Since land use changes have a significant impact on a watershed, I examined three points in history by measuring total land use areas with aerial photographs. Using a device called a planimeter, I outlined and measured forested, agricultural, and urban land use in 1949, 1963, and 1990. I used Dickinson College Environmental Studies Department’s aerial composite of 1963’s Perry County (1:20,000). The 1949 composite (1:20,000) and 1990 photographs (1:40,000) were property of the United States Geological Survey in Harrisburg, Pennsylvania.

The greatest land use change has occurred in the amount of urban area. As the graph illustrates, the Shermans Creek Watershed contained 2.4 square miles of urban land in 1949. It had increased to 13.1 square miles by 1990. Forested and agricultural land has a direct relationship. For example, in 1963, agricultural land decreased as forested land increased. It is also interesting to note that the amount of forested land in 1949 is about the same in 1990.