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National Water and Climate Center


Soil Moisture Equation Change

The Natural Resources Conservation Service (NRCS), in cooperation with the Agricultural Research Service (ARS), has implemented a new Soil Moisture Equation for use on select Soil Climate Analysis network (SCAN) sites. This work has been peer reviewed and published (Seyfried, M.S., L.E. Grant, E.Du, and K Humes. 2005. Dielectric loss and calibration of the hydra probe soil water sensor. Vadose Zone J. 4:1070-1079).

On February 19, 2010, selected SCAN sites were remapped with the new 'loam' equation, which has been shown to better represent the volumetric moisture content in these soils (Seyfried et.al 2005). Further evaluation is currently being done before the new equation is implemented on the remaining SCAN sites and the SNOTEL database. Site metadata will reflect this change and all historic and current data will be calibrated using the same equation (Historical soil moisture data will be remapped by March 5, 2010).  Additional information concerning the original 'silt' equation is available (Vitel, Inc. 1994. Hydra soil moisture probe user's manual, version 1.2. Vitel Inc., Chantilly, VA).