Auglaize River, Connections Between Land Management And Biological Conditions1 (11/8/04 version)


The Auglaize watershed covers about 391 miles of drainage area and nearly three dozen streams in parts of Allen, Auglaize, Paulding, Putnam, and Van Wert counties. About 89 percent of the area is farmland, about 8 percent is forest, and 2 percent is residential and commercial. In 1998, the Upper Auglaize was listed as a "state priority impaired watershed", but water quality assessment data collected and compiled since then indicates that many of its stream segments now meet water quality standards.

Changes in Upper Auglaize River water quality illustrate the power of integrating biological and other data. Before 1990, few farmers implemented management practices such as conservation tillage or no tillage (<5% of cultivated acres). An intensive program to change tillage practices began in 1990; most farmed acres were treated by 1993 (Figure 3, upper panel). According to data collected by USGS, annual loadings of total suspended solids (TSS) in the river decreased by 50% in the late 1990s (Figure 3, middle panel; Myers et al. 2000).

The 60% decrease in summer TSS was even more striking; high summer TSS, when flows are generally low, are probably due to excessive algal growth rather than suspended mineral soils. Most important perhaps, these changes in land practices were followed by improved biological condition, as assessed by the fish index of biological integrity (IBI; Figure 3 lower panel). Median IBI increased by about 15 points, from the high 30s (fair) to the low 50s (exceptional), after a decade of conservation tillage on most of the basin's cultivated lands. Changes in fish assemblages captured in IBI metrics were expected with reduction in nonpoint stressors such as suspended solids, nutrients, and their primary (e.g., substrate quality) and secondary (e.g., diel dissolved oxygen regime) effects. As a result, the river came into compliance with Ohio's biological criteria for "warmwater" and even attained an "exceptional warmwater" rating (as defined in Ohio Administrative Code 3745-1-07.

Figure 3 (PDF 66kb), Connections between land management changes and improvements in biological condition in the Auglaize River mainstem, Ohio.1

Summary Data (JPG 123kb)

1. Karr, James R. and Yoder, Chris O. "Biological Assessment and Criteria Improve TMDL Decision Making." Journal of Environmental Engineering, Volume 130, No.6, June 1, 2004. pp. 594-604.