The early 1960’s were a time of increasing environmental awareness. Pollution of the nation’s rivers and streams was a significant concern. One of the many questions of the day was, “If a contaminant is spilled in a river, how long will it take for that contaminant to reach the intake for the water supply for a city downstream from the spill?” A method was needed for determining the ‘time of travel’ for contaminants in a river.
I went to work for the U. S. Geological Survey (USGS) Nebraska District in 1965 as a Chemist in a USGS laboratory in Lincoln, Nebraska. In 1968 our laboratory team was informed that we would be participating in a time of travel study on the Missouri River which forms the border between Nebraska and Iowa. It had been determined that a fluorescent dye, Rhodamine, could be used to estimate the travel time of a contaminant in a river. Our office was instructed to purchase instruments called fluorometers that would measure the fluorescence of the dye in collected water samples. For our reach of the river, the dye would be poured from a bridge at Nebraska City and measured downstream successively at bridges at Brownville, Auburn, and Rulo, all towns in Nebraska located about 20 miles apart. Our lab team was assigned to the Brownville site. Other personnel from Nebraska and Iowa were assigned to the Auburn and Rulo sites.
Prior to beginning the project, the discharge (flow) of the Missouri River at Nebraska City for the day of the study was estimated to assure that sufficient dye would be used so that it could be detected at the downstream sites. The dye arrived in five-gallon cans at an Iowa USGS office in Council Bluffs, IA. A few days before the study took place, I was assigned to go to Council Bluffs, Iowa, and work with a person from the Iowa office to transfer the dye to gallon containers. It was not easy and before we were done we both were splattered with dye, as was the floor of the room where we were working.
When the study day arrived, the dye was injected into the river at Nebraska City at 9:00 am. Our crew of four arrived at a motel near the Brownville Bridge where we set up and tested our fluorometer. It was predicted that the leading edge of the dispersing dye cloud would begin arriving at Brownville late that afternoon, so we began sample collection at 3:00 pm. We used a sampler into which we inserted an 8-ounce sample bottle. We used a rope to lower the sampler about 60 feet to the water. When the leading edge of the dye arrived late that afternoon we collected samples at 10-minute intervals ferrying them every half hour to the motel for analysis. The dye peak arrived around 9:00 pm and we continued to sample until noon the next day by which time the samples were showing that the dye cloud had passed. During the night we had two crew members on the bridge collecting samples and ferrying them to the motel, a third person at the motel using the fluorometer to measure the fluorescence of the samples, and a fourth person at the motel trying to sleep. We alternated tasks every two hours. We were successful in determining the longitudinal shape of the dye cloud as it passed our location, but, as you might guess, none of us got much sleep.
The study was successful as were several others around the country carried out at the same time. The use of dye became a preferred method for simulating the movement of contaminants in a river and provided background information for future contaminant models still being used and refined today. Although it was hard work at the time, looking back on it, it was fun playing a small part in a revolutionary scientific study.