Institute of Ecosystem Studies

2008 BES Annual Meeting Presentation and Poster Abstracts

Determining values of soil hydraulic conductivity in and around the Gwynns Falls watershed using automated mini-disk tension infiltrometers
Poole, Sarah
Co-Authors: Sarah Poole, Peter Lapa-Lilly, Claire Welty
Abstract: Saturated hydraulic conductivity was measured at a watershed scale during August to September 2008. The measurements were taken within the Gwynns Falls watershed with approximately 1 km between sites, and outside the Gwynns Falls boundary with approximately 2 km between sites. Differential pressure transducers were used to automate infiltrometer measurements of saturated hydraulic conductivity, using an adaptation of a design by Madsen and Chandler (2007). The pressure in the head space (above the water level in the reservoir) of the infiltrometer has a direct linear relationship with the level of water in the reservoir, so the output voltage of the pressure transducers was read with a data logger to give a time series of water levels. Automation allowed four simultaneous in situ measurements, which were used to quantify variability at site. The tension at which water was restricted from entering the soil was changed four times over the course of measurement at each point, giving a paired series of tensions and infiltration rates. The measurements ranged from highly spatially variable to nearly uniform among measurements at a site. Over the watershed, the saturated hydraulic conductivity varied from .00011 cm/s to .012 cm/s. The average was .0023 cm/s, with a standard deviation of .0029 cm/s. The distribution of values appears to be lognormal, based on the Kolmogorov-Smirnov test. Using the data collected, curves for hydraulic conductivity as a function of tension can also be calculated.