Flat Creek, a nearly 54-mile stream in southwest Indiana, had faced years of water quality problems.
Between 2006 and 2012, monitoring by the Indiana Department of Environmental Management found low dissolved oxygen, excessive nutrients, and poor biological communities in several sections. As many as 45 of the creek's 54 stream miles were listed as impaired.
In 2012, a source water protection plan for the larger Middle Patoka River watershed led to years of improvement efforts. Follow-up monitoring later documented progress across several sections of Flat Creek, resulting in multiple delistings in 2022.
Flat Creek faced multiple water quality challenges
Flat Creek flows through Pike and Dubois counties and is part of the Middle Patoka River watershed.
The Flat Creek watershed is mostly forested but also includes agricultural land and hay and pastureland. Numerous land-disturbing activities, including mining, had occurred in areas draining into the creek.
Monitoring identified four stream segments with impairments involving biological communities, dissolved oxygen, nutrients and other pollutants. Nonpoint pollution sources included agriculture, on-site sewage disposal systems and wildlife, among other sources.
A 2012 plan led to years of watershed work
The Alliance of Indiana Rural Water Foundation developed the Middle Patoka Source Water Protection Plan in 2012.
Between 2013 and 2016, the plan was implemented with Clean Water Act Section 319 funding. Best management practices were installed alongside education and outreach efforts, including a septic workshop where participants observed the installation of a septic system and learned about its proper function and maintenance.
The first round of implementation reached nearly 50% of its sediment load reduction goal and 20% of its phosphorus reduction goal.
A second round of work followed from 2017 to 2021. Across the larger Middle Patoka River watershed, the project implemented nearly 10,000 acres of cover crops.
Other measures included nutrient management, conservation tillage, grassed waterways and riparian forest buffers.
2019 monitoring resulted in delistings
IDEM conducted follow-up monitoring in 2019 and found improvements across multiple sections of Flat Creek.
The headwaters showed passing scores for both fish and macroinvertebrate biological communities, leading to the removal of its impaired biotic communities listing in 2022.
The middle and lower sections also recorded improvements. Monitoring found passing biological scores in some segments, improved dissolved oxygen levels and reduced phosphorus values.
These results led to multiple removals from the 2022 impaired waters list, including listings related to biological communities, dissolved oxygen and nutrients.
Further improvement was recorded in 2024
Additional monitoring in 2024 focused on a middle section of Flat Creek that had previously continued to show failing macroinvertebrate biological scores.
The latest results found passing scores for both fish and macroinvertebrates. IDEM will propose removing the impaired biotic communities listing for that segment in 2026.
