A Comparison and Validation of Saturated Hydraulic Conductivity Models

Saturated hydraulic conductivity (K-sat) is fundamental to shallow groundwater processes. There is an ongoing need for observed and model validatedK(sat)values. A study was initiated in a representative catchment of the Chesapeake Bay Watershed in the Northeast USA, to collect observedK(sat)and validate fiveK(sat)pedotransfer functions. Soil physical characteristics were quantified for dry bulk density (bdry), porosity, and soil texture, whileK(sat)was quantified using piezometric slug tests. Averagebdryand porosity ranged from 1.03 to 1.30 g/cm(3)and 0.51 to 0.61, respectively. Surface soil (0-5 cm)bdryand porosity were significantly (p< 0.05) lower and higher, respectively, than deeper soils (i.e., 25-30 cm; 45-50 cm).bdryand porosity were significantly different with location (p< 0.05). Average soil composition was 92% sand. AverageK(sat)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-scaleK(sat)estimates was small (CV < 0.5) and one model performed better whenK(sat)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 m(2)/day(2); RMSE = 1.36 m/day). Results validate the use of simple, soil-property-based models to predictK(sat), thereby increasing model applicability and transferability.