ORVEC Ohio River Alluvial Aquifer EC EarthCache

Alluvium (from the Latin, alluvius, from alluere, "to wash against") is soil or sediments deposited by a river or other running water.

Alluvium is typically made up of a variety of materials, including fine particles of silt and clay and larger particles of sand and gravel.

An aquifer is an underground layer of water-bearing permeable rock or unconsolidated alluvial materials (gravel, sand, silt, or clay) from which groundwater can be usefully extracted using a water well.

The study of water flow in aquifers and the characterization of aquifers is called hydrogeology. Related terms include: an aquitard, which is an impermeable layer along an aquifer, and an aquiclude (or aquifuge), which is a solid, impermeable area beneath an aquifer. The surface of saturated material in an aquifer is known as the water table.

The Ohio River Alluvium aquifer is an important resource for the citizens and industries of Louisville. Observation sites and test measurement data are shown above and below. A link to this and other data is provided at the bottom of the page.

The aquifer area is located in north Jefferson County, Kentucky and consists of approximately 39,600 acres. The Ohio River Alluvium aquifer is bounded by the Ohio River and terraces deposits. The land surface in the river valley ranges from 383 to 440 feet above mean sea level with occasional terraces as high as 460 feet. Most of the area is used for industrial or residential purposes.

The Ohio River Alluvium physiographic region of Kentucky deposits in the county include limestone, shale, dolomite, lacustrine, and alluvial deposits. The Ohio River Alluvium is primarily made up of Pleistocene glacial outwash material and unconsolidated alluvium, which consists of sand, gravel, clay, and silt. Regionally, the lithology is comprised of a 5 to 45-feet thick layer of clay, silt, and fine sand that overlays sand and gravel containing discontinuous lenses of clay.

Beneath the aquifer are relatively tight shale and limestone bedrock. Recharge The Ohio River is hydraulically connected to the Ohio River Alluvium aquifer. Small streams in the area also influence the aquifer but to a much lesser degree than the Ohio River. Recharge to the aquifer occurs through flow from small streams, valley walls, precipitation, and infiltration from the Ohio River during high river stages and periods of high groundwater withdrawal.

Discharge of the aquifer occurs to the Ohio River and human-use production wells.

The Ohio River Alluvium is the most dependable source of groundwater for Jefferson County.

Domestic wells drilled in the alluvium are generally drilled to a depth of 100 feet below ground surface and can produce approximately 1,000 gallons of water per minute. Of the domestic wells located in the upland region outside of the alluvium, less than half produce adequate amounts of water for domestic purposes and often suffer during dry periods.

Water is often described in terms of its “hardness,” or the degree to which lather produces when using soap. Hard water primarily results from an abundance of magnesium and calcium. The groundwater throughout Jefferson County is typically classified as hard to very hard. The magnesium and calcium in the groundwater are likely due to leaching from carbonate and sedimentary rocks in the region.

Groundwater quality continues to be a major consideration in growing communities such as Louisville. In general, groundwater water supply systems are significantly less costly to operate and maintain than are surface water systems. Once aquifers become contaminated they are difficult and expensive to remediate.

The coordinate above will bring you to the Ohio River waterfront at a spot above the aquifer and to an object 'on loan' (see plaque on abstract).

To log this EC, email answers to the following FOUR questions:

1. What is the approximate size of the aquifer in acres?

2. What is the primary make-up of the Ohio River Alluvium?

3. What causes 'hard water?

4. What is the name of the 15,000 pound loaned object located at this coordinate?