Groundwater level trends

Were groundwater levels high in 1999?

Wet and dry climatic conditions are often reflected in the position of the water table. Generally, precipitation and snowmelt infiltrate the ground surface and accumulate in the saturated portion of the soil below. As a result, the water table, representing the top of the saturated soil zone, rises closer to the surface. The water contained in this saturated zone contributes to three processes of hydrologic importance:

  1. Water drains downward to underlying aquifers
  2. Water drains toward lakes and streams where it enters the surface water flow system
  3. Water is taken up by plant roots and used for plant growth or lost to the atmosphere via transpiration.

 

Over time, and without additional rainfall, the increased groundwater will disappear from the soil and the water table will recede to positions deeper below the land surface. These decreases and increases of the depth to water table make up the normal fluctuations that occur seasonally as well as in longer cycles of climatic variation.

Check the position of the water table in May of 1999 relative to years in the past. At points around the state where DNR Waters maintains water table monitoring wells, the May 1999 water table at each point is compared to the point's average May water table. The averages were determined from the past data available for each well. The length of data records for these calculations varied for each well, but in most cases there were 15 to 20 years of data. The dots on the figure are color coded to represent the magnitude of the 1999 departure from the average, with blue colors representing higher water tables and reds showing lower tables. That departure is measured in feet.

The water table, in May of 1999, was generally higher than average in the western north and central parts of the state and tended to be lower in the eastern central and western south parts. These results are generally in alignment with the climatic influences shown in the precipitation ranking of Jan-Aug of 1999.