Indian Lake Watershed Project: Agricultural Sediment Reduction Case Study (8/3/04)
Lewistown Reservoir was constructed in 1851 at the headwaters of the Great Miami River to serve as a feeder lake for the Miami-Erie Canal System. The area was designated as a state park in 1898 when the name changed to Indian Lake.
Located in west central Ohio, Indian Lake is a vacation destination, attracting over 1.5 million visitors each year. While the lake and most of its 67,000 acre watershed is located in Logan County, portions of Hardin and Auglaize counties also drain to Indian Lake. The watershed, drained by 178 miles of streams and ditches, is dominated by agricultural land use (89%). Just over 7% percent of the watershed is forested land and only 3% is urbanized. The remaining land is open area or water.
In 1988, the Natural Resources Conservation Service (NRCS) conducted a sediment transect and found that Indian Lake had lost about 35 percent of the storage capacity due to sedimentation. Armed with this information and anecdotal testimony, the local lake association, ILDC (formerly Indian Lake Development Corporation), raised the sedimentation issues to the attention of state and federal agencies and legislators. As a result, in 1990 the United States Department of Agriculture (USDA) selected the watershed as a Hydrological Unit Area project. This designation, and an influx of other state and federal grants totaling $640,000 through the first half of the 1990s, brought significant human and financial resources to focus on resolving sedimentation in the watershed.
Much of the NPS implementation was based on the Ohio EPA authored report, Indian Lake Diagnostic/Feasibility Study: Phase I Report Under the Clean Lakes Program, Section 314, Public Law 92-500 (1990). The central recommendation of this plan was reduction of sheet erosion and overland transport of sediment through implementation of no-till and other conservation management practices. Although implementation continues in the watershed, the largest increase in implementation occurred in during the first five years of the project, as illustrated in Table 1.
Table 1. Indian Lake Watershed Sediment Reduction Implementation, 1991-1995
By 1995, over 65 percent of the watershed crop fields were no-tilled, and today the percentage typically approaches 80% according to the Indian Lake Watershed Project. NRCS estimates the program has saved three to ten tons of soil per acre per year from eroding into tributaries and eventually Indian Lake. Indian Lake sedimentation from watershed sources has been reduced from an estimated 89,000 tons per year in 1988 to less than 12,000 tons per year today.
Ohio EPA monitoring within the watershed provides additional evidence of success. In 1988, biological monitoring in the Indian Lake Watershed found no tributary of the lake fully attaining warm water habitat aquatic life use designation based on fish and macroinvertebrate criteria. Ohio EPA now reports that 78% of the watershed is in full attainment. Moreover, "sedimentation" is no longer listed as one of the primary causes of non-attainment within the watershed.
Finally, since 1990, volunteers of the Citizen Lake Awareness and Monitoring (CLAM) program have documented change in both the clarity and color of Indian Lake. Secchi disk readings in 1990 averaged 12 inches and never exceeded 22 inches. The color was generally brown due to heavy sediment loads. Today, the color of Indian Lake has shifted toward green, suggesting improved light penetration and a greater influence of algae production on clarity. Although the average secchi disk reading has shown slight improvement, volunteers have recorded maximum clarity measurements exceeding 70 inches in recent years.
Those involved in the project report success has been due to several factors: