John Brakebill

A unique, high-resolution, hydroclimate reanalysis, 40-plus-year (October 1979–September 2021), 4 km (named as CONUS404), has been created using the Weather Research and Forecasting Model by dynamically downscaling of the fifth-generation European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric reanalysis of the global climate dataset (ERA5) over the conterminous United States. The paper describes the approach for generating the dataset, provides an initial evaluation, including biases, and indicates how interested users can access the data. The motivation for creating this National Center for Atmospheric Research (NCAR)–U.S. Geological Survey (USGS) collaborative dataset is to provide research and end-user communities with a high-resolution, self-consistent, long-term, continental-scale hydroclimate dataset appropriate for forcing hydrological models and conducting hydroclimate scientific analyses over the conterminous United States. The data are archived and accessible on the USGS Black Pearl tape system and on the NCAR supercomputer Campaign storage system.

This data set contains county-level estimates of nitrogen and phosphorus from fertilizer, for both farm and nonfarm uses, for the conterminous United States, for 1987 through 2012. State-level farm and nonfarm nitrogen and phosphorus were derived from the Association of American Plant Food Control Officials (AAPFCO) commercial fertilizer sales data. State estimates were then allocated to the county-level using fertilizer expenditure from the Census of Agriculture as county weights for farm fertilizer, and effective population density as county weights for nonfarm fertilizer. Data computations for 2007 - 2012 estimates are results of methods applied directly from Gronberg and Spahr, 2012. Data for 1987 - 2006 are exactly those published in Gronberg and Spahr, 2012. Gronberg, J.M., and Spahr, N.E., 2012, County-level estimates of nitrogen and phosphorus from commercial fertilizer for the Conterminous United States, 1987 2006: U.S. Geological Survey Scientific Investigations Report 2012-5207, 20 p. - https://pubs.usgs.gov/sir/2012/5207/

Land use, land cover, and water-quality data were used in a statistical model to help determine the distribution and relative importance of nutrient sources to Chesapeake Bay. Nutrient enrichment, one of the more serious issues facing the Chesapeake Bay and its tributaries, can be attributed directly or indirectly to the varying land uses within the 64,000-square-mile watershed that covers parts of Delaware, Maryland, New York, Pennsylvania, Virginia, West Virginia, and Washington, D.C. Potential contributions of nutrients from agricultural sources can be estimated by using State and county agricultural census information, but this data typically lacks spatial detail. The use of such census data in conjunction with digital land-use imagery, however, can improve the spatial detail required to evaluate nutrient sources at larger scales. Several digital data sets that represent the spatial variability of land uses and their potential for nutrient contributions to the Chesapeake Bay and its tributaries have been generated. Estimates of nitrogen and phosphorus loading for manure and commercial fertilizer sources based on county statistics and agricultural application rates were used with digital land-use and land-cover data derived from satellite imagery to further distribute the estimated nutrient loading within agricultural areas. Septic systems, urban runoff, atmospheric deposition, and other point and nonpoint sources are also represented by spatial data sets. Utilizing the spatial detail provided by these data sets, the U.S. Geological Survey has developed a set of spatially referenced regression models that statistically relate water-quality measurements to nutrient sources. Referred to as SPAtially Referenced Regressions On Watershed attributes (SPARROW), these models produce detailed estimates of the relative importance of each nutrient source and their spatial variability within the watershed. These estimates provide resource managers with a spatial tool that can be used to formulate nutrient-reduction strategies designed to improve the water-quality conditions in the Chesapeake Bay and its watershed.

6 Atmospheric Nitrogen Flux From the Watersheds of Major Estuaries of the United States: An Application of the SPARROW Watershed Model Richard B. Alexander, Richard A. Smith, Gregory E. Schwarz, Stephen D. Preston, John W. Brakebill, Raghavan Srinivasan, and Percy A. ...

USGS report WRIR-98-4177, Nutrient and Suspended-Sediment Concentrations, Trends, Loads, and Yields From the Nontidal Part of the Susquehanna, Potomac, Patuxent, and Choptank Rivers, 1985-96 by Linda C. Darrell, Brenda Feit Majedi, Joy S. Lizárraga, and Joel D. Blomquist

Two watershed modeling tools are currently being applied in the Chesapeake Bay watershed to support the management of nutrient loading to tidal waters. SPAtially Referenced Regressions On Watershed attributes (SPARROW) models were developed by the United States Geological Survey to relate sources of nutrients (total nitrogen and total phosphorus) to stream loads throughout the 164,000 km2 watershed. In a separate effort, the Chesapeake Bay Program has developed a watershed model using the Hydrologic Simulation Program FORTRAN (HSPF) modeling framework. These two modeling approaches are quite different in structure. The SPARROW models are statistically based and are spatially explicit. In contrast, the HSPF model is deterministic and is temporally explicit. Both modeling efforts provide information about nutrient loading in the Chesapeake Bay watershed and their combined use is now being explored. SPARROW and HSPF provide different perspectives on nutrient loading that may be used as complementary information to support management decisions. SPARROW models provide a framework for utilizing data that are available in greater spatial detail than can be utilized by current versions of HSPF. SPARROW models also provide empirical information on those sources or watershed characteristics that best explain the spatial variation in nutrient loading. The HSPF model includes components that account for management actions and can be used to evaluate potential land-use or nutrient-management scenarios. Preliminary comparisons indicate that the models provide similar predictions of total nitrogen and total phosphorus loads and yields, particularly for drainage basins larger than 2,000 km2. Nutrient budgets for the two types of models also are similar, although there are some differences in the percentage of the budgets attributed to certain sources. The Chesapeake Bay Program is now evaluating the two modeling approaches for joint use in an allocation and targeting process that is being developed to guide nutrient management actions designed to achieve new tidal water-quality criteria. Nutrient-load allocations are being established for watersheds and jurisdictions through mass-balance principles using the HSPF model. The SPARROW models offer supplementary information that enhances the spatial scale of the targeting process. HSPF model units are approximately 2,000 km2 on average. SPARROW model units average approximately 120 km2 and nest within most HSPF model units, so that they can provide supplementary information on source locations and nutrient budgets for smaller streams.

U.S. Environmental Protection Agency's River Reach File 1 (RF1) to ensure the hydrologic integrity of the digital reach traces and to quantify the mean water time of travel in river reaches and reservoirs see USEPA (1996) for a description of the original RF1].

Management of suspended sediment in large watersheds is complicated by the complexity and spatial variability of landscape factors affecting sediment supply and transport. SPAtially Referenced Regressions on Watershed attributes (SPARROW) is a spatially explicit mass-balance watershed modeling technique that uses nonlinear regression equations to relate stream constituent flux to land and stream sources and transport factors. A calibrated SPARROW model was used to illustrate the cumulative effects of interacting landscape factors on sediment transport from uplands to stream corridors in the Chesapeake Bay watershed. Suspended- sediment transport to Chesapeake tributaries is observed to be more efficient in steeper areas with relatively impermeable soils and few impoundments. Sediment delivery to streams also is greater in the Piedmont Uplands than in other physiographic settings. Relatively erosive soils and high suspended-sediment yields have previously been reported in this region...

U.S. Environmental Protection Agency's River Reach File 1 (RF1) to
ensure the hydrologic integrity of the digital reach traces and
to quantify the mean water time of travel in river reaches and reservoirs
see USEPA (1996) for a description of the original RF1].

Citation for proceedings: Stringer, Christina E.; Krauss, Ken W.; Latimer, James S., eds. 2016. Headwaters to estuaries: advances in watershed science and management—Proceedings of the Fifth Interagency Conference on Research in the Watersheds. March 2-5, 2015, North Charleston, South Carolina. e-Gen. Tech. Rep. SRS-211. Asheville, NC: U.S. Department of Agriculture Forest Service, Southern Research Station. 302 p. PUBLICALLY ACCESSIBLE DECISION SUPPORT SYSTEM OF THE SPATIALLY REFERENCED REGRESSIONS ON WATERSHED ATTRIBUTES (SPARROW) MODEL AND MODEL ENHANCEMENTS IN SOUTH CAROLINA

... flow and groundwater nitrate loads were compiled and analyzed to assess the significance ofgroundwater discharge as ... ground-water discharge is an important component of the total nontidal streamflow, and that ground-water discharge varies ... Compilation of water-quality data. ...