Well Hydrographs
Well HydrographsJust as river hydrographs are used to record and visualize variations in flow with time (as discussed in Module 4), a well hydrograph is a time series of hydraulic head recorded in a well. This provides information about the fluctuation of hydraulic head (equivalent to the water table in an unconfined aquifer), which reflects the combined effects of temporal variations in climate, recharge, and pumping (Figures 30-31). The U.S. Geological Survey maintains a database of active monitoring wells in major aquifer systems across the United States. Hydrographs provide information about seasonal patterns that may be associated with pronounced wet and dry seasons typical of some regions (for example, Central CA), as well as long-term trends driven by climate change, decadal-scale climate patterns like el nino, prolonged groundwater extraction, or human-induced modifications to natural recharge. We’ll cover examples of the latter two processes in the next section of the module (Module 6.2: Water budgets).
USGS
Video: Slag Heap Experiment (3:46)
Transcript: Slag Heap Experiment
Text On Screen: Slag Heap Experiment
Text On Screen: What would happen to groundwater if it rained on the slag heap?
Presenter: Now that we've thought about how and why groundwater is moving through this system, we want to use the groundwater model to make some predictions about how a contaminant would move through the groundwater system. So let's imagine our model represents a geologic cross-section under the East Helena smelter site and we want to think about how contamination from the slag heap would move through the groundwater system. So if the slag heap was rained on, arsenic and selenium from the slag would leach into the groundwater system. How do we think that contamination will move through this system and why? Take a minute to think about how and why contamination will move through this groundwater system.
Text On Screen: Where do you predict contamination will go if it rains on the slag heap? Why?
Presenter: Okay, so now we're going to add some dye at the location of the slag heap and see where that contamination moves in our model of a groundwater system.
Text On Screen: Watch in 8X fast motion
Text On Screen: Discuss: What happened and why? How was what happened in the model similar to the real world? How was what happened in the model different from the real world?