Abstract

In the Canadian prairies, eutrophication is a widespread issue, with agriculture representing a major anthropogenic nutrient source in many watersheds. However, efforts to mitigate agricultural nutrient export are challenged by the lack of coordinated monitoring programs and the unique hydrological characteristics of the prairies, notably, the dominance of snowmelt in both water flows and nutrient loads, variable runoff, variable contributing area and the issues of understanding how scale affects nutrient concentrations and prevalence of dissolved nutrient transport (over total nutrients). Efforts are being made to integrate these characteristics in process-based water quality models, but the models are often complex and are not yet ready for use by watershed managers for prioritizing implementation of beneficial management practices (BMPs). In this study, a screening and scoping approach based on nutrient export coefficient modeling was used to prioritize BMPs for the 55,700 km² Qu’Appelle Watershed, Saskatchewan. By integrating land use information, in-stream monitoring data, stakeholder input and nutrient export coefficient modeling, the study assessed potential efficiencies of six BMPs involving fertilizer, manure, grazing, crop and wetland management in nutrient load reductions for nine tributaries of the watershed. Uncertainty around the effectiveness of the BMPs was assessed. Field-level export coefficients were adjusted with nutrient delivery ratios for estimating watershed-level exports. Of the BMPs examined, in general, wetland restoration had the greatest potential to reduce both nitrogen and phosphorus loads in most tributaries, followed by fertilizer management. The importance of wetland restoration was supported by positive, significant, linear correlations between nutrient delivery ratios and drainage intensity in the tributaries (nitrogen: R² = 0.67; phosphorus: R² = 0.82). Notably, the relative ranking of BMP efficiencies varied with tributaries, as a result of differing landscape characteristics, land uses and nutrient inputs. In conclusion, the approach developed here acknowledges uncertainty, but provides a means to guide management decisions within the context of an adaptive management approach, where BMP implementation is partnered with monitoring and assessment to revise ongoing plans and ensures selected practices are meeting goals for nutrient abatement.

摘要

在加拿大大草原，富营养化是一个普遍存在的问题，农业是许多流域的主要人为营养来源。然而，减少农业养分输出的努力受到缺乏协调监测计划和草原独特水文特征的挑战，特别是融雪在水流和养分负荷中的主导地位、可变径流、可变贡献面积以及了解规模如何影响养分浓度和溶解养分运输的普遍性（超过总养分）。正在努力将这些特征整合到基于过程的水质模型中，但这些模型通常很复杂，尚未准备好被流域管理者用于优先实施有益管理实践 (BMP)。²Qu'Appelle 流域，萨斯喀彻温省。通过整合土地利用信息、流域监测数据、利益相关者输入和养分输出系数模型，该研究评估了六种 BMPs 在减少流域九个支流养分负荷方面的潜在效率，这些 BMP 涉及肥料、粪肥、放牧、作物和湿地管理。评估了 BMP 有效性的不确定性。田间出口系数根据养分输送率进行了调整，以估算流域出口。在检查的 BMP 中，一般而言，湿地恢复最有可能减少大多数支流的氮和磷负荷，其次是肥料管理。湿地恢复的重要性得到了积极、显着、R ² = 0.67；磷：R ² = 0.82)。值得注意的是，由于不同的景观特征、土地利用和养分投入，BMP 效率的相对排名因支流而异。总之，这里开发的方法承认不确定性，但提供了一种在适应性管理方法的背景下指导管理决策的方法，其中 BMP 的实施与监测和评估合作，以修订正在进行的计划并确保选定的实践满足减少营养物质的目标.