GIS analyses

A geology map of the Upper Colorado River Basin was created by obtaining geology maps from Arizona, Colorado, New Mexico, Utah, and Wyoming. These maps were then clipped to the basin layer, and finally merged to the basin layer for one contiunous geology layer of the basin.

This layer was then reclassified to group all of the rock types shown in the map above to four new groups: Granitic, Volcanic, Young Sedimentary, and Old Sedimentary.  

Reservoir coordinates were obtained from google earth, saved to a text-file, imported into ArcGIS, transformed from the WGS 1984 projection into NAD 1983 projection (based off of base map), and added as a shapefile to the above layers.

Watersheds with reservoirs were selected and a new layer was selected.

Flow direction layer was created from the original base map dem. Next, the flow direction layers were clipped to the selected watersheds above.

Overlaying the above layer with a stream layer obtained from the USGS Water Resources and clipped to the basin. Since I was only interested in the geology of areas that influence the water chemistry into the reservoir, new reservoir watershed polygons were then digitized to capture all areas upstream of a reservoir's input.

The merged geology layer of the basin was then intersected to the digitized polygons shown above.

With the intersected layers of geology and the upstream watersheds of reservoirs. I then used summary statistics from the attribute tables to obtain a percent of each aggregate rock type for each reservoir watershed.