Cold Water Refugia
As stream temperatures continue to rise in many of Cook Inlet’s salmon streams in the years ahead, cold water refugia – areas within a stream which are persistently colder than adjacent areas – will be critical to the survival and persistence of salmonids and other fish species. Researchers on other rivers in the Western United States have identified deep pools, overhanging vegetation and undercut banks as potentially important for providing refuge from the warmest temperatures. Stream reaches with groundwater interactions (i.e. springs and seeps) may also result in measurably cooler water. Mapping these cold water habitats is valuable to plan future fisheries research, direct monitoring efforts and protect and restore critical fish habitat as thermal change continues.
Inletkeeper Strategies - Thermal Imagery
Cook Inletkeeper worked with here.. to map cold water habitat and provide airborne thermal infrared (TIR) imagery for the Anchor River and Ninilchik River. The focus for this work is to identify springs and upwellings that provide salmon with the cold-water stepping stones needed to make their way up and down otherwise warming streams, and also the warmer, ice-free nooks for overwintering juvenile salmon. Watershed Sciences flew the South Fork Anchor River on June 30th, 2010 and the North Fork Anchor River and Ninilchik River on July 10, 2012. They flew at an altitude of 2,000 feet and the TIR sensors collected images every second which resulted in a 2-foot image resolution. To learn more about thermal infrared imagery and the results from this work, please check out the completed report
With TIR images and GPS in hand, Inletkeeper went out in the field “ground truthing” the data. We searched out these cold water inputs so we know what they look like along the river. We discovered springs and seeps that are in fact contributing cold water to the main stem, sometimes as much as 5oC (9oF) colder. These areas often are rust colored as the iron-rich groundwater reaches the surface and is oxidized. This ground truthing is an important step to validate the TIR images. With on-the-ground confidence that the images accurately reflect thermal conditions, we can look to take this work into new watersheds.
Kachemak Heritage Land Trust has now incorporated these cold water refugia into their prioritization process on lower Kenai Peninsula watersheds. We are please to report that based on this effort, the Land Trust is having discussions with landowners of key salmon habitat on 13 parcels that may result in the protection of over 400 acres.
With this experience on the lower Kenai Peninsula, Cook Inletkeeper has now interpreted thermal imagery in the Big Lake basin in the Mat-Su Borough and provided information about key cold water inflows to Great Land Trust. By linking state-of-the-art technology with conservation planning, we are pioneering innovative actions to improve landscape-scale resilience for Alaska’s salmon.