Wetlands are an often misunderstoond but critical part of the functioning of the sand country ecosystem. Sand is highly permeable to rainfall; very little surface runoff occurs after a rain or snow melt in sand country. Instead, the water travels directly downward into a shallow aquifer, which in most places in no more than seventeen to twenty feet (about five meters) below the surface. These two factors: (1) the ease with which water can travel down into the sand; and (2) the shallow aquifer or water table, have a tremendous influence of sand country ecology.
The countryside of northwest Indiana is mostly flat and level. However, the relatively minor variations in local surface elevation--usually no more than fifteen to twenty feet within a few hundred yards--are sufficient to result in extremes in hydrological conditions in the soil.
Pictured above is a small sand marsh. It is simply a slight depression in an upland sand deposit. The depression is perhaps a meter deep, but because a group of sand hills three or four meters higher are nearby, the water table is nearly always near or above the surface. The result is an intriguing and rich assemblage of plants and animals, which is similar to that found in pannes along Lake Michigan about forty miles to the north.