Montana Water Science Center
Clark Fork near Galen
USGS IN YOUR STATE
USGS Water Science Centers are located in each state.
Historically, scientists have assumed that a properly collected water sample will provide an accurate assessment of constituent concentrations in a water body on a given day assuming constant hydrologic conditions. However, an increasing body of evidence indicates that the concentration of many potentially toxic trace elements (such as arsenic, cadmium, copper, manganese, zinc) in streams can vary over a large range (up to 500 percent) during a 24-hour period irrespective of changes in streamflow. These diel concentration cycles have been shown to be robust and reproducible, having been documented in many streams separated by large distances, in different geologic environments, and over a large range of metal concentrations.
Graph of diurnal variation of metals in Prickly Pear Creek and High Ore Creek, Montana
Recent conferences on diel biogeochemical processes:
Effects of Diel Cycling on Stream Conditions
Fascinating Biogeochemistry: How Diel Cycling Complicates Surface-Water Monitoring
Diurnal Biogeochemical Processes in Rivers, Lakes, and Shallow Groundwater
Diurnal (Diel) Cycling of Chemical Constituents in Surface Water and Related Media—Scientific and Regulatory Considerations