Date of this Version Estimates of streambed water fl ux are
needed for the interpretation of streambed chemistry and
reactions. Continuous temperature and head monitoring in stream
reaches within four agricultural watersheds (Leary Weber Ditch,
IN; Maple Creek, NE; DR2 Drain, WA; and Merced River, CA)
allowed heat to be used as a tracer to study the temporal and
spatial variability of fluxes through the streambed. Synoptic
methods (seepage meter and differential discharge measurements)
were compared with estimates obtained by using heat as a tracer.
Water flux was estimated by modeling one-dimensional vertical
flow of water and heat using the model VS2DH. Flux was
influenced by physical heterogeneity of the stream channel and
temporal variability in stream and ground-water levels. During
most of the study period (April–December 2004), flux was upward
through the streambeds. At the IN, NE, and CA sites, high-stage
events resulted in rapid reversal of flow direction inducing
short-term surface-water flow into t