Lake Wawasee is the largest natural lake in Indiana. The lake is late Wisconsin age and occupies a massive ice-block depression in the classic interlobate area that lay between the Saginaw and Erie Lobes. The lake is located in northeastern Kosciusko County, but a large part of the watershed is located in southwestern Noble County. The major tributary is Turkey Creek, which flows into the southeastern corner of the lake. Upstream of the lake, Turkey Creek connects a chain of ten much smaller lakes. Lake Wawasee is hydraulically connected to and at the same elevation as Syracuse Lake, which lies just to the west in the same basin; the two lakes and their associated wetlands cover almost 8 square miles. Turkey Creek discharges from the west end of Syracuse Lake, and thus also acts as the principal outlet for the system. The outlet is regulated by the Indiana Department of Natural Resources to maintain lake levels at slightly less than 859 feet above mean sea level (858.66 ft).
Turkey Creek is the primary source of surface water that drains into Lake Wawasee. Dillon Creek is the other main tributary, and empties into the east end of the lake. The outlet of this drainage is severely disturbed by development and no longer follows its original course. Several other smaller, mostly intermittent ravines that emanate from the uplands to the south and north also discharge surface water into both Lake Wawasee and Syracuse Lake. Collectively, the surface streams provide a significant, though probably not the major, proportion of the water budget of the lake. The lake basin is surrounded by extensive glacial uplands whose summits are commonly greater than 950 feet, and locally exceed 1,000 feet in elevation. These uplands are the source of a large amount of ground water that discharges into the lake. Ground-water discharge also supports the base flows of the two major tributaries. Indeed, it is no coincidence that both tributaries are located on the east side of the lake. Extensive deposits of saturated gravel and sand in that area provide abundant ground-water discharge into both streams on a year-round basis. Similarly, much of the water that leaves the Wawasee basin is also in the form of ground water. Even a cursory review of basin geology and geography makes it clear that the interaction of ground water with the lakes is a key process in the overall water budget and water quality picture.
Saturated sand and gravel aquifers of widely-ranging sizes occur at various depths under and around the basin, and most of these are capable of contributing at least some ground water to the lake. The ground water closest to the land surface is typically recharged at a much greater rate than ground water in aquifers buried beneath clay layers, and such near-surface ground water is generally characterized by faster flow rates. Because of these qualities, the shallow ground water likely contributes the majority of ground water that discharges into the lake. Also, by virtue of its proximity to the land surface, the shallow ground water is considerably more susceptible to contamination from a variety of anthropogenic sources. This discussion is intended to supplement the “Water Table Map of the Lake Wawasee Basin”, and highlights the key characteristics of the shallow ground water of the basin, as revealed by the water table map.