...

1. Again, go back to the Raster Calculator tool. Delete the previous expression.
2. In the list of 'Rasters’, double-click the DEMft layer.
3. In the calculator, double-click the <= button.
4. In the equation box, type “15”.
5. For ‘Output raster’, rename the raster from “demft_raster” to “Flood15ft”.
6. Ensure your ‘Raster Calculator’ window appears as shown below and click Run.
   
   
   
7. Close Geoprocessing pane.
8. 
   
9. Right-click the Flood15ft layer. Click Symbology.
10. In the table of values, right-click the 0 value and click Remove.
    
    
    
    
11. Click the rectangle symbol to the left of the 1 value and select Blue.
    
    
12. Save your project.

...

1. Rename “ANN-PRCP-NORMAL” to “ANNPRCPHI”“ANNPRCPHI”, for annual precipitation in hundredths of inches.
2. Along the top of the worksheet, drag across the column letters to select columns A through H.
3. Copy the columns. Along the bottom of the worksheet, click the "plus" icon to create a new sheet. In the A1 cell, paste your previously copied columns. 
4. Delete the previous sheet. 
5. Along the top of the worksheet, drag across the column letters to select columns A through H.
6. Hover your mouse between columns G and H until the cursor changes to two outward facing arrows and double-click to auto-size the column widths.
7. At the bottom left of the worksheet, rename the worksheet “PrecipStations”.
8. Click the File menu and select Save As.
9. Navigate to your Lab 1HydrologyLab folder.
10. For ‘File name:’, type PrecipStations.
11. Use the ‘Save as type:’ drop-down menu to select Excel 97-2003 Workbook.
12. Click Save.
13. Close Excel.

Displaying XY data

Now you are ready to start a new map document and display the tabular rain gage data you just downloaded.

1. Return to ArcGIS Pro.
2. Click the Insert menu and select New Map…Map.
3. Click “Map1” in the contents pane to rename it as “Lab2Precip”. Click Save.
4. Drag Watersheds_Stateplane onto the map display.
5. Click the Geoprocessing tab and search for ‘Excel to Table’.
6. For the Input Excel File, selectPrecipStations. Rename the output table PrecipStations.
7. Click Run.
8. In the Contents pane, right-click the PrecipStations table and select Display XY Data.
9. For ‘X Field:’, select the LONGITUDE field.
10. For ‘Y Field:’, select the LATITUDE field.
11. Click the Atlas to the right of the Spatial Reference box.

...

1. Next to ‘Output feature class’, click the Browse button.
2. Navigate to the HydrologyLab geodatabase.
3. Double-click your HydrologyLab geodatabase to save your feature class in it.
4. For ‘Name:’, type “PrecipStations_Features” and click Save.
   
   
   
   
5. Click Run.

Since you are now using a permanent feature class, you may remove your temporary Events layer and the corresponding Excel table.

1. Right-click the PrecipStations_Layer layer and select Remove.
2. Right-click the PrecipStations table and select Remove.

Projecting vector data

...

1. In the Contents pane, Ctrl-select the PrecipStations_StatePlane and Watersheds_StatePlane layers.
2. Right-click either selected layer and select Zoom To Layers.
3. Open Geoprocessing pane by clicking Tools from Analysis tab.
4. Double-click the Analysis toolbox  then the Proximity toolset then the Create Thiessen Polygons tool.

...

1. At the top of the Geoprocessing window, click the Environments button tab on the right.
2. For Extent, use the drop-down menu to select Current Display Extent and go back to Parameters.
3. For ‘Input Features’, drag in the PrecipStations_StatePlane layer.
4. For ‘Output Feature Class’, rename the feature class from “PrecipStations“PrecipStations_StatePlane_Cr” to “PrecipThiessen”Cr” to “PrecipThiessen”.
5. Use the ‘Output Fields’ drop-down menu to select All All fields.
6. Ensure your ‘Create Thiessen Polygons’ window appears as shown below and click Run.
   
   
   

You will notice that polygons now fill the entire Map Display indicating which areas are closest to which rain gages.

1. Open the PrecipThiessen layer attribute table.

Notice that all of the fields that you originally downloaded from CDO are still included, because you selected to output all fields when running the Create Thiessen Polygons tool. If you do not see all of the same fields, re-run the tool and this time output all fields.

1. Close the Table.

Intersecting two polygon layers

...

1. In the Analysis Tools toolbox, click the Overlay toolset then the Intersect tool.
2. For ‘Input Features’, drag in the PrecipThiessen and the Watersheds_StatePlane layers.
3. For ‘Output Feature Class’, rename it from “PrecipThiessen_Intersect” to “ThiessenWatershedIntersect”.
4. Ensure your ‘Intersect’ window appears as shown below and click Run.
   
   
   
   
5. Remove the PrecipThiessen layer from the Contents pane.
6. Zoom to the ThiessenWatershedIntersect layer.

The resulting layer integrates all of the boundaries from both the Thiessen polygons and the watersheds, limited to the extent of their overlap.

1. Open the ThiessenWatershedIntersect layer attribute table.
   
   Notice that the original 8 watersheds have now been divided into 42 sections indicating which areas of each watershed are closest to each rain gage. Let P_k denote the annual precipitation associated with each rain gage and A_ik denote the area of the intersected polygon associated with rain gage _k and watershed _i. The area weighted precipitation associated with each watershed is
   
   
   You will add a new field to the table to calculate the elements of the numerator of the equation.|
   
   
2. Click Add Field… button on top of the table display.
   
   
   
   
3. For ‘Name:’, type “APProd”.
4. Use the ‘Type:’, drop-down menu to select Double and click Save on the Fields tab.
   
   
   
   
5. Right-click the APProd field name and select Calculate Field.
6. Using the fields and buttons or by typing, enter “!ANNPRCPHI! * !Shape_Area!”.

7. Ensure your ‘Field Calculator’ appears as shown below and click Run.

   

1. Right-click the HU_10_NAME field name and select Summarize….

2. For statistics fields, use the drop-down menu to select the Shape_Area field and select Sum.

3. Select the APProd field and select Sum.
4. For ‘Output Table’, rename the table from “ThiessenWatershedInteract_St” to “WatershedPrecip”.
5. Ensure your ‘Summarize’ window appears as shown below and click Run.
   
   
   
   

The resulting table gives the numerator and denominator in the equation for each watershed.

1. Open the WatershedPrecip table.

...

1. Turn off the ThiessenWatershedIntersect layer.
2. Right-click the Watersheds_StatePlane layer and select Zoom to Layer.
3. Open Toolbox.
4. In the Spatial Analyst Tools toolbox, click the Interpolation toolset then the Spline tool.
5. On the top of the window, click the Environments.
6. For Extent, use the drop-down menu to select Current Display Extent.
7. Use the ‘Mask’ drop-down menu to select the Watersheds_StatePlane layer.
8. Go back to Parameters. For ‘Input point features’, drag in the PrecipStations_StatePlane layer.
9. Use the ‘Z value field’ drop-down menu to select the ANNPRCPHI field that contains the values you wish to interpolate.
10. For ‘Output raster’, rename the exported raster from “Spline_Preci1” to “AnnPrecip”.
11. Use the ‘Spline type’ drop-down menu to select TENSION.
12.  Ensure your ‘Spline’ window appears as shown below, and click Run.
    
    
    
    

The result is a solid surface estimating the rainfall at each cell, based on the data collected at each rain gage. Turn the Thiessen polygons back on to give them a hollow fill. Symbolize the rain gages as you desire.

...

FOR MAP LAYOUT TO BE TURNED IN

Create an 8.5 x 11 layout showing the Thiessen polygon boundaries, interpolated rainfall layer and rain gage locations.

...

Create a table containing the total annual precipitation for each watershed, as calculated using the spline interpolation method, along with the total annual precipitation over the entire subbasin. 

Deliverables

1. Create an 8.5 x 11 layout showing the DEM clipped to the subbasin with areas less than or equal to 15 feet in elevation highlighted.
2. Create an 8.5 x 11 layout showing transparent elevation in graduated colors on top of a hillshade, with watershed boundaries and flowlines visible.
3. Create a table highlighting the minimum and maximum values for the minimum, maximum, range, mean, and standard deviation of all elevation values within each watershed.
4. Create a table containing the weighted mean annual precipitation for each watershed, as calculated using Thiessen polygons, along with the total mean annual precipitation over the entire subbasin.
5. Create an 8.5 x 11 layout showing the Thiessen polygon boundaries, interpolated rainfall layer, and rain gage locations.
6. Create a table containing the total annual precipitation for each watershed, as calculated using the spline interpolation method, along with the total annual precipitation over the entire subbasin.