Aquifer Types
In the Miami Valley Region, aquifers can be divided hydrogeologically into two general groups: Buried Valley Aquifers and Upland Aquifers.
- Buried Valley and Upland aquifer types in the Miami Valley
The buried valley aquifers consist primarily of thick sequences of glacial sand and gravel deposits filling ancient bedrock valleys. In most cases these buried valleys underlie the Region's major present-day river and stream valleys. The saturated buried valley sand and gravel deposits are extremely permeable and regionally connected, allowing for the transmission and storage of vast amounts of groundwater. As a result, these deposits are highly vulnerable to contamination. The sand and gravel aquifer deposits are separated intermittently by discontinuous zones of clay and clay-rich till which complicate groundwater flow patterns on a local level. Much of the recharge to the buried valley aquifers occurs through streambed infiltration from the overlying rivers and streams. Development patterns in the Miami Valley's buried valley areas generally consist of intense urban and related land uses.
The upland aquifers are composed of both bedrock and glacial aquifers. The bedrock aquifers that underlie the uplands are mainly composed of fractured limestone formations that are capable of storing and yielding varying amounts of groundwater. The overlying glacial aquifers are composed of mixtures of sand, gravel, clay, and till materials that are deposited in various configurations and thicknesses across the upland terrain. Because of the greater variety of deposits, their distribution, and the wide variations in their hydraulic capabilities, the upland aquifers are generally less connected in terms of regional groundwater movement. In the uplands, groundwater is most often found in fractures in the bedrock and in small sand and gravel pockets and buried stream channels in the glacial till. Permeable bedrock and buried stream channel deposits are the most highly sensitive aquifers in the uplands. Till deposits are less vulnerable to contamination. In addition, groundwater production in the uplands is considerably less than in the buried valley areas, consisting of scattered smaller community water supplies and numerous private wells. Development patterns in the upland areas mainly consist of scattered small and moderately sized communities and agricultural land uses.