Delineation is the process of defining the area of land in which activities are likely to impact the quality of the drinking water source.  Surface sources of water that are fed by large watersheds are divided into three zones, the largest of which may be smaller than the entire watershed upstream of the intake.

What follows are the minimum criteria defined by the Ohio River Valley Water Sanitation Commission (ORSANCO) used to define these protection zones on the Ohio River.  Delineation criteria for intakes on the Ohio River differ from those used elsewhere in the state of Kentucky.  The size and flow of this river exposes surface intakes to a much larger array of potential contaminants than those found in smaller watersheds.

In 1997, Ohio River Valley Water Sanitation Commission (ORSANCO) initiated a work group to discuss interstate aspects of Source Water Protection Program activities for the Ohio River. The work group is comprised of representatives of state and federal drinking water agencies, including: Indiana Department of Environmental Management; Illinois Environmental Protection Agency; Kentucky Division of Water; Ohio Environmental Protection Agency; Pennsylvania Department of Environmental Protection; West Virginia Bureau of Public Health; U.S. EPA Regions 3, 4, & 5; and ORSANCO's Water Users Advisory Committee. As a result of work group meetings, ORSANCO agreed to develop an approach for states to delineate and inventory the 32 Ohio River surface water intakes.

Due to the size of the Ohio River, ORSANCO developed a tiered delineation system consisting of three protection zones. The purpose of this tiered approach is to define the level of source inventory within the Ohio River Basin.

Zone I - Zone of Critical Concern extends 1/4 mile below a water intake to 25 miles upstream in the Ohio River.  The lateral extent includes 1/4 mile on both sides of the river bank and major tributaries.
Zone II - Zone of High Concern extends 1/4 mile below the surface of a water intake upstream, to 1/4 mile below the next Ohio River intake.  The lateral extent includes all 14-digit hydrologic units adjacent to the banks of the Ohio River and major tributaries.
Zone III - Source Water Area the entire portion of the Ohio River Basin upstream from a surface water intake.
 

Ohio River states are responsible for performing potential contaminant source inventories for drinking water intakes within their respective boundaries. ORSANCO then coordinates an information exchange between neighboring states so that the interstate aspects of source water protection activities can be addressed. To facilitate a data transfer between states, minimum requirements for available information on point sources of contamination was established. State agencies may choose to provide additional data beyond the minimum requirements.