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What We Know About the Upper Iroquois Watershed



Glacial Geology

Wisconsinan Age is the most recent glacial period to impact the Upper Iroquois Watershed. The first two retreats of the Lake Michigan and Lake Erie Lobes of the Wisconsinan Age glaciers deposited the Iroquois, Shelbyville, and Crawfordsville/Chatsworth Moraines and established the current topography of the watershed about 20,000 years ago. A glaciated plain was created where a variety of unconsolidated deposits are present including dune sand, lacustrine sediments, outwash plain sediments (sand and gravel), and till. The glacial deposits on these end moraines, recessional moraines, ground moraines, outwash plains and lacustrine plains range in thickness from a few feet to more than 100 feet. Many of the depressional potholes within the watershed are the remnants of old kettle holes.



The study of Indiana’s geology is commonly divided into the study of the rocks that are sometimes at, but mostly below, the earth’s surface and the unlithified materials that occur at the earth’s surface.

Bedrock Geology

The term “bedrock geology” describes the study of the rocks at and below the bedrock surface. Different types of geological bedrock differ in their resistance to erosional conditions and therefore can have an effect on a landscape region.  Geological bedrock in a watershed can also be an important factor that affects the conditions and physical, chemical and biological processes occurring in the watershed’s streams.  Water in its natural state is never pure, absorbing minerals and salts from the land over which it passes.  For example, some contaminates such as arsenic and radon are released into groundwater and surface water through natural processes of erosion and sedimentation. Radon, which is a by-product of uranium erosion, is found in the earth’s crust and is undetectable. However, if it enters a drinking water supply it can increase the risk for cancer.

Since the physical, chemical and biological conditions in a watershed are often directly or indirectly related to bedrock and underlying geologic formations, the bedrock can often provide an explanation why a stream has certain characteristics, especially the composition of the streambed.  For example, bedrock consisting of limestone will act as a buffer to acidic waters.  This chemical property can be advantageous in areas which receive more acidic precipitation due to air pollution.  The limestone bedrock helps stabilize pH levels, reducing the impact of acid rain.

Bedrock geology of the Upper Iroquois watershed is comprised mostly of limestone, dolomite, and shale bedrock.  These materials can be grouped into four basic areas or regions of the watershed.

  1. The Borden Group lies within the Mississippian bedrock system and is primarily located south of U.S. Highway 24 in the southern part of the watershed.  This bedrock group consists mostly of siltstone with lenses of crinoidal limestone in the upper part. There is much cherty and silty limestone and dolomite in the southwest.

  2. The New Albany Shale rock unit lies in the central part of the watershed, north of U.S. Highway 24.  It is mostly black and greenish gray shale.  It is part of the Devonian-Mississippian bedrock system.

  3. The Muscatatuck Group consists of dolomite and limestone and lies in the northern part of the watershed.  It is part of the Devonian Bedrock system.

  4. The Wabash Formation is part of the Silurian bedrock system.  This unit lies in the northwest area of the watershed, primarily west of U.S. Highway 41. It consists of limestone, dolomite and argillaceous dolomite.

Depth to bedrock varies throughout the watershed and can range from a few feet to more than 100 feet below the soil surface.  Of note, is a 1-2 mile stretch of the Iroquois River running through Rensselaer where the bedrock is very close to the soil surface.  Bedrock in this area is typically within two feet, or less, of the soil surface of the floodplain, and the rock itself forms the sides and bottom of the river.  The Hydrogeological Atlas of Aquifers in Indiana shows the bedrock in Rensselaer. 

Kettle Horn Formation

Extent of  the Wisconsin Glaciation in Indiana



Streams, rivers, and lakes are an important part of the landscape, as they provide water supply, recreation, and transportation for humans, and a place to live for a variety of plants and animals.  Groundwater also is an important water resource that serves as a source of drinking water for more than 140 million people in the United States.


In some areas, contamination from natural and human sources has affected the use of surface water and groundwater.  For example, naturally occurring minerals within bedrock can impair the taste of groundwater and in some cases limit its use.  The spilling, leaking, improper disposal, or intentional application of chemicals at the land surface can result in runoff that contaminates nearby streams and lakes, or infiltration that contaminates underlying aquifers and water wells.


The Upper Iroquois Watershed is drained by the Iroquois River and its tributaries.  The Iroquois River flows westward and empties into the Kankakee River in Illinois.  There are no large lakes within the watershed, only a few man-made ponds, filled quarries, and backwater areas which are scattered throughout the watershed.

The hydrology and groundwater function of the Iroquois River is unique to Indiana.  The upper reaches of the watershed north of Rensselaer are dominated by pockets of sand and muck that tend to slow flows downstream. Closer to Rensselaer, the hydrology of the watershed becomes more defined and the typical clay till found in much of Indiana becomes the controlling soil type (Banning Engineering, P.C., 2010).

Water Supply


Residents living in the Iroquois watershed get their potable water from deep wells that have been drilled into unconfined aquifers comprised of unconsolidated sand and gravelly sand or

confined aquifers located in Silurian, Devonian, and Mississippian age carbonate bedrock. Factors that can affect the movement of contaminants from surface water sources to water wells are the chemical nature of the contaminant(s), the physical properties of the soil and aquifer material, the amount and timing of recharge, and the direction and velocity of groundwater movement.


Four primary consolidated aquifer subsystems lie within the Upper Iroquois Watershed.

The Borden Bedrock Group lies primarily south of U.S. Highway 24.  It consists mostly of gray argillaceous siltstone and shale. Some fine-grained sandstone and some minor interbedded discontinuous lenses of limestone are also present in this region.  Aquifer thickness ranges from 0 to 800 feet and typically yields 1 to 10 gallons per minute with significant drawdown.

  1. The New Albany Shale Group lies, for the most part, between U.S. Highway 24 and Indiana State Road 16.  It consists of black and greenish gray shale ranging from 0 to 340 feet in thickness.  It commonly yields 1 to 10 gallons per minute.

  2. The Silurian and Devonian Carbonates Group lies in the northern part of the watershed.  This group is predominantly carbonate rock units (limestone and dolomite) with some interbedded shale units.  It is difficult to distinquish between the bedrock materials and therefore this unit is considered as a single water-bearing system.  Aquifer thickness ranges from 0 to 1,000 feet and typically yields 10 to 25 gallons per minute with yields decreasing southward.

  3. The Kentland Anomaly Aquifer System is confined to a relatively small area in Newton County.  The system is located just east of Kentland and is adjacent to the border of Benton County.  The bedrock in this area has been faulted and folded by undetermined forces that brought deeply buried Ordovician rocks, consisting mostly of sandstone and carbonates, to the bedrock surface.  Bedrock in this area also includes the Borden Group, the New Albany Shale Group, Silurian and Devonian Carbonates, and Pennsylvanian age rocks consisting of the Raccoon Creek Group which is composed mostly of sandstone and shale with minor amounts of mudstone, coal, and limestone.  Aquifer characteristics in this area are unknown because of the area’s small size and extremely limited number of registered groundwater withdrawal facilities.  This system has a moderate susceptibility to surface contamination because the bedrock is highly fractured and the surface materials that overly the system are relatively thin.

There are three primary unconsolidated aquifer subsystems within the watershed.

  1. The Iroquois Valley Subsystem lies adjacent to the Iroquois River and west of Interstate 65.  It consists of intertill sand and gravel within a buried bedrock valley.  Aquifer thickness is commonly 5 to 20 feet but ranges from 3 to 40 feet.  It typically yields 10 to 40 gallons per minute.

  2. The Iroquois Basin Subsystem lies within the southern portion of the watershed.  It consists of isolated surface sands, thin intertill sand and gravel and some deeply buried aquifers in buried valleys.  Aquifer thickness is commonly 2 to 3 feet and yields 4 to 20 gallons per minute.

  3. The Iroquois Moraine Subsystem lies along the northern edge of the watershed.  It consists of isolated and discontinuous intertill sand and gravel.  Aquifer thickness typically ranges from 3 to 25 feet in thickness and yields 4 to 10 gallons per minute.



Geological bedrock determines the slope of a watershed basin and its drainage patterns.  This can influence how surface water moves through the watershed, have an impact on flooding/flashiness, and have an effect on groundwater recharge.  Topography throughout the Iroquois Watershed can be characterized as relatively flat to gently rolling with inter-dispersed depressional areas and sand ridges which rise a few feet above the general ground level.  Narrow, steep slopes can be found in some areas adjacent to the Iroquois River and some of its tributaries.

The difference between the highest elevation and the lowest elevation in a watershed is defined as topographic relief.  Topographic relief of a watershed’s landscape and gravity influence stream velocity and discharge, stream flow direction, watershed drainage, and creation of watershed divides, streambed composition, and ultimately, the water quality parameters in a stream.  For example, areas with rugged topography may be more subject to erosion due to runoff.  The steeper surfaces are a vehicle for faster water flow.  This in turn, can cause more widespread erosion, depositing sediment into lakes and streams


Elevations in the upper reaches of the watershed are approximately 710 feet above sea level. The lower reaches near the Indiana/Illinois State Line are near 625 feet. The average elevation is about 655 feet above sea level (Rogers, 1955). The highest elevation in the watershed is about 770 feet above sea level and can be found near the intersection of Benton, Jasper and Newton Counties. In Jasper County this elevation is located southwest of Remington in the southwest corner of Section 32 in Carpenter Township. In Newton County the highest point is located southeast of Goodland in the southeast corner of Section 36 in Grant Township.


There are approximately 55 miles between the upper reaches of the watershed and the Indiana/Illinois border. Average slope of the watershed is approximately 1.5 feet per mile (Banning Engineering, P.C., 2010).




Soils provide five primary functions .  Most people are aware that they provide a medium for plant growth, serve as a material on which we build our homes and businesses, provide a habitat for some forms of animals and organisms, and contribute to our domestic water supplies.  Two of their lesser known benefits are that they recycle nutrients and organic wastes and they help purify our water supplies by removing pollutants from surface water

runoff and groundwater as it moves through the soil. As water percolates through the soil some pollutants are attached to soil particles. Pollutants, depending on their type and characteristics, may then be removed by plants, most of which depend on soil for growth and survival, through root absorption and plant uptake.


Soils, if not properly managed and protected from erosive forces, can also have a negative impact on water quality. Sediment is eroded and transported mostly during heavy rainfall events and the associated high streamflows, particularly floods. Sediment can become a problem because its deposition in streams and lakes can ruin the habitat for aquatic plants and animals. It can also fill stream channels, lakes, and harbors, which then require costly dredging. Studies have shown that the amount of suspended sediment in surface-water bodies can be related to natural factors such as soil type and geology. In general, however, the most important factor for sediment transport is the amount of land cleared of vegetation. Sediment sources typically are lacking in developed areas, but during tillage or construction, when little vegetative cover or pavement exists, the exposed soil can be easily eroded during storms and deposited in downstream waterways. Sediment in rivers and lakes is a concern because many contaminants can attach and move with the sediment particles. (Source:


The Iroquois Watershed consists of several soil types. Soils in the southern portion of the watershed, predominantly south of Indiana State Road 14, formed under prairie/grassland conditions whereas the soils in the northern part of the watershed were influenced by forested and savannah conditions. In general the soils in the watershed can be characterized as deep to very deep, nearly level to strongly sloping, very poorly drained to moderately well drained, fine to medium textured soils on upland glacial till plains and moraines. Soils in the watershed are generally well suited for agricultural production when drained. The main management concerns are wetness, ponding, flooding and erosion. The Natural Resources Conservation Service has several conservation management practices in the arsenal of tools they use to combat and prevent erosion. Some key conservation practices they use to prevent soil erosion are shown in the picture above.


Land Use


The type and severity of water contamination often is directly related to human activity, which can be quantified in terms of the intensity and type of land use in the source areas of water to streams and aquifers. The analysis of patterns of land use and population provides a tool in the investigation of sites with known contamination, and in the prediction and prevention of future contamination of downstream waters. Studies of contamination sources and transport pathways that affect surface water and groundwater draw upon several disciplines, including hydrology, geology, biology, soil science, agriculture, physics, chemistry, and engineering.


Land use and land cover largely determine the type and amount of contaminants entering streams, lakes, and underground pathways, including aquifers.  Some contaminants occur and move naturally (white arrows), whereas others are produced by human activities (hatched arrows), and their movement often is accelerated as a result of rainfall that accentuates runoff and infiltration.

A relatively simple way to study the effects of land use on groundwater quality is to compare the predominant land uses within a given area to the concentrations of selected contaminants in water drawn from shallow aquifers within that area.  Analysis of the relation between land use and the magnitude of contamination in a specific area primarily is based on the following two assumptions.

First, it is assumed that contaminated groundwater at a well originated as uncontaminated recharge (precipitation) that passed through a contaminated area before reaching the well.  The area from which a well derives its water (and associated contaminants) is known as the well’s groundwater “contributing area.”  A well’s contributing area can be delineated on a map.

Second, it is assumed that the contaminants detected in groundwater were present within the well’s contributing area and were transported by groundwater flow to the well.  The source(s) of contaminants within a contributing area, such as buried septic systems and leaking underground fuel tanks, can be difficult to identify and locate.  In many instances, these sources can be inferred from the type and intensity of land use within the contributing area.


Soil erosion and water runoff from cropland into nearby streams can be a major source of sediment, nutrients, and pesticides in watersheds dominated by agricultural land. This photograph shows poor cropland management in which the tilled field extends to the edge of an unvegetated (and eroding) streambank. Implementation of soil and water conservation measures, such as buffer strips of undisturbed land between cropland and adjacent streams, can provide an effective control that reduces contaminant entry into aquatic systems. 

Row crop agricultural is the predominant land use in the Upper Iroquois Watershed.  Agricultural land use accounts for more than 84% of the watershed. The Iroquois watershed was predominantly marsh and wetlands with interspersed islands prior to the area being settled. Over the years, human kind has cleared the land and created an extensive system of open ditches and subsurface drainage tile for the purpose of agricultural crop production.  This change in land use has resulted in the loss of wetland function, groundwater recharge, and flood storage.

Forest and developed/urban lands are the next largest land use within the watershed. Each accounts for a little more than 6 percent of the watershed. Developed areas are generally concentrated in and around cities and towns within the watershed. However, in recent years there has been a trend of residential strip development taking place along county and state roads. This type of development requires more individual wells and on-site septic systems which can have a greater effect on water quality verses public/communal wells and sewage treatment plants which allow greater flexibility in the control of pollutants.

Hay/pasture, grasslands and shrubs make up another 3% of the watershed. The remainder of the watershed consists of isolated pockets of wetlands and open water. There are no large lakes within the watershed. Most open water areas consist of man-made ponds, water-filled quarries, and backwater areas which are scattered throughout the watershed.



On a state listing basis, 45 species which are listed in the Natural Heritage Database as state endangered have been observed within the watershed: Bristly SarsaparillaLake CressHill’s ThistleToothed SedgeSmall-fruited Spike-rushCarolina FimbryCreeping St. JohnswortBrown-fruited RushSandplain FlaxGlobe-fruited False-loosestrifeNorthern Bog Clubmoss, Sessile-leaved Bugleweed, Cutleaf Water-milfoil, Eastern Eulophus, Yellow-fringed Orchid, Prairie ParsleySnail-seed PondweedSpotted PondweedGlobe Beaked-rush, Torrey’s Bulrush, Muehlenberg’s NutrushHidden-fruited Bladderwort, and Small Swollen Bladderwort.

(More information on these species can be found here)




Freshwater mussels are one of the most endangered animals in North America due to pollution, habitat alteration and overharvesting.

Other factors that impact the native mussel’s population negatively include: dredging, pollution, siltation and zebra mussels.

The invasive Zebra Mussel is an aquatic hitchhiker. They like to use water filtration to collect nutrients. An adult zebra mussel can filter up to a liter a day. They also interrupt the food web. Zebra mussels attach to native mussels with their byssal threads and smother them by filtering all the food out of the water. They rapidly multiply. They can damage watercrafts, clog power plants and public water pipes, and cover the beaches with broken shells.

Three amphibian species are listed as state species of special concern: Blue-spotted Salamander, Plains Leopard Frog, and Northern Leopard Frog.  While these three species are listed as state species of special concern in Indiana, these species have a G5 ranking, stating them to be widespread and abundant globally. The Plains Leopard Frog is ranked as S1 and to be critically imperiled in the state. The Blue-spotted Salamander and Northern Leopard Frog have an S2 ranking of being imperiled in the state.

Habitat preferences for the state listed species vary. Warm water temperatures,high turbidity, and loss of habitat can all impact fish and mussel diversity. Deforestation or forest fragmentation likely affect the peregrine falcon and Indiana bat species. These species require large hunting areas where dense forests are present and small stream corridors with well developed riparian forests. The elimination of these habitats could result in the loss of roost and hunting habitat thus eliminating these species. Other listed species, including Franklin’s ground squirrel (found within Newton County), eastern massasauga, smooth green snake, and several bird and vascular plant species rely on prairie habitat. Many live on the border between forested and prairie habitats hunting in one habitat and nesting in the other. The conversion of prairies and forests to agricultural and urban land uses could have resulted in the decline in these populations (WREC, 2010).

Check out this 14 Year Study of Amphibian Populations and Metacommunities!

A study of amphibian populations and metacommunities by Dr. Robert Brodman, of the Biology Department at Saint Joseph’s College, Rensselaer, IN used data from 14 species of amphibian fauna in Jasper County to detect population and diversity trends. Hypotheses regarding the influence of landscape, climatic, and biotic

factors on abundance, occupancy, and diversity were also tested. A total of 11,438 breeding populations were recorded in Jasper County from 1994-2007. An average of 339 sites with amphibian breeding activity and 817 populations were identified. A total of 630 wetland clusters and isolated wetlands were identified. Of these, 94.4% had at least one year with amphibian breeding activity and 81.3% had metacommunities with at least two coexisting species.

The 23 wetland clusters that exhibited the highest abundance were defined as megametacommunities. These megametacommunities are associated with several landscape variables with 78% including upland habitat identified by the IBI conservation tool as km2 sections with greater than 50% cover by important native plants or core habitat for any of the six species designated for the region as umbrella wildlife species. This association with priority habitats is related to the stakeholder’s concerns list, particularly in regards to protecting and creating healthy fish habitat. The megametacommunities are associated with all but two of the large areas in Jasper County that have large numbers of wetlands and important native plant or umbrella animal habitats. Figure 23 Amphibian Megametacommunities shows the location of the 23 megametacommunities.

Wetland clusters and isolated wetlands are indicated by the blue, amphibian megametacommunities are indicated by the red circles, and IBI (Index of Biological Integrity) priority habitats are indicated by open squares. Yellow circles indicate areas with wetlands, and priority habitat, but no amphibian megametacommunities (Brodman, 2009).


On a state listing basis, 45 species which are listed in the Natural Heritage Database as state endangered have been observed within the watershed including:

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