Semi-Analytical Modeling of Transient Stream Drawdown and Depletion in Response to Aquifer Pumping

Area of Science:

• Hydrology
• Hydrogeology
• Environmental Science

Background:

• Existing stream depletion models often assume a fixed stream stage, which is unrealistic.
• Field observations confirm that groundwater pumping near streams causes stream stage to decrease (drawdown).
• This limitation can lead to inaccurate predictions of water availability.

Purpose of the Study:

• To develop analytical and semi-analytical models for stream depletion that incorporate transient stream stage drawdown.
• To address the deficiency in current models that use a fixed stream stage condition.
• To provide a more accurate tool for assessing the impact of groundwater pumping on surface water resources.

Main Methods:

• Developed new models based on stream channel mass conservation and finite stream channel storage.
• Validated models against field data measuring aquifer and stream drawdown.
• Analyzed model results to estimate aquifer hydraulic parameters, streambed conductance, and stream channel storage.

Main Results:

• The new models accurately predict stream depletion with transient stream drawdown.
• Models reduce to existing fixed-stage models under conditions of infinite stream channel storage.
• Models simplify to confined aquifer flow with a no-flow boundary when stream storage is negligible.
• Applied models to field data, yielding estimates of key hydrogeologic parameters.

Conclusions:

• Transient stream stage drawdown is a critical factor in stream depletion modeling.
• The developed models offer a more realistic approach to predicting stream depletion.
• Findings have significant implications for sustainable groundwater management and water resource allocation.