Prairie Pothole Region Wetlands and Subsurface Drainage Systems: Key Factors for Determining Drainage Setback Distances

Abstract

Use of agricultural subsurface drainage systems in the Prairie Pothole Region of North America continues to increase, prompting concerns over potential negative effects to the Region's vital wetlands. The U.S. Fish and Wildlife Service protects a large number of wetlands through conservation easements that often utilize standard lateral setback distances to provide buffers between wetlands and drainage systems. Because of a lack of information pertaining to the efficacy of these setback distances for protecting wetlands, information is required to support the decision making for placement of subsurface drainage systems adjacent to wetlands. We used qualitative graphical analyses and data comparisons to identify characteristics of subsurface drainage systems and wetland catchments that could be considered when assessing setback distances. We also compared setback distances with catchment slope lengths to determine if they typically exclude drainage systems from the catchment. We demonstrated that depth of a subsurface drainage system is a key factor for determining drainage setback distances. Drainage systems located closer to the surface (shallow) typically could be associated with shorter lateral setback distances compared with deeper systems. Subsurface drainage systems would be allowed within a wetland's catchment for 44–59% of catchments associated with wetland conservation easements in North Dakota. More specifically, results suggest that drainage setback distances generally would exclude drainage systems from catchments of the smaller wetlands that typically have shorter slopes in the adjacent upland contributing area. For larger wetlands, however, considerable areas of the catchment would be vulnerable to drainage that may affect wetland hydrology. U.S. Fish and Wildlife Service easements are associated with > 2,000 km2 of wetlands in North Dakota, demonstrating great potential to protect these systems from drainage depending on policies for installing subsurface drainage systems on these lands. The length of slope of individual catchments and depth of subsurface drainage systems could be considered when prescribing drainage setback distances and assessing potential effects to wetland hydrology. Moreover, because of uncertainties associated with the efficacy of standard drainage setback distances, exclusion of subsurface drainage systems from wetland catchments would be ideal when the goal is to protect wetlands.

Cap. 25. Grandes Llanuras del Norte. En: La Quinta Evaluación Nacional del Clima

“…En la región oriental de la pradera de Pothole de Minnesota, Dakota del Norte, Dakota del Sur y Iowa el aumento de las precipitaciones en primavera ha agravado los problemas de exceso de aguas subterráneas poco profundas en los campos de cultivo. Los agricultores han respondido drenando esta agua con tuberías de plástico perforadas (conocidas como tuberías de panel; Figura 25.11) 224,225 enterradas a la profundidad de enraizamiento de las plantas de maíz maduras, una práctica que mejora el rendimiento de los cultivos 226. El uso de tuberías de panel ha aumentado rápidamente en el este de Dakota del Norte y del Sur, sobre todo en el valle del río Rojo 227,228,229,230 . Hasta la fecha, aproximadamente la mitad de los humedales de las Grandes Llanuras del Norte han sido desecados, lo que ha alterado sus servicios ecosistémicos, como protección contra inundaciones, secuestro de carbono y forraje y agua para el ganado 231,232 .…”

Synergistic Interaction of Climate and Land-Use Drivers Alter the Function of North American, Prairie-Pothole Wetlands

“…Wetland drainage in the PPR has been primarily surface drainage. However, subsurface drainage of uplands surrounding wetlands in the PPR is increasing [30] and can alter subsurface water flows to wetlands [30,51]. Wetland losses in the PPR have disproportionately impacted small wetlands [52,53], which are usually categorized as seasonally or temporarily ponded wetlands.…”