Habitat variables associated with stream temperature resiliency in the White Mountains of Arizona with implications for Apache trout distribution in response to climate change
January 2010 to December 2013
The distribution of Apache trout, Oncorhynchus apache, a threatened species endemic to eastern Arizona, and that of other Southwestern coldwater species may be compressed due to increased stream temperatures associated with climate change. Knowledge of habitat conditions which best buffer stream temperatures against increase and fluctuation may help preserve current Apache trout distribution. Our goal is to use a stream temperature model, ground-truthed with field data from various streams in Eastern Arizona, to predict how increases in air temperature may affect temperatures of streams containing Apache trout. We used the Stream Segment Temperature Model (SSTEMP) to predict the effects of stream habitat variables on water temperatures, and how planned management activities will affect stream temperatures. SSTEMP uses the time of year, location of study, and meteorological data to compute the solar radiation available at a specific point on the surface of the Earth. It reduces the estimate by accounting for topography and riparian vegetation on-site that can block radiation in order to predict downstream temperatures. We used the model to determine how different management actions: regulating groundwater withdraws, planting riparian vegetation, and altering stream channel shape, can moderate water temperature increases. We found that discharge had the greatest effect on regulating stream temperature, regardless of the amount of riparian shade. Streams with greater discharge exhibited lower downstream temperatures than streams with less discharge even when the streams with low discharge had a higher density of riparian vegetation. However, planting vegetation can increase the longitudinal distance it takes for a stream to heat to a certain point. We found that conifers commonly found in the area shade the streams far better than the native deciduous trees such as alders and willows. Furthermore, decreasing the width of the stream also had a cooling effect on the streams we modeled. A comprehensive understanding of which parameters most affect stream temperature is needed both to manage existing populations of Apache trout, and to help identify suitable stocking locations. The research has been completed and a thesis is in its final stages.