High stream temperatures are known to be a problem for fish during mid- to late-summer in some streams in B.C. The highest stream temperatures typically occur on clear summer days when streamflows are low and mid-day solar angles are still high. Direct solar radiation is the major source of stream heating at this time so shade has a strong moderating effect on daytime temperatures.
Stream shade is one of the most important forestry-related variables affecting maximum summertime stream temperatures because it moderates stream heating and is subject to large changes over time due to harvesting and revegetation of riparian areas. Therefore, knowing how to measure, inventory, estimate, and manage it is critical to managing stream temperature. However, until recently such knowledge has been a significant knowledge gap. In a report to the Ministry of Forests Temperature Sensitive Streams Working Group, Teti (2000) recommended three projects related to stream shade. These were:
1. Develop a measurement method and field sampling procedure for inventorying stream shade.
2. Inventory riparian shade in priority watersheds
3. Develop methods to estimate riparian shade from surrogate variables
This project builds on the substantial accomplishment of number 1 and has the specific purpose of addressing number 3. Because this project is incomplete, the purpose of this report is to describe the incremental work during the 2003/2004 fiscal year. The stated deliverable was an Extension Note on preliminary results with the intended outcome of creating awareness by forest practioners that stream shade can be quantified and possibly predicted.
Teti, Patrick, Moore, R. Dan. 2004. Tools for managing the impacts of forest practices on stream temperature. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report