Average annual Actual Evapotranspiration (AET) rates for basins in east-central and northeast Florida from 2000 to 2017 were calculated using a water-budget balance equation. These AET rates are used to assess the reliability of the AET rates calculated using the Simplified Surface Energy Balance operational (SSEBop) method. The 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 method were provided in the shapefile AET_SJR_Basin_Cells, explained in the metadata file AET_SJR_Basins.
Measured AET monthly rates in file AET_Monthly_Totals.csv were calculated at these ET monitoring stations in central and east-central Florida: Duda Farms, Blue Cypress, Reedy Lake, Orlando Urban, Disney Preserve, Lyonia Preserve. The monthly AET rates measured at these sites are compared side by side with the monthly AET rates calculated using the SSEBop method. The SSEBop AET rates were obtained from Gabriel Senay, one of the authors of Savoca and others, 2013, where the SSEBop methodology is explained. The measured AET monthly rates at the ET sites are presented as another way to assess the reliability of the SSEBop AET rates. The Florida ET network grid pixel numbers used for this comparison are: Duda Farms - pixel 106578, Blue Cypress - pixel 91413, Reedy Lake - pixel 92321, Orlando Urban - pixel 115088, Disney Preserve - pixel 100383, and Lyonia Preserve - pixel 123618. The AET rates under the SSEBop fields were used to validate the rates by comparing them to the measured AET rates at the ET stations.
The calculation of the annual average AET rates using a water-budget analysis (WBA) is presented in the metadata file WB_8_Basins.xml and the AET rates are presented in csv files for each of the eight basins in east-central and northeast Florida. A comparison of the average annual SSEBop AET rates and those derived from the WBA shows the overall average annual differences is consistently less than 10 percent for all eight basins. 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 shapefile 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 estimated from water use data published in 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.