This U.S. Geological Survey data release presents monthly evaporation estimates from Lake Mead, Nevada and Arizona. Data are updated approximately annually. The spreadsheet includes five worksheets: (1) Read_Me worksheet contains information relevant to understanding the data contained in the rest of the worksheets. (2) Monthly_EC_Met worksheet includes data measured at a land-based station (USGS site identification number 360500114465601) using primarily eddy covariance measurement methods: uncorrected evaporation, latent- and sensible-heat fluxes, net radiation, air temperature, wind speed, and relative humidity. Values are monthly averages computed by averaging daily values except as noted. Monthly values are marked as estimated when a significant portion of daily values are estimated. (3) Monthly_Energy-Budget_Data worksheet includes computed data used to correct measured evaporation for energy balance. Computed data include monthly values for change in stored heat, net advection, turbulent flux, available energy, energy balance ratio, energy balance closure, and Bowen ratio. Change in stored heat was calculated based on methods in Earp and Moreo (2021). Net advection was calculated based on data estimated by the Bureau of Reclamation 24-Month Study (2022). Values are monthly averages or computed from monthly averages. (4) Annual_Energy_Balance worksheet includes annual averages of the Monthly_Energy_Balance data and the annual average values for energy-balance corrected sensible and latent heat fluxes. Values are annual averages or computed from annual averages. (5) Monthly_Evaporation_Estimates worksheet includes measured evaporation, corrected (most probable) evaporation, and energy balance ratio (EBR) adjusted evaporation, in feet. Values are monthly averages or computed from monthly averages. Data were processed according to methods described in Moreo and Swancar (2013) and Earp and Moreo (2021). References Cited: Bureau of Reclamation, Lower Colorado Region website: Operation Plan for Colorado River System Reservoirs (24-Month Study), accessed September 1, 2022 at https://www.usbr.gov/lc/region/g4000/24mo/index.html. Earp, K.J., and Moreo, M.T., 2021, Evaporation from Lake Mead and Lake Mohave, Nevada and Arizona, 2010–2019: U.S. Geological Survey Open-File Report 2021–1022, 36 p., https://doi.org/10.3133/ofr20211022. Moreo, M.T., and Swancar, A., 2013, Evaporation from Lake Mead, Nevada and Arizona, March 2010 through February 2012: U.S. Geological Survey Scientific Investigations Report 2013–5229, 40 p., http://dx.doi.org/10.3133/sir20135229.

Evaporation rates were measured at Lake Mead from March 2010 through February 2012 for phase 1 of an evaporation study (Moreo and Swancar, 2013). Phase 2 of the study (March 2012 through September 2017) continues evaporation measurements at Lake Mead and begins evaporation measurements at another lower Colorado River Basin reservoir, Lake Mohave. Eddy covariance is the primary measurement method. Data currently (10/6/2015) are being collected for the phase 2 study. This USGS data release represents tabular data in support of the evaporation study. The data release was produced in compliance with the new 'open data' requirements as way to make the scientific products associated with USGS research efforts and publications available to the public. The data release consists of 2 separate items: 1. Lake Mead evaporation data from March 2010 through April 2015 (Microsoft Excel workbook) 2. Lake Mohave evaporation data from May 2013 through April 2015 (Microsoft Excel workbook)

Evaporation rates were measured at Lake Mead from March 2010 through February 2012 for phase 1 of an evaporation study (Moreo and Swancar, 2013). Phase 2 of the study (March 2012 through September 2017) continues evaporation measurements at Lake Mead and begins evaporation measurements at another lower Colorado River Basin reservoir, Lake Mohave. Eddy covariance is the primary measurement method. Data currently (10/6/2015) are being collected for the phase 2 study. This USGS data release represents tabular data in support of the evaporation study. The data release was produced in compliance with the new 'open data' requirements as way to make the scientific products associated with USGS research efforts and publications available to the public. The data release consists of 2 separate items: 1. Lake Mead evaporation data from March 2010 through April 2015 (Microsoft Excel workbook) 2. Lake Mohave evaporation data from May 2013 through April 2015 (Microsoft Excel workbook)

In cooperation with the Bureau of Reclamation (Lower Colorado Region), the U.S. Geological Survey collected meteorological data from 4/22/2013 to 4/25/2017 at Lake Mead and 4/11/2013 to 9/30/2016 at Lake Mohave. Meteorological monitoring equipment were mounted to a floating platform located at each lake. The data presented in this data release includes 30-minute mean air temperature, relative humidity, wind speed and direction, water surface temperature, net radiation, and incoming solar radiation. Quality assurance consisted of (1) monthly site visits to inspect and clean sensors, (2) recalibrating each sensor as necessary according to manufacturer guidelines, and (3) manual and graphical analysis for out-of-range values and anomalous patterns. Net radiation data were corrected for sensitivity to wind speed (Campbell Scientific, Inc, 2016) and calibrated following the procedures outlined in Moreo and Swancar (2013, p. 7-10). Meteorological data were collected in support of ongoing evaporation research at both lakes.

In cooperation with the Bureau of Reclamation (Lower Colorado Region), the U.S. Geological Survey collected meteorological data from 4/22/2013 to 4/25/2017 at Lake Mead and 4/11/2013 to 9/30/2016 at Lake Mohave. Meteorological monitoring equipment were mounted to a floating platform located at each lake. The data presented in this data release includes 30-minute mean air temperature, relative humidity, wind speed and direction, water surface temperature, net radiation, and incoming solar radiation. Quality assurance consisted of (1) monthly site visits to inspect and clean sensors, (2) recalibrating each sensor as necessary according to manufacturer guidelines, and (3) manual and graphical analysis for out-of-range values and anomalous patterns. Net radiation data were corrected for sensitivity to wind speed (Campbell Scientific, Inc, 2016) and calibrated following the procedures outlined in Moreo and Swancar (2013, p. 7-10). Meteorological data were collected in support of ongoing evaporation research at both lakes.

Actual evapotranspiration (ETa) values estimated for specified areas including 1) total county areas; 2) potentially irrigated areas within each county; and 3) mapped extents of irrigated lands within each county provided by some states. These ETa estimates were provided to the USGS National Water Use Science Project by the USGS Earth Resources Observation and Science (EROS) Center (Gabriel Senay and MacKenzie Friedrichs, written communication, 2/20/2017) and are based on 1-square kilometer resolution 2015 Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data analyzed through the operational Simplified Surface Energy Balance (SSEBop) model using methods of Senay and others (2013). Reference: Senay, G.B., Bohms, S., Singh, R.K., Gowda, P.H., Velpuri, N.M., Alemu, H., and Verdin, J.P., 2013, Operational evapotranspiration mapping using remote sensing and weather datasets: A new parameterization for the SSEB approach; Journal of the American Water Resources Association, 49 (2013), pp. 577–591.

Actual evapotranspiration (ETa) values estimated for specified areas including 1) total county areas; 2) potentially irrigated areas within each county; and 3) mapped extents of irrigated lands within each county provided by some states. These ETa estimates were provided to the USGS National Water Use Science Project by the USGS Earth Resources Observation and Science (EROS) Center (Gabriel Senay and MacKenzie Friedrichs, written communication, 2/20/2017) and are based on 1-square kilometer resolution 2015 Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data analyzed through the operational Simplified Surface Energy Balance (SSEBop) model using methods of Senay and others (2013). Reference: Senay, G.B., Bohms, S., Singh, R.K., Gowda, P.H., Velpuri, N.M., Alemu, H., and Verdin, J.P., 2013, Operational evapotranspiration mapping using remote sensing and weather datasets: A new parameterization for the SSEB approach; Journal of the American Water Resources Association, 49 (2013), pp. 577–591.

This USGS data release represents supplemental tabular data for an annual groundwater discharge by evapotranspiration (ET) from areas of spring-fed riparian vegetation, Stump Spring and Hiko Springs, Clark County, Nevada, 2016-18. The raw ET dataset contained multiple data gaps that were simulated and gap-filled with the water-level model utility in SeriesSEE, a USGS developed Microsoft Excel® addin. Continuous time-series data, including net radiation, sensible-heat flux, latent-heat flux, and ground-heat flux, from before and after the data gap(s) were used to simulate turbulent fluxes with multivariate regressions and the gramma transform, used for latent heat gaps after precipitation events. ET data were gap filled using methods outlined in A process to estimate net infiltration using a site-scale water-budget approach, Rainier Mesa, Nevada National Security Site, Nevada, 2002–05. Data used to simulate gap periods for Stump Spring and Hiko Springs were acquired from USGS ET stations 364555117412401 and 355846116160401, respectively. This release consists of the following: (1) inventory of latent-heat flux, sensible-heat flux gap-filled periods, and model goodness-of-fit, Stump Springs, Clark County, NV, 2016, (2) inventory of net radiation, latent-heat flux, sensible-heat flux, ground-heat flux gap-filled periods, and model goodness-of-fit, Hiko Springs, Clark County, NV, 2017-18, (3) gap-filled latent-heat flux and sensible-heat flux data, Stump Spring evapotranspiration station, Clark County, NV, 2016, and (4) gap-filled net radiation, latent-heat flux, sensible-heat flux, and ground-heat flux, Hiko Springs evapotranspiration station, Clark County, NV, 2017-18.

This USGS data release represents supplemental tabular data for an annual groundwater discharge by evapotranspiration (ET) from areas of spring-fed riparian vegetation, Stump Spring and Hiko Springs, Clark County, Nevada, 2016-18. The raw ET dataset contained multiple data gaps that were simulated and gap-filled with the water-level model utility in SeriesSEE, a USGS developed Microsoft Excel® addin. Continuous time-series data, including net radiation, sensible-heat flux, latent-heat flux, and ground-heat flux, from before and after the data gap(s) were used to simulate turbulent fluxes with multivariate regressions and the gramma transform, used for latent heat gaps after precipitation events. ET data were gap filled using methods outlined in A process to estimate net infiltration using a site-scale water-budget approach, Rainier Mesa, Nevada National Security Site, Nevada, 2002–05. Data used to simulate gap periods for Stump Spring and Hiko Springs were acquired from USGS ET stations 364555117412401 and 355846116160401, respectively. This release consists of the following: (1) inventory of latent-heat flux, sensible-heat flux gap-filled periods, and model goodness-of-fit, Stump Springs, Clark County, NV, 2016, (2) inventory of net radiation, latent-heat flux, sensible-heat flux, ground-heat flux gap-filled periods, and model goodness-of-fit, Hiko Springs, Clark County, NV, 2017-18, (3) gap-filled latent-heat flux and sensible-heat flux data, Stump Spring evapotranspiration station, Clark County, NV, 2016, and (4) gap-filled net radiation, latent-heat flux, sensible-heat flux, and ground-heat flux, Hiko Springs evapotranspiration station, Clark County, NV, 2017-18.

The supplemental data presented here contains raster data in .tif format of the empirically estimated mean annual (1987-2015) net evapotranspiration (ETnet) for the Harney Basin Groundwater Evapotranspiration Area. The final mean annual ETnet estimate for the Harney Basin was determined using both empirical and physics-based methods. The final ETnet estimate was combined with additional data to estimate groundwater discharge through evapotranspiration (ET) in the Harney Basin. See Garcia and others (2022) for a detailed description of how these data were estimated and evaluated.