Minnesota Water Resources Conference - Water Resources Center ...

BOOK OF ABSTRACTS
Tuesday, Monday, October 27 23
Poster Session 4:45–5:45
Measuring the Volume of Lake Water Losses to Groundwater through Wintertime Water Surface
Elevation Surveys
Matthew Redington, HDR Engineering, matthew.redington@hdrinc.com; Adam Kessler, HDR Engineering; John Nieber,
Chisago Lakes Lake Improvement District
There are approximately 22 lakes within the CLLID, many of which are connected by wetlands, channels or
pipes. Water budget analyses had been performed in the past for some of the lakes. These studies indicated
there were water losses occurring from the lake system that could not be explained through evaporation or
surface flow. It was suspected that water losses from the system were related to interaction between lakes and
groundwater.
In order to confirm and quantify water losses from lakes, 10 lakes were monitored over the winter of 2007-8. Ice
cover on the lakes limited the evaporation and inflow factors of the water budget. Fluctuations in water level
during the winter could then be attributed primarily to groundwater interactions. The lake monitoring involved
biweekly measurements of water surface elevation through holes cored in the lake ice. By tracking elevation
changes through the winter, and pairing elevation changes with aerial contour data, volume losses were
confirmed and quantified. The presentation will include methodology, results, and conclusions.
Vertical Agricultural Drains as a Source of Phosphorus to Streams
Jason Roth, University of Minnesota, roth0293@umn.edu; Paul Capel, U.S. Geological Survey, University of Minnesota
Subsurface drainage networks are common in agricultural areas which have poorly-drained, glacially-deposited
soils. In local topographical depressions, a vertical drain is often connected to the horizontal subsurface
drainage network to expedite the removal of the ponded water from the field. These vertical drains act as
sources of particle-associated phosphate and sediment to the stream via the subsurface drain network. For
this study, the concentrations of major anions, nutrients and sediment are measured in the ponded areas
around vertical drains, in the water moving through these vertical drains, and in the horizontal subsurface
drain in a field in north-central Iowa. After a June 2007 precipitation event of 1.3 cm of rain, concentrations
of orthophosphate increased from 0.05 mg/L to 0.12 mg/L-in a tile drain connected to vertical drains.
Orthophosphate concentrations in the ponded water surrounding a drain after the precipitation event was
observed at concentrations up to 0.30 mg/L.
51 Minnesota Water Resources Conference, October 27–28, 2008