 In 1936, the federal government acquired the Chautauqua Drainage and Levee District parcel, including the dikes that enclosed the pool, and began to manage it for wildlife-refuge and flood control purposes.The flood-control aspects of this management have grown more challenging in the years since, as continued agricultural runoff and siltation of the Illinois River has made much of Chautauqua Lake shallower.On some shoreline strips of the lake, the silt has built up to the level of the lake surface, and an alluvial topography of sloughs and floodplain woodlands may be slowly re-establishing itself.