 This is Keyhole Dam on the Belfouche River in northeast Wyoming. It was created to provide water storage for irrigation and flood control downstream. It also provides recreation at the reservoir. The dam does all of those things. Not surprisingly, dams like Keyhole affect the ecology along the stream below in a number of ways. Most prairie rivers actually have more mature, stable and diverse plant and animal communities than they had before the dams. However, there are trade-offs. Before dams, prairie rivers often flooded in the spring and nearly dried up in the late summer. Spring floods meandered across wide flood plains changing channels frequently and eroding cut banks like this on the outside of river bends and sand gravel point bars like this on the inside of the curve. Cottonwood and willow seedlings need point bars for their establishment. Age, disease, fire, agricultural activities and browsing by wild animals and the changing water tables take their toll on the older cottonwoods and the species associated with them. Once in a while, streams like the Belfouche need a high water event to flush them out and renew them. I'm Gene Gade from the University of Wyoming Cooperative Extension Service.