The Oahe Reservoir in this southeast-looking, low-oblique photograph is one of many dams and reservoirs constructed in the late 1940s and the 1950s along the Missouri River, from eastern Montana through North Dakota and South Dakota. These reservoirs were built to provide flood control, hydroelectric power, irrigation, and recreation. Dams like the Oahe serve to impound, for later use, water from spring rains and snowmelt that swells the volume of the Missouri River during early and mid-spring. The dams also protect the countryside from a second flood stage that frequently occurs in June as the snow melts in the remote mountain systems to the west. As of 1984, the Oahe Dam was the largest rolled-earth dam in the United States. Problems continue to occur with the construction of these dams and large reservoirs. They cause large areas of once valuable farmland to be flooded permanently, resulting in losses in millions of dollars in farm revenue yearly. In addition, silt, fertilizers, and pesticides in the runoff from agricultural lands pollute the waters of these reservoirs. The positive and negative debates regarding the usefulness of these reservoirs continue today. Pierre, the capital of South Dakota, is barely discernible near the center of the photograph just southeast of the Oahe Dam, where the Bad River from the southwest joins the Missouri River.