Groundwater response to stream stage fluctuations in a regulated stream, New Martinsville, WV Madan...

Groundwater response to stream stage fluctuations

in a regulated stream, New Martinsville, WV

Madan MaharjanJoe Donovan

West Virginia University

Research interest

• Regulated streams are also transportation corridors for rail as well as industrial areas and tend to be sites of groundwater contamination, including some public water supplies.

• If the management of dams alters or controls groundwater flow here, then we may benefit from understanding how these controls work.

Background

a

b

Purpose• To develop an analytical model that explains spatial and

temporal aspects of surface-and groundwater interaction during an annual cycle of stream stage fluctuation;

• To estimate induced infiltration rate and bank storage using this model; and

• To distinguish vertical (i.e. recharge) from lateral (i.e. induced infiltration) stress.

Hypothesis• Lateral (stream-induced) stress is more prominent

than vertical stress (recharge) during high flow periods and vice-versa in low flow periods.

• A convolution-integral method was written in MATLAB to simulate aquifer heads in response to stream stage fluctuations (Hall and Moench, 1972).

Approach

Geology & A Conceptual Model

Assumptions

• Aquifer has a negligible head gradient towards a pumping well;

• Stream stage fluctuation was the main and only source of

aquifer head fluctuation;

• End of the baseflow recession was at steady state condition;

• Recharge from precipitation was uniformly distributed.

River stage and well heads across the dam

Negative correlation

High flow period Low flow period

Vertical and lateral infiltration

Observed and modeled well heads across dam

Vertical infiltration

Vertical infiltration and lateral groundwater flow from upper pool

Lateral infiltration only

Observed and modeled well heads in the lower pool

50 cm

20 cm

182.15m

181.7m

Bank storage and seepage rate in the upper pool

Outflow from aquifer

Inflow into aquifer

Bank storage and seepage rate in the lower pool

Storms

High flow period

Low flow period

Inflow period

Outflow period

Limitation of the model

• Estimated values could differ significantly from the actual values, in settings where

• significant regional gradient and/or aquifer heterogeneity are present; and

• the stream partially penetrates the aquifer.

Conclusions1. Stream stage fluctuations exerted greater control over

groundwater levels than recharge especially during high flow periods;

2. Anthropogenic activities could change groundwater flow paths and velocity; and

3. This method could be a useful tool identifying potential threats to water quality and planning future well field expansion or management.

Thank youQuestions

Method

(1)

h(x,t)= ΔH* erfc ( (2)

h(x,t)= (3)

V= (4)

v= V*n (5)

Q= (6)

H=Stream stageh= Aquifer headD= Aquifer diffusivityErfc=Complimentary error functionV=Unit-width saturated aquifer volumev=Bank storage Q=Seepage rate

River Stage Across Hannibal Locks and Dam

Glen Dale PWS