Nutrients, such as nitrogen and phosphorus, are essential for plant and animal growth and nourishment, but the overabundance of bioavailable nitrogen and phosphorus in water can cause adverse health and ecological effects. It is generally accepted that major increases in the primary production of surface-water bodies due to high inputs of nutrients is now the most important polluting effect in surface water in the developed world. The Fish Creek watershed is located along the southwestern margin of the city of Jackson Hole. Fish Creek is an important water body because it is used for irrigation, fishing, recreation, and adds scenic value to the Jackson Hole properties it flows through. Recent U.S. Geological Survey (USGS) studies indicated there is a greater biovolume of aquatic plants in Fish Creek than is typically observed in streams of similar size. Studies by the USGS also indicated that (1) the amount of biovolume in Fish Creek was inversely correlated to nitrate concentration, suggesting that the aquatic vegetation was likely consuming most or all of the nutrients available to the plants and (2) land-use activities in the west bank area of the watershed can affect groundwater quality, which can then affect Fish Creek’s water quality. The Fish Creek watershed has multiple natural and anthropogenic sources of nutrients (nitrogen and phosphorus species) that can eventually migrate into Fish Creek. These sources include (1) atmospheric deposition, (2) fertilizers applied to lawns, trees, and golf courses, (3) wastewater (septic systems and sewage treatment plans), (4) livestock, (5) surface-water diversions entering the watershed, and (6) avalanche explosives. The U.S. Geological Survey, in cooperation with the Teton Conservation District (TCD), completed a study to identify and quantify nitrogen and phosphorus sources and inputs into the Fish Creek watershed. Geospatial datasets, values from literature reviews, water-quality data, and questionnaires distributed by the TCD were used to identify locations of sources and to quantify nitrogen and phosphorus inputs. This study did not address the transformation and uptake of nitrogen species (ammonia, ammonium, nitrite, nitrate, nitrogen gas, organic nitrogen) and phosphorus species (orthophosphate, organic phosphorus), because complex hydrological and chemical modeling are required for this depth of understanding. Human activities in the watershed predominately occur in the valley, on the east-south-eastern part of the watershed, and that area shows the greatest input of nitrogen and phosphorus. To characterize spatial patterns of nutrient inputs to the Fish Creek watershed, a grid of 10-acre cells was created and overlaid on the study area. Nutrient inputs were then aggregated for each 10-acre cell. The largest 10-acre cell input values are generally associated with cells that coincide with sewage treatment plant injection sites, livestock, and distributed land use where septic systems and lawns are located. Annual nitrogen input ranged from 25 to over 4,000 pounds in a 10-acre cell and annual phosphorus input ranged from about 3 to about 1,200 pounds in a 10-acre cell. Atmospheric deposition represented the largest overall source of estimated nitrogen input (46 percent) into the watershed, and represented the second highest percentage (26 percent) of total phosphorus input into the watershed. It is noteworthy that much of nutrient input from atmospheric deposition are likely used by canopy vegetation before it reaches Fish Creek. The next largest sources of nitrogen input associated with human activities are cattle and lawns, and the next largest phosphorus inputs are cattle and horses. Although cattle are not in the watershed for the entire year, the large number of cattle grazing on the land produced higher input for both nitrogen and phosphorus than many of the other sources. Lawns had higher application rates of nutrients and had larger acreages than other fertilized

Nutrients, such as nitrogen and phosphorus, are essential for plant and animal growth and nourishment, but the overabundance of bioavailable nitrogen and phosphorus in water can cause adverse health and ecological effects. It is generally accepted that major increases in the primary production of surface-water bodies due to high inputs of nutrients is now the most important polluting effect in surface water in the developed world. The Fish Creek watershed is located along the southwestern margin of the city of Jackson Hole. Fish Creek is an important water body because it is used for irrigation, fishing, recreation, and adds scenic value to the Jackson Hole properties it flows through. Recent U.S. Geological Survey (USGS) studies indicated there is a greater biovolume of aquatic plants in Fish Creek than is typically observed in streams of similar size. Studies by the USGS also indicated that (1) the amount of biovolume in Fish Creek was inversely correlated to nitrate concentration, suggesting that the aquatic vegetation was likely consuming most or all of the nutrients available to the plants and (2) land-use activities in the west bank area of the watershed can affect groundwater quality, which can then affect Fish Creek’s water quality. The Fish Creek watershed has multiple natural and anthropogenic sources of nutrients (nitrogen and phosphorus species) that can eventually migrate into Fish Creek. These sources include (1) atmospheric deposition, (2) fertilizers applied to lawns, trees, and golf courses, (3) wastewater (septic systems and sewage treatment plans), (4) livestock, (5) surface-water diversions entering the watershed, and (6) avalanche explosives. The U.S. Geological Survey, in cooperation with the Teton Conservation District (TCD), completed a study to identify and quantify nitrogen and phosphorus sources and inputs into the Fish Creek watershed. Geospatial datasets, values from literature reviews, water-quality data, and questionnaires distributed by the TCD were used to identify locations of sources and to quantify nitrogen and phosphorus inputs. This study did not address the transformation and uptake of nitrogen species (ammonia, ammonium, nitrite, nitrate, nitrogen gas, organic nitrogen) and phosphorus species (orthophosphate, organic phosphorus), because complex hydrological and chemical modeling are required for this depth of understanding. Human activities in the watershed predominately occur in the valley, on the east-south-eastern part of the watershed, and that area shows the greatest input of nitrogen and phosphorus. To characterize spatial patterns of nutrient inputs to the Fish Creek watershed, a grid of 10-acre cell was created and overlaid on the study area. Nutrient inputs were then aggregated for each 10-acre cells. The largest 10-acre cell input values are generally associated with cells that coincide with sewage treatment plant injection sites, livestock, and distributed land use where septic systems and lawns are located. Annual nitrogen input ranged from 25 to over 4,000 pounds in a 10-acre cell and annual phosphorus input ranged from about 3 to about 1,200 pounds in a 10-acre cell. Atmospheric deposition represented the largest overall source of estimated nitrogen input (46 percent) into the watershed, and represented the second highest percentage (26 percent) of total phosphorus input into the watershed. It is noteworthy that much of nutrient input from atmospheric deposition are likely used by canopy vegetation before they reach Fish Creek. The next largest sources of nitrogen input associated with human activities are cattle and lawns, and the next largest phosphorus inputs are cattle and horses. Although cattle are not in the watershed for the entire year, the large number of cattle grazing on the land produced higher input for both nitrogen and phosphorus than many of the other sources. Lawns had higher application rates of nutrients and had larger acreages than other fertilized

Nutrients, such as nitrogen and phosphorus, are essential for plant and animal growth and nourishment, but the overabundance of bioavailable nitrogen and phosphorus in water can cause adverse health and ecological effects. It is generally accepted that major increases in the primary production of surface-water bodies due to high inputs of nutrients is now the most important polluting effect in surface water in the developed world. The Fish Creek watershed is located along the southwestern margin of the city of Jackson Hole. Fish Creek is an important water body because it is used for irrigation, fishing, recreation, and adds scenic value to the Jackson Hole properties it flows through. Recent U.S. Geological Survey (USGS) studies indicated there is a greater biovolume of aquatic plants in Fish Creek than is typically observed in streams of similar size. Studies by the USGS also indicated that (1) the amount of biovolume in Fish Creek was inversely correlated to nitrate concentration, suggesting that the aquatic vegetation was likely consuming most or all of the nutrients available to the plants and (2) land-use activities in the west bank area of the watershed can affect groundwater quality, which can then affect Fish Creek’s water quality. The Fish Creek watershed has multiple natural and anthropogenic sources of nutrients (nitrogen and phosphorus species) that can eventually migrate into Fish Creek. These sources include (1) atmospheric deposition, (2) fertilizers applied to lawns, trees, and golf courses, (3) wastewater (septic systems and sewage treatment plans), (4) livestock, (5) surface-water diversions entering the watershed, and (6) avalanche explosives. The U.S. Geological Survey, in cooperation with the Teton Conservation District (TCD), completed a study to identify and quantify nitrogen and phosphorus sources and inputs into the Fish Creek watershed. Geospatial datasets, values from literature reviews, water-quality data, and questionnaires distributed by the TCD were used to identify locations of sources and to quantify nitrogen and phosphorus inputs. This study did not address the transformation and uptake of nitrogen species (ammonia, ammonium, nitrite, nitrate, nitrogen gas, organic nitrogen) and phosphorus species (orthophosphate, organic phosphorus), because complex hydrological and chemical modeling are required for this depth of understanding. Human activities in the watershed predominately occur in the valley, on the east-south-eastern part of the watershed, and that area shows the greatest input of nitrogen and phosphorus. To characterize spatial patterns of nutrient inputs to the Fish Creek watershed, a grid of 10-acre cell was created and overlaid on the study area. Nutrient inputs were then aggregated for each 10-acre cells. The largest 10-acre cell input values are generally associated with cells that coincide with sewage treatment plant injection sites, livestock, and distributed land use where septic systems and lawns are located. Annual nitrogen input ranged from 25 to over 4,000 pounds in a 10-acre cell and annual phosphorus input ranged from about 3 to about 1,200 pounds in a 10-acre cell. Atmospheric deposition represented the largest overall source of estimated nitrogen input (46 percent) into the watershed, and represented the second highest percentage (26 percent) of total phosphorus input into the watershed. It is noteworthy that much of nutrient input from atmospheric deposition are likely used by canopy vegetation before they reach Fish Creek. The next largest sources of nitrogen input associated with human activities are cattle and lawns, and the next largest phosphorus inputs are cattle and horses. Although cattle are not in the watershed for the entire year, the large number of cattle grazing on the land produced higher input for both nitrogen and phosphorus than many of the other sources. Lawns had higher application rates of nutrients and had larger acreages than other fertilized

Nitrogen and phosphorus losses from agricultural areas have impacted the water quality of downstream rivers, lakes, and oceans. As a result, investment in the adoption of agricultural best management practices (BMPs) has grown but assessments of their effectiveness at large spatial scales have been sparse. This study applies regional Spatially Referenced Regression On Watershed-attributes (SPARROW) models developed for the Midwest, Northeast, and Southeast regions of the United States to quantify regional effects of BMPs on nutrient losses from agricultural lands. These models were used because they account for specific BMPs in the prediction of instream nutrient loads. This data release accompanies the journal article "Quantifying regional effects of best management practices on nutrient losses from agricultural lands" (https:// doi:10.5066/pending), and it contains the input and output data for the modeling scenarios that were evaluated relative to the 2012 regional SPARROW models.

Nitrogen and phosphorus losses from agricultural areas have impacted the water quality of downstream rivers, lakes, and oceans. As a result, investment in the adoption of agricultural best management practices (BMPs) has grown but assessments of their effectiveness at large spatial scales have been sparse. This study applies regional Spatially Referenced Regression On Watershed-attributes (SPARROW) models developed for the Midwest, Northeast, and Southeast regions of the United States to quantify regional effects of BMPs on nutrient losses from agricultural lands. These models were used because they account for specific BMPs in the prediction of instream nutrient loads. This data release accompanies the journal article "Quantifying regional effects of best management practices on nutrient losses from agricultural lands" (https:// doi:10.5066/pending), and it contains the input and output data for the modeling scenarios that were evaluated relative to the 2012 regional SPARROW models.

We explored the possible causes of change in Mississippi River nutrient load trends through an impact evaluation that utilizes counterfactual scenarios to compare observed changes in river loads to changes in river load that might have occurred in the absence of potential causal factors. Prior to the counterfactual analysis, we developed a multiple linear regression model to predict TN and TP load changes over time. We modeled annual FN river loads as a function of current nutrient balances, lagged nutrient balances, and a latent variable representing the aggregate effect of other potential causal factors. We examined two different counterfactual scenarios, using hypothetical inputs to the calibrated TN and TP regression models. For Counterfactual A, the hypothetical inputs were current and lagged nutrient balances held constant at 1975 levels through 2017, and the Year terms were the same as the original inputs. The objective of holding the nutrient balance inputs constant was to investigate how river nutrient loads might have changed between 1975 and 2017 in the absence of any variability in nutrient balances after 1975. For Counterfactual B, the hypothetical inputs were the latent Year term held constant at 1975 levels through 2017, and the current and lagged nutrient balance inputs were the same as in the original inputs. The objective of holding the Year input constant at 1975 was to investigate how river nutrient loads might have changed between 1975 and 2017 in the absence of any variability in latent processes, potentially including BMP implementation, watershed buffering capacity, and other factors. The impact analysis compared the mean annual counterfactual analysis results to the mean original regression results for the time period 2013 to 2017. The original regression results refer to the predicted river loads estimated from the calibrated regression model using the original data.

We explored the possible causes of change in Mississippi River nutrient load trends through an impact evaluation that utilizes counterfactual scenarios to compare observed changes in river loads to changes in river load that might have occurred in the absence of potential causal factors. Prior to the counterfactual analysis, we developed a multiple linear regression model to predict TN and TP load changes over time. We modeled annual FN river loads as a function of current nutrient balances, lagged nutrient balances, and a latent variable representing the aggregate effect of other potential causal factors. We examined two different counterfactual scenarios, using hypothetical inputs to the calibrated TN and TP regression models. For Counterfactual A, the hypothetical inputs were current and lagged nutrient balances held constant at 1975 levels through 2017, and the Year terms were the same as the original inputs. The objective of holding the nutrient balance inputs constant was to investigate how river nutrient loads might have changed between 1975 and 2017 in the absence of any variability in nutrient balances after 1975. For Counterfactual B, the hypothetical inputs were the latent Year term held constant at 1975 levels through 2017, and the current and lagged nutrient balance inputs were the same as in the original inputs. The objective of holding the Year input constant at 1975 was to investigate how river nutrient loads might have changed between 1975 and 2017 in the absence of any variability in latent processes, potentially including BMP implementation, watershed buffering capacity, and other factors. The impact analysis compared the mean annual counterfactual analysis results to the mean original regression results for the time period 2013 to 2017. The original regression results refer to the predicted river loads estimated from the calibrated regression model using the original data.

We explored the possible causes of change in Mississippi River nutrient load trends through an impact evaluation that utilizes counterfactual scenarios to compare observed changes in river loads to changes in river load that might have occurred in the absence of potential causal factors. Prior to the counterfactual analysis, we developed a multiple linear regression model to predict TN and TP load changes over time. We modeled annual FN river loads as a function of current nutrient balances, lagged nutrient balances, and a latent variable representing the aggregate effect of other potential causal factors. We examined two different counterfactual scenarios, using hypothetical inputs to the calibrated TN and TP regression models. For Counterfactual A, the hypothetical inputs were current and lagged nutrient balances held constant at 1975 levels through 2017, and the Year terms were the same as the original inputs. The objective of holding the nutrient balance inputs constant was to investigate how river nutrient loads might have changed between 1975 and 2017 in the absence of any variability in nutrient balances after 1975. For Counterfactual B, the hypothetical inputs were the latent Year term held constant at 1975 levels through 2017, and the current and lagged nutrient balance inputs were the same as in the original inputs. The objective of holding the Year input constant at 1975 was to investigate how river nutrient loads might have changed between 1975 and 2017 in the absence of any variability in latent processes, potentially including BMP implementation, watershed buffering capacity, and other factors. The impact analysis compared the mean annual counterfactual analysis results to the mean original regression results for the time period 2013 to 2017. The original regression results refer to the predicted river loads estimated from the calibrated regression model using the original data.