ALL IN A DAY’S HYDROGEOLOGY FIELD WORK

Hands on experience with some instrumentation in a hydrogeology course taught at Indiana University Purdue University Fort Wayne (IPFW) was demonstrated over an 8-hour out-door lab. Eagle Marsh, Allen County, Indiana, which is within an hour’s drive of the IPFW campus, was selected as the field site. The aims of the field trip were to examine the water chemistry of some ponds within Eagle Marsh and to identify groundwater flow direction using seepage meters, minipiezometers and a well nest. A further objective was to determine if there is any groundwater discharge into the ponds within the marsh. Water samples from the marsh were tested for nitrate, and the pH, temperature, conductivity, total dissolved solid (TDS) and dissolved oxygen (DO) were measured in-situ. A Guelph permeameter was used to determine the hydraulic conductivity of the soils.

The water chemistry shows that most of the ponds within the marsh have neutral pH, low conductivity, and low nitrate except for drainage ditch where the nitrate level was 18 ppm, above the 10ppm upper limit for drinking water standard. Seepage measurement and minipiezometers indicate groundwater recharge within the pond, that is, the marsh is losing water. Seepage velocity from seepage meter was 1.177 x 10^-3 cm/sec (6.18 m/yr.). The constructed well field was not successful even after three attempts. Analyses of soil samples indicate that the soil is the silty clay type. There is a strong positive correlation (r=0.999) between hydraulic conductivity and TDS as should be expected. Also, DO has a strong negative correlation with temperature (r=-0.939). In-spite of the failure of the permeameter and well nest, the weekend fieldwork demonstrated field techniques to students and how instruments discussed in lecture were used. The failure of equipment or method is also a learning experience of itself.