Abstract. Water temperature is a primary physical factor regulating the persistence and distribution of aquatic taxa. Considering projected increases in air temperature and changes in precipitation in the coming century, accurate assessment of suitable thermal habitats in freshwater systems is critical for predicting aquatic species' responses to changes in climate and for guiding adaptation strategies. We use a hydrologic model coupled with a stream temperature model and downscaled general circulation model outputs to explore the spatially and temporally varying changes in stream temperature for the late 21st century at the subbasin and ecological province scale for the Columbia River basin (CRB). On average, stream temperatures are projected to increase 3.5 °C for the spring, 5.2 °C for the summer, 2.7 °C for the fall, and 1.6 °C for the winter. While results indicate changes in stream temperature are correlated with changes in air temperature, our results also capture the important, and often ignored, influence of hydrological processes on changes in stream temperature. Decreases in future snowcover will result in increased thermal sensitivity within regions that were previously buffered by the cooling effect of flow originating as snowmelt. Other hydrological components, such as precipitation, surface runoff, lateral soil water flow, and groundwater inflow, are negatively correlated to increases in stream temperature depending on the ecological province and season. At the ecological province scale, the largest increase in annual stream temperature was within the Mountain Snake ecological province, which is characterized by migratory coldwater fish species. Stream temperature changes varied seasonally with the largest projected stream temperature increases occurring during the spring and summer for all ecological provinces. Our results indicate that stream temperatures are driven by local processes and ultimately require a physically explicit modeling approach to accurately characterize the habitat regulating the distribution and diversity of aquatic taxa.
[1] This paper presents an electron plasma density data set for Jupiter's outer magnetosphere derived from high-resolution wideband measurements of low-frequency radio and plasma waves obtained by Voyagers 1 and 2 during their 1979 flybys. This work utilizes a new data processing tool that makes important improvements in the identification of the plasma frequency and other characteristic frequencies of the plasma, thereby allowing for the determination of the electron density within the Jovian magnetosphere. Furthermore, this work includes the interpretation of complex spectra including sometimes overlapping wave phenomena including continuum radiation, Z mode emissions, and whistler mode waves. Using the theory of cold plasmas and measurements of the magnetic field from which the electron cyclotron frequency can be calculated, we establish an extensive set of reasoning for interpreting cutoffs and resonances in the wave spectra to identify characteristic frequencies of the plasma, including the electron plasma frequency, R = 0 cutoff, L = 0 cutoff, and upper hybrid resonance frequency. While most Voyager plasma wave data used are obtained in the plasma sheet where the plasma frequency is greater than the cyclotron frequency, this investigation also analyzes observations in the lobe where the cyclotron frequency is greater than the plasma frequency to interpret the various cutoffs and resonances in the spectrum. The resulting data set for the electron densities has higher temporal resolution than any others that exist today. Also, given the identification of spectral features to accuracies of $100 Hz or better, the density measurements are among the most accurate for Jupiter's magnetosphere.
Please cite this article as: Ficklin, D.L., Barnhart, B.L., SWAT hydrologic model parameter uncertainty and its implications for hydroclimatic projections in snowmelt-dependent watersheds, Journal of Hydrology (2014), doi: http://dx. AbstractThe effects of climate change on water resources have been studied extensively throughout the world through the use of hydrologic models coupled with General Circulation Model (GCM) output or climate sensitivity scenarios. This paper examines the effects of hydrologic model parameterization uncertainty or equifinality, where multiple unique hydrologic model parameter sets can result in adequate calibration metrics, on hydrologic projections from downscaled GCMs for three snowmeltdependent watersheds (upper reaches of the Clearwater, Gunnison, and Sacramento River watersheds) in the western United States. The hydrologic model used in this study is the Soil and Water Assessment Tool (SWAT) and is calibrated for discharge at the watershed outlet in each watershed. Despite achieving similar calibration metrics, a majority of hydrologic projections of average annual streamflow during the 2080s were statistically different, with differences in magnitude and direction (increase or decrease) compared to historical annual streamflows. At the average monthly time-scale, a majority of the hydrologic projections varied in peak streamflow timing, peak streamflow magnitude, summer streamflows, as well as overall increases or decreases compared to the historical monthly streamflows. Snowmelt projections from the SWAT model also widely varied, both in depth and snowmelt peak timing, for all watersheds. Since a large portion of the runoff-producing regions in the western United States is snowmelt-dependent, this has large implications for the prediction of the amount and timing of streamflow in the coming century. This paper shows that hydrologic model parameterizations that give similar adequate calibration metrics can lead to statistically significant differences in hydrologic projections under climate change. Therefore, researchers and water resource 3 managers should account for this uncertainty by assembling ensemble projections from both multiple parameter sets and GCMs.
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