Impounded in the autumn of 1974, the C. J. Brown Reservoir was built principally for flood control. The 2,120-acre lake with over 12 miles of shoreline is located on Buck Creek approximately 7 miles above its confluence with the Mad River. The U.S. Army Corps of Engineers maintains a visitor center. The land surrounding the reservoir included Buck Creek State Park and is dominated by sub-climax oak-hickory and northern floodplain forest. There is a sand beach to the south on the reservoir and shallow marshy areas at the north end. The upland area surrounding the lake is a mosaic of old fields and early successional woodlands as a result of allowing old farm fields to mature and the planting of trees in the 1970s. Two sensitive alkaline fen communities exist at the park and are associated with remnant tallgrass prairie. Twenty acres of restored tallgrass prairie have been added to the park.

This lake is deep enough for diving waterfowl and regularly attracts large numbers of waterfowl until freeze-up in January and post-freeze from February to the peak in March. All of the regular species occur annually. This is the only annual inland site for American White Pelicans in Ohio. Bell’s Vireo is regular in summer most years since 1985, through declining recently. Yellow-breasted Chats nest. Shorebirds include several records of Buff-breasted Sandpiper and at least two of Piping Plover. With the lowering of the lake level, there are extensive mudflats by October to attract shorebirds. Over 250 species of birds have been recorded in the surrounding Buck Creek State Park.