Wednesday, November 7, 2007 - 9:30 AM
283-1
Near-Surface Infiltration Estimation under Snowmelt using Heat-Pulse-Based Water Flux Sensors.
The fate of precipitation and snowmelt are important inputs to hydrological modeling. Higher soil moisture content in springtime often results in increased runoff due to limited storage capacity and reduced infiltration rate (i.e., near long term rates) of the soil. Accurate measurements of subsurface water flux are difficult to make and in fact are virtually non-existent compared to water content measurements. The major difficulty stems from the impact a measurement apparatus has on both the gradient and flow path, which are dynamic both temporally and spatially. Recent work using heat-pulse measurements to assess water flux in soil have shown promise for determination of water flux densities ranging between 1 to 1000 mm h-1. While these flux rates exclude many finer textured and unsaturated soil transport rates, they include the higher infiltration rates associated with significant rainfall and snowmelt events where the soil matrix is satiated. In addition, heat pulse-based sensors can provide estimates of soil moisture and measures of soil temperature. A forest test site was instrumented with heat-pulse-based water flux sensors at 10 and 30 cm depths under 4 native vegetation regimes to evaluate the sensor capabilities to monitor snow melt infiltration as inputs to hydrologic modeling. Numerical simulations were carried out to optimize the sensor placement for a specified soil depth above an impermeable layer. Water flux measurement errors were numerically modeled to estimate the effect of heater size on the water velocity calculations based on analytical models.
Recorded presentation