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NPS pollution, unlike pollution from industrial and sewage treatment plants, comes from many diffuse sources. NPS pollution is caused by rainfall or snowmelt moving over and through the ground. As the run-off moves, it picks up and carries away natural and human-made pollutants, finally depositing them into lakes, rivers, wetlands, coastal waters, and even underground sources of drinking water. These pollutants include:
Atmospheric deposition and hydromodification are also sources of NPS pollution.
The origins of NPS pollutants are diffuse and often difficult to trace. Human-related origins of NPS pollution that have been identified as most prevalent in Indiana include:
To place this information in context, the following section provides an overview of Indiana’s water resources and a summary of current water quality conditions in Indiana, based on the 2008 Integrated Water Quality Monitoring and Assessment Report.
The data represents total stream miles assessed in each year. This includes all stream sizes, from the smallest to the largest river systems. Since IDEM is assessing more streams each year, these numbers represent running totals and do not, per se, indicate trends.
Indiana has monitored 55.7 percent of its streams to determine whether they are capable of supporting a well balanced, warm water aquatic community. Of the streams monitored, 79.4 percent were supporting their designated aquatic life use. Indiana has monitored 38.1 percent of its streams for recreational uses. Of the streams monitored, 31.1 percent fully support recreational uses, while 68.9 percent of its streams were found to be impaired.
Indiana is located on the eastern edge of the North American great interior plains. The North South continental divide traverses through northern Indiana, draining watersheds into the Great Lakes basin and the Mississippi River and Ohio River systems. Surface water in the northern one-quarter of the state flows north into the Great Lakes and then through the St. Lawrence River to the Atlantic Ocean. The southern three-quarters of the state drain into the Ohio River or Illinois River and flow into the Mississippi River, then south to the Gulf of Mexico. There are 35,673 miles of rivers, streams, ditches, and drainage ways in Indiana (Table 1-1).
|Description||Number||Unit of Measurement|
|Indiana population: (2006 estimated)1||6,313,520||people|
|Indiana surface area2||36,291||sq. mi.|
|Total miles of rivers and streams3||35,673||miles|
|Number of publicly-owned lakes/reservoirs/ponds4||575+|
|Great Lakes shoreline5||59||miles|
|Fresh water wetlands6||813,000||acres|
Based on current information, 79 percent of the 17,535 stream miles assessed for aquatic life use were found to be fully supporting. Approximately 30 percent of the 12,073 stream miles assessed for recreation use were found to be fully supporting. Almost all of Indiana’s 59 miles of Lake Michigan shoreline outside the Indiana Harbor fully supports aquatic life use, while almost none of the Lake Michigan shoreline waters support full body contact recreational use.
Table 1-2 summarizes use supports assessed and reported from 1998 through 2007.
|Table 1-2: Summary of Use Support - Assessed and Reported 1998 through 2007|
|Designated Use||Support||Threatened1||Non Support||Assessed||Not Assessed|
|Aquatic Life Use||13,913||--||3,622||17,535||14,606|
|Drinking Water Supply||--||--||1||1||101|
|Recreational Use (Human Health)||3,700||--||8,374||12,073||20,100|
|Great Lakes Shoreline (miles)|
|Aquatic Life Use||59||--||--||59||--|
|Drinking Water Supply||33||--||--||33||--|
|Recreational Use (Human Health)||--||--||59||59||--|
|Lake Michigan (acres)|
|Lakes and Reservoirs (acres)|
|Aquatic Life Use||3,690||--||6,625||10,315||21,826|
|Drinking Water Supply||230||--||16,615||22,905||12,926|
|Recreational Use (Human Health)||21,922||--||983||22,905||104,662|
|Recreational Use (Aesthetics)||29,035||--||8,006||37,041||90,526|
Source: IDEM’s Assessment Database
IDEM does not currently assess the water quality and use support of wetlands. IDEM utilizes the work of Indiana University’s Clean Lakes Program (funded by a Section 319 grant), to gather data needed to assess lakes. The overall assessment of NPS categories and subcategories for streams is addressed on a watershed-by-watershed basis. This approach is also reflected in IDEM’s programmatic NPS activities, such as grant activity prioritization and development of TMDLs.
Protecting our water resources from the impacts of NPS pollution is a complex challenge. Indiana uses a watershed approach as its water quality management strategy to protect and restore water quality. The watershed approach is used by IDEM and others to examine and address water quality concerns in each waterbody in the context of its watershed, thereby attempting to address all the potential sources of pollution within the watershed.
Environmental problems, such as NPS pollution, often cut across media and political jurisdictions. Consequently, environmental mitigation and protection requires a comprehensive and collaborative approach that works with a multitude of programs and agencies. The watershed approach is a coordinating framework for management that focuses public and private sector efforts to address the highest priority, water-related problems within geographic areas, considering both surface and ground water flow. By examining water quality issues on a watershed basis, problems can be observed in relationship to their sources so that the causes can be effectively addressed.
IDEM’s ongoing effort to implement the watershed approach includes:
Two key steps needed to solve NPS problems within a watershed context are the development of a watershed-based plan that addresses a waterbody’s water quality problems (including the incorporation of any TMDLs that have been developed) and the actual implementation of the plan. Careful analysis of the sources of water quality problems, their relative contributions to the problems, and alternatives to solve those problems, provide the best basis for sound decision making and implementation that will actually solve those water quality problems. For this reason, IDEM will emphasize using watershed-based planning and implementation processes to realize the long-term goal for the state’s NPS management program.