The Water Availability Tool for Environmental Resources (WATER-KY; Williamson and others, 2009) provides the ability to simulate streamflow for ungaged basins. This model integrates TOPMODEL (Beven and Kirkby, 1979) for pervious portions of the landscape with simulation of flow generated from impervious surfaces (USDA, 1986). A restructured version of this decision support tool translates the abilities of WATER to a format that can be used without proprietary software (Williamson and others, 2021). Additional functionality has also been added to include hydrologic response units (HRUs) that are defined based on three fundamental land-use categories: forest, agricultural land, and developed areas, based on subsequent development of WATER for the Delaware River Basin (Williamson and others, 2015). This refinement for agricultural areas, combined with the new software environment that enables easy substitution of precipitation and temperature data was used to develop a method focused on recent conditions in order to simulate daily peak streamflow for forecasted precipitation totals as well as the associated stage in order to identify if flood conditions are possible. Beven, K.J., and Kirkby, M.J., 1979, A physically based, variable contributing area model of basin hydrology / Un modèle à base physique de zone d'appel variable de l'hydrologie du bassin versant: Hydrological Sciences Bulletin v. 24, p. 43-69, https://doi.org/10.1080/02626667909491834. U.S. Department of Agriculture [USDA], 1986, Urban hydrology for small watersheds: Natural Resources Conservation Service, Conservation Engineering Division, Technical Release 55, Revised June 1986, Update of Appendix A January 1999, https://www.nrc.gov/docs/ML1421/ML14219A437.pdf. Williamson, T.N., Hoefling, D.J., Headman, A.O., and Gerzan, M.N., 2021, Water Availability Tool for Environmental Resources for the Commonwealth of Kentucky updated for 2019: U.S. Geological Survey data release, https://doi.org/10.5066/P9AQH027. Williamson, T.N., Lant, J.G., Claggett, P.R., Nystrom, E.A., Milly, P.C.D., Nelson, H.L., Hoffman, S.A., Colarullo, S.J., and Fischer, J.M., 2015, Summary of hydrologic modeling for the Delaware River Basin using the Water Availability Tool for Environmental Resources (WATER): U.S. Geological Survey Scientific Investigations Report 2015–5143, 68 p., https://doi.org/10.3133/sir20155143. Williamson, T.N., Odom, K.R., Newson, J.K., Downs, A.C., Nelson Jr., H.L., Cinotto, P.J., and Ayers, M.A., 2009, The Water Availability Tool for Environmental Resources (WATER)—A water-budget modeling approach for managing water-supply resources in Kentucky—Phase I—Data processing, model development, and application to non-karst areas:U.S. Geological Survey Scientific Investigations Report 2009–5248, 34 p., https://doi.org/10.3133/sir20095248.

This database was developed for the Water Availability Tool for Environmental Resources (WATER) for the Delaware River Basin (DRB), a decision support tool that provides a consistent and objective method of simulating streamflow under historical, forecasted, and managed conditions (Williamson and others, 2015). This database provides historical spatial and climatic data for simulating streamflow for 2001–11, in addition to land-cover forecasts and general circulation model (global climate model; GCM) projections that focus on 2030 and 2060. The database provides for geospatial sampling, at a 10-30 m resolution, of landscape characteristics, including topographic and soil properties, land cover and impervious surface, water use, and GCM change factors for precipitation, temperature, and a radiation-based potential evapotranspiration. These data are available as a cohesive unit, that provides the file structure required by the hydrologic tool, in addition to some layers being provided as individual files. Williamson, T.N., Lant, J.G., Claggett, P.R., Nystrom, E.A., Milly, P.C.D., Nelson, H.L., Hoffman, S.A., Colarullo, S.J., and Fischer, J.M., 2015. Summary of hydrologic modeling for the Delaware River Basin using the Water Availability Tool for Environmental Resources (WATER): U.S. Geological Survey Scientific Investigations Report 2015-5143, 68 p., http://doi.org/10.3133/sir20155143.

In 2009, the Kentucky Water Science Center completed the Water Availability Tool for Environmental Resources (WATER-KY), which provided the ability to simulate streamflow for the period 1980-2000. This model integrated TOPMODEL (Beven and Kirkby, 1979) for pervious portions of the landscape with simulation of flow generated from impervious surfaces (USDA, 1986). Associated products included a flow-duration curve, load-duration curves when water-quality data were available, and general water balance. WATER-KY required a dedicated ArcGIS license with the Spatial Analyst extension, which made it difficult to use for some cooperators and limited integration with other hydrologic approaches. This new version translates the abilities of WATER to a format that can be used without proprietary software or local updating of software. Additional functionality has also been added to include hydrologic response units (HRUs) that are defined based on three fundamental land-use categories: forest, agricultural land, and developed areas, based on subsequent development of WATER for the Delaware Basin (Williamson and others, 2015). Beven, K.J., and Kirkby, M.J., 1979, A physically based, variable contributing area model of basin hydrology / Un modèle à base physique de zone d'appel variable de l'hydrologie du bassin versant: Hydrological Sciences Bulletin v. 24, p. 43-69, http://dx.doi.org/10.1080/02626667909491834. U.S. Department of Agriculture [USDA], 1986, Urban hydrology for small watersheds: Natural Resources Conservation Service, Conservation Engineering Division, Technical Release 55, Revised June 1986, Update of Appendix A January 1999, https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb1044171.pdf. Williamson, T.N., Lant, J.G., Claggett, P.R., Nystrom, E.A., Milly, P.C.D., Nelson, H.L., Hoffman, S.A., Colarullo, S.J., and Fischer, J.M., 2015, Summary of hydrologic modeling for the Delaware River Basin using the Water Availability Tool for Environmental Resources (WATER): U.S. Geological Survey Scientific Investigations Report 2015–5143, 68 p., http://dx.doi.org/10.3133/sir20155143.

For about 10 years, the U.S. Geological Survey (USGS) has monitored water quality and streamflow in three agricultural drainage ditches in an effort to evaluate the influence of best management practices on water quality. These ditches are small tributaries to oxbow lakes located in the Mississippi Alluvial Plain of northwestern Mississippi--two sites (LWSR and LWT2) drain to Lake Washington and one site (BLT1) drains to Bee Lake. Streamflow was intermittent at these sites and the ditches were dry much of the year. When streamflow was present, flows were measured on 15-minute intervals and water-quality samples were collected over the course of the flow event using an automated sampler. These datasets were aggregated by flow event and include various flow statistics (mean flow, peak flow, total flow volume, and event duration), flow-weighted mean concentration (total constituent load divided by total flow volume) and total constituent load for each flow event. The water-quality constituents include total nitrogen, organic nitrogen, ammonia, ammonia plus organic nitrogen (total Kjeldahl nitrogen), nitrate plus nitrite, total phosphorus, organic carbon, chloride and suspended sediment; USGS parameter codes 00600, 00605, 00610, 00625, 00630, 00665, 00680, 99220, and 80154. All samples were unfiltered. Data were collected from approximately 2007-2016, depending on the site.

For about 10 years, the U.S. Geological Survey (USGS) has monitored water quality and streamflow in three agricultural drainage ditches in an effort to evaluate the influence of best management practices on water quality. These ditches are small tributaries to oxbow lakes located in the Mississippi Alluvial Plain of northwestern Mississippi--two sites (LWSR and LWT2) drain to Lake Washington and one site (BLT1) drains to Bee Lake. Streamflow was intermittent at these sites and the ditches were dry much of the year. When streamflow was present, flows were measured on 15-minute intervals and water-quality samples were collected over the course of the flow event using an automated sampler. These datasets were aggregated by flow event and include various flow statistics (mean flow, peak flow, total flow volume, and event duration), flow-weighted mean concentration (total constituent load divided by total flow volume) and total constituent load for each flow event. The water-quality constituents include total nitrogen, organic nitrogen, ammonia, ammonia plus organic nitrogen (total Kjeldahl nitrogen), nitrate plus nitrite, total phosphorus, organic carbon, chloride and suspended sediment; USGS parameter codes 00600, 00605, 00610, 00625, 00630, 00665, 00680, 99220, and 80154. All samples were unfiltered. Data were collected from approximately 2007-2016, depending on the site.

As part of the Coastal Carolinas Focus Area Study of the U.S. Geological Survey National Water Census Program, the Soil and Water Assessment Tool (SWAT) was used to develop models for the Pee Dee River Basin, North Carolina and South Carolina, to simulate future streamflow and irrigation demand based on land use, climate, and water demand projections. SWAT is a basin-scale, process-based watershed model with the capability of simulating water-management scenarios. Model basins were divided into approximately two-square mile subbasins and subsequently divided into smaller, discrete hydrologic response units based on land use, slope, and soil type. The calibration period for the historic model was 2000 to 2014. The best available data on water-use from this time period were used, including public water supply, industrial water use, irrigation needs and golf courses. Six future scenario models simulated streamflow during the period 2055 to 2065 based on incorporation of two alternative land use projections, an ensemble of three global climate models, and water demand forecasts. This USGS data release contains all the input and output files for the simulations described in the associated model documentation report (https://doi.org/10.3133/sir20235036).

As part of the Coastal Carolinas Focus Area Study of the U.S. Geological Survey National Water Census Program, the Soil and Water Assessment Tool (SWAT) was used to develop models for the Pee Dee River Basin, North Carolina and South Carolina, to simulate future streamflow and irrigation demand based on land use, climate, and water demand projections. SWAT is a basin-scale, process-based watershed model with the capability of simulating water-management scenarios. Model basins were divided into approximately two-square mile subbasins and subsequently divided into smaller, discrete hydrologic response units based on land use, slope, and soil type. The calibration period for the historic model was 2000 to 2014. The best available data on water-use from this time period were used, including public water supply, industrial water use, irrigation needs and golf courses. Six future scenario models simulated streamflow during the period 2055 to 2065 based on incorporation of two alternative land use projections, an ensemble of three global climate models, and water demand forecasts. This USGS data release contains all the input and output files for the simulations described in the associated model documentation report (https://doi.org/10.3133/sir20235036).

This section of the data release supports an archive of the models used in the associated publication. The U.S. Geological Survey and the University of Wisconsin – Green Bay collected hydrologic and water-quality data to assess the effectiveness of agricultural conservation management practice (CMP) implementation at Mainstem Plum Creek and West Plum Creek in northeastern Wisconsin. Monitoring data from 2010–2020 at Mainstem Plum and 2013–2020 at West Plum were used to detect changes in hydrologic and water-quality responses during runoff events. Runoff events were defined by hydrographers and used to compute event loads and event flow-weighted mean concentrations of total phosphorus and total suspended solids – all of which are included in the associated data release. Additionally, changes in these parameters were assessed between two time periods (“initial” and “post-CMP implementation”) using the models included in this model archive. Because event discharges, loads, and concentrations are influenced by factors such as weather and the conditions preceding events, random-forest and regression models were developed to control for these factors and to elucidate water-quality changes more directly associated with CMP implementation. Residuals from random-forest models were used to detect changes between the two time periods via Wilcoxon signed-rank tests, and multiple linear regression models were used to determine percent change in responses via time-period dummy variable coefficients. Results indicate statistically insignificant changes in most responses during runoff events.

This section of the data release supports an archive of the models used in the associated publication. The U.S. Geological Survey and the University of Wisconsin – Green Bay collected hydrologic and water-quality data to assess the effectiveness of agricultural conservation management practice (CMP) implementation at Mainstem Plum Creek and West Plum Creek in northeastern Wisconsin. Monitoring data from 2010–2020 at Mainstem Plum and 2013–2020 at West Plum were used to detect changes in hydrologic and water-quality responses during runoff events. Runoff events were defined by hydrographers and used to compute event loads and event flow-weighted mean concentrations of total phosphorus and total suspended solids – all of which are included in the associated data release. Additionally, changes in these parameters were assessed between two time periods (“initial” and “post-CMP implementation”) using the models included in this model archive. Because event discharges, loads, and concentrations are influenced by factors such as weather and the conditions preceding events, random-forest and regression models were developed to control for these factors and to elucidate water-quality changes more directly associated with CMP implementation. Residuals from random-forest models were used to detect changes between the two time periods via Wilcoxon signed-rank tests, and multiple linear regression models were used to determine percent change in responses via time-period dummy variable coefficients. Results indicate statistically insignificant changes in most responses during runoff events.

The study results and data used and produced in this study are available through the Texas Data Repository at https://doi.org/10.18738/T8/A9X5ET (Srinivasan et al., 2023). The data also includes the necessary information to reproduce the figures and tables presented in the study. This dataset is associated with the following publication: Bawa, A., K. Mendoza, R. Srinivasan, F. O'Donncha, D. Smith, K. Wolfe, R. Parmar, J. Johnston, and J. Corona. Enhancing Hydrological Modeling of Ungauged Watersheds through Machine Learning and Physical Similarity-based Regionalization of Calibration Parameters. ENVIRONMENTAL MODELLING & SOFTWARE. Elsevier Science, New York, NY, 186: 106335, (2025).