Developing a rapid method to estimate near-surface hydraulic conductivity

Dylan Begley and Ty P.A. Ferré

Hydrology and Atmospheric Sciences
The University of Arizona

Estimating saturated hydraulic conductivity (Ks) at the ground surface is essential for quantifying infiltration. This is important for applications ranging from irrigation planning to flood forecasting. Current methods for estimating Ks require much time, water, and are semi-quantitative. This project is the first step in developing a rapid method to estimate near-surface Ks. The steady-state drip method was modified to develop a fixed-time drip method by dripping water on the surface at a measured rate for one minute. In designing the method, it was determined the wetted area depends on the slope of the surface. To test and document this phenomenon, experiments were conducted on clean, dry sand at multiple drip rates for several slopes. Analysis of a photograph of the wetted area is used to estimate Ks.  Diameter of the wetted area and its uncertainty was determined with a python script that fits circles to points digitized on the perimeter of the wetted area. Uncertainty of the flow rate was determined by repeat measurement. Results show a linear dependence of the wetted diameter on drip rate and slope, allowing for simple correction of each factor when determining Ks. Results show the method is ready for testing on various soils.

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