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)

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.

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.

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.

This report presents hydrometeorological observations and estimates of reservoir evaporation from two monitoring locations at Lake Powell from November 2018 to December 2021. We compare evaporation estimates from two independent methods, aerodynamic mass transfer and eddy covariance, to provide updated reservoir evaporation estimates based on best available science and methodologies.

This Excel workbook contains evapotranspiration (ET) data measured at two field sites near Bridgeport, California, from June 2012 through September 2013. One site consisted of irrigated dense pasture grass and was labeled as the Bridgeport high-density vegetation site (BPHV). The second site consisted of drier pasture grasses with patches of bare soil and was labeled as the Bridgeport low-density vegetation site (BPLV). The data measured include net radiation, latent heat flux, sensible heat flux, soil heat flux, soil water content, air temperature,water vapor density, wind speed, wind direction, and precipitation. The data are aggregated to a 30-minute interval and presented in four worksheets: two for each site, one containing tabular data and one containing data plots. There is an additional worksheet that gives a brief description of the field sites and data collection methods.

This Excel workbook contains evapotranspiration (ET) data measured at two field sites near Bridgeport, California, from June 2012 through September 2013. One site consisted of irrigated dense pasture grass and was labeled as the Bridgeport high-density vegetation site (BPHV). The second site consisted of drier pasture grasses with patches of bare soil and was labeled as the Bridgeport low-density vegetation site (BPLV). The data measured include net radiation, latent heat flux, sensible heat flux, soil heat flux, soil water content, air temperature,water vapor density, wind speed, wind direction, and precipitation. The data are aggregated to a 30-minute interval and presented in four worksheets: two for each site, one containing tabular data and one containing data plots. There is an additional worksheet that gives a brief description of the field sites and data collection methods.

This data set consists of 1:1,000,000-scale areas where shallow ground water is consumed by evapotranspiration (ET) in the Great Basin. The source of this data set is sheet 2 of a 1988 U.S. Geological Survey hydrologic investigations atlas map (Harrill and others, 1988.) Reference Cited Harrill, J.R., Gates, J.S., and Thomas, J.M., 1988, Major ground-water flow systems in the Great Basin region of Nevada, Utah, and adjacent states: U.S. Geological Survey Hydrologic Investigations Atlas HA-694-C, scale 1:1,000,000, 2 sheets.

Daily evaporation rates were calculated at the open-water LZ40-platform in the interior of Lake Okeechobee, Florida, from December 1, 2012 through December 31, 2016 using five methods (Shoemaker et al., 2024); specifically, the Penman, Priestly-Taylor, Mass-Transfer, Simple, and Turc equations. Bowen-ratio energy-budget derived daily evaporation rates calculated from micro-meteorological data at the LZ40 site (Wacker, 2020) are considered a standard by which to evaluate the five alternative evaporation methods. Parameterization of each of method and comparison of evaporation using each of the five methods to the Bowen ratio estimates are published by Shoemaker and others (2024).