McMaster University, Department of Biology, 1280 Main Street West, Hamilton, ON, L8S 4K1, Canada.
J Environ Manage. 2019 Mar 15;234:357-366. doi: 10.1016/j.jenvman.2018.12.114. Epub 2019 Jan 9.
Eutrophication from agricultural runoff is a global problem, often resulting in formation of anoxic zones in receiving water bodies. The Nottawasaga River Watershed (NRW) is dominated by agricultural land-use, and drains into Nottawasaga Bay, Georgian Bay (Lake Huron). A fundamental feature of the NRW is the Minesing Wetlands, a Ramsar site and the largest inland wetland in southern Ontario. We used total phosphorus (TP) concentration-discharge relationships to estimate annual loading from six sub-watersheds and compared these against published models, which did not offer a way to account for the unique properties of the Minesing Wetlands. We developed predictive loading models specifically for the NRW to account for these characteristics, which accurately predict daily summer base-flow TP (r = 0.76, p = <0.0001) and total suspended solids (TSS; r = 0.65, p = <0.0001) loads for 11 subwatersheds using geomorphic and land-cover variables. Drainage area and % pasture land were the most significant predictive variables driving spatial variability in TP and TSS loading rates among subwatersheds. The positive relationship between TP and % wetland (r = 0.22, p = 0.0063) also suggested that the Minesing Wetlands are a source of nutrients to the Nottawasaga River. Watershed geomorphology (e.g. slope) was a good predictor of land cover, and produced accurate loading estimates. This study is the first to offer a new approach to predict TP and TSS loading rates during the growing season using readily available geospatial data.
农业径流引起的富营养化是一个全球性问题，通常会导致受纳水体形成缺氧区。诺特瓦萨加河流域（NRW）以农业土地利用为主，流入诺特瓦萨加湾，乔治亚湾（休伦湖）。NRW 的一个基本特征是明辛湿地，这是一个拉姆萨尔湿地和安大略省南部最大的内陆湿地。我们使用总磷（TP）浓度-流量关系来估计六个子流域的年排放量，并将其与已发表的模型进行比较，这些模型无法说明明辛湿地的独特性质。我们专门为 NRW 开发了预测性加载模型，以考虑这些特性，这些模型可以准确预测夏季每日基流 TP（r=0.76，p<0.0001）和总悬浮固体（TSS；r=0.65，p<0.0001）的负荷，使用地形和土地覆盖变量。排水面积和牧场面积百分比是驱动子流域之间 TP 和 TSS 加载率空间变化的最重要预测变量。TP 与湿地百分比之间的正相关关系（r=0.22，p=0.0063）也表明明辛湿地是诺特瓦萨加河的营养物质来源。流域地貌（如坡度）是土地覆盖的良好预测指标，并产生了准确的负荷估计。本研究首次提供了一种新方法，使用现成的地理空间数据预测生长季节的 TP 和 TSS 负荷率。
