EPA Using Aircraft to Study Eutrophication in Lakes

[EPA press release - May 7, 1972]

The Environmental Protection Agency plans to use specialized Army aircraft in a project beginning this month to study eutrophication in lakes and impoundments.

The Agency will employ both fixed wing aircraft and helicopters in a nationwide aerial survey of approximately 1,200 lakes. The purpose of the project is to identify bodies of water in the United States with potential or actual eutrophication (accelerated aging) problems brought on by the discharge of excessive amounts of phosphates into them from various sources. The survey is an integral part of an EPA control program to assist state and local governments, through construction grants, in reducing excess phosphates by additional municipal waste treatment.

Phosphates are nutrients that cause rapid growth of algae in bodies of water. When the algae decay, the process depletes the supply of oxygen and results in premature "aging" of a lake or pond, including the disappearance of desirable varieties of fish. Lake Erie has been widely cited as a classic example of eutrophication.

William D. Ruckelshaus, EPA Administrator, said the survey would determine the present conditions of the lakes, where the overabundance of nutrients is coming from, and where the condition of the lakes can be improved by curbing the phosphorus reaching the water from municipal treatment plants.

"Once we have this blueprint for a lake, EPA will offer the States and cities both financial and technical assistance in carrying out the requirements for phosphorus removal," Ruckelshaus said.

EPA will use two Huey helicopters and two Otter fixed wing aircraft in the project. The Huey is the Army work horse helicopter, capable of carrying up to 2,600 pounds of equipment, and the Otter is a single-engine utility plane with large wing surface.

The 18-month, $3 million survey will include sampling of each lake four times during the growing season. Airborne scientists will also make use of afield laboratory trailer on the ground.

The aircraft will be equipped with remote and contact sensors. First, they will fly over lakes using a device called a differential radiometer to detect chlorophyll levels in the water and another device, a thermal radiator, to measure surface temperature. Then the pontoon equipped aircraft will land on the lakes, and scientists will lower probes into the water to measure dissolved oxygen, conductivity, the acid-alkaline balance in the water, temperature and turbidity.

At the same time they will collect water samples from various depths and examine them by photomicroscopy for algae and concentration of chlorophyll. The samples later will be sent to EPA's Western Environmental Research Laboratory in Las Vegas for analysis of phosphates and nitrates.

Chemical data will be evaluated by EPA's National Environmental Research Center in Corvallis, Oregon, to classify the lakes as to degree of euthrophication.

The final step in the survey is to determine what percent of the phosphate in a lake comes from a sewage treatment plant and what effect a phosphate control strategy would have on that lake. EPA will have water samples taken from tributaries and outfalls to measure phosphate concentrations, input and output flow volume, conductivity, temperature, and nitrogen. With the assistance of the U.S. Geological Survey, EPA will also determine the sources of phosphates by studying aerial maps to ascertain the land uses of the areas surrounding the lake. For example, scientists can calculate that the use of fertilizers in a cornfield near a lake will drain a specific amount of phosphates into the water.

The survey will provide city, state, and Federal officials with appropriate knowledge about whether a lake can be improved by reducing municipal phosphates before a decision is reached to invest large sums of money in municipal phosphate removal facilities. In some cases, additional removal of phosphates at municipal treatment plants will not be sufficient because of significant amounts of phosphorus coming from natural run-off and from other non-point sources such as animal wastes and over-fertilization of crops.

For some lakes, these low cost survey techniques may prove inadequate to determine if additional municipal phosphate removal would be appropriate. In these instances, further studies will be necessary by state and other public and private agencies.

EPA has determined by questionnaires that of the Nation's 12,500 waste treatment facilities, 3,000 to 4,000 discharge into some 1,200 lakes or impoundments.

The aerial survey will inspect 400 lakes in 10 northeastern and northern states during 1972, and the remaining 800 next year. In addition to New York where 38 lakes will be sampled, the survey will cover New England states, Michigan, Minnesota and Wisconsin this year.