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Iowa Source Water Protection Program

Diagram showing 2-year capture zones

The term "Source Water" is used to define drinking water in its original environment, either as surface water (rivers, streams, reservoirs, lakes) or as groundwater (aquifers), before being withdrawn, treated, and distributed by a water system. Source Water Protection (SWP) is the act of preventing contaminants from entering public drinking water sources.

The quality of the source water can be influenced by both natural and human activities. The concept of Source Water Protection (SWP) is to manage the areas through which water travels and the activities that occur on the land, in order to protect the quality of the resource. These protection efforts save the community money through improved water quality requiring less treatment, longer life cycle for a well, and less likelihood of having to seek an alternate source or replace the well due to contamination.

Surface water is more susceptible to contamination incidents from natural or man-made causes, such as a flood or a chemical spill, but it also recovers much more quickly than does groundwater. Groundwater is much less susceptible to contamination, but when that happens, natural recovery is very slow to occur. Source Water Protection includes both groundwater (wellhead) protection and surface water protection.

SWP Program Logo

The Iowa DNR's SWP Program is a voluntary program, although there are numerous benefits for a water system to protect its water supply. There are three components to the Source Water Protection Program.

  1. Phase 1 Assessment: The DNR provides the initial source water assessments, called Phase 1 assessments, to all public water supplies in Iowa. This assessment details the water system's active wells, delineates the source water protection areas, lists the susceptibility to contamination classification, and provides the known potential contamination sources.
  2. Source Water Protection Plan: In the second step, the system then develops its SWP Plan through a local team effort. These plans are sometimes called Phase 2 plans. The components are listed in a templated plan that is used to guide the team through the process to determine how the system will protect its drinking water resource.
  3. Implementation: In the third step, the SWP Plan is implemented, addressing the specific items that the community and system will use to protect its drinking water resource.

The development of a good SWP Plan doesn't require any assistance or involvement of an engineer or consultant. A system may wish to contact an outside entity for assistance. The Conservation Districts of Iowa and the Iowa Rural Water Association provide experienced source water consultation and assistance for developing the SWP Plan, at no charge to the public water supply.

Source Water Applications

Contact Information:

SWP Program Coordinator: 
Matt Dvorak
Telephone: 515-322-7727

Source Water Planning Guides and Tools

  • Source Water Protection Guidebook details the seven steps needed for source water protection in Iowa, where to go for assistance, and what information is available.  Each of the steps listed in the document are vital for increased confidence that the water will be safe and plentiful for years to come.  Provided in the guide are informational web links, examples, lists of potential contacts, and helpful tools to make source water planning as easy as possible.
  • Source Water Protection Workbook contains form-fillable worksheets and checklists designed to help with meeting preparation, work assigned, schedules, and deliverables.  Also included are information web links, an introduction to Geographic Information Systems (GIS) resources as a tool to help with contaminant and well inventories, and contact information for submitting a completed SWP Plan.
  • Source Water Mapper is an online version of the Phase 1 Assessments that maps the inventory of public wells, other wells, potential contaminant sources, and capture zones.
  • SW Mapper Capture Zone
  • Source Water Tracker contains all Phase 1 Assessments, Source Water Protection Plans (Phase 2 Plans), DNR Sanitary Survey Reports, and Water Operator contact information for all active and inactive public water supply systems.
  • Susceptibility to Contamination Classification: The determination of susceptibility recognizes that certain aquifers are better protected than others. Research has shown that subsurface layers that impede the movement of water, such as clay, till, or shale, can be used to estimate the probability of contaminants entering the aquifer. For this reason, the SWP Program has designated four categories of susceptibility to contamination based on the cumulative confining layer thickness above the aquifer. 

Highly susceptible: less than 25 feet confining layer thickness
Susceptible: 25 to 50 feet confining layer thickness
Slightly susceptible: 51 to 100 feet confining layer thickness
Low susceptibility: more than 100 feet confining layer thickness