Land use and land cover changes resulting from the urban El Molinito reservoir in the drying Sonoran River Basin

Although the impacts of dams on the environment and human populations have been widely documented, many developing countries continue constructing large dams. In Mexico, impact studies have neglected to analyze downstream effects of dams. Thus, we analyzed land use and land cover (LULC) changes downstream of El Molinito dam, constructed on the Sonora River in northwest Mexico. We used Landsat Thematic Mapper (TM) to generate classifications (for 1993, 2002 and 2011), from which an assessment is performed to identify the principal changes. In addition, we analyzed changes in photosynthetic activity using the simple but informative Normalized Difference Vegetation Index (NDVI). We found a drastic decline between 1993 and 2011 in agricultural LULC because of water diversions from El Molinito. This study demonstrates the need for agencies responsible for water management to better assess the negative effects of dam construction and operation, especially on the livelihoods of downstream rural communities.