Abstract
Saturated hydraulic conductivity (Ksat) is fundamental to shallow groundwater processes. There is an ongoing need for observed and model validated Ksat values. A study was initiated in a representative catchment of the Chesapeake Bay Watershed in the Northeast USA, to collect observed Ksat and validate five Ksat pedotransfer functions. Soil physical characteristics were quantified for dry bulk density (bdry), porosity, and soil texture, while Ksat was quantified using piezometric slug tests. Average bdry and porosity ranged from 1.03 to 1.30 g/cm3 and 0.51 to 0.61, respectively. Surface soil (0–5 cm) bdry and porosity were significantly (p < 0.05) lower and higher, respectively, than deeper soils (i.e., 25–30 cm; 45–50 cm). bdry and porosity were significantly different with location (p < 0.05). Average soil composition was 92% sand. Average Ksat ranged from 0.29 to 4.76 m/day and significantly differed (p < 0.05) by location. Four models showed that spatial variability in farm-scale Ksat estimates was small (CV < 0.5) and one model performed better when Ksat was 1.5 to 2.5 m/day. The two-parameter model that relied on silt/clay fractions performed best (ME = 0.78 m/day; SSE = 20.68 m2/day2; RMSE = 1.36 m/day). Results validate the use of simple, soil-property-based models to predict Ksat, thereby increasing model applicability and transferability.
Highlights
Saturated hydraulic conductivity (Ksat ) is an important hydraulic parameter [1,2,3,4], as Ksat represents the ability of soils to transmit water throughout the saturated zone, which is essential for relating water transport rates to hydraulic gradients [5,6,7]
Average bdry was below the NRCS range for the region (i.e., 1.34–1.54 g/cm3 ) but within the range expected for sandy soils [63,93]
Model predictions were improved with the inclusion of a second particle size parameter, as root of the mean-square error (RMSE) for the Campbell [40] and Saxton et al [11] models decreased, or was similar to the one particle size parameter models (i.e., Puckett et al [39] and Smettem and Bristow [41])
Summary
Saturated hydraulic conductivity (Ksat ) is an important hydraulic parameter [1,2,3,4], as Ksat represents the ability of soils to transmit water throughout the saturated zone, which is essential for relating water transport rates to hydraulic gradients [5,6,7]. Accurate Ksat estimates are needed to characterize and predict how soil–water dynamics influence local water balances [8,9,10]. Ksat estimates can inform resource management decisions related to water conservation, irrigation systems, fertilizer application, drainage, solute mitigation, and plant growth [11,12,13]. Field-based Ksat estimates can be limited by incomplete aquifer geometry information, while laboratory methods can present problems with obtaining representative sample numbers. These challenges suggest the need for methods to estimate
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