ALTON, Ill. — To say that there is a powerful river in the Midwest that is threatening to flood communities nearby hardly narrows it down.

The Illinois, the Missouri, the Arkansas and the Mississippi Rivers were all at risk of spilling over in the coming days. The prospect put a patchwork of local and state officials on high alert on Friday, as they prepared sandbags, assembled barriers and nervously eyed the rising waters.

This spring has been a season of record-breaking floods across the Midwest, submerging farms, businesses and houses. Scientists have predicted that the flooding this year could be worse than the historic floods of 1993, which devastated the region.

And once again, the people who live along the four rivers were reminded of the delicate compact they have made, enjoying the beauty, recreation and commerce that the rivers provide, but also accepting their regular capability for destruction.