Climate Change Impacts on Freshwater Ecosystem Health

River restoration efforts are increasingly focusing on reconnecting floodplain habitats to promote species recovery, but the dynamic nature of these habitats is often overlooked in planning and evaluation. According to a study published in River Research and Applications, the hydro-ecological modeling approach used to examine habitat availability for splittail and Chinook salmon in the San Joaquin River in California revealed that only 13 streamflow events in the past 80 years had the magnitude and duration required for splittail spawning and rearing, and 14 events had flows long enough for salmon rearing benefits. Under climate change, the modelled results suggest that only 4-17% of the years in the rest of this century are likely to produce required flow-related habitat conditions for splittail and salmon rearing.

Key Takeaways:

• Freshwater ecosystem health is increasingly linked to floodplain connectivity, and river restoration efforts are now focusing on reconnecting floodplain habitats for species recovery.
• The dynamic nature of floodplain habitats is not typically accounted for in efforts to plan and evaluate potential floodplain reconnection projects.
• A novel hydro-ecological modeling approach was used to quantify species-specific habitat availability using hydraulic modeling, spatial analysis, and statistical measures of flow regime.
• The study examined the potential habitat for splittail and Chinook salmon under two restoration treatments and two climate change flow scenarios for a study site on the San Joaquin River in California.
• Only 13 streamflow events in the past 80 years had the magnitude and duration required for splittail spawning and rearing, and 14 events had flows long enough for salmon rearing benefits.
• Under climate change, the modelled results suggest that only 4-17% of the years in the rest of this century are likely to produce required flow-related habitat conditions for splittail and salmon rearing.
• Restoration efforts will require a more natural flow regime to make use of restored floodplain and achieve the desired hydrologic habitat connectivity.
• The study demonstrates the need for a more holistic approach to river restoration that considers the dynamic nature of floodplain habitats.

Statistics:

• 13 streamflow events in the past 80 years had the magnitude and duration required for splittail spawning and rearing.
• 14 events had flows long enough for salmon rearing benefits.
• Only 4-17% of the years in the rest of this century are likely to produce required flow-related habitat conditions for splittail and salmon rearing.
• 80 years of data were used to evaluate the habitat availability for splittail and Chinook salmon.

Sources:

• Scenarios For Restoring Floodplain Ecology Given Changes To River Flows Under Climate Change: Case From The San Joaquin River, California. River Research and Applications, 2015;31(3):280-290.
• River Research and Applications, Wiley-Blackwell, 111 River St, Hoboken 07030-5774, NJ, USA (www.wiley.com/, onlinelibrary.wiley.com/journal/10.1002/(ISSN)1535-1467)
• M.K. Matella, University of California, Environm Sci Policy & Management, Berkeley, CA 94720, United States