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Title: Temporal stability of soil water content and soil water flux patterns across agricultural fields

Author
item GUBER, A - UNIV. OF CA
item Gish, Timothy
item Pachepsky, Yakov
item Van Genuchten, Martinus
item Daughtry, Craig
item NICHOLSON, T - US NUCLEAR REG COM
item CADE, C - US NUCLEAR REG COM

Submitted to: Catena
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2007
Publication Date: 3/1/2008
Citation: Guber, A.K., Gish, T.J., Pachespsky, Y.A., van Genuchten, M., Daughtry, C.S., Nicholson, T.J., Cade, C.S. 2008. Temporal stability of soil water content and soil water flux patterns across agricultural fields. Catena. 73:125-133.

Interpretive Summary: 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. Temporal stability also presents significant interest for upscaling observed soil water contents, improving soil water monitoring strategies, and correcting the monitoring results for missing data. The objective of this work was to evaluate temporal stability patterns in soil water content using extremely frequent multi-depth measurements with Moisture Capacitance Probes (MPC). Results show that although soil water contents vary dramatically with time, temporal stability for a specific location and depth served as a good predictor of the ability of this location to estimate the area-average soil water content for that depth. Consequently, temporal stability patterns can be efficiently used to correct the area-average average water contents for missing data. Analysis also suggests that soil water contents and soil water fluxes can be upscaled and efficiently monitored using the temporal stability of soil water.

Technical Abstract: When an agricultural field 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. Temporal stability presents significant interest for upscaling observed soil water content, improving soil water monitoring strategies, and correcting the monitoring results for missing data. The objective of this work was to evaluate the temporal stability in soil water patterns using extremely frequent multi-depth measurements with Moisture Capacitance Probes (MPC) installed in coarse-texture soil under multi-year corn production. Data on soil water contents at 10, 30, 50, and 80 cm depths were collected every 10 min for 20 months from May 2001 to December 2002. Temporal stability increased with depth. Locations that were best for estimating the field average water contents were different for various depths. However, three locations over the whole observation period were the best locations for estimating field averages about 60% of the time. Temporal stability for a specific location and depth could serve as a good predictor of the ability of this location to estimate the area-average soil water content for that depth. Consequently, temporal stability patterns can be efficiently used to correct the area-average average water contents for missing data. Analysis also suggests that soil water contents and soil water fluxes can be upscaled and efficiently monitored using the temporal stability of soil water.