Inundation Patterns of Farmed Pothole Depressions with Varying Subsurface Drainage

Abstract

HighlightsFarmed pothole depressions in the Des Moines Lobe were observed to fill due to runoff and shallow subsurface flow.Six of the eight observed potholes flooded for five or more days some time during the two years of observation.Subsurface drainage and surface inlets reduced but did not prevent yield-limiting flooding in the observed potholes. Abstract. The prairie pothole region (PPR) ranges from central Iowa to the northwest into Montana and south central Canada, totaling around 700,000 km2. This area contains millions of potholes, or enclosed topographical depressions, which often inundate with rainfall. Many are located in areas that have been converted to arable agricultural land through installation of artificial drainage. However, even with drainage, potholes will pond or have saturated soil conditions during and after significant rain events. The portion of the PPR that extends into Iowa is known as the Des Moines Lobe. In this two-year study, surface water depth data were collected hourly from eight prairie potholes in the Des Moines Lobe in central Iowa to determine the surface water hydrology. These potholes included surface and subsurface drained row crops and undrained retired land, allowing for drainage comparisons. Inundation lasted five or more days at least once at six of the eight potholes, including four potholes with surface inlets and subsurface drainage, which resulted in four of fourteen growing seasons not producing a yield in part of the pothole. Water balances of four different drainage intensities showed increased infiltration due to subsurface drainage and up to 78% of outflow due to surface inlet drainage. Overall, drainage decreased the number of average inundation days, but heavy precipitation events still caused lengthy inundation periods that resulted in crop loss. Keywords: Farmed wetlands, Prairie pothole, Tile drainage, Water balance.

Seasonal and Intra-Event Nutrient Levels in Farmed Prairie Potholes of the Des Moines Lobe

“…However, soil mapping inaccuracies led to hydric soils extending outside of the elevation boundaries of the potholes, while some depressions in this study had inundation but were not mapped as hydric soils. Depth to surface area and volume relationships were derived in ArcMap 10.2 (ESRI, 2013) and are described in detail by Martin et al (2019). Surface area and volume were calculated at 10 cm depth intervals, and a combination of second-order equations and linear interpolation was applied to each pothole.…”

“…Surface drainage estimates were used to calculate the nutrient load export from the potholes. Surface drainage for Bunny and Walnut was estimated as part of a water balance that included direct rainfall, runoff and interflow, evapotranspiration, infiltration, and surface drainage, and details are available in our companion article (Martin et al, 2019). Briefly, daily water fluxes were determined and adjusted for evapotranspiration and direct rainfall.…”

“…This trend was also observed in other events that occurred soon after fertilizer application, but those events lasted longer than ten days and had reductions by the end. Nitrate increases are likely caused by additional nitrate entering via interflow (Zhu et al, 2009), as additional interflow can enter a pothole for up to six days after a rainfall event (Martin et al, 2019). It is expected that the NO 3 -N concentration would have been lower by the end of this event had nitrate from the recent fertilization not entered with interflow.…”

Assessment of Input Parameters and Calibration Methods for Simulating Prairie Pothole Hydrology using AnnAGNPS

“…1). Their field and more detailed discussion of management is described in Logsdon (2015), Upadhyay et al (2018), andMartin et al (2019a). The adjacent research field is similarly managed and includes the potholes Plume, Hen, Cardinal, Potatoes, Turkey, and Yam.…”

“…Data for Potatoes was collected in 2016 and 2017 while Yam data was collected in 2017 and 2018. This data is further described and summarized in Martin et al (2019a).…”