|Van Genuchten, Martinus|
Submitted to: International Agrophysics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/21/2008
Publication Date: 9/3/2008
Citation: Guber, A.K., Gish, T.J., Pachepsky, Y.A., Van Genuchten, M.T., Daughtry, C.S., Nicholson, T., Cady, R. 2008. Temporal stability of estimated soil water flux patterns across agricultural fields. International Agrophysics. 22:209-214. Interpretive Summary: Knowing infiltration losses of water from soil over large areas is important to address key water quality issues, and in particular, to estimate groundwater recharge and the transport of surface applied chemicals to groundwater. Direct measurements of infiltration losses are not possible so estimates are commonly obtained from observations of the soil water budget. The objective of this work was to evaluate the network of multisensor soil moisture capacitance probes as a data source for estimating infiltration water losses from sandy soils across agricultural fields at the USDA-ARS Beltsville Agricultural Research Center, MD. The temporal stability of infiltration losses was observed, i.e. deviations of local infiltration losses from the average infiltration loss across the field were approximately constant for each probe location during the 20- month observation period. It was possible to identify the most representative probe locations where the estimated infiltration losses best mimicked the average losses across the field. The results of this work are important for researchers and industry involved in estimating groundwater recharge, as they show the opportunity for substantial resource savings in estimating infiltration losses by first identifying the most representative locations, and then continuing monitoring soil moisture only in those locations.
Technical Abstract: When a field or a small watershed is repeatedly surveyed for soil water content, sites often can be spotted where soil is consistently wetter or consistently dryer than average across the study area. This phenomenon has been called time stability, temporal stability, temporal persistence, or rank stability in spatial patterns of soil water content or in soil water contents. The temporal stability has been demonstrated for soil water contents but has not been researched for soil water fluxes. The objective of this work was to see whether the temporal stability in estimated soil water fluxes can be demonstrated using extremely frequent multi-depth measurements of soil water content with Multisensor Capacitance Probes installed in soil in multi-year corn production.. Data on water contents at 10, 30, 50, and 80 cm depths were collected every 10 min for 20 months of continuous observations from May 2001 to December 2002 at the USDA OPE3 site in Beltsville Maryland. Temporal stability was well pronounced for soil water fluxes estimated from soil water balance for the depth of 60 m. Soil water fluxes can be upscaled and efficiently monitored using the temporal stability of soil water patterns.