Groundwater Hydrology and Quality in Drained Wetlands of the Des Moines Lobe in Iowa

Groundwater monitoring at the watershed scale: An evaluation of recharge and nonpoint source pollutant loading in the Clear Creek Watershed, Iowa

“…However, we used the measured floodplain concentration at the transect in our load allocation and then estimated the average groundwater NO 3 ‐N concentration beneath upland and sideslope row crop areas (12 mg/L) using the load allocation model (Table ). This estimated concentration is a reasonable approximation of typical NO 3 ‐N values in shallow groundwater beneath row crop fields (Schilling, Jacobson, et al, ; Schilling, Streeter, et al, ; Wheeler et al, ).…”

“…The well transect at this location was placed in a grass border strip between two fields, and NO 3 ‐N concentrations likely reflected recharge through the grass field border rather than a fertilized, row‐cropped field. As described later, NO 3 ‐N concentrations beneath row‐cropped fields are more likely in the range of 10 mg/L or higher (Schilling, Jacobson, et al, ; Schilling, Streeter, et al, ; Wheeler, Nolan, Flory, DellaValle, & Ward, ). Indeed, a water table well located in a different part of the same landowner's property had NO 3 ‐N concentrations averaging approximately 25 to 30 mg/L (unpublished data).…”

“…OP concentrations averaged 0.074 to 0.09 mg/L in fractured Wisconsin till (Dows Formation) and 0.093 mg/L in a Northwest Iowa alluvial aquifer (Burkart, Simpkins, Morrow, & Gannon, ). In a study of eight farmed wetlands in Iowa, Schilling, Jacobson, et al () reported average dissolved P concentrations in shallow groundwater ranging from 0.04 to 1.5 mg/L and averaging 0.36 mg/L. Tomer, Schilling, Cambardella, Jacobson, and Drobney () reported median dissolved P concentrations of 0.02 mg/L in upland landscape positions, 0.175 mg/L in footslopes and 0.115 mg/L ‐1 in drainage way locations in a small catchment in South Central Iowa.…”

“…Urban areas with a greater proportion of impervious surfaces should have less groundwater recharge (Jeong, Kannan, & Arnold, ; Schoonover, Lockaby, & Helms, ). Schilling, Jacobson, et al () and Schilling, Streeter, et al () reported that the water table behaviour beneath urban pavement was vastly different than the water table behaviour under row crop and grass sites, failing to exhibit any seasonal trends and showing no correlation to precipitation and baseflow. They estimated that urban areas under pavement received only 10% as much groundwater recharge as vegetated areas.…”

Groundwater Nutrient Concentrations and Mass Loading Rates at Iowa Golf Courses

“…As part of watershed scale assessment of a large recreational lake in northwest Iowa, Schilling et al . (, ) reported mean NO 3 ‐N concentrations of 0.3 mg/L at a golf course. Hence, study results of six courses in Iowa are consistent with other national and Iowa‐specific monitoring studies and show typically low NO 3 ‐N concentrations in groundwater beneath Iowa golf courses.…”