I. Introduction (Last Update: October 6, 2010)II. Solution Steps STEP 1: Adding Data ThemesSTEP 2: Merging Data Layers (Union)STEP 3: Calculating the Composite Score for Contamination PotentialSTEP 4: Setting Classification IntervalsSTEP 5: Formatting and Plotting the MapGEO/GY461 Applied GIS: EnvironmentalSRWMD ProjectI. Introduction (Last Update: October 6, 2010)For this project you will analyze several base maps containing polygons of numerical data withinseveral digitized map files. The data was collected to model the aquifer characteristics of theFloridan Aquifer system, one of the largest aquifer systems in North America. The base mapcovers the Suwannee River Water Management District (SRWMD), a state agency that monitorsground water quality in the region drained by the Suwannee river in north-central Florida. Thisregion stretches from just east of Tallahassee, Florida (west of Jefferson Co.) to nearGainesville, Florida (Alachua Co.). Your project will calculate the susceptibility of the aquifer tocontamination using four parameters: (1) Recharge, (2) Degree of confinement, (3) Aquiferthickness, and (4) the elevation of the potentiometric surface. From these values you are toderive a composite value that “scores” the potential of this aquifer to become contaminated bysurface infiltration. The higher the value of any of these parameters, the more likely thatcontamination will occur. The equation that calculates the composite value is listed below:composite = Thickness/10 + Confinement(1.25) + Recharge(1.75)+PotentiometricThe following rules are used for confinement classification:Unconfined = 30Semi-confined = 20Confined = 10Recharge classification rules:Range ValueNone 0.00-5 2.55-10 7.510-15 12.515-20 17.520-25 22.5All other parameter values are to be used in the above equation as they are recorded on the basemaps. The base maps have been constructed by assigning an average value to each polygon. Thenumerical value of each polygon thus formed will be a one-half contour interval value betweenthe two bounding contour lines. For example, if a polygon formed by contours of aquiferthickness had bounding values of 1100 and 1000 feet (contour interval = 100), the polygon valuewould be 1050 feet.Page -1-GEO/GY461 Applied GIS: EnvironmentalSRWMD ProjectII. Solution Steps The key to solving this problem, as with most any GIS problem, is organization. The followingsteps, if followed, should help you to remain organized while working toward a solution. Beloware the files that you will be working with for this problem. After downloading the project filearchive (http://www.usouthal.edu/geography/allison/gy461/SRWMD.exe), you should copy thesefiles to your own subdirectory before beginning the problem:aqthick.shp, aqthick.shx, aqthich.dbf, aqthick.prj These files contain a polygon coverage of f the average thickness of the Floridan aquifer in feetunits.Border.shp, border.shx, border.dbf, border.prj Files containing the SRWMD boundary.Conf.shp, conf.shx, conf.dbf, conf.prjFiles containing a polygon coverage of Floridan aquifer confinement rank.Countyboundaries.shp, countyboundaries.shx, countyboundaries.dbf, countyboundaries.prjFiles containing the various county borders that fall within the SRWMD region.Countynames.shp, countynames.shx, countynames.dbf, countynames.prjFiles containing the various county borders that fall within the SRWMD region.Potentio.shp, potentio.shx, potentio.dbf, potentio.prjFiles containing the aquifer potentiometric surface in units of feet above M.S.L.Recharge.shp, recharge.shx, recharge.dbf, recharge.prjFiles containing polygons ranked by recharge potential. Values of “none” mean that the aquifer isexposed at the surface. See the above rules for assigning numerical values to the polygons.All of the above files were digitized using the NAD1927 Florida North State Plane coordinatesystem, therefore units are feet.Using the above files, your goal will be to classify the entire SRWMD region based on the aboveequation. Because this equation calculates the degree to which the aquifer may be contaminatedby effluent products, the map that you construct will be a map of aquifer contaminationsusceptibility. The higher the value calculated by the equation, the more likely the aquifer will becontaminated by any effluent released at the surface or in a land fill. To apply the equation to theSRWMD map area, you must first combine all four layers of information into a compositePage -2-GEO/GY461 Applied GIS: EnvironmentalSRWMD Projectpolygon topology that preserves the four raw data values. From this file, you will then calculatethe composite score using the equation for each polygon. The “manual” equivalent of thisprocedure would be to overlay Mylar maps of all four data layers and trace all of the resultingpolygons on a fifth sheet. Each polygon on the fifth sheet would have four values from each ofthe data layers. We will use the GIS to overlay the four data layers producing the fifth layer ofcomposite polygons. Since there will be a large number of polygons in the final product, eachwill be ranked into one of seven categories that range from extremely low to extremely highscores of contamination potential. STEP 1: Adding Data ThemesThe first step in the process of producing the final product is to create a an ArcMap project filefor all four of the data themes. Start the ArcMap application and create a new blank project file. Figure 1 displays the appearance of the opening dialog window. Next, right-click on the“Layers” label in the left layer window and select “properties”. Under the “Coordinate System”tab select the Florida North State Plane coordinate system under the “Predefined Projectedcoordinates> NAD1927 Datum”. Figure 2 displays the dialog where the Florida North zoneSPCS is set. In the “General” tab set change the “Layers” title to “SRWMD AquiferContamination Project”. In addition, set the reference scale to 1:100,000. Now click on the “adddata” button in the main button bar. Use the “add data” toolbar button in the main menu to selectthe “aqthick, conf, recharge and potentio” data layers that contains the aquifer thickness, aquiferconfinement, aquifer recharge and aquifer potentiometric values respectively. All of these layersare polygon topologies. Figure 3 displays the appearance of the dialog activated by the “adddata” tool. Note that you can select all 4 layers and add them at the