Date of Award
Master of Science (MS)
Groundwater discharge is an important contributor to the water budget of a lake. The variability of hydraulic parameters of lake and groundwater systems causes difficulties in estimating the contribution of groundwater to a lake water budget. This study attempts to show that amount of variability for a small portion of the lake and shore (8 x 15 meter section, starting approximately five meters from shore and extending nine meters into the lake).
Piezometers were installed at a depth of one half and one meter in nests at 70 locations in the rectangular study site. Water levels were collected from the piezometers and used to determine gradients. Temperature and conductance data of the water in the piezometers were collected. Hydraulic conductivity was estimated with slug tests on a number of the piezometers. The horizontal and vertical gradients generated from the water levels and the hydraulic conductivity data were used to compute horizontal and vertical flux. Seepage meters also were installed on two occasions to obtain data on groundwater flow entering the lake through different parts of the lake.
At this site, the variability of the studied parameters could be quite large over small distances. The shore area was found to be an influence on the discharge to the that there were downward gradients on shore.
Most of the flow into the lake system was concentrated at the shore, except for an area where increased seepage was found in the lake. The area of largest estimated flux into the lake was at the shoreline in very shallow waters where seepage meters could not be used.
A general application of the results suggests that care should be taken to avoid developing areas where groundwater discharge is taking place and the groundwater system is shallow, such as the Shingobee site. Construction of homes and installation of wells and septic systems near the shoreline may affect groundwater discharge to the lake. This could increase nutrient addition to the lake, which would adjust the ecology significantly.
Kishel, Hans F., "Small-scale variability of groundwater-lake interaction at Shingobee Lake, Minnesota" (2000). Theses and Dissertations. 160.