Nitrogen and phosphorus are essential nutrients found naturally in the environment. They help plants and aquatic organisms grow. But too much nitrogen and phosphorus in rivers and streams can contribute to excessive algae growth and other water quality problems.
The Miami Conservancy District (MCD) has studied nutrients and water quality in the Great Miami River Watershed for more than two decades. Our work includes long-term surface water monitoring, nutrient source research, water quality modeling and implementation of innovative nutrient-reduction strategies.
That long-term scientific record helps MCD and our regional partners better understand where nutrients come from, how they move through the watershed and which strategies are most likely to improve water quality.
Excess nitrogen and phosphorus can change the ecological balance of rivers, streams and lakes.
Under the right conditions, elevated nutrients can contribute to excessive algae growth. As algae grow, die and decompose, they can affect dissolved oxygen—the oxygen in water that fish and other aquatic organisms need to survive.
Nutrients leaving the Great Miami River Watershed also contribute to water quality problems downstream, including nutrient enrichment in the Ohio and Mississippi river systems and the Gulf of Mexico. MCD's earlier water quality materials identified excessive nutrients as a continuing challenge both locally and downstream.
Nutrients enter rivers and streams from many sources.
Nonpoint sources are diffuse sources carried across or through the landscape. They can include runoff and drainage from agricultural land, stormwater runoff, soil erosion and other sources.
Point sources enter waterways from identifiable discharge points, such as wastewater treatment plants.
Agriculture is particularly important when considering nutrient sources in the Great Miami River Watershed because more than 70 percent of the watershed's land is used for agriculture.
Farmers throughout the watershed have implemented conservation practices to reduce soil erosion and nutrient loss. MCD has worked with agricultural producers, Soil and Water Conservation Districts and other partners to support and evaluate those efforts.
Understanding both point and nonpoint sources is essential to understanding nutrient conditions across an entire watershed.
MCD has collected extensive water quality data from the Great Miami River and its tributaries.
MCD's nutrient-focused surface water monitoring program provides information about nitrogen and phosphorus concentrations and loads and how they vary across the watershed and over time.
Rainfall, river flow, season, land use and other conditions can all influence the amount of nutrients moving through a river. Long-term monitoring helps distinguish individual measurements from broader patterns and trends.
This scientific record also provides data needed to investigate nutrient sources, evaluate potential management strategies and support additional research.
There isn't a single answer to the nutrient question.
MCD's research demonstrates that nutrients are part of a complex river system. The amount of nitrogen or phosphorus present is important, but so are river flow, nutrient sources, algae, dissolved oxygen, physical habitat and other environmental conditions.
Over more than two decades, MCD has conducted, funded or partnered on research examining different parts of that system.
MCD has studied nitrogen and phosphorus concentrations and loads throughout the Great Miami River Watershed.
A major MCD report published in 2012, Nitrogen and Phosphorus Concentrations and Loads in the Great Miami River Watershed, Ohio, 2005–2011, documented nutrient conditions using years of monitoring data.
Subsequent work evaluated nutrient loads, yields and mean concentrations using monitoring data through 2016.
[Internal link: Nutrient Concentrations and Loads Research]
MCD has also supported research designed to better understand the sources of nitrate in the Great Miami River Watershed.
Identifying nutrient sources matters because effective water quality strategies depend on knowing where nutrients originate and how they reach rivers and streams.
[Internal link: Dual Isotope Tracing of Nitrate Contaminant Sources, 2019]
Nutrients don't simply enter a river and immediately move downstream.
MCD-supported research has examined phosphorus associated with the riverbed and the potential movement of phosphorus between sediments and the water column.
This work helps scientists understand the role the river itself can play in nutrient cycling.
[Internal link: Benthic Phosphorus Fluxes in the Lower Great Miami River]
That question was at the center of one of MCD's most extensive nutrient research efforts.
MCD and regional wastewater treatment providers commissioned the Lower Great Miami River Nutrient Management Project, completed by LimnoTech in 2017.
Researchers developed a water quality model to examine relationships among nitrogen, phosphorus, algae, dissolved oxygen, river flow and other environmental conditions and then tested different nutrient-reduction scenarios.
One of the important findings was that large reductions in phosphorus from major wastewater treatment facilities were not predicted to result in correspondingly large improvements in algae or dissolved oxygen conditions in the Lower Great Miami River.
The research demonstrated that the relationship among nutrients and river conditions is more complex than assuming that reducing one source of phosphorus will produce an equivalent improvement in water quality.
Explore the Lower Great Miami River Nutrient Management Study
- Read the 2017 Technical Report
MCD has also tested an innovative, market-based approach to reducing nutrients.
The Great Miami River Watershed Water Quality Credit Trading Program began as a pilot in 2004. It connected wastewater treatment providers with voluntary agricultural conservation projects designed to reduce nitrogen and phosphorus entering rivers and streams.
By December 2015, the program had:
Contracted 467 agricultural projects
Generated more than 1.14 million water quality credits
Committed more than $1.76 million to agricultural producers
Produced an estimated 626-ton reduction in nutrient discharges over the life of the projects.
The U.S. Environmental Protection Agency later featured the Great Miami River Watershed program as a case study in water quality trading.
Learn about the Water Quality Credit Trading Program
Water quality decisions can have significant environmental and economic consequences.
MCD's role is to provide sound watershed science that helps communities and partners understand water resources and evaluate potential solutions.
Long-term monitoring allows us to see how conditions change. Research helps us understand why. Modeling allows scientists to test possible management strategies. Collaborative programs allow promising approaches to be put into practice.
Together, those tools help answer the questions that matter:
Where are nutrients coming from?
How are nutrient levels changing?
How does the river respond to them?
Which actions are most likely to produce meaningful water quality improvements?
MCD's nutrient work includes long-term monitoring, applied research, modeling and on-the-ground nutrient reduction projects.
Water Quality Credit Trading Program begins
MCD and its partners launch a pilot program using voluntary agricultural conservation practices to generate nitrogen and phosphorus reductions.
Long-term nutrient monitoring provides a watershed-wide dataset
MCD collects data used to evaluate nitrogen and phosphorus concentrations and loads throughout the watershed.
Nitrogen and Phosphorus Concentrations and Loads report
MCD publishes an analysis of nutrient conditions using monitoring data collected from 2005 through 2011.
Water Quality Credit Trading pilot reaches 467 projects
Projects contracted through the program represent an estimated 626 tons of nutrient reductions over their project lives.
Additional nutrient and phosphorus research
Research expands understanding of nutrient loads and the movement of phosphorus between river sediment and the water column.
Lower Great Miami River Nutrient Management Project
A sophisticated water quality model evaluates how different nutrient-reduction scenarios may affect algae and dissolved oxygen in the Lower Great Miami River.
Research investigates nitrate sources
Isotope analysis provides another tool for investigating where nitrate in the watershed originates.
Monitoring continues
MCD continues collecting and evaluating water quality data to better understand the Great Miami River Watershed and inform regional water resource decisions.
Explore MCD Water Studies and Research
Nitrogen and phosphorus are naturally occurring nutrients needed by plants and aquatic organisms. Problems can occur when excessive amounts enter waterways and contribute to excessive biological growth or other changes in water quality.
Nitrogen and phosphorus come from both point and nonpoint sources. Sources can include agricultural runoff and drainage, wastewater treatment plant discharges, stormwater and other pathways.
Yes. Agriculture can contribute nitrogen and phosphorus through runoff and drainage. Because more than 70 percent of the Great Miami River Watershed is agricultural land, understanding and reducing nutrient losses from farmland is an important part of watershed nutrient management.
Yes. Treated wastewater can contain nitrogen and phosphorus and is a point source of nutrients. MCD's research emphasizes the importance of understanding the relative contributions and environmental effects of multiple nutrient sources when evaluating management strategies.
Phosphorus can contribute to algae growth, but MCD's Lower Great Miami River research demonstrated that the relationship among phosphorus, algae and dissolved oxygen is complex. Modeling found that large reductions in point-source phosphorus alone were not predicted to produce similarly large improvements in algae or dissolved oxygen conditions.
Learn what the Lower Great Miami River study found
A nutrient concentration describes the amount of a nutrient in a given volume of water. A nutrient load describes the total amount transported by a river or stream over a period of time.
Both measurements are useful. A river can have a relatively low nutrient concentration but transport a large nutrient load because of the volume of water flowing through it.
Water quality credit trading is a market-based approach that creates economic incentives for reducing pollutants. MCD's pilot Water Quality Credit Trading Program supported voluntary agricultural conservation projects that reduced nitrogen and phosphorus entering rivers and streams.
How MCD's Water Quality Credit Trading Program worked
MCD's modern nutrient research and program work spans more than two decades, including the launch of its Water Quality Credit Trading Program in 2004, long-term surface water monitoring, nutrient load studies, source research and Lower Great Miami River water quality modeling.
Water Quality Credit Trading Program
How MCD and its partners tested a market-based approach to reducing nitrogen and phosphorus.
Learn about Water Quality Credit Trading →
Lower Great Miami River Nutrient Management Study
What scientific modeling tells us about phosphorus, algae and dissolved oxygen in the Lower Great Miami River.
Explore the Nutrient Management Study →
Surface Water Monitoring
Learn how MCD monitors the rivers and streams of the Great Miami River Watershed.
Explore Surface Water Monitoring →
Water Studies and Research
Access MCD technical reports, scientific studies and watershed research.
