1980s: Extensive water quality data collected on the Aroostook

    Over an 11-year period ending Aug. 21, 1985, the U.S. Geological Survey (USGS) collected a wide-ranging set of chemical and biological water quality data on the Aroostook River at USGS Station No. 01017100. The sampling location was just upstream of Caribou’s sewage treatment plant.
Joseph P. Neilson, USGS supervising hydrologist in Augusta, responding in an email in 2001, said no known analysis of the web-based data “available for all to see and use” had ever been done. He added “USGS could continue water quality work provided matching funds were made available. Exposure that comes to the network through its web system and real-time groundwater and surface water data may spur interest from cooperating agencies.”
Key findings follow from my analysis of the USGS Caribou data – truly a labor of love. Sharon Behar’s book “Testing the Waters – Chemical and Physical Vital Signs of a River,” published by River Watch Network in 1997, was a major help to me.
Based on monthly USGS data, the median measure of dissolved oxygen (DO) in milligrams per liter (parts per million) was 10.6, the most frequent (modal) reading was 12.0. Median July and August readings, when DO may be depressed by higher temperatures and reduced water flow, were 8.4 and 9.0 mg/L respectively; sufficient for cold water fisheries (i.e. brook trout).
The median measure of alkalinity, one of the best measures of a river’s sensitivity to acid pollution (rain, snow, dry particles), was 26 mg/L of calcium carbonate. Sufficient alkalinity is important for aquatic life as it protects against pH changes (acidic shock) and so affects the waters’ ability to support life. Alkalinity of 20 mg/L and higher provides rivers a good buffer. However, high alkalinity systems are often highly productive in terms of algae and plant growth.
Most aquatic animals prefer a pH range of 6.5 to 8.0. First through fourth quarter median pH values at Caribou were 6.7 (Jan-Mar), 6.9 (Apr-Jun), 7.4 (Jul-Sep), and 6.9 (Oct-Dec). First through fourth quarter median water temperatures (degrees Fahrenheit) were 32, 46, 68, and 33.
An indicator of suspended sediment and other particles that can impact aquatic environments is turbidity, measured in Nephelometric Turbidity Units (NTUs). Generally, readings should not top 10 NTU. First through fourth quarter median NTUs at Caribou were only 0.75, 1.25, 1.05, and 1.0.
River segments generally have a consistent specific conductivity range (ability of water to pass an electrical current at a given temperature) that, once established, can be used as a baseline for comparison with regular measurements of conductivity. Significant changes in conductivity (higher or lower) could indicate a pollution discharge has entered the river. Higher conductivity readings indicate more total inorganic dissolved solids such as chloride, nitrate, sulfate, and phosphate anions; or sodium, magnesium, calcium, iron, and aluminum cations. On the Aroostook, the USGS has collected conductivity samples at Masardis, Washburn and Caribou. Median conductivity measures (microsiemens/centimeter at 25 °C) were 56 at Masardis, 75 at Washburn, and 90 at Caribou.
The USGS also tested (1975-85) for selected dissolved metals. Maximum detections of dissolved copper and aluminum were 20 and 140 parts per billion, respectively. These concentrations topped the “LC10s” for early-life stages of the Northern Leopard Frog and Spring Peeper. LC10 is the concentration of toxicant that kills 10 percent of the organisms being tested, usually over the period of one hour. A part per billion is equal to a teaspoon per one million gallons of water.
The median measure of nitrates at Caribou was 2.9 mg/L. Levels greater than 5 mg/L will generally impact fresh water eco-systems. Only seven of the 76 USGS samples at Caribou (9 percent) topped 5 mg/L. However, a nutrient of concern that emerged from this treasure trove of water quality data was total phosphorus (TP). The overall median measure was .05 mg/L. Generally, a TP concentration over 0.05 mg/L will likely have an impact on a river in terms of excessive algal and weed growth. In the Caribou data set, 37 (42 percent) of the 89 samples exceeded 0.05 mg/L.
And the USGS even sampled the water column for algae! The agency detected 83 genera of free-floating algae (plankton). Genera detected 15 or more times from 1975-81 were Achnanthes, Anacystis, Ankistrodesmus, Chlamydomonas, Cyclotella, Cymbella, Diatoma, Gomphonema, Melosira, Navicula, Nitzschia, Oscillatoria, Scenedesmus, and Synedra.
    Steve Sutter is a retired agricultural and resource economist living on a Presque Isle riverfront property that has been in his family since April 12, 1854. This is the tenth installment of his series on the history of the Aroostook River.