Wellhead Protection Area Delineation for Identifying Potential Contamination Sources

Background

In 1986, amendments to the federal Safe Drinking Water Act established a Wellhead Protection Program to protect wells and well fields which supply public water from contamination. Two key elements within this plan are the definition of wellhead protection areas (WHPA) and inventory of potential groundwater contamination sources within the WHPA.

Objective

Investigate the feasibility of using a geographic information system (GIS) for WHPA delineation and contamination source identification on a statewide basis.

Methods

A pilot study was undertaken to evaluate various approaches for delineating a WHPA and compiling a contamination source inventory. The adopted approach consists of the following steps:

• Creating the WHPA boundaries using a one-mile fixed radius for each water supply.
• Determining which county assessor maps were needed to map each water supply area and ordering the maps.
• Developing the land use categories for the contamination source inventory
• Scanning the county assessor maps.
• Georeferencing the digitized county assessor maps.
• Photo-interpreting county assessor maps using heads-up digitizing.
• Creating land use maps for each WHPA.
• Creating land use booklets for each water supply for ground reconnaissance.

Major Findings

The pilot study indicates that a fixed-radius method for determining the WHPA and detailed aerial photos (county assessor maps) for the contamination source inventory is the most practical approach for statewide wellhead protection programs. The county assessor maps vary in quality and photo-acquisition date, and may or may not have coordinate grids for georeferencing. Such variations result in differences in amount of time needed for land use photo-interpreting and interpretation accuracy across different WHPA. Heads-up digitizing has time-saving and quality control advantages relative to hand drawn interpretation and digitizing.

Major Products

• A standard series of maps was produced for each WHPA, including a 36" x 36" wall map and a booklet of 17" x 24" maps for ground reconnaissance.
• A heads-up digitizing menu was created using ARC Macro Language (AML) to streamline the delineation of land use.

Publications and Presentations

Barnett, Chris, Yan Zhou, Steven Vance and Chris Fulcher. Wellhead Protection Delineation for Identifying Potential Contamination Sources. Proceedings: 1995 ESRI User Conference Proceedings, Palm Springs, CA, May 22-26, 1995.

Barnett, Chris, Yan Zhou, Steven Vance and Chris Fulcher. Wellhead Protection Delineation for Identifying Potential Contamination Sources. 1995 ESRI User Conference, Palm Springs, CA, May 22-26, 1995.

Investigators: Chris Barnett, Yan Z. Barnett, Steven Vance and Chris Fulcher

Funding Amount: $54,999

Funding Source: Missouri Department of Natural Resources

Project Duration: October 1994 - December 1994