Maintaining “Instream Flows” to Protect Critical Ecosystems

Historically, Indiana water management programs have been concerned primarily with protecting water quality (keeping water clean) and preventing flood damage (keeping water in its place). As demand for water increases in our state, we are now finding that withdrawing too much water from a stream or river at the wrong time can have negative effects on the ecological health of that waterbody. Flows that are too low in summer may limit rearing habitat, concentrate fish in shrinking pools with declining water quality and dry up portions of the channel inhabited not only by fish but by mussels, crayfish, and other invertebrates that are important in fish and wildlife food chains. Low flows in winter may limit suitable overwintering habitat and ice-free refuges. Sustaining a minimum flow to keep an endangered species from extinction may also interfere with watering crops during dry times and boaters from enjoying a lake full of water. There is a balance that needs to be struck between ecosystem protection and necessary water resource development.

Managing our water resources in a way that sustains both human and aquatic life needs is an increasingly important topic, both in Indiana and throughout the United States. Nine states now have regulations that protect their water resources from the removal of too much water at the wrong time of year. This type of planning requires input and interactions from biologists, engineers, hydrologists, farmers, utilities, politicians, lawyers, boaters, environmental groups, and ordinary citizens. This problem is far from being resolved – much discussion is still needed on this important topic, and relevant information is necessary to support sound decision-making.

Optimal management of instream flows requires data related to streamflow and fish populations. This information enables scientists to link flow conditions with increases or decreases for various fish species. It’s also important to track the populations of other aquatic animals during winter months and times of drought to gauge the overall health of streams when our aquatic ecosystems are stressed.

Water Resource Professionals in Indiana with Experience Addressing “Instream Flow” Issues

  • Greg Bright (Commonwealth Biomonitoring)
  • Jeff Frey (USGS)
  • Mark Pyron (Ball State University)
  • Jack Wittman (Intera)

Related Resources

Indiana Water Resource Management Code, IC 14-25-7-14:

Arthington, A.H. et al, 2006. The challenge of providing environmental flow rules to sustain river ecosystems. Ecological Applications 16(4), Ecological Society of America, pp. 1311-1318:

Pritchett, T. and Pyron, M., 2011. Fish assemblages respond to habitat and hydrology in the Wabash River, Indiana. River Research and Applications 28, pp. 1501-1509.

Katapodis, C., 2005. Developing a tool kit for fish passage, ecological flow management and fish habitat works. Journal of Hydraulic Research 43(5), pp. 451-467.