Coupling high-resolutionmonitoring and modelling to verify restoration-based temperature improvements

Abstract

Rivers are dynamic, complex integrators of their environment, which makes verification of the beneficial outcomes of restoration challenging. Thermal regime is central to habitat suitability and is often a focus in planning and evaluating the impact of restoration and climate resilience. Among these concerns, high summer stream temperature has frequently been identified as a limiting factor for salmon, steelhead, and trout. Our objective was to demonstrate the utility of combining high resolution thermal observation and modelling to evaluate restoration designed to mitigate stream thermal processes. This was demonstrated on the Middle Fork of the John Day River which is a critically impacted salmonid fishery in northeast Oregon, USA. We employed distributed temperature sensing and energy-balance modelling to define the thermal regime. Restoration was predicted to result in a 0.7 degrees C reduction of peak daily stream temperatures while increasing night temperatures by 0.9 degrees C. This combined modelling and monitoring approach suggests that the 2012 restoration offered relief for native fish species stressed by excessive stream temperatures. This powerful combination of technology can be used in many projects to make optimal use of restoration investments to achieve durable and quantifiable improvements in habitat.