I certainly appreciate the time and effort that Mr. Barceló put into responding to my questions, but the question of accuracy has never been addressed.
How accurate does a model need to be to be useful in meeting its intended function? Back in 1994 the USGS published report 94-4254 with the title “Analysis and Simulation of Ground-Water Flow in Lake Wales Ridge and Adjacent Areas of Central Florida”. In that study, residuals were established such that 68 percent of all simulated heads must be within plus or minus 2 feet of observed surficial aquifer heads and lake levels. Intermediate and Upper Floridan Aquifer heads were to be within plus or minus 5 feet of observed levels.
The stated calibration goals for the ECFTX model is 50 percent of the wells are to have a residual within plus or minus 2.5 feet. There are no stated goals for lake levels.
So based on the above, it would appear that calibration goals are somewhat arbitrary as there is considerable difference between the two examples listed.
Back when I first heard about the ECFT model I was very excited. I thought finally we would have a very scientific way of managing our water resources. I have researched modeling efforts and I now know that models are a very good planning level (conceptual) tool, but they are not accurate enough to be all that useful. I fully support the development of hydraulic models, but we must be very careful in how the results are used. When you consider how complex the groundwater system is and how little actual information there is to provide "real" input data for each model "grid" it's no wonder that a "success" is measured with a water level difference of up to 5 feet between observation points.
The final model report must clearly state its level of uncertainty, its capabilities and the additional work that will be required to improve the model's accuracy.
In the introductory section of the USGS report for the ECFT model, Mr. Sepulveda lists the following: "The purpose of this report is to describe the hydrologic flow system and water budget in east-central Florida (fig. 1) from 1995 to 2006, a time period associated with a wide range in hydrologic conditions in east-central Florida. Specifically, this report documents the development of the groundwater flow model used to (1) refine the conceptual understanding of the water exchanges between the surficial aquifer system (SAS) and the FAS and (2) improve the estimates of the recharge rates to the SAS from infiltration through the unsaturated zone." Any other use of the model, as prepared by Mr. Sepulveda, would be outside of its intended scope.