Abstract
Soil moisture is an important state variable in the hydrologic cycle, and its spatiotemporal distribution depends on many geophysical processes operating at different spatial and temporal scales. To achieve a better accounting of the water and energy budgets at the land‐atmosphere boundary, it is necessary to better understand the spatiotemporal variability of soil moisture under different hydrologic and climatic conditions and at different hierarchical space scales and timescales. During the Southern Great Plains 1997 (SGP97) Hydrology Experiment the 0–6 cm soil water content was measured on consecutive afternoons at 400 locations in a small, gently sloping range field (Little Washita field site 07). The soil moisture measurements were made using portable impedance probes. Spatiotemporal data analyses of the two sampling events showed a significant change in the field variance but a constant field mean, suggesting moisture was redistributed by (differential) base flow, evapotranspiration, and condensation. Among the different relative landscape positions (hilltop, slope, valley) the slope was the largest contributor to the temporal variability of the soil moisture content. Using a sequential aggregation scheme, it was observed that the relative position influencing the field mean and variance changed between the two sampling events, indicating time instability in the spatial soil moisture data. Furthermore, high‐resolution (impedance probe) sampling and limited (gravimetric) sampling gave different field means and variances.
Highlights
Kachanoskai nd deJong[1988]showedthat temporalstability The near-surface soil moisture content is critical for address- may not exist over all scalesbecausesoil water storageat a ingissuesrelatedto landsurfacehydrologys, ubsurfacehydrol- point is the productof hydrologicprocessesoperatingat difogy, and the transfer of mass and energy acrossthe land- ferentspatialscalesF. or example,localizedsurfacerunoffmay atmosphereboundary
A possiblereasonfor this niquesat Little Washitafieldsite07 (LW07) duringthe samedatesare alsopresentedin behavior is that once surface overland flow and/or subsurface varianceof the daily soil moisturecontentreducedwhile nor- we found that within the 24-hour period the soil moisture
On June19the sitionswerethe largestcontributorsto the temporalvariability runningmean and field mean soil moisturecontentare ap- of the surfacesoilmoisture.Redistributionoccurredthrough proximatelyequalat block23, indicatingthat at leastobserva- thiszoneassubsurfacbeaseflowandaspect-driveanccelerated tionsbetweenblocks1 and 22are neededfor estimatingthe field average.Corre- parisonpurposeswe plottedrunningmeansandvariancesfor spondinglyt,he runningvarianceindicatesthat at leastobser- the twosamplingeventsstartingfrom (1) the SW corner(hillvationsbetweenblocks1 and 32 and (2) the SE corner(valley,Figure8)
Summary
Hydrology Experiment a dryingphase.Secondaryobjectivesareto identifytherelative contributionof differentrelativelandscapepositions(hilltop, slope,valley)to thefield-scalevariabilityof soilmoisturecon-. The SouthernGreatPlains1997(SGP97)HydrologyExper- tent andto investigatethe time stablebehaviorof thedifferent iment was a coordinated,collaborativeeffort by an interdis- positions
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
