Figure 1. Location of water-level gages in Everglades Depth Estimation Network (EDEN). Water Conservation Areas (WCA) 2 and 3 are subdivided by canals. WCA3A is further subdivided into a northern (WCA3AN) and a southern (WCA3AS) region (from Pearlstine and others, 2007). [larger image]

Figure 2. Example of Everglades Depth Estimation Network (EDEN) water-surface map for a (A) wet season day and (B) dry season day (from Pearlstine and others, 2007). Vertical datum is North American Vertical Datum of 1988. [larger image]

To increase the accuracy of the daily water-surface elevation model, linear regression equations to estimate missing data for each gaging station in EDEN were developed (Conrads and Petkewich, 2009). To minimize the occurrences of no estimation of data due to missing data for an input station, a minimum of three linear regression equations were developed for each station using different input stations. For each site, an order was established for the regression equation to be used to fill a data gap.

The 726 equations were incorporated into a database application that automatically estimates missing record (EDEN GAP). The performance statistics computed for each equation provides documentation of the "goodness-of-fit" of the equations (table 1). In addition, although the majority of the equations provide satisfactory estimations of water levels, the performance statistic provides a prioritization for identifying stations where improved equations are needed to provide more satisfactory water-level estimates.

Figure 3. Flow diagram showing the transmission, storage, processing, inferential sensing, and access of data from the water-level data collected in the field to website access by users (modified from Telis, 2006). [larger image]

The development of the EDEN Data Evaluation Program (EDEN DEP) is the first phase of a project to address these data validation issues by developing an intelligent software application to automate the validation and correction of the data. As shown in Figure 3, the software, hereafter referred to the Inferential Sensor, will reside between the National Water Information System (NWIS) server and EDEN web applications.

As part of Phase I of the development of the Inferential Sensor software, the EDEN DEP was developed to pre-process raw data to prepare it for automated analysis. A series of tunable filters were developed from the EDEN database and are used to evaluate the data for each site based on historical behaviors. Filters include thresholds based on historical values and user-specifications and time derivatives of rates of changes over specified periods

Other elements of EDEN DEP are:

• Import raw data
• Pre-process raw data to prepare it for automated analyses
• Validate raw data using a univariate filter analysis
• Provide for user review of the validated data
• Save validated data to a Microsoft ACCESS¹ database for use by 3^rd party programs

Data-quality evaluation and estimation of missing data can be a time-consuming process, especially for a network as large as EDEN with 253 gaging stations. To increase the accuracy of the daily water-surface elevation model, two applications were developed to address data-quality issues from the network. One program, EDEN GAP, estimates water levels to fill data gaps. The other program, EDEN DEP, uses a series of tunable filters to validate the data. The two programs effectively and efficiently address data-quality issues by automating many of the processes for data estimation and data validation and will improve the consistency and utility of the EDEN data.

Conrads, P.A., and Petkewich, M.D., 2009, Estimation of missing water-level data for the Everglades Depth Estimation Network (EDEN): U.S. Geological Survey Open-File Report 2009-1120, 53 p.

Pearlstine, L., Higer, A., Palaseanu, M., Fujisaki, I., and Mazzotti, F., 2007, Spatially continuous interpolation of water stage and water depths using the Everglades Depth Estimation Network (EDEN): Gainesville, Fl, Institute of Food and Agricultural, University of Florida, CIR 1521, 18 p., 2 apps.

Telis, Pamela A., 2006, The Everglades Depth Estimation Network (EDEN) for Support of Ecological and Biological Assessments: U.S. Geological Survey Fact Sheet 2006-3087, 4 p.