Water sampling and monitoring equipment becomes more automated.
As the push for cleaner water continues, water resource managers are charged with knowing what is in the water and how to improve it. In some cases, water-quality reports are required annually, and many consumers want to be able to check water purity often; for example, on a Web site. Even though the National Pollutant Discharge Elimination System Phase II is a "narrative rule," many permittees want numerical data to help them gauge how well the best management practices they're using are performing. For developing total maximum daily loads (TMDLs), an accurate measure of pollutants of concern is essential. Historical data are needed to show improvement in water quality. Getting accurate numbers requires a large quantity of data from monitoring devices..
What to Measure
As environmental monitoring technology advances, it is possible to measure more parameters continuously. Besides the "big four"—temperature, pH, conductivity, and turbidity—you can measure dissolved oxygen (DO), biological oxygen demand, phosphorus, nitrogen, metals, and pesticide and herbicide residues. What you measure depends on your terrain. If you are monitoring streams draining from farmland, you will probably be concerned with pesticide and herbicide residues. If you are handling land along freeways, you probably need to know heavy metal concentrations. Determine what might be a pollution source for your area and you can find a probe to measure it in runoff.
Parameters
The parameters that determine the health of a water body are closely interconnected. For example, a stream with high temperature is probably low in DO and high in turbidity. Waters low in pH often have a higher concentration of metals. Because of the interactivity, one measurement can sometimes provide feedback on the range of others. Or using more probes will yield a more precise reading of a stream's health.
Solar-Powered Monitoring in Kentucky
Barry Nichols, aquatic restoration specialist for the Metropolitan Sewer District of Louisville, KY, reports that the city and Jefferson County have 28 sites with permanently installed long-term monitoring devices. The US Geological Survey (USGS) also has placed discharge gauges around the county.
The biggest advantage of long-term, continuous monitoring is the well-defined data set it provides, Nichols states. For example, DO rises significantly in daylight hours when photosynthesis is occurring. In many streams, the concentration reaches supersaturation level during the day. The lowest level will be at dawn. A stream that is affected by low DO levels might appear to be fine with only a few readings a week. But four readings an hour, day or night, give a more accurate profile.
Better data also provide the opportunity to focus on real problems. Nichols says the district found that much of the data-gathering was a duplicated effort. "We were able to pare down the number of monitoring sites, and it allowed us to select sites that give us the best data and coverage."
Field teams maintain the monitors. They change batteries, clean the membranes, and retrieve the data. The cost of telemetry has prevented its use so far, but that might change. Parameters measured include temperature, pH, conductivity, DO, and DO saturation. The probes record readings every 15 minutes.
The bulk of the district's fleet is the Hydrolab MiniSondes from Hydrolab Corporation in Austin, TX, which manufactures the DataSonde 4a and the MiniSonde 4a. The DataSonde has seven expansion ports and the MiniSonde contains four ports that can be filled with whatever probes a particular site requires, including temperature, pH, oxygen reduction potential, DO, conductivity, depth, turbidity, chlorophyll, total dissolved gas, and nutrients. Hydrolab also makes the Surveyor 4a, a handheld data recorder that easily uploads data from the sondes and then transfers them to a PC.
Two situations affect the permanent monitoring stations. One is streams that tend to be "flashy" (a high flood peak of short duration) and carry a lot of sediment. The accuracy of the probe is decreased by the sediment packed around it and, Nichols notes, "we get weird readings and know that it needs maintenance." Another higher-risk position is a shallow stream that receives a lot of sunlight, increasing algae growth, which also fouls the probe.
Solar panels have replaced the batteries on most of the probes Nichols uses. The district originally used extended-life batteries, but if a battery was found to be 40-60% discharged during a routine maintenance check, it was replaced because it probably would be dead by the next maintenance cycle. "It doesn't make sense from the environmental perspective; we [were] throwing away more batteries," Nichols says. So the district began installing solar panels.
Some of the solar panels are under leaf canopy, so the district typically overestimates the size needed. Another reason for oversizing the panels is that they make good targets for "shooters." Nichols says the panels, from a local supplier, cost about $200 (the panel and associated equipment costs about $1,000), and with a long battery life they will last for years. "So far they work fantastically," he reports. The higher initial cost is paid off in about two and a half years of not buying new batteries.
Texas Lakes
Denton, TX, has an active water-monitoring program. Kenneth Banks, water resources program manager and a faculty member at University of North Texas, says the city samples the water in three creeks that eventually drain into Lake Lewisville, the city's drinking-water source. Because Denton is the largest municipality in the watershed, its activities strongly affect water quality for the region.
Parameters tested in the creeks include temperature, conductivity, total suspended solids (TSS), salinity, DO, pH, and turbidity. The city uses probes made by Hydrolab and by YSI Inc. of Yellow Springs, OH, which manufactures a popular multiprobe system and the Clean Sweep wiper assembly to clean probes even in difficult environments, allowing longer intervals between maintenance.
The probes are placed inside protective cages of square metal tubing. Some probes have telemetry hookups, and others use internal log capabilities. Data are downloaded to a Hydrolab Surveyor during the maintenance check and then to a PC in the office. The department also built its own data transfer capability for two sites using a cell phone modem to hook up to a Web page. Banks thinks they will expand this program to save data transfer time. So far, even with occasional battery failures, bad probes, and some vandalism, the city gets good data at least 90% of the time. Banks says the "vandalism" usually consists of someone pulling a probe out of the water to see what it is.
Because of money from an Environmental Monitoring for Public Access and Community Tracking (EMPACT) grant from the United States Environmental Protection Agency, the Denton department has been able to buy twice the number of probes needed at any one time, allowing the probes to be retrieved and replaced every two to three weeks. The used ones are brought in for cleaning and recalibration. This also cuts down on time waiting for parts for broken probes.
Denton is also using a biosensor to monitor a colony of clams in Lake Lewisville. The clams close their valves when they detect unfavorable conditions. Closed valves trigger automatic sampling for toxicity.
Kansas Water
The City of Olathe, KS; the USGS; EPA; the and Kansas Department of Health and Environment are conducting research on Lake Olathe. Development in the watershed is increasing, so watershed managers want to keep an eye on the water quality of the lake that serves as drinking water for the area. They installed YSI multiprobes to analyze specific conductance, pH, water temperature, turbidity, DO, and chlorophyll on Cedar Creek and at Lake Olathe near the water intake. An organic chemical of interest in Lake Olathe is the herbicide atrazine.
The probes sample every 15 minutes and transmit data to satellites that send them to USGS computers. The data are available to the public on a Web site. Officials hope to educate the public as well as improve the lake's water quality.
California Freeways
The California Department of Transportation has contracted with Law/Crandall Inc. to perform a study with automatic samplers along freeways, highways, park-and-ride lots, and rest-stop areas. Flow meters and rain gauges from American Sigma have been placed at 26 stations. Senior Engineer Nathan Schaedler of Law/Crandall in San Diego says the company is two years into a three-year study.
Locations where stormwater will drain are scouted, and the rain gauges and flow meters are placed in pipes near catch basins or intake strainers. When rain is predicted, crews program the units for the expected amount of rain. The usual aim is to collect 36 samples during a rain event, with a sampling of every 200 ml. This gives a flow-weighted measurement. No field testing is done. The samples are analyzed in the lab. Measurements are a combination of the usual parameters, such as TSS, DO, and pH, as well as herbicides, total metals, and dissolved metals.
Maintenance includes weekly downloads of rainfall totals to a laptop and then to a PC. Equipment and battery checks are done at the same time. Some units have solar panels for power. Prestorm prep includes calibration and programming.
Schaedler says the basis for the study is to see what is required to meet regulation permits and to characterize runoff more accurately. Also, it will provide a baseline to establish TMDLs and evaluate future treatment methods. "We've learned that the nature of stormwater is quite variable," he says. This also makes it challenging to program the units to collect representative samples of each rain.
Erosion Protection in Georgia
Qore Inc. in Gainesville, GA, is using automatic samplers on construction sites. Erosion control measures must be in place for sites that disturb more than 5 ac., and much of Qore's work consists of monitoring runoff along water- and sewer-line replacement jobs and road-widening construction. For example, the City of Gainesville is replacing water and sewer lines. The trenches cross a creek five times and run parallel to it for about 2 mi. Any sediment runoff from the project would pollute the creek that eventually flows into Lake Lanier, the drinking-water source for two counties. Sediment counts must be less than 25 nephelometric turbidity units.
Rodney Clark, senior engineering technician, says Qore installs erosion control measures and then situates TR3000 Storm Water Samplers both upstream and downstream from the project. The TR3000, from Durham Geo of Stone Mountain, GA, includes a microprocessor and a liquid crystal display and is powered by a field-replaceable gel cell rechargeable battery. A peristaltic pump fills a sample bottle and then reverses flow to clean the line. When rainfall occurs, the TR3000 collects a sample that can be examined for sediment. Some projects involve only sampling; others combine sampling and inspection of the erosion control measures after a half inch of rain.
Clark notes that Qore performs routine maintenance about every two weeks, checking the pump and sampler and changing the battery. Because of drought conditions in Georgia, some samplers haven't been used in two or three months, but they still need to be checked. One of the things that Clark likes about the Durham Geo sampler is that it resets itself every month.
There have been some incidents of vandalism, Clark adds, but most of the damage is done by animals, such as beavers that chew through hoses. A few units have been pulled out of the water by curious people and left nearby.
Advanced Environmental Monitoring in Albany, GA, performs similar tasks. Ronnie Bridges, geotechnical director, says about 60% of the company's projects are linear ones, such as road development or pipeline construction, and the other 40% involve construction areas. The company also uses Durham Geo products; some of the units include telemetry add-ons to send data to the office. Based on the amount of rainfall, the office staff knows when to check the devices. "Anytime you have an inch of rain, you will have runoff," Bridges maintains. He says the units have worked well and receive a weekly maintenance check. One problem, however, has come with the rain they are measuring: A few of the units have been hit by lightning. Another precaution the staff has learned is to watch for snakes when performing maintenance checks.
"The Dirtiest Lake"
Onondaga Lake, near Syracuse, NY, has been described as "the dirtiest lake in the United States." About 90% of the lakeshore is urban, and some pollution is still coming from industrial sites that haven't been used in 15 years. High algae growth, low DO, and high salinity (sometimes three or four times higher than allowed standards) make this lake a perfect place for learning about impaired waters.
A nonprofit group called Upstate Freshwater Institute (UFI) is studying the water in the lake. In 2000, UFI received an EMPACT grant and began collecting data. Partners in the study are the Syracuse schools, which use the lake data in teaching about the environment.
Dave O'Donnell, engineer for the group, says UFI installed three remote underwater sampling station (RUSS) buoys from Apprise Technology Inc. of Duluth, MN. A RUSS buoy includes solar cells, rechargeable batteries, and a platform that can raise and lower a probe package to collect samples at different depths. One buoy has three floating arms and solar panels and is anchored in Onondaga Lake. Two smaller buoys are in the Seneca River, which flows out of the lake. Each buoy supports a package of Hydrolab DataSondes. O'Donnell says they are measuring temperature, conductivity, pH, DO, turbidity, and chlorophyll.
Data are communicated through a cell phone-modem connection and loaded into a PC. The sondes sample every hour; those in the river download data early every morning. The buoy and sonde package in the lake also does a profile of a vertical column of water at noon and downloads the data at 1 p.m.
O'Donnell says the main reason for the purchase of the combo RUSS and Hydrolab DataSondes was the capability to sample at different depths. This ability provides much more data and therefore a more accurate characterization of the water quality.
Zebra mussels have invaded the river, and O'Donnell says the probes are sensitive enough to pinpoint colonies of mussels. After the water flows through mussels colonies, its turbidity and DO are lower and phosphate and nitrogen levels are higher. The lower turbidity is causing a heavier growth of weeds on the river bottom because sunlight penetrates to a greater depth.
UFI tries to perform weekly maintenance, especially on the lake buoy. Past pollution has given the lake a high concentration of hydrogen sulfide, which contaminates the oxygen probe. It needs to be changed every week. The river buoys are more likely to receive attention every other week.
"We had reasonably good success with the setup in 2000, about 80% uptime," O'Donnell reports, and uptime has increased to 99% since then. "We used to sample weekly from April to October," he notes, but now data sampling occurs several times a day, and understanding the lake has increased immensely.
Specialized Monitoring
As the need for more specialized monitoring and testing grows, especially in monitoring waters for which TMDLs are being developed, probes for additional substances are being developed. For example, CHEMetrics in Calverton, VA, manufactures a handheld water analysis system that samples colorimetrically and can be changed for the pollutant of concern. The Pittsburgh Airport and FedEx requested a probe to measure propylene glycol, the ingredient used for deicing airplanes; CHEMetrics recently developed a test specifically for the chemical.