Determining and Comparing Deep Drainage between Two Years – Dry (2012) and Wet (2013) – using Darcy’s Law

Abstract

Understanding of the downward flux of water below the plant root zone, known as deep drainage (DD), is significant in agriculture and soil water conservation. It plays a key role to determine the amount of water that travels below the plant root zone and can potentially cause groundwater recharge. The DD in soil varies with location, soil texture, and topography. Thus, the objectives of this study were to determine the unsaturated hydraulic conductivity, soil water storage, and DD for the years 2012 (dry year) and 2013 (wet year) at the University of Guelph’s Arboretum. The depths to the water table data were collected using a Mini Water Level Meter. CS616 sensors were used to determine the soil volumetric water content. The soil temperature was extracted with the use of T107 Temperature Probes. The slug test, based on the Hvorslev method, was performed to determine the field saturated hydraulic conductivity. The soil moisture retention curve was produced based on the data collected in the lab with the use of pressure plate systems, using van Genuchten’s equation. The unsaturated hydraulic conductivity was also determined using van Genuchten’s equation. Darcy’s law was used to determine the specific discharge, which was then converted to the total DD. In general, the soil water storage was 38.5 mm higher in 2013 relative to 2012. The unsaturated hydraulic conductivity was approximately 2 times higher in 2013 than 2012. The average DD was approximately 25 mm higher in 2013. This study provides information needed to better understand the movement and amount of water flux and DD in larger details.