from Bouchie Lake Factsheet prepared by Ministry of Environment
Phosphorus is the primary nutrient of concern contributing to the algal growth that is resulting in poor water quality. Large algae blooms, excessive aquatic plant growth, and decreased water clarity have all been identified as concerns to residents. Two studies were conducted prior to 2007 looking at phosphorus inputs to the watershed.
The Bouchie-Milburn Watershed encompasses the west side of Milburn Mountain, Mit Lake, Milburn Lake, Bouchie Lake, and all associated creeks. There is a sub-surface water connection between the outlet of Milburn Lake and the inlet of Bouchie Lake. The main water bodies in the watershed are Milburn Lake and Bouchie Lake. Both lakes have development on the lakeshore to varying degrees.
An analysis was completed in 2002 by J.S. Hart and Associates to examine the phosphorus sources in the Bouchie-Milburn watershed.
| Phosphorus source | Annual phosphorus input to Bouchie Lake from the watershed: amount (kg) |
% of total |
| Agriculture land (including hobby farms) | 190.2 | 42.2 |
| Lakeshore sewage disposal systems | 70.0 | 15.5 |
| Livestock wintering areas | 60.2 | 13.4 |
| Crown land (excluding lakes and ponds) | 37.6 | 8.3 |
| Lakeshore residential land | 36.0 | 8.0 |
| Rural residential land | 28.2 | 6.3 |
| Atmospheric contributions to lakes and ponds | 28.2 | 6.3 |
| Total | 450.3 | 100.0 |
Hart estimates an increase of 30.9% input from lakeshore sewage systems (to 91.6 kg/year) by 2027 assuming no further development and no upgrades to sewage systems.
For a more complete synopsis of septic system impacts on the Bouchie-Milburn watershed, please see this document prepared by Chris Swan with the BC Ministry of Environment.
Internal phosphorus loading is also a significant source of nutrients to Bouchie Lake. Internal phosphorus loading is estimated to be 52% of the entire annual phosphorus load (C. Perrin 2005). This internal loading is a result of build-up of lakeshore and upland sources over time and was estimated using Phosphorus levels in the water column throughout the year.
