groundwater response to stream stage fluctuations in a regulated stream, new martinsville, wv madan...
TRANSCRIPT
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