Submitted to: Journal of Hydrology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/1/2012
Publication Date: 1/1/2013
Citation: Dinka, T., Morgan, C., McInnes, K., Kishne, A., Harmel, R.D. 2013. Shrink-swell behavior of soil across a Vertisol catena. Journal of Hydrology. 476:352-359. Interpretive Summary: Shrinking and swelling of clay soils as they dry and wet and the associated formation and closing of cracks is an environmentally and economically important process. The shrinking and swelling of process affects water movement and therefore the movement of pollutants, and it creates extensive damage to buildings, roads, and parking lots. This important process is, however, typically ignored in models used to simulate water and pollutant movement. The objective of the study was to determine if variability in soil cracking could be explained by a shrink-swell potential of the soil (coefficient of linear extensibility, COLE) and the changes in soil water content. The research was conducted in Vertisol soils (Houston Black and Heiden series) at the USDA-ARS Riesel Watersheds. Soil subsidence and soil water were measured in the field at four landscape positions. Results showed that the shrink-swell potential decreased as the inorganic carbon content of the soil increased. Because the COLE values at most landscape positions were high, soil water content was the primary driver in the spatial and temporal variability in vertical shrinking and swelling. The lack of vertical shrinking during drying suggests that there are more large horizontal cracks in these soil layers, which is useful to hydrology models.
Technical Abstract: Shrinking and swelling of soils and the associated formation and closing of cracks can vary spatially within the smallest hydrologic unit subdivision utilized in surface hydrology models. Usually in the application of surface hydrology models, cracking is not considered to vary within a hydrologic unit having the same soil and land cover. The objective of the study was to determine if variability in soil cracking could be explained by a shrink-swell potential of the soil as determined by the coefficient of linear extensibility (COLE) and the changes in soil water content. The research was conducted in a Vertisol catena of Houston Black and Heiden series. Soil subsidence and soil water were measured in situ at the Summit, Shoulder, Backslope and Footslope positions. The shrink-swell potential of site positions and soil horizons were was inversely related to inorganic carbon content of the soil. Because COLE values at most landscape positions were high, soil water content was the primary driver in the spatial and temporal variability in vertical shrinking and swelling. The trend of the relationship between the measured soil thickness and water content loosely agreed with the theoretical model; however, the relationship at the surface soil layers of the Summit and Shoulder were not well predicted, because these soils with high shrink-swell potential did not subside. The lack of vertical subsidence during drying suggests that there are more large horizontal cracks in these soil layers and this information could be useful to hydrology models. The magnitude of soil subsidence at the Footslope was lower than at the Summit and Shoulder because the change in soil water storage at the Footslope was less and subsoils dried less frequently.