Restoring Nutrients in Kootenay Lake

Project Year: 2016-2017

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Photo: B. Sperling

Project Lead

Ministry of Forests, Lands and Natural Resource Operations

Watershed/Sub-region

Columbia Region

Project Type

Habitat-Based Actions

FWCP Contribution

$873,053

Action Plan Alignment

Large Lakes Action Plan

Project ID

Annual/Ongoing

Kootenay Lake Nutrient Restoration

This project includes the coordination, oversight and implementation of nutrient additions to the North Arm of Kootenay Lake, and the associated monitoring and reporting. Kootenay Lake has been influenced by the construction of Duncan Dam and Libby Dam, impacting native fish populations by permanently changing the hydrograph and nutrient loading to Kootenay Lake, flooding and/or blocking migration to spawning and rearing habitat and decreasing downstream lake productivity. Nutrient additions (nitrogen and phosphorus in the form of liquid agricultural grade fertilizer) support phytoplankton populations that are suitable for the production of Daphnia, a main food source for Kokanee. Additions have occurred in Kootenay Lake since 1992 and are added from the end of April through early to mid-September.

The program replaces nutrients lost to Kootenay Lake as a result of upstream impoundments. The goal is to maintain sufficient abundance of Kokanee as forage fish to meet targets for large piscivores through the continued application of appropriate quantities of nutrients. Output targets for Kokanee are between the lower acceptable threshold for spawners of 19/ha or 747,000 total, and the upper threshold of 31/ha or 1,200,000 in total. The average size of Kokanee spawners is targeted as 23 centimetres.

 


Final Report: Executive Summary

This report summarizes results from the Nutrient Restoration Program in 2016: the 25th year of nitrogen and phosphorus additions to the North Arm of Kootenay Lake and the 13th year of nitrogen additions to the South Arm. The program was conducted using an adaptive management approach in an effort to restore lake productivity lost as a result of nutrient retention and uptake in upstream reservoirs. The primary objective of this program is to restore kokanee (Onchorhynchus nerka) populations, which are the major food source for Gerrard rainbow trout (Oncorhynchus mykiss) and bull trout (Salvelinus confluentus).

Kootenay Lake is a warm, monomictic lake with a water renewal time of approximately two years. It is 395 km2 in area with an average depth of 94 metres and a maximum depth of 154 metres. Surface water temperatures are typically warmest in August. The lake is well oxygenated from the surface to bottom depths at all stations throughout the year. It has two main inflows into the South and North Arms and one outflow through the West Arm of the Lake.

Click the provincial database link below to read the full final report for this project.

View more about this project on the provincial database