Mapping Historical Change in the Irrigated Agriculture of the Lower Boise River Valley, Idaho

Changes in irrigated agricultural land use were mapped using 1938-1939 and 1994 aerial photographs for 2,600 square kilometers of the lower Boise River Valley of Idaho. The project was a joint effort between the U.S. Bureau of Reclamation and the Idaho Department of Water Resources to develop land use change data that will be used for comprehensive water management and administration. The method involved scanning aerial photographs to produce image files that were rectified and mosaicked using geographic information system (GIS) software. The images were interpreted on-screen into 24 land use and land cover classes for the 1994 data and into two classes for the 1938-1939 data. Commercial GIS software and custom-developed programs facilitated the image interpretation and helped create land use change data, maps, and tables.