This dataset includes 1km resolution monthly timescale estimates of evapotranspiration (ET) for the 2000-2015 timespan. These new SSEBop-WB estimates were developed by combining a previously published long-term annual average evapotranspiration map based on water balance constraints with the SSEBop remote sensing ET product (see Associated Items). The combination aims to leverage the advantages of each approach in gaining both the temporal resolution of remote sensing data and the long-term magnitude constraints of ground-based data. This data release also includes other supporting data associated with the publication of these estimation methods in a concurrent journal article. Analyses in the journal article included comparisons between SSEBop ET, the MOD16 remote sensing ET product, and the new SSEBop-WB ET in a variety of settings against ET data from 119 flux towers across the U.S. Residuals between the remote sensing methods and the flux tower data were mapped spatially, and these maps are included in the data release as well. The methods are fully described in the forthcoming article accepted for publication in Remote Sensing as of November 2017; this dataset will be updated with its full citation when available. See also the metadata file for additional information, or contact the authors with questions.

This USGS data release is a result of using the OpenET Google Earth Engine (GEE) implementation of the USGS EROS Operational Simplified Surface Energy Balance (SSEBop, Senay and others, 2013; Senay and others, 2023) Evapotranspiration (ET) model to create Actual ET (ETa) estimates from remote sensing data at 30-m spatial resolution, supporting spatiotemporal ET coupling analysis with the USGS National Hydrologic Model (NHM; Regan and others, 2019). The results are Landsat-based monthly products generated from satellite imagery with <60% cloud cover and made available as a raster image collection from 2000-2020 for the conterminous United States (CONUS). SSEBop derivatives were used within the NHM to estimate consumptive use and effective precipitation on irrigated lands. Data products are spatially constrained and provided via modified Military Grid Reference System (MGRS) tiles which is based on the Universal Transverse Mercator (UTM) projection. Please refer to the Supplemental Information element of this metadata record for further information on this data.

Actual evapotranspiration (AET) annual rates, from 2000 to 2017, for the Simplified Surface Energy Balance operational (SSEBop) method and from 2000 to 2016 for the land-cover based method, provided in shapefiles AET_SJR_Basin_Cells, are explained in the metadata file AET_SJR_Basins. The calculation of the annual average AET rates using a water-budget analysis (WBA) is explained in this metadata file referring to csv files for the eight basins in east-central and northeast Florida. A comparison of the average annual SSEBop AET rates and those derived from the WBA is then possible by using the average annual AET rates for each basin. The eight basins for which the WBA analysis was completed are: 1. St. Johns near Christmas basin (number 02232500), 2. Econlockhatchee River basin (number 02233484), 3. Wekiva River basin (number 02235000), 4. Eau Gallie River basin (number 02249007), 5. South Prong at St. Sebastian River basin (number 02251000), 6. Black Creek basin (number 02245500), 7. North Fork Black Creek basin (number 02246000), and 8. Deep Creek basin (number 02245260). The locations of these basins are shown in the shapefiles AET_SJR_Basin_Cells. Average annual rainfall (Rainfall), average annual net stream outflow (NetOutflow), average annual downward leakage from the surficial aquifer (Leakage) to the underlying hydrogeologic unit, net annual changes in storage calculated from measured water levels in surficial aquifer wells (Sy*dh/dt), and total annual return flow to land surface through irrigation and other water uses (Return_Flow) for all 8 basins were used to calculate the AET from the water-budget balance equation WB_AET = Rainfall – NetOutflow – Leakage -Sy*dh/dt + Return_Flow. Note that parameter Leakage is negative for discharge areas of the surficial aquifer. The results of the WBA method provided average annual AET rates for each basin, which can be compared with calculated annual averages from the SSEBop method for each entire basin, all rates in inches per year. The Return Flow estimates were obtained from the publication Marella, R.L., 2014, Water withdrawals, use, and trends in Florida, 2010: U.S. Geological Survey Scientific Investigations Report 2014-5088, 59 p., http://dx.doi.org/10.3133/sir20145088.

Actual evapotranspiration (AET) annual rates, from 2000 to 2017, for the Simplified Surface Energy Balance operational (SSEBop) method and from 2000 to 2016 for the land-cover based method, provided in shapefiles AET_SJR_Basin_Cells, are explained in the metadata file AET_SJR_Basins. The calculation of the annual average AET rates using a water-budget analysis (WBA) is explained in this metadata file referring to csv files for the eight basins in east-central and northeast Florida. A comparison of the average annual SSEBop AET rates and those derived from the WBA is then possible by using the average annual AET rates for each basin. The eight basins for which the WBA analysis was completed are: 1. St. Johns near Christmas basin (number 02232500), 2. Econlockhatchee River basin (number 02233484), 3. Wekiva River basin (number 02235000), 4. Eau Gallie River basin (number 02249007), 5. South Prong at St. Sebastian River basin (number 02251000), 6. Black Creek basin (number 02245500), 7. North Fork Black Creek basin (number 02246000), and 8. Deep Creek basin (number 02245260). The locations of these basins are shown in the shapefiles AET_SJR_Basin_Cells. Average annual rainfall (Rainfall), average annual net stream outflow (NetOutflow), average annual downward leakage from the surficial aquifer (Leakage) to the underlying hydrogeologic unit, net annual changes in storage calculated from measured water levels in surficial aquifer wells (Sy*dh/dt), and total annual return flow to land surface through irrigation and other water uses (Return_Flow) for all 8 basins were used to calculate the AET from the water-budget balance equation WB_AET = Rainfall – NetOutflow – Leakage -Sy*dh/dt + Return_Flow. Note that parameter Leakage is negative for discharge areas of the surficial aquifer. The results of the WBA method provided average annual AET rates for each basin, which can be compared with calculated annual averages from the SSEBop method for each entire basin, all rates in inches per year. The Return Flow estimates were obtained from the publication Marella, R.L., 2014, Water withdrawals, use, and trends in Florida, 2010: U.S. Geological Survey Scientific Investigations Report 2014-5088, 59 p., http://dx.doi.org/10.3133/sir20145088.

On vegetated landscapes, Evapotranspiration (ET) can be simplified as the combination of evaporation from the soil and transpiration from vegetation. Actual ET (ETa) is produced using the Operational Simplified Surface Energy Balance (SSEBop) model Version 6 (Senay et al., 2013, 2020, 2023) from 2012 to Present using a data stream from the Visible Infrared Imaging Radiometer Suite (VIIRS) aboard the NASA/NOAA Suomi National Polar-Orbiting Partnership (Suomi NPP) and NOAA-20 satellites. The SSEBop model is a thermal-based simplified surface energy model for estimating ETa based on the principles of satellite psychrometry (Senay, 2018). SSEBop Version 6 implementation uses land surface temperature (Ts) from VIIRS with key model parameters (cold/wet-bulb reference, Tc, and surface psychrometric constant, 1/dT) derived from a combination of observed surface temperature, normalized difference vegetation index (NDVI), climatological average daily maximum air temperature (Ta, 1-km) from Daymet and CHELSA, and net radiation data from ERA-5. SSEBop Version 6 also uses the Forcing And Normalizing Operation (FANO), a novel parameterization to better estimate ET in all landscapes and all seasons regardless of vegetation cover density, thereby improving model accuracy by avoiding extrapolation of Tc to non-calibration regions (Senay et al., 2023). Final ETa is generated as a product of ET fractions generated from remotely sensed VIIRS thermal imagery, summarized every dekad (~10 days) with reference ET generated from weather data fields using the Penman-Monteith Equation (TerraClimate and CSIRO-based datasets). ETa data and anomaly products (current vs. 2013 – 2022 median), produced at 1 km resolution, are available at: https://earlywarning.usgs.gov/fews.

On vegetated landscapes, Evapotranspiration (ET) can be simplified as the combination of evaporation from the soil and transpiration from vegetation. Actual ET (ETa) is produced using the Operational Simplified Surface Energy Balance (SSEBop) model Version 6 (Senay et al., 2013, 2020, 2023) from 2012 to Present using a data stream from the Visible Infrared Imaging Radiometer Suite (VIIRS) aboard the NASA/NOAA Suomi National Polar-Orbiting Partnership (Suomi NPP) and NOAA-20 satellites. The SSEBop model is a thermal-based simplified surface energy model for estimating ETa based on the principles of satellite psychrometry (Senay, 2018). SSEBop Version 6 implementation uses land surface temperature (Ts) from VIIRS with key model parameters (cold/wet-bulb reference, Tc, and surface psychrometric constant, 1/dT) derived from a combination of observed surface temperature, normalized difference vegetation index (NDVI), climatological average daily maximum air temperature (Ta, 1-km) from Daymet and CHELSA, and net radiation data from ERA-5. SSEBop Version 6 also uses the Forcing And Normalizing Operation (FANO), a novel parameterization to better estimate ET in all landscapes and all seasons regardless of vegetation cover density, thereby improving model accuracy by avoiding extrapolation of Tc to non-calibration regions (Senay et al., 2023). Final ETa is generated as a product of ET fractions generated from remotely sensed VIIRS thermal imagery, summarized every dekad (~10 days) with reference ET generated from weather data fields using the Penman-Monteith Equation (TerraClimate and CSIRO-based datasets). ETa data and anomaly products (current vs. 2013 – 2022 median), produced at 1 km resolution, are available at: https://earlywarning.usgs.gov/fews.

Actual evapotranspiration (ETa) rates from the Operational Simplified Surface Energy Balance (SSEBop) method, before and after bias corrections (Sepúlveda, 2021), are presented for basins located wholly or partially within the Suwannee River Water Management District (SRWMD) and parts of Georgia. The SSEBop annual rates are provided at about a one square-kilometer scale from 2000 to 2017. Annual ETa rates calculated from the application of the water-balance method (wbETa) to 6 basins in the SRWMD and annual land-use ETa (luETa) rates calculated from monthly average crop coefficient ratios are also provided in this data set. A GIS shapefile provides land-use type and annual ETa rate for each year of record. Data are tabulated in spreadsheets for each basin and are referred to by the name between parenthesis: Alapaha River basin (Alapaha), Withlacoochee River – SRWMD basin (Withla_SRWMD), Upper Suwannee River basin (Upper_Suwannee), Santa Fe River basin (Santa_Fe), Suwannee River basin (Suwannee_River), and Aucilla River basin (Aucilla). Inflows and outflows from various sources in the water-balance equation used to calculate annual average wbETa rates for each basin in the SRWMD area are presented in this dataset.

Actual evapotranspiration (ETa) rates from the Operational Simplified Surface Energy Balance (SSEBop) method, before and after bias corrections (Sepúlveda, 2021), are presented for basins located wholly or partially within the Suwannee River Water Management District (SRWMD) and parts of Georgia. The SSEBop annual rates are provided at about a one square-kilometer scale from 2000 to 2017. Annual ETa rates calculated from the application of the water-balance method (wbETa) to 6 basins in the SRWMD and annual land-use ETa (luETa) rates calculated from monthly average crop coefficient ratios are also provided in this data set. A GIS shapefile provides land-use type and annual ETa rate for each year of record. Data are tabulated in spreadsheets for each basin and are referred to by the name between parenthesis: Alapaha River basin (Alapaha), Withlacoochee River – SRWMD basin (Withla_SRWMD), Upper Suwannee River basin (Upper_Suwannee), Santa Fe River basin (Santa_Fe), Suwannee River basin (Suwannee_River), and Aucilla River basin (Aucilla). Inflows and outflows from various sources in the water-balance equation used to calculate annual average wbETa rates for each basin in the SRWMD area are presented in this dataset.

Actual evapotranspiration (ETa) rates from the Operational Simplified Surface Energy Balance (SSEBop) method, before and after bias corrections (Sepúlveda, 2021), are presented for basins located wholly or partially within the Southwest Florida Water Management District (SWFWMD). The SSEBop annual rates are provided at about a one square-kilometer scale from 2000 to 2017. Annual ETa rates calculated from the application of the water-balance method (wbETa) to 12 basins in the SWFWMD and annual land-use ETa (luETa) rates calculated from monthly average crop coefficient ratios are also provided in this data set. A GIS shapefile provides land-use type and annual ETa rate for each year of record. Data are tabulated in spreadsheets for each basin and are referred to by the name between parenthesis: Peace Creek Canal – Brush Lake basin (02293987), Saddle Creek at SR 542 near Lakeland basin (02294217), Joshua Creek at Nocatee-Honey Run basin (02297100), Prairie Creek at Fort Ogden basin (02298123), Shell Creek nr Punta Gorda basin (02298202), Myakka River near Sarasota basin (02298830), Big Slough at Tropicaire Blvd basin (02299450), Manatee River at Fort Hamer basin (02300021), Jumper Creek Canal near Bushnell basin (02312640), Panasoffkee Lake basin (02312700), Withlacoochee River near Holder basin (02313000), and Withlacoochee River Inglis & Bypass basin (02313230). Inflows and outflows from various sources in the water-balance equation used to calculate annual average wbETa rates for each basin in the SWFWMD area are presented in this dataset.

Actual evapotranspiration (ETa) rates from the Operational Simplified Surface Energy Balance (SSEBop) method, before and after bias corrections (Sepúlveda, 2021), are presented for basins located wholly or partially within the Southwest Florida Water Management District (SWFWMD). The SSEBop annual rates are provided at about a one square-kilometer scale from 2000 to 2017. Annual ETa rates calculated from the application of the water-balance method (wbETa) to 12 basins in the SWFWMD and annual land-use ETa (luETa) rates calculated from monthly average crop coefficient ratios are also provided in this data set. A GIS shapefile provides land-use type and annual ETa rate for each year of record. Data are tabulated in spreadsheets for each basin and are referred to by the name between parenthesis: Peace Creek Canal – Brush Lake basin (02293987), Saddle Creek at SR 542 near Lakeland basin (02294217), Joshua Creek at Nocatee-Honey Run basin (02297100), Prairie Creek at Fort Ogden basin (02298123), Shell Creek nr Punta Gorda basin (02298202), Myakka River near Sarasota basin (02298830), Big Slough at Tropicaire Blvd basin (02299450), Manatee River at Fort Hamer basin (02300021), Jumper Creek Canal near Bushnell basin (02312640), Panasoffkee Lake basin (02312700), Withlacoochee River near Holder basin (02313000), and Withlacoochee River Inglis & Bypass basin (02313230). Inflows and outflows from various sources in the water-balance equation used to calculate annual average wbETa rates for each basin in the SWFWMD area are presented in this dataset.