Nutrient Loading from Point and Non-Point Sources on Surface Waters by Adam Lanning

Why are Nutrients a Concern? Nutrients refer to nitrogen and phosphorous. Excessive levels in waters causes eutrophication. Eutrophication leads to diminished aquatic life. This limits availability for drinking water due to buildup of nitrates. Unsightly, odorous, nuisance for recreation.

Objectives of Paper Gain a thorough understanding of the impact of nutrient enrichment on surface waters. Learn the current status of U.S. surface waters. Learn the sources and proportion of nutrient discharges to surface waters? Examine the feasibility of nutrient regulation.

Effects of Nutrient Enrichment Enrichment means nutrient inputs beyond the ‘naturally occuring levels’. Nutrients are ‘naturally occurring’ and necessary for aquatic plant growth. Elevated levels unnatural and lead to toxic conditions.

Effects of Nutrient Enrichment Under normal conditions, a water body is able to buffer nutrients. Sediment will adsorb excessive inputs to some degree. Aquatic plants will cycle, absorbing during growth and releasing during the decay process.

Effects of Nutrient Enrichment When a water body is unable to adsorb input levels, excess levels will migrate downstream. Eventually downstream levels will build up and unwanted growth will occur. Excess growth is primarily the buildup of algal mass.

Effects of Nutrient Enrichment Excessive growths of algae will cause wide fluctuations in dissolved oxygen (photosynthesis). High levels during periods of light. Low levels of D.O. during periods of low light. Extended periods of low light can cause D.O. depletion.

Effects of Nutrient Enrichment As a watershed drains to the coastal areas, nutrient enrichment occurs. This leads to the same dissolved oxygen depletion. Hypoxic zones will form as a result of decaying algal growths. Most forms of life will suffer the hypoxic conditions.

Trophic State Trophic state refers to the ‘age’ of a water body. Can also be thought of as the amount of biological activity occurring at any given time. Younger water means less activity. The older the water, the more activity that is occurring within the ecosystem.

Eutrophication Nutrient enrichment leads to eutrophication. Characterized by excessive levels of nutrients. Excessive levels of biological activity. Characterized by algal blooms. Algae dies and decomposes. Decomposition process uses oxygen.

Conceptual Model

Clean Water Act Enacted in Meant to improve water quality of public waters. Focused on point source discharges (municipal and industrial). Minimal regulation on nutrients. Focused primarily on the more acutely toxic parameters (NH3-N, BOD, TSS).

Current Trophic State of Waters USGS studied 250 waters over 19 years across the United States. Monitored the trophic state of these waters. As defined by the USEPA. 25% of locations improved. 70% remained the same. 5% worsened.

Current Trophic State of Waters These numbers indicate that CWA did slow eutrophication. But, limited success on improving the trophic state. This was due to the multitude of nutrient sources. CWA has limited authority over non point sources.

Sources of Nutrient Inputs Non-Point sources include:  Agricultural  Urban runoff  Atmospheric deposition. Point Sources include:  Wastewater discharges  Industrial discharges.

Agricultural Inputs (Non-Point) Fertilizer Application  Fertilizer application deposits N and P on the soil.  During rain events, excess will run off via erosion or infiltration.  Unregulated application rates allows for this to occur.

Agricultural Inputs (Non-Point) Fertilizer Application  Field run off is sporadic and difficult to track.  P adheres to soil particles and can be eroded to waterways.  N is dissolved and will easily move through the underlying geology.

Agricultural Inputs (Non-Point) Manure containment and disposal  Majority of the cattle in the U.S. are raised on feed lots.  Feed lots produce large amounts of manure on small areas of land.  Manure is high in P and N and must be disposed of.

Agricultural Inputs (Non-Point) Manure can be spread back on the farm fields as a fertilizer. Lack of regulation allows for over-application. This results in nutrient enrichment of the soil. Excess nutrients will eventually run off to the waterways.

Urban Runoff (Non-Point) Urban runoff includes:  Construction site runoff  Lawn fertilizer runoff  Septic tank discharges  Pet wastes

Atmospheric Deposition (Non-Point) Fixed nitrogen is deposited back on the surface waters and lands. Originates from:  Combusted fossil fuels  Agricultural plant fixation

Wastewater and Industrial Discharge (Point Source) Wastewater discharge is a known contributor of nutrients to surface waters. Discharges are easy to monitor as the effluent is typically constant. Little regulation exists on N and P. These nutrients originate primarily from phosphate detergents and industrial processes.

Nutrient Contributions Contributions to the Gulf of Mexico were estimated using current modeling software by the USGS. Total nutrient (N and P) load rates:  Point Sources contribute <30%  Non-Point Sources contribute ~70%

Some Solutions to Nutrient Runoff Non-point sources typically require some buffer vegetation to stop P laden soil from eroding to surface waters. Natural wetlands can be used to accomplish this. Grass strips along waterways are also effective in filtering the water.

Grass Buffering Strip

Some Solutions to Nutrient Runoff Target fertilizer applications to meet the crop needs will minimize runoff. Land applying manure can be done in the same manner, meet the crops nutrient needs. No-till practices will leave the soil less erodible. No-till practice also uses less fuel and manpower, a benefit to the farmer.

Point Source Regulation Regulating wastewater dischargers will require massive infrastructure upgrades. It would be a very costly endeavor to upgrade plants to achieve USEPA proposed limits (.5 mg/L P and 3.0 mg/L N) Illinois alone would cost ~5.3 billion dollars in capital costs. ~500 million dollars/year annually to operate the upgraded facilities.

Summary Regulation to achieve low levels of nutrients will require a focus on all inputs. A ‘holistic’ approach to reducing inputs would provide the most benefit. Wetlands, buffer strips, target fertilization, and no-till practices would all benefit the farmer as well as the surface waters. Wastewater dischargers should be regulated in conjunction with the ag community.