Figure 3 - uploaded by Maria ML Armstrong
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3. Example of wetland impact classification in the basin. Black lines represent stream beds. Wetland areas enclosed by red lines represent drained wetlands (converted to cropland). Wetland areas enclosed by blue lines represent undrained wetlands and wetland areas enclosed by orange lines represent partially drained wetlands (remnant wetland breached by drain). Note that undrained wetland area also includes the perimeter area of a partially drained wetland that has been converted to cropland.
Source publication
The Canadian Prairies contains a high density of hydrologically isolated wetlands, termed “potholes”, which have been identified as important to hydrology and water quality. These wetlands have increasingly been drained for expanding agriculture with some evidence of ecohydrological impacts. In addition there is evidence the hydrology of the Prairi...
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Citations
... Pothole pond connectivity, or lack thereof, largely influences specific conductivity of individual ponds, with higher conductivity in the more stagnant, discharge ponds where salts can accumulate. Pothole ponds within SDNWA range from under 300 µS cm -1 (fresh) to over 137,000 µS cm -1 (saline) (Armstrong, 2018;Pham et al. 2008), while also being temporally dynamic, dependent on seasonal temperatures, hydroperiods, and pond characteristics. ...
The Prairie Pothole Region of Canada is under substantial anthropogenic stress associated with climate change, land-use modification, and pollutant release. As food production demands increase in concert with the global population, the need for agricultural fertilizers to supplement plant growth has also increased. This, combined with other anthropogenic activity, has caused an accumulation of nitrogen (N) compounds in managed and natural aquatic ecosystems which pose a significant threat to biodiversity, water quality, and human health. Prairie pothole wetlands have high nutrient holding and transformation capacity and may help to offset the risk of downstream nutrient export and pollution through many transformative biogeochemical processes, thereby retaining N on the local landscape. The goal of this research was to quantify the rates of planktonic uptake, denitrification, and dissimilatory nitrate reduction to ammonium (DNRA) across a gradient of parameters observed in pothole wetlands. Planktonic uptake was rapid, reaching a maximum rate of 16,100 µg N L −1 hr −1 at ambient concentrations, and displayed a preference for NH4 +. Additionally, uptake was prevalent across light and dark conditions, suggesting bacteria may play a larger role in pelagic N cycling than previously thought. Benthic NO3-reduction was dominated by DNRA, reaching a maximum rate of 0.756 µg N g-1 hr-1 , while comparatively low rates of denitrification were occurring, reaching a maximum of 0.014 µg N g-1 hr-1. This research is one of the first to quantify pelagic and benthic N cycling in prairie potholes. The rapidity at which N cycling via uptake and DNRA occurs highlights the importance of potholes as transformers on the landscape, capable of harnessing and recycling N within the system. However, anthropogenic inputs and modifications can alter the rates of transformations and retention capacity of potholes. With the looming threat of climate change that may bring more extreme weather events, continued nutrient inputs, and widespread wetland drainage that increases the frequency of hydrologic connectivity necessary for nutrient export, it is imperative that we recognize the role of pothole wetlands for healthy water resources, including their capacity to transform N on the landscape.
Conversion of wetlands in cultivated agricultural landscapes is one of the primary drivers of wetland loss in Alberta, Canada, despite a provincial wetland policy that prioritizes wetland avoidance. While other sectors of the agricultural industry have established initiatives to maintain wetlands, a common narrative within the conventional cropping sector is that wetland retention leads to lost acreage and overlap of crop inputs, and that there are financial benefits associated with wetland drainage. The objective of this research was to explicitly quantify crop productivity within drained wetland basins, in an effort to better understand the extent to which producers financially benefit from drainage practices. Working collaboratively with canola producers in central Alberta over the 2019 growing season, wetland basins within four quarter sections were mapped using an Unmanned Aerial Vehicle, and wetland basins with clear evidence of surface drainage were identified. Agricultural input and yield data provided by producers was then used to quantify profitability within each drained basin. Average profit for drained basins for each producer ranged between − $145/acre and $76/acre, with an average of $55/acre across all operations. This is compared to an average profit of $203/acre for non-wetland areas across all operations. The results suggest that the financial benefits of drainage are highly variable, and for many drained basins, producers may experience financial losses that may be overlooked when profits are examined only at the field- or operation-level. While this study included a small number of operations, and was limited to one type of crop over a single growing season, the results still provide important insight into the extent to which producers benefit financially from the practice of wetland drainage.
The Northern Great Plains is a key region to global food production. It is also a region of water stress that includes poor water quality associated with high concentrations of nutrients. Agricultural nitrogen and phosphorus loads to surface waters need to be reduced, yet the unique characteristics of this environment create challenges. The biophysical reality of the Northern Great Plains is one where snowmelt is the major period of nutrient transport, and where nutrients are exported predominantly in dissolved form. This limits the efficacy of many beneficial management practices (BMPs) commonly used in other regions and necessitates place-based solutions. We discuss soil and water management BMPs through a regional lens—first understanding key aspects of hydrology and hydrochemistry affecting BMP efficacy, then discussing the merits of different BMPs for nutrient control. We recommend continued efforts to “keep water on the land” via wetlands and reservoirs. Adoption and expansion of reduced tillage and perennial forage may have contributed to current nutrient problems, but both practices have other environmental and agronomic benefits. The expansion of tile and surface drainage in the Northern Great Plains raises urgent questions about effects on nutrient export and options to mitigate drainage effects. Riparian vegetation is unlikely to significantly aid in nutrient retention, but when viewed against an alternative of extending cultivation and fertilization to the waters’ edge, the continued support of buffer strip management and refinement of best practices (e.g., harvesting vegetation) is merited. While the hydrology of the Northern Great Plains creates many challenges for mitigating nutrient losses, it also creates unique opportunities. For example, relocating winter bale-grazing to areas with low hydrologic connectivity should reduce loadings. Managing nutrient applications must be at the center of efforts to mitigate eutrophication. In this region, ensuring nutrients are not applied during hydrologically sensitive periods such as late autumn, on snow, or when soils are frozen will yield benefits. Working to ensure nutrient inputs are balanced with crop demands is crucial in all landscapes. Ultimately, a targeted approach to BMP implementation is required, and this must consider the agronomic and economic context but also the biophysical reality.
