https://hdl.handle.net/10388/16650

Salts in the Prairie Pothole Region (PPR) are abundant and present risks of soil and wetland salinization which could harm agricultural producers and wetland habitats. Climate change is likely to alter precipitation amounts and intensity in the PPR which will have implications for hydrology and salt transport. This study observed and analyzed how historical climate phases have affected salt transport and accumulation in the PPR to better understand and conceptualize how salts may re-distribute under future climates. Data including climate, pond volume and chemistry from three ponds across the landscape, and groundwater was collected over several decades at the St. Denis National Wildlife Area (SDNWA). Three distinct climate phases occurred in the observed period, beginning with dry conditions, then transitioning into an extended wet period, and finally a short drying period. Dry periods resulted in salt accumulation on pond perimeters, while salt in ponds remained relatively low (~0.01 kg m−2 in a recharge pond, ~0.20 kg m−2 in a flow-through pond, ~0.77 kg m−2 in a discharge pond). Salinization of soils in dry periods is unlikely as groundwater is well below ground surface and movement of water is limited. During wet periods, groundwater rises and subsurface water inputs to ponds occur, bringing large amounts of salt stored in pond perimeters into the ponded water. In the wet period, recharge ponds show large salinity increases and transition from freshwater (~50 mg L−1) to slightly saline (~600 mg L−1), while flow-through and discharge ponds have slightly increased salinity. While salinity increases vary, the total salt mass per ponded area in all ponds was extremely high in wet periods (~0.45 kg m−2 in a recharge pond, ~2.1 kg m−2 in a flow-through pond, and ~2.5 kg m−2 in a discharge pond). The movement of salt from pond perimeters to ponds during wet periods may have consequences for wetland habitat, and high groundwater tables could increase risks of surface salinization in pond perimeters. As conditions begin to dry, groundwater elevations around ponds decrease allowing for subsurface output of pond water, transporting salts from ponds back to their perimeters. The transition from wet to drying led to the highest measured pond salinities for one season, as high amounts of salt from the wet period remained in the pond. This research is unique as it provides a multi-decadal analysis of wetland salinity across three types of wetlands in the PPR, providing knowledge on how climate phases re-distribute salt across the landscape. Additionally, groundwater inputs to ponds during wet periods were a major source of salt to ponds and have the potential to create highly saline wetlands. This work provides valuable insights towards the effect of high and low precipitation climates on wetland salinity, allowing for projection of salt distribution in potential future climates.