Supplemental Streamflow Measurements

Streamflow in a surface inflow can be determined by tracer injection if synoptic-sampling sites are positioned on the mainstem just upstream and downstream from the inflow. The increase in streamflow between the two mainstem sites generally can then be assumed to equal the streamflow contributed by the inflow. However, if mainstem sampling sites are widely spaced, part of the downstream increase in streamflow could come from subsurface inflow. In this circumstance, flow cannot be apportioned between surface and subsurface contributions using data from the tracer injection. In this study, mainstem sites along Daisy Creek, particularly the reach upstream from mainstem site 1,340, were too widely spaced to individually bracket every surface inflow. Therefore, streamflow in most of the surface inflows to Daisy Creek was determined during the synoptic sampling on August 26 by the volumetric (bucket-and-stop-watch) method or by measurements of channel cross-sectional area and flow velocity. These streamflow data are in table 5 (at back of report). The magnitude of subsurface inflow between two mainstem sites was then calculated as the difference between the tracer-calculated increase in streamflow between mainstem sites and the sum of the measured surface inflows entering the reach between the mainstem sites.

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