CALL FOR PROPOSALS:

ORGANIZERS

  • Harvey Thorleifson, Chair
    Minnesota Geological Survey
  • Carrie Jennings, Vice Chair
    Minnesota Geological Survey
  • David Bush, Technical Program Chair
    University of West Georgia
  • Jim Miller, Field Trip Chair
    University of Minnesota Duluth
  • Curtis M. Hudak, Sponsorship Chair
    Foth Infrastructure & Environment, LLC

 

Paper No. 11
Presentation Time: 4:15 PM

HYDRAULIC RELATIONSHIPS BETWEEN BURIED VALLEY SEDIMENTS AND ADJACENT BEDROCK FORMATIONS


SEYOUM, Wondwosen Mekonnen, Geology, Kent State University, McGilvrey Hall 221, Kent, OH 44242 and ECKSTEIN, Yoram, Department of Geology, Kent State University, McGilvrey Hall, Kent, OH 44242, wseyoum@kent.edu

A buried valley is an ancient river or stream valley that predates the recent glaciation and since has been filled with glacial till and/or outwash. Outwash deposits are known to store and transmit large amounts of ground water. Their productivity largely depends on their hydraulic properties, rate of recharge and their hydraulic relationship with the adjacent bedrock formations. We illustrate these relationships by using MODFLOW to simulate steady-state three-dimensional flow through a section of a buried valley in Northeastern Ohio. The flow domain was divided into five hydrostratigraphic units: low conductivity (K) till and high K outwash within the buried valley and three bedrock units: Pottsville Formation, Cuyahoga Group and Berea Sandstone, while the pre-Berea formations served as a no-flow boundary. Model input data, e.g. spatial distribution of the hydrostratigraphic units and their hydraulic properties were estimated using the data from Well Log and Drilling Reports of residential water wells. The model was calibrated using observed hydraulic heads and flow data with mean residual head error of 0.3m (1.0’). The calibrated model was used to quantify flux between buried valley and bedrock formations. Mass balance for the model consists of 2.74 Mm3/yr ≈ 85% of inflow by recharge from precipitation and 0.48 Mm3/yr ≈ 15% of inflow across the upstream model boundary. Within the model, buried valley receives 1.6 Mm3/yr from the adjacent bedrock aquifers. Mass balance along the buried valley/bedrock contact indicates that Pottsville Formation contributes 0.96 Mm3/yr (or 0.34 Mm3/yr/km) while the Berea Sandstone contributes 0.64 Mm3/yr (or 0.22 Mm3/yr/km). Model outflow consists of baseflow 0.715 Mm3/yr drain, 2.88 Mm3/yr discharge at the lower boundary and 0.66 Mm3/yr outflow along a section of buried valley/bedrock interface. The calculated mass balance error is -2.2%.

Groundwater mass balance for the buried valley sediments

Inflows

Outflows

Units

m3/d

%

m3/d

%

Drain (baseflow)

0

0

-1960

-17

Flow across the model boundaries

1015

9

-7880

-68

Recharge

5975

52

0

0

Bedrock aquifers

Pottsville Formation

2650

23

-1800

-15

Berea Sandstone

1750

15

Total Flow

11390

100

-11640

100

Inflow - Outflow

-250

-2.2

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