A remote sensing and GIS analysis of riparian vegetation change along the San Pedro River, Arizona

Landsat imagery of the San Pedro River was acquired for the years 1973, 1986, and 2000 to detect changes in the riparian vegetation of the San Pedro River. A supervised classification was performed based on USGS land cover data. Polygons were then digitized of the area surrounding the San Pedro River that contained riparian vegetation. The area of the riparian vegetation was then calculated. These calculations revealed that the area of riparian vegetation increased from 1973 to 1986, but decreased from 1986 to 2000.; Precipitation and streamflow discharge records were compiled and analyzed to investigate the relationship between these two parameters and riparian vegetation. There were no statistically significant changes in precipitation; however, there was the streamflow discharge change from 1986 to 2000 was statistically significant. The trends in streamflow discharge matched the trends in riparian vegetation area, which led to the assumption that the area of riparian vegetation is dependent on streamflow. Precipitation variations were considered as a cause for the decrease in streamflow, but were discounted based on previous trends. The likely causes for the decrease in streamflow are changes in vegetation that increased aridity and a rise in groundwater pumping to support the growing human population of the region.