Deborah M. Olszowka, Environmental Specialist

Jason P. Heath, Water Quality Monitoring & Assessment Programs Manager

Peter A. Tennant, P.E., Deputy Executive Director

Ohio River Valley Water Sanitation Commission (ORSANCO)

The seasonal development of a zone of hypoxia in the Gulf of Mexico, which poses a threat to commercial aquatic communities, has been associated with nutrient loadings from the Mississippi River. This oxygen-depleted zone occurs in bottom-waters and currently includes an area of approximately 7000 square miles, extending from the mouth of the Mississippi River, westward along the coast towards the Texas border. The Ohio River Basin constitutes approximately 20 percent of the Mississippi Watershed, and contributes about 35 percent of the river’s total flow. It is therefore logical to suspect that nutrient loadings from the Ohio River could be contributing to eutrophication problems in the Gulf. In the fall of 1997, the Ohio River Basin Water Sanitation Commission (ORSANCO) began conducting a study to evaluate nutrient loads and sources in the Ohio River Basin. The objectives of this project are to document present water quality conditions concerning nutrients in the Ohio River and its major tributaries, to quantify nutrient loads from major sub-basins to the Ohio River through water quality monitoring activities, and to assess the relative magnitude of nutrient sources (i.e., agriculture, POTWs, industrial discharges, urban runoff, etc.). In addition, the identification of priority watersheds within the Ohio River Basin will provide a basis for implementing and measuring the effectiveness of control programs to reduce stream nutrient loads in the Ohio River Basin and, ultimately, to the Gulf of Mexico.

The Ohio River Valley Water Sanitation Commission (ORSANCO) is an interstate water pollution control agency that was created in 1948 to administer an agreement among eight states. That agreement, the Ohio River Valley Water Sanitation Compact, committed the states to certain goals for the water quality of the Ohio River and its tributaries, and established the Commission as a body corporate with regulatory powers to oversee its execution. The Compact was signed by the Governors of the eight states- Illinois, Indiana, Kentucky, New York, Ohio, Pennsylvania, Virginia, and West Virginia, and was approved by the United States Congress.

In the Compact’s key provisions, the states pledge action to clean up the Ohio River and protect it from further abuse with the Commission providing information and a forum for the states to coordinate their activities. A guiding principle of the Compact is that pollution originating from one state shall not injuriously affect the waters of another state. Therefore, programs carried out by the Commission are designed to complement efforts by the states. Today, ORSANCO manages and operates programs for water quality monitoring and assessment, assists in emergency response management, establishes pollution control standards for the Ohio River, and facilitates interstate cooperation and coordination through an extensive committee structure.

The Ohio River Basin encompasses portions of 14 states with an area of more than 200,000 square miles, constituting over five percent of the total United States land mass. The mainstem itself forms in Pittsburgh at the confluence of the Allegheny and Monongahela Rivers. Extending 981 miles, the Ohio River forms the border between Ohio, Indiana, and Illinois to the north, and West Virginia and Kentucky to the south. When the Ohio River joins with the upper Mississippi River at Cairo, IL, it provides approximately two-thirds of the total flow of the Mississippi River at the confluence. As such, the Ohio River watershed may have a substantial influence on water quality of the lower Mississippi River, and subsequently the Gulf of Mexico.

Historically, nutrients have not been considered a water quality problem in the Ohio River. Data collected by ORSANCO from 1980 to 1990 for total phosphorus, nitrate/nitrite nitrogen, and ammonia nitrogen indicates either no change or decreasing concentrations in nutrient parameters at most of the 16 Ohio River sampling locations. However, while nutrients have not been seen as an Ohio River problem, they have been identified as a concern on tributaries. In 1994 305(b) reports, states’ collectively ranked nutrients as the fourth greatest cause of water use impairment in the Basin. In addition, public water suppliers are reporting increased algal populations and trends toward earlier seasonal algal blooms on some portions of the Ohio River and major tributaries. Therefore, further investigation of nutrients is necessary to quantify loadings from major tributaries that are not routinely monitored, estimate the relative contributions of point and nonpoint sources, and determine the level of reduction that is being achieved by current control programs within the Basin.

A zone of hypoxia in the Gulf of Mexico has recently been associated with nutrient loadings, primarily nitrogen, from the Mississippi River. Hypoxia occurs when dissolved oxygen concentrations occur at less than 2.0 mg/L. In the Gulf of Mexico this condition has been found to develop as early as April and continue into as late as October in bottom waters (Sabins, 1992). The size of the zone varies each year but typically extends from the mouth of the Mississippi River, westward towards the Upper Texas Coast. Since the Ohio River Basin constitutes approximately 20 percent of the Mississippi Watershed, and contributes about 35 percent of the river’s total flow, it is therefore logical to suspect that nutrient loadings from the Ohio could be contributing to the problems in the Gulf.

In the fall of 1997, ORSANCO received a $100,000 grant from the United States Environmental Protection Agency to evaluate nutrient loads in the Ohio River Basin. The purpose of this project is to quantify nutrient loads from major Ohio River sub-basins and to assess the relative magnitude of point and nonpoint sources. Ultimately, this data will document baseline water quality conditions upon which to measure future improvements and identify what is needed to achieve meaningful reductions in nutrient loading from the Ohio River Basin and eventually, the Gulf of Mexico. In order to achieve the project objectives five tasks have been established.

1. Compile and assess existing stream nutrient data.
2. Monitor tributaries to quantify loads where existing data is not sufficient.
3. Generate a mass balance of nutrient loads.
4. Estimate relative load contributions by source type.
5. Inventory control programs in the Ohio River Basin.

The purpose of this task is to assist in designing a sampling program to supplement existing data. Historical data for nutrients were compiled from five of ORSANCO’s bimonthly sampling stations for the period 1990 through 1996. From Figure 1 it is apparent that nutrient loads increase by more than 50 percent between mile points 279.2 and 531.5 over the seven-year period. On a temporal scale the mean monthly loading for total nitrogen increases significantly in December and tails off in June (Figure 2).

On major tributaries, average daily nitrogen loads were estimated over a seven-year sampling period (Figure 3). Based upon this data, loading is typically higher on major tributaries in the lower portion of the Ohio River indicating a correlation between loading and agricultural land use. Overall, the largest loadings originate from the Wabash River, Tennessee River, Great Miami River, and the Scioto River.

The objective of this task is to monitor significant tributaries during periods of higher nutrient loading. Existing ambient monitoring data was used to develop a monitoring program for the Ohio River Basin. Additional monitoring is necessary to supplement existing data to more accurately assess and estimate nutrient trends and loadings from Ohio River sub-basins. Data indicated that the upper portion of the Ohio River and several major tributaries were not significant due to relatively small loadings. Therefore, nutrient monitoring is being conducted in the lower two-thirds portion of the Ohio River at four mainstem sites and on 12 major tributaries (Figure 4). Biweekly samples are being collected and analyzed for total phosphorus, ammonia-nitrogen, nitrate-nitrogen, nitrite-nitrogen, and total kjeldahl nitrogen. Sample collection is being conducted during months when average monthly loads are relatively high. Therefore, sample collection took place from March through May, 1998 and will resume again in November, 1998 until February, 1999.

The objective of this task is to estimate relative contributions of nutrients from point and nonpoint sources for each eight digit hydrologic unit within the study area. Currently, there are no adopted water quality criteria for phosphorus concentrations in the Ohio, while the criterion for nitrate/nitrite nitrogen is 10 mg/L based upon the protection of water supplies. A review of NPDES permits for direct discharges in the Ohio River Basin in 1996 indicated that of approximately 11,000 permits, 2220 contained limits for ammonia nitrogen, 224 contained limits for total kjeldahl nitrogen, 34 contained limits for nitrate, 31 contained limits for nitrite, and 228 contained limits for total phosphorus. Using this information loadings for nutrient parameters will be calculated and incorporated into a Geographic Information System (GIS) format.

Better Assessment Science Integrating Point and Nonpoint Sources (BASINS) software is being used to estimate nonpoint source contributions within the Basin. BASINS integrates GIS, data analysis, and modeling systems to support a watershed based analysis.

The purpose of this task is to identify locations where control programs exist and to ascertain their adequacy in reducing nutrient loading. In the Ohio River Basin thirty-one non-point source (NPS) control programs focusing on the abatement of water quality problems associated with nutrients have been identified. Programs are being implemented in all five Ohio River states on small watersheds through partnerships among state and local governments, environmental groups, and communities. Typically, programs focus on public education activities and the implementation of Best Management Practices (BMPs).

In order to complete the project objectives the following work remains need to be completed.

• Continue monitoring for nutrients in the Fall of 1998.
• Estimate nutrient loadings from major Ohio River sub-basins using additional monitoring data.
• Estimate point source contributions using Permit Compliance System (PCS) data.
• Estimate nonpoint source contributions of nutrients BASINS software.
• Compile data and results into a final report.