Working at the Platte River State Fish Hatchery in Honor, John starts by making sure that our YSI instrument (which measures temperature, depth, dissolved oxygen, conductivity, oxygen reduction potential and pH) is calibrated correctly to ensure we get accurate readings and good data.
He then travels to each of the eight sampling points on the tributaries and carefully submerges the YSI into the water. Readings he obtains from them will be downloaded directly from the instrument to our database. He also collects three “grab samples” which are flowing water specimens. Even in the dead of winter he is out there plunging his sample bottle into the frigid flowing water.
On the lake, samples are taken in the deep area at the west end of the lake. Secchi disc readings are obtained to track the clarity of the water. The YSR instrument takes readings at the surface and various depths down to the bottom, 90 feet below. When sampling is complete, the samples and the sampling log are returned to the Hatchery Lab for analysis. One final check, a post-sampling calibration, is performed on the YSR to assure that it is delivering accurate results.
At the Platte River State Fish Hatchery, Nicole Sherretz analyzes all of the samples collected from the tributaries and the lake. Nicole follows a very specific documented procedure to analyze samples. First, she carefully checks and sorts samples from the lake and tributary rivers to insure there is no misplaced specimens.
Because this lab also analyzes all of the samples from the Hatchery itself, as well as the other five DNR hatcheries across the state, the first step in the process is to avoid any cross contamination of samples with one another or the lab environment. Nicole also insures that every sample container is acid washed and rinsed with purified water between uses.
Phosphorus (the main element we’re concerned with) cannot be measured directly. Elemental phosphorus never occurs by itself in water, but always as some type of compound. Those compounds need to be broken down and phosphorus doesn’t breakdown easily.
So now the recipe calls for acid reagents and heat (250 degrees F for two and a half hours in a device called the “Digester”). This creates a colored organic material, which can now be measured to calculate the amount of phosphorus in the sample. Nicole makes sure the spectrophotometer is properly calibrated, so our results will be reliable. After the Digester does its job, a Jenway Spectrophotometer reads the color density to calculate the phosphorus concentration. This data is uploaded directly to our database, eliminating potential data entry errors. John and Nicole do a second review. If any data point looks “off” that sample can be re-analyzed if necessary.
Once all of the samples have been collected and analyzed, the results need to be studied by the Platte Lake Improvement Association. Our Science and Research Committee, specifically Wil Swiecki and Mike Pattison rely on their years of experience to identify any trends that may need attention. In the past, they’ve identified unusual loadings coming from tributaries feeding into the Lake. This is what led to us adding river tributaries to our sampling program.
With this program of sampling, analysis and monitoring we are able to carefully monitor the lake monitor for future problems.