A visit to Ohio over the past few days took us along I-70, crossing Illinois and Indiana. From the Mississippi eastward, all of the rivers and creeks were at or near capacity and many had spilled across their floodplains, creating vast, shallow lakes. While most of the flooding invaded valley fields and bottomland woods, even upland pastures and croplands were partly covered by water.
The warm, moist, southerly flow of this past week triggered the deluge, dropping large amounts of rain and melting a thick snowpack that had covered northern portions of these States. Some degree of flooding is common across the Midwest, especially from February through early April. In late winter and early spring, the clash of cold and warm, moist air masses produces an abundance of precipitation which cannot be absorbed by the cold, hard ground. Furthermore, what moisture does percolate into the soil is not taken up by the dormant trees and foliage; the upper soil is rapidly saturated, runoff is accentuated and widespread flooding occurs.
Of course, there is some benefit gained from all of this shallow water. Migrant waterfowl and shorebirds are especially attracted to these temporary wetlands, which provide nutritious rest stops on their way to northern breeding grounds.