Recovery Potential Screening Scenario Fact Sheet Series I Nutrients oEPA July 2022 Background & Purpose The Recovery Potential Screening (RPS) Tool provides a systematic method to compare a group of watersheds and evaluate priorities for watershed management. Key steps in the RPS process include selecting watersheds to screen and choosing indicators that serve as the basis for comparison and prioritization (Figure 1). Recognizing that these steps can be challenging for beginner RPS Tool users, the US Environmental Protection Agency (EPA) developed the RPS Scenario Fact Sheet Series to support users who have a basic understanding of RPS concepts but are uncertain about how to begin their own screening. Readers that are new to the RPS Scenario Fact Sheet Series can first review the RPS Scenario Fact Sheet Introduction to understand how to apply the concepts presented in this Fact Sheet. This Fact Sheet describes concepts for watershed and indicator selection for a screening that focuses on addressing excess levels of nutrients (nitrogen and phosphorus) in surface waters. While the approaches described in this Fact Sheet offer a starting point for conducting a screening with the RPS Tool, users can refine and customize their watershed and indicator selections based on their own specific objectives and initial results (Figure 1). Select Watersheds Although a screening can include ail HUC12 subwatersheds1 in a state or river basin,2 RPS Tool users often target a subset of relevant HUC12s to compare within a screening. The HUC Subsets tab of the RPS Tool contains an interactive menu to define a HUC12 subset. Table 1 lists example indicators that could be used to create a HUC12 subset for a nutrients-focused screening. The indicators measure characteristics that are relevant to nutrient loading and can help to identify HUC12s with nutrient issues. Table 1. Example indicators in the RPS Tool for identifying HUC12s with known or potential nutrient issues. Indicator Subcategory Example Indicators Pollutant Loading Severity Nitrogen Yield in HUC12; Phosphorus Yield in HUC12 Impaired Waters Nutrient Impaired Waters Count in HUC12 Urban/Developed Cover % Urban in HUC12 Impervious Cover % Impervious Cover in HUC12 Agricultural Cover % Cultivated Crops in HUC12 Nutrient Application and Deposition Manure Nitrogen Application in HUC12; Manure Phosphorus Application in HUC12 Hazardous Waste & Wastewater National Pollutant Discharge Elimination System (NPDES) Permit Count in HUC12 RPS Tool files for contiguous US states are pre-loaded with the indicators listed in Table 1, which include; • Average annual nitrogen and phosphorus yields from a HUC12 (i.e., the amount of nitrogen and phosphorus exported to surface waters from sources within the HUC12), • The number and extent of nutrient-impaired waters in a HUC12 (i.e., waters included on a state impaired waters list due to nutrient-related causes of impairment), • The extent of developed and agricultural land cover, agricultural nutrient applications, and wastewater dischargers in a HUC12. Several studies have highlighted relationships between nutrient levels in waterbodies and these characteristics.3 4 1 HUC12s are subwatershed delineations in the National Watershed Boundary Dataset. HUC12s are referenced by their 12-digit Hydrologic Unit Code. 2 The RPS Tool files available on the RPS website are configured for single states, however, RPS Tool files can be customized for river basins or other regions of interest. Email us at HWP-Team(S>epa.gov for more information on developing a custom RPS Tool. 3 Preston, SD, et. al. 2011. Factors Affecting Stream Nutrient Loads: A Synthesis of Regional SPARROW Model Results for the Continental United States. Journal of the American Water Resources Association (JAWRA) 47(5):891-915. 4 EPA. 2014. Wisconsin Integrated Assessment of Watershed Health. EPA 841-R-14-001. Figure 1. The RPS process. This Fact Sheet focuses on the Select Watersheds and Indicators step. 1 ------- RPS Scenario Fact Sheet Series I Nutrients As a starting point for HUC12 subsetting, users could enter one or more of the following criteria in the RPS Tool to select HUC12s with known or potential nutrient issues: • Phosphorus Yield greater than the state median yield in kilograms per square kilometer • Nitrogen Yield in Watershed greater than the state median yield in kilograms per square kilometer • Nutrient Impaired Waters Count greater than zero Selection criteria for subsetting HUC12s can be refined to better match a user's specific geographic setting and screening objective by including additional indicators or adjusting thresholds for HUC12 selection. Examples include refining thresholds for nitrogen and phosphorus yields or adding minimum levels of urban or agricultural cover as subsetting criteria. Select Indicators The indicators selected for a screening serve as the basis for users to compare watersheds and evaluate priorities for restoration and protection. For a nutrients-focused screening, the Ecological indicator selections can reflect attributes that are associated with healthy aquatic ecosystems and functional watershed processes; the Stressor indicator selections can reflect the presence of key nutrient sources in a user's geographic area; and the Social indicator selections can reflect social or programmatic factors that are favorable for successful nutrient reduction. A complete list of indicators available in the RPS Tool and indicator descriptions are provided on the Indicator Info tab of the RPS Tool for users to review when selecting indicators As a starting point for indicator selection, Table 2 highlights example indicators for a nutrients-focused screening. The example indicators in Table 2 are intended to assist users in setting up an initial screening in the RPS Tool to understand how the RPS Tool functions and the results that are generated. Table 2. Example indicators for an initial screening to identify priority HUC12sfor nutrient management Category Subcategory Indicator Name Description Ecological Integrated Watershed Health Index & Sub-Indices PHWA Watershed Health Index, State The statewide Watershed Health Index score for the HUC12 from the EPA Preliminary Healthy Watersheds Assessment (PHWA). Stressor Agricultural Cover % Cultivated Crops in HUC12 Percent of the HUC12 that is classified as cropland cover. Livestock Livestock Density in HUC12 Livestock population density in the HUC12, measured in animal equivalent units (1,000 pounds of animal weight per acre). Nutrient Application and Deposition Manure Phosphorus Application in HUC12 Average annual rate of phosphorus applied to agricultural lands as animal manure in 2012 (kilograms of phosphorus per hectare per year). Synthetic Fertilizer Phosphorus Application in HUC12 Average annual rate of phosphorus applied to agricultural lands as inorganic fertilizer in 2012 (kilograms of phosphorus per hectare per year). Impervious Cover % Impervious Cover in HUC12 Percent of the HUC12 with impervious cover. Urban/Developed Cover % Urban in HUC12 Percent of the HUC12 classified as urban cover. Social Participation in Conservation Programs USDA Conservation Reserve Program Area in HUC12 Area of land enrolled in the US Department of Agriculture (USDA) Conservation Reserve Program (CRP) in the HUC12. Nutrient Nonpoint Source (NPS) Project Presence in HUC12 Presence or absence of nutrient-related nonpoint source pollution control projects funded by Clean Water Act Section 319 grants in the HUC12, s>EPA 2 ------- RPS Scenario Fact Sheet Series I Nutrients Below is additional discussion of the example indicators for an initial screening listed in Table 2 and their relevance to a nutrients-focused screening: • The Ecological indicator listed in Table 2 is the Watershed Health Index from the EPA Preliminary Healthy Watersheds Assessment (PHWA). The Watershed Health Index is an integrated measure of watershed condition that combines several indicators which reflect six key attributes of watershed health: Landscape Condition, Geomorphology, Habitat, Water Quality, Hydrology, and Biological Condition. Higher Watershed Health Index scores correspond to greater potential for a HUC12 to support healthy aquatic ecosystems and provide important ecosystem services to surrounding communities. An Overview of the Preliminary Healthy Watersheds Assessments Project provides additional background and methodology on the PHWA. By including the Watershed Health Index in a screening, users can factor overall watershed condition into the identification of priority HUC12s for nutrient management. Depending on the interests and perspectives of a reader, both high and low scoring HUC12s could be considered priorities. Higher scoring HUC12s may contain aquatic ecosystems that are healthy but threatened by increased nutrient loading while lower scoring HUC12s may be good candidates for efforts to restore degraded ecosystems. • The Stressor indicators listed in Table 2 describe the extent of developed, impervious, and cultivated crop land cover types in the HUC12, the magnitude of agricultural nutrient applications, and the density of livestock populations. Each of these reflect typical sources of nutrients in a HUC12 that could be the focus of management practices to reduce nutrient loading. • The Social indicators listed in Table 2 describe the extent of lands protected through conservation easements and the presence of nutrient reduction projects that are funded by Clean Water Act Section 319 grants. These highlight past stakeholder engagement in the HUC12 and the potential for partnerships to implement additional nutrient management strategies. Users may choose an alternative set of ecological, stressor, and social indicators depending on a user's specific geographic setting and screening objective. For example, stressor indicator selections could be refined to target nutrient sources that are most relevant to a user's area while social indicators could be refined to align with a user's organization's preferences and approach to priority-setting. After running a screening and reviewing results, users may refine their initial watershed and indicator selections. For example, a user could be interested in evaluating how the screening results change when an indicator is removed or a new indicator is added. Iterative adjustments to watershed or indicator selections are an important part of the RPS process (Figure 1) and the RPS Tool is designed to allow users to easily adjust watershed and indicator selections. Links to RPS Tools and Additional Information RPS Tool files are available for download from the EPA RPS website. The training and user support page of the EPA RPS website includes several reports that provide detailed descriptions of projects that applied the RPS Tool to identify potential priority watersheds for addressing excess nutrients in Kentucky, Tennessee, Louisiana, New Mexico, Iowa, North Dakota, Kansas, and Massachusetts. oEPA 3 ------- |