Rivers and Streams
Rivers and streams carry moving water in steady currents throughout the state and are an integral part of Indiana’s history and geography. These ecosystems vary greatly in size, water flow, and plant and wildlife populations. Indiana waterways also have a variety of human uses, from recreation, to agriculture and irrigation, to transportation. Characteristic species in these habitats include aquatic plants like comb pondweed (Stuckenia pectinata), reptiles such as snapping turtles (Chelydra serpentina), fish including rock bass (Ambloplites rupestris), and mussels. Relevant Species of Greatest Conservation Need include hellbender salamander (Cryptobranchus alleganiensis), Northern riffleshell (Epioblasma torulosa rangiana), and gilt darter (Percina evides).
Areas classified as river and stream ecosystems in Indiana.
- Ecosystem Services and Human Benefits
Indiana’s rivers and streams provide an important supply of fresh water to the state. More than half of Indiana’s clean freshwater comes from rivers, lakes, and streams. This is crucial for household and agricultural needs, supporting Hoosiers directly and allowing the growth of the living things that benefit them. The flow of Indiana rivers also powers the five hydroelectric plants in the state, providing clean and reliable electricity with the force of flowing water. Indiana rivers and streams also provide opportunities for recreation, such as fishing, kayaking, canoeing, and tubing. These ecosystems make up habitat for unique communities of aquatic species. Ensuring their health provides continued opportunity for study and appreciation.
- Ecosystem Status
Peak flows of Indiana rivers and streams are evolving because of changes in climate. Increases in precipitation have coincided with increased streamflow during the last 30 years. With predicted changes, the risk of flooding from river and stream systems will continue to increase.
Much of the pollution in Indiana’s rivers and streams stems from extensive farmland runoff and industrial activities. Low-head dams on streams and rivers in Indiana also cause significant risks to human safety and fragment the aquatic ecosystem. The spread of invasives is also apparent, with many mobilizing through human behavior. Fish, such as invasive carp species; and aquatic plants, including purple loosestrife (Lythrum salicaria); have begun to infiltrate, taking up resources and displacing native species.
- Ecosystem Pressures
Pollutants and effluents from nearby development and agriculture present pressures for Indiana streams and rivers. Nearly 60% of Indiana's land area is dedicated to agriculture, contributing to livestock waste and fertilizer becoming the main sources of pollutants in these ecosystems, while sediment is listed as the No. 1 water quality pollutant by volume in the state. Excessive sedimentation clouds water and introduces nutrient pollution, blocking native plants from sunlight and burying habitats on the bottom of waterways. Sedimentation can alter waterway structures, leading to unnatural erosion and destruction. Escherichia coli has been identified as the top cause of recreational impairment for Indiana residents, with Indiana’s many concentrated animal feeding operations theorized to be major contributors. Excess nutrient runoff from animal waste and chemical fertilizers is also associated with water quality degradation. Specifically, nutrients such as nitrogen and phosphorus promote the growth of cyanobacteria, a blue green alga. This alga causes excessive toxin release into the waterways and can lead to a reduction of oxygen in these systems. The effects on Indiana’s rivers and streams extend beyond state lines, as nearly 90% of waterways drain into the Mississippi River and contribute to eutrophication in the Gulf of Mexico.
Aquatic invasive species present another threat to the vitality of Indiana rivers and streams. Invasive carp, including bighead carp (Hypophthalmichthys nobilis), silver carp (Hypophthalmichthys molitrix), black carp (Mylopharyngodon piceus), and grass carp (Ctenopharyngodon idella), are all found in Indiana. Black carp are especially impactful on river ecosystems, feeding on up to 4 pounds of mussels a day. As numerous mussel species are noted as species of concern within the state, this is an especially serious threat to their native populations. This feeding pattern also competes with other native wildlife such as turtles, birds, and fish, reducing their available food and disturbing river food webs. Aquatic plants also pose risks within rivers and streams, altering soil composition and shading native plants. Purple loosestrife (Lythrum salicaria) and reed canary grass (Phalaris arundinacea) quickly dominate areas in and around waterways, pushing out native plants for space. This hinders the natural biodiversity of the ecosystem, with downstream effects on animals using native vegetation for shelter or food.
Aquatic ecosystems may also be affected by changes in climate patterns, which are discussed in this supplemental report.
Additional pressures that affect river and stream ecosystems in Indiana can be explored here.
- Ecosystem Conservation Opportunities
Conservation professionals highlighted two opportunities for reducing pressures on river and stream ecosystems. The first is to identify and target management in priority wildlife corridor areas. These quality, intact ecosystems serve as buffers for rivers and streams and help limit pollutant runoff to maintain healthy conditions in lotic ecosystems. They also serve as sites for ecological connectivity between habitats. Identifying and protecting these areas of riparian corridors around Indiana’s river and stream ecosystems will support future rehabilitation efforts throughout the state.
The second opportunity is to establish a scalable system to remove or improve existing dams. Dams disrupt the natural flow of stream and river systems, altering habitat and removing connectivity for aquatic species. They can also act as sediment traps, capturing nutrients upstream that fail to make it to downstream ecosystems. Because sediment and agricultural contamination are major stressors on Indiana rivers and streams, scaling systems to improve dams may provide additional opportunities to clean our waterways. Identification of current dam systems and necessary removals will be important in outlining funding options and priority dam repairs.