Quantifying stream channel water fluxes in the southwestern US

Tianyi Zhu1, Erika L. Gallo2

1The Gregory School, Tucson, Arizona

2The University of Arizona, Department of Hydrology and Atmospheric Sciences, Tucson, Arizona

Ephemeral and intermittent streams comprise over 90% of the regional waterways in the southwestern US, provide substantial ground-water recharge to regional aquifers, and are critical components of desert ecosystems. Yet much remains unknown about their basic hydrologic function.  The larger objective of this study is to address some of these knowledge gaps by using heat as a tracer to estimate streambed water exchanges in ungauged channels of the southwestern US.  We use Hydrus-1D and a vertical array of temperature sensor data to model vertical water exchanges in hyper-arid and semi-perennial stream channels. This presentation focuses on Hydrus-1D model parameterization and performance assessment. Preliminary results indicate that there is good agreement between the observed and the modeled temperatures (r2 > 0.8, p < 0.05) in the hyper-arid channels.  Analyses of the observed data residuals indicate that modeling performance varies over time, with residual departures being large during the initial time steps of the model run, decreasing and then increasing over time.

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