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ARS Home » Plains Area » Fort Collins, Colorado » Center for Agricultural Resources Research » Water Management and Systems Research » Research » Publications at this Location » Publication #412483
Research Project: Improving Resiliency of Semi-Arid Agroecosystems and Watersheds to Change and Disturbance through Data-Driven Research, AI, and Integrated Models

Location: Water Management and Systems Research

Title: Dependence of soil moisture and strength on topography and vegetation varies within a SMAP grid cell

Author
item BINDNER, JOSEPH - Colorado State University
item PROULX, HOLLY - Colorado State University
item WICKHAM, KEVIN - Colorado State University
item NIEMANN, JEFFREY - Colorado State University
item SCALIA IV, JOSEPH - Colorado State University
item Green, Timothy
item GRAZAITIS, PETER - Colorado State University

Submitted to: Hydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/11/2025
Publication Date: 2/15/2025
Citation: Bindner, J.R., Proulx, H., Wickham, K., Niemann, J.D., Scalia IV, J., Green, T.R., Grazaitis, P. 2025. Dependence of soil moisture and strength on topography and vegetation varies within a SMAP grid cell. Hydrology. 12(2). Article 34. https://doi.org/10.3390/hydrology12020034.
DOI: https://doi.org/10.3390/hydrology12020034

Interpretive Summary: Soil moisture and soil strength vary with landscape topography, vegetation, and soil attributes, but such variability within a grid cell is poorly understood. The objective of this study was to examine spatial variations in the dependence of soil moisture and strength on topography, vegetation, and soil characteristics across a 9-km (approximately 5.6 miles) satellite image (SMAP) grid cell. We collected data in four geographically separated regions within a SMAP grid cell located in the Front Range foothills of northern Colorado. The nature of soil moisture dependence on topography, vegetation, and soil is shown to behave similarly in all regions. However, we observed spatial variations in the soil strength of relationships. We conclude that soil moisture downscaling procedures which use spatially constant parameters across a coarse grid cell do not adequately capture variable soil moisture dependencies, resulting in suboptimal predictions of soil moisture and associated soil strength.

Technical Abstract: Off-road vehicle mobility assessments rely on fine resolution (~10 m) estimates of soil moisture and strength across the region of interest. Such estimates are often produced by downscaling soil moisture from a microwave satellite like SMAP and then using the soil moisture in a soil strength model. Soil moisture downscaling methods typically assume consistent relationships between the moisture and topographic, vegetation, and soil composition characteristics within the microwave satellite grid cells. The objective of this study is to examine whether soil moisture and strength exhibit heterogenous dependencies on topography, vegetation, and soil composition characteristics within a SMAP grid cell. Soil moisture and strength data were collected at four geographically separated regions within a 9-km SMAP grid cell in the Front Range foothills of northern Colorado. Laboratory methods and pedotransfer functions were used to characterize soil attributes, and remote sensing data were used to determine topographic and vegetation attributes. Linear Pearson correlation analyses were used to quantify the direction, strength, and significance of the relationships of both soil moisture and strength with topography, vegetation, and soil composition. Contrary to the common assumption, spatial variations in the slope and correlation of the relationships are observed for both soil moisture and strength. The findings indicate that improved predictions of soil moisture and soil strength may be achievable by soil moisture downscaling procedures that use spatially variable parameters across the downscaling extent.