| Popis: |
The mid-Klamath River is heavily impacted by altered streamflow and warm water temperatures, which contribute to the decline of native salmonids. In an effort to restore critical salmonid habitat, the Karuk Tribe, National Forest Service, and Mid-Klamath Watershed Council have created a variety of off-channel floodplain ponds that provide habitat for juvenile Coho Salmon (Oncorhynchus kisutch) and other juvenile salmonids such as Steelhead (O. mykiss). One purpose of these ponds is to provide cool water refuges for juvenile salmonids during high summer water temperatures. However, no studies have quantified how these ponds vary in temperature regimes across the river floodplain. In July 2020, we placed 30 temperature sensors in 9 off-channel ponds and 2 creeks (Seiad Creek and Horse Creek) in the mid-Klamath floodplain. We used a multivariate auto-regressive state space (MARSS) models to determine the number and spatial arrangement of distinct thermal regimes in floodplain ponds and tributaries. We found that pond temperatures have lower daily maximums and fluctuate less than tributary temperatures. We also found that Seiad Creek, Seiad Creek ponds, Horse Creek, and Horse Creek ponds all have different patterns of temperature change throughout the summer. Historical data (2010-2019) for Alexander and Stender Ponds showed that over time, daily fluctuations in pond water temperature became less drastic. This pattern was also observed by MKWC in their reports on Alexander and Stender Ponds (MKWC 2020; Wickman et al. 2020). More stable water temperatures in the ponds contrast to creek temperatures, which continue to fluctuate widely on a daily basis during summer. Fish monitoring data from MKWC show that coho growth rates are higher in these two ponds, which suggests that coho experience a metabolic benefit from more stable water temperatures (MKWC 2020; Wickman et al. 2020). Overall, our analysis provides deeper insight into the thermal benefits of floodplain habitats and off-channel ponds on the mid-Klamath River, and informs the future collection of fish data that will reveal more precise information about how floodplains benefit salmonids. |
