork River in Montana and local sources in Idaho. The Technical Team’s charge was to set open water nutrient concentration targets which support the lake’s designated beneficial uses, and nutrient loading targets to meet those concentrations. The team reviewed and analyzed existing data on Pend Oreille Lake and the Clark Fork to establish a solid scientific foundation for technical guidance and a proposed agreement for consideration by the two states. Team members included representatives from Montana Department of Environmental Quality (MDEQ), Idaho Department of Environmental Quality (IDEQ), the University of Idaho, and the Clark Fork Coalition. The U.S. Environmental Protection Agency (EPA) Regions 8 and 10, and the U.S. Geological Survey, participated in the team in an advisory capacity. Land & Water Consulting, contractor to the Council, provided technical expertise to the team. Driven by citizen concerns over Pend Oreille Lake water quality, the Council, MDEQ, IDEQ and EPA concurred that development of nutrient targets at the Montana/Idaho border would be timely to help prevent pollution of the lake’s open waters. Because about 90 percent of the flow and 80 percent of the loading of total phosphorus into Pend Oreille Lake comes from the Clark Fork River, targets are established for the Clark Fork River at the border to address this predominate influence on lake water quality. By establishing these targets, a major objective of the Clark Fork-Pend Oreille Watershed Management Plan is fulfilled, which is to protect Pend Oreille Lake water quality by maintaining or reducing the rate of nutrient loading from Montana’s Clark Fork River, as well as reducing nutrient loading from the lake’s watershed in Idaho. The targets focus on the lake’s open water and do not address the nearshore, shallow areas of the lake that are influenced predominately by sources located within one mile of the shoreline. Nearshore issues will be addressed in a future document. Establishing targets at the interstate boundary will help apportion nutrient management responsibilities between the two states for future water quality planning and implementation activities. The targets will also provide a framework for water quality management decisions related to new sources.

Please click here to view the entire TECHNICAL GUIDANCE DOCUMENT .  You can also view the actual MONTANA AND IDAHO BORDER NUTRIENT LOAD MEMORANDUM OF AGREEMENT signed by the parties involved.


The 100,000-acre, 40-mile long Pack River is the second largest tributary to Lake Pend Oreille, but contributes the highest per-acre loading of nitrogen and phosphorous to the lake. Besides nutrient pollution, the Pack River suffers from high water temperatures, low levels of dissolved oxygen, and excess amounts of fine sediment which are negatively affecting drinking water, agricultural water, and heavy recreational uses of the river, as well as endangered Bull Trout.

The Council has implemented a program to improve the Pack River by:

  • Developing a water quality monitoring program with students from Lake Pend Oreille and Sandpoint High Schools.
  • Launching a new Pack River Watershed Council consisting of landowners, businesses, and state, federal and local agencies in partnership with the Natural Resources Conservation Service (NRCS) and the Bonner Soil & Water Conservation District.
  • Informing and educating stakeholders on water quality issues and empowering them to appropriate action with technical assistance.
  • Developing a cohesive strategy for long-term monitoring and protection.
  • Coordinating restoration projects and funding with private landowners and agencies.
  • Assisting the Pack River Watershed Council to draft a sediment and nutrient TMDL implementation and management plan for the Pack River.

A result of all these activities the Pack River Watershed Management Plan and TMDL Implementation Plan was completed this year.