Poster 210 – Click on poster below to view presentation from author.
UC Davis Center for Watershed Sciences
Co-Authors: Robert Lusardi, Ann Willis
Conservation in working landscapes is an important aspect of stream restoration. Landowners with agricultural water rights are increasingly adding instream flow as a beneficial use of their allocated water. However, stream restoration projects commonly focus on the quantity of water dedicated to the environment while overlooking the quality of the sources. For coldwater ecosystems, the preservation of natural thermal regimes, along with natural flow regimes, will be vital for success in the face of a changing climate. This study explores the effects of increasing stream flow using alternative water sources – instream runoff versus off-channel springs – to enhance cold-water stream habitat on an active cattle ranch. Using observed data from Evans Spring and the Little Shasta River (Northern California) to create a water temperature model, this case study evaluates the temperature benefits and management tradeoffs for ecological and agricultural water use. The results of our water temperature simulations show that both the source of the additional flow and the method used to deliver the water to the channel affects the quality of instream habitat. Off-channel springs cool MWMT and MWAT by as much as 3.7°C and 2.9°C, though only if potential off-channel aquatic habitat is sacrificed for mainstem habitat. When off-channel, spring-fed habitat is provided, the value of spring water to the main channel decreases. When surface water diversions from the main runoff channel are left instream and no spring water is contributed, temperature benefits of augmented streamflow are minimal. Our findings show that the thermal quality of source water used to enhance instream ecosystem function is important to the viability of coldwater habitat, and that the restoration of a historic spring channel may provide added ecosystem benefits through the enhancement of aquatic habitat in the system.
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2 thoughts on “Same size, different quality: Evaluating spring-fed versus runoff water sources to enhance cold-water stream habitat in a working landscape”
Hi Amber, interesting work and great presentation! How would you decide what the better option is in terms of the tradeoff between lowering temperatures in the main stem vs losing off-channel habitat diversity? It seemed like Pipe Scenario B was the best option – but losing off-channel habitat seems a high price to pay. What option would you chose if you were a water resource manager in the Little Shasta River?
Hi Ani, thanks for your question. The decision for how to proceed with a restoration project like this is up to the landowners/those funding the project. These particular landowners were interested in the idea of restoring Evans Spring to benefit the mainstem of the Little Shasta River and asked for our recommended options. It is likely, since these are private landowners operating a cattle farm, that they will be most keen on the least expensive and most thermally effective option of Pipe Scenario B. From an environmental scientist’s perspective, of course, the reconnected channel with riparian restoration will provide more ecosystem benefits, even though it may not look as effective on paper.