Nutrient Reduction (Midwest Conservation Blueprint 2026 Indicator)

Definition This indicator represents the minimization of nutrient loading that leads to issues in downstream waters (e.g. harmful and nuisance algal blooms) in both the Gulf and the Great Lakes. It prioritizes areas based on a catchment's contribution to the loading of nitrogen, phosphorus, and suspended sediments into water. Pixels can take the following values: 1 – Low nutrient load, not a natural asset 2 – Low nutrient load, natural assets 3 – Medium nutrient load, not a natural asset 4 – Medium nutrient load, natural assets 5 – High nutrient load, not a natural asset 6 – High nutrient load, natural assets Selection This indicator was chosen as a targetable, important feature of the MLI goals that will be used to track conditions over time and prioritize areas for conservation. Indicators were defined through elicitation and prioritization exercises with federal and state participants. Criteria for the indicators includes 1) actionable, 2) measurable, 3) relevant to multiple groups across the region, and/or 4) representative of other social and/or environmental values. Input Data & Mapping Steps This indicator originates from the USGS 2012 SPARROW Model for the Midwest. To create this layer, MLI partners, members, and staff completed the following mapping steps: projected all input data to NAD83 (2011) UTM Zone 15N, joined the nitrogen, phosphorus, and suspended sediment data with catchment boundaries to spatially depict the nutrient loading of each catchment, mosaicked the results of each nutrient into a single raster, and emphasized natural assets within each catchment in the final raster resulting in the following values: 1 – Low nutrient load, not a natural asset, 2 – Low nutrient load, natural assets, 3 – Median nutrient load, not a natural asset, 4 – Median nutrient load, natural assets, 5 – High nutrient load, not a natural asset, 6 – High nutrient load, natural assets. Finally, we removed highly altered areas using our Highly Altered Areas mask. For full mapping details, please refer to the Midwest Conservation Blueprint Development Process. For a complete download of all Blueprint input and output data, visit the Midwest Conservation Blueprint 2026 Data Download.一、定义 本指标旨在量化可对下游水域造成不良影响的养分负荷削减目标，涵盖墨西哥湾与五大湖区域的有害藻华及 nuisance藻华问题。该指标基于各流域向水体输入氮、磷与悬浮沉积物的贡献量对区域进行优先级排序。像素值可分为以下类别： 1 – 低养分负荷，非自然资产 2 – 低养分负荷，自然资产 3 – 中等养分负荷，非自然资产 4 – 中等养分负荷，自然资产 5 – 高养分负荷，非自然资产 6 – 高养分负荷，自然资产 二、指标遴选 本指标被选为MLI目标中具备可操作性的重要特征，将用于长期跟踪区域环境状况并划定保护优先级。指标通过与联邦及州级参与者开展的专家征询与优先级排序工作确定，其遴选标准包括：1）可落地执行；2）可量化评估；3）对区域内多类群体具有相关性；及/或4）可代表其他社会与/或环境价值。 三、输入数据与制图流程 本指标源自美国地质调查局（USGS）2012年针对中西部地区开发的SPARROW模型。为生成该图层，MLI的合作伙伴、成员与工作人员完成了如下制图步骤：将所有输入数据投影至NAD83 (2011) UTM 15N带；将氮、磷与悬浮沉积物数据与流域边界进行空间关联，以可视化呈现各流域的养分负荷情况；将各养分的计算结果拼接为单一栅格图层；在最终栅格中突出显示各流域内的自然资产，最终得到如下像素值： 1 – 低养分负荷，非自然资产；2 – 低养分负荷，自然资产；3 – 中位数养分负荷，非自然资产；4 – 中位数养分负荷，自然资产；5 – 高养分负荷，非自然资产；6 – 高养分负荷，自然资产。 最后，我们通过高度受损区域掩膜移除了高度受干扰的区域。如需完整的制图细节，请参阅《中西部保护蓝图开发流程》。若需完整下载所有蓝图的输入与输出数据，请访问《中西部保护蓝图2026数据下载》页面。