Groundwater levels recorded in Qb35-08, a 14-foot deep monitoring well located approximately 5 miles west of Laurel, DE show a remarkable response to tropical storms Irene and Lee, which occurred in August and September, 2011, respectively. Groundwater levels and temperatures in Qb35-08 were collected with an automated pressure-temperature datalogger system. At the same time, rainfall and soil moisture data were recorded by the DEOS Laurel Airport station located approximately 5 miles from the well. In the following illustrations daily mean groundwater levels and groundwater temperatures, total daily rainfall, and daily maximum volumetric soil water content are plotted to show how groundwater,
rainfall, and soil moisture are related.
Note the two big storms were 6.6 (Irene, August 27-28) and 3.7 (Lee, September 8) inches. In response, groundwater level (gwl) rose more than 9-1/2 feet, with the largest rise occurring after the second storm. Though a 9-1/2- foot rise in groundwater level within a few weeks’ time is remarkable, long term the gwl are within the range of previously observed gwl. The shallowest groundwater levels observed in this well, about 3 feet below land surface, are very common in this part of Delaware and a primary reason why there are very few homes with basements in the area. Daily mean groundwater temperatures do not show a noticeable affect from the storm events.
The timing and magnitude of groundwater level rise is related to the rainfall amount and the antecedent maximum daily volumetric water content (VWC) or soil moisture conditions. Prior to t