Multi-model evaluation of longitudinal temperature fluctuations and the
dominant influencing factors among Michigan streams
Abstract
Stream temperature is an important determinant of fish growth,
migration, and survival, and can thus impact the structure and function
of stream ecosystems. Fluctuations in water temperature can occur
spatially and temporally, occurring naturally or because of
anthropogenic pressures. Many streams in Michigan and elsewhere in North
America receive groundwater inputs that help regulate instream
conditions by stabilizing discharge as well as stream temperature.
However, groundwater withdrawal through high-capacity wells is important
to the agricultural industry and water users for irrigation or municipal
water supplies. Withdrawal can cause reductions in streamflow which
typically results in increased stream temperature. Other atmospheric and
hydrologic variables (i.e. overland discharge) also impact the rate at
which stream temperature changes as it flows downstream. In this study
we deployed paired up- and downstream water pressure and temperature
loggers within 21 stream reaches throughout the state of Michigan to
quantify and model relationships between stream discharge, air
temperature, and longitudinal change in stream temperature (i.e.,
temperature flux). Using multi-model selection criteria, we evaluated
the performance of a hierarchical suite of models that predict
temperature flux rates as a function of potential driving variables. The
multi-model selection criteria identified a best-fitting model that was
able to model the diurnal, seasonal, and annual variations in rates of
longitudinal temperature fluctuations across a majority of sample
streams. Partial regression analysis indicated that proxy variables
representing solar radiation at the stream surface were generally the
most influential predictors of longitudinal changes in stream
temperature, but air temperature and components of streamflow including
groundwater input were significant predictors and important in many
streams.