New Report Released
Since 2006, the Miami Conservancy District has operated an automated water quality sampling station on the Upper Great Miami River, downstream of Taylorsville Dam. The station monitors nutrient concentrations and suspended solids in a river system draining a primarily agricultural watershed of 3,000 square kilometers.
This report analyzes nearly two decades of data on nitrate-nitrogen and total phosphorus—two essential nutrients that, in excess, contribute to water quality degradation. The U.S. Geological Survey’s EGRET (Exploration and Graphics for River Trends) software was used to assess long-term trends in nutrient concentrations in relation to river discharge, seasonality, and time.
Key findings:
River flows have increased steadily since 1960 across all flow percentiles—maximum, mean, median, and minimum—affecting nutrient transport and sediment dynamics.
Nitrate concentrations remained relatively stable, with minor declines at high flows. However, average levels consistently exceeded the Ohio EPA’s threshold (1.5 mg/L) for biological over-enrichment.
Total phosphorus concentrations declined through 2017 but increased afterward, especially during low flows. Concentrations remained well above the Ohio EPA benchmark (0.13 mg/L), indicating ongoing nutrient loading.
While nitrogen and phosphorus are vital for aquatic ecosystems, elevated concentrations can disrupt trophic dynamics, fuel algal blooms, reduce dissolved oxygen, and degrade aquatic habitats. These impacts are documented in the Upper Great Miami River and downstream, including the Gulf's hypoxic zone.
Long-term monitoring remains essential for evaluating watershed health, guiding nutrient management strategies, and protecting water quality across the region.
Nutrients like nitrogen and phosphorus are essential for life. They support the growth of aquatic plants and algae that form the base of the food web. But just like too much fertilizer on your lawn can cause problems, too many nutrients in our rivers and streams can harm water quality.
When nitrogen and phosphorus become overabundant in rivers and streams, they disrupt the natural balance of aquatic ecosystems. This process—called nutrient enrichment—can lead to:
Algal blooms that reduce water clarity
Low dissolved oxygen levels, which stress or kill fish and other aquatic life
Toxic algae, which can pose risks to pets, people, and wildlife
Shifts in aquatic species, from healthy, diverse ecosystems to degraded habitats
See a side by side of a healthy river vs a river with an algal bloom:
Nutrients in the Upper Great Miami River and its tributaries mostly come from human activities, including:
Fertilizer runoff from agricultural fields
Wastewater discharges from treatment plants and septic systems
Stormwater runoff from urban areas
Atmospheric deposition from fossil fuel emissions
Despite decades of progress in treating wastewater, nutrient enrichment remains one of the most widespread causes of stream impairment in our region.
📷 Sources of nutrient pollution—farms, cities, rain, etc.
MCD has been monitoring nutrient levels in the Upper Great Miami River since 2006 using automated water sampling stations.
Our monitoring focuses on:
Nitrate-nitrogen
Total phosphorus
These nutrients are closely tracked because they can trigger water quality problems when concentrations are too high. Our analysis shows that:
Nitrate levels have remained elevated but stable over time.
Phosphorus levels initially decreased, but have increased again in recent years—especially during low-flow conditions.
Both nutrients exceed Ohio EPA thresholds for potential over-enrichment in large rivers.
Nutrient pollution doesn’t just impact fish and wildlife—it affects all of us:
It reduces recreational value of rivers for boating, paddling, and fishing.
It can threaten drinking water sources.
Nutrients from our watershed travel downstream, contributing to “dead zones” in the Gulf of Mexico.
Everyone has a role to play in protecting water quality. Here’s how you can help reduce nutrient pollution:
Use fertilizer responsibly and avoid applying before rain.
Plant native vegetation to absorb runoff.
Maintain your septic system.
Support local farmers using conservation practices.
Get involved with watershed groups and river cleanups.
🌱 Learn more about conservation practices →https://mcdwater.org/blog/get-the-dirt-on-the-benefits-of-healthy-soil
🛶 Explore recreation opportunities → https://www.mcdwater.org/river-fun
💧 Learn how MCD protects your water → https://www.mcdwater.org/about-mcd/preserving-water-resources
MCD Studies on Nutrients
