Riparian Zone Evapotranspiration Using Streamflow Diel Signals

Riparian zones are crucial regions of semi-arid and arid watersheds. In the summer, riparian zones provide an important habitat for the watershed since they have sufficient water supply throughout the year. However, little is known about the impact of riparian zone evapotranspiration (ET) at a watershed scale. The use of streamflow diel signals can provide a more thorough understanding of riparian zone processes, particularly evapotranspiration. The streamflow diel signals were analyzed for Dry Creek Experimental Watershed (DCEW), for the summer of 2014, to determine riparian evapotranspiration. The riparian zone evapotranspiration was compared to a spatially distributed evapotranspiration model to determine the influence of riparian ET, in comparison to watershed scale ET. The analyses showed that streamflow diel signals were complex and varied in both space and time. The amplitude of the diel signals played a key role in understanding riparian processes and showed that plant transpiration, water availability, and diel signal mixing all had an effect on the amplitude throughout the watershed. The diel signal was most accurate in the headwaters of the catchment, where diel signal mixing was at a minimum. Based on the headwaters of the catchment, riparian ET attributed up to 11% of the watershed scale ET. When taking into account the uncertainty associated with the spatially distributed ET model, the amount of riparian ET was negligible compared to watershed scale ET. Meteorological data and sap flux calculations support the conclusion that there was little riparian ET relative to watershed scale ET. Although riparian ET was minor compared to watershed scale ET, it was a relatively large portion of streamflow during low flow in DCEW. The research provided insight into the analysis of diel signals and possible factors affecting diel signal characteristics