Consequences of Groundwater-Model Vertical Discretization in Risk-Based Decision-Making.

Area of Science:

• Hydrogeology
• Numerical modeling
• Environmental science

Background:

• Vertical discretization is a critical early decision in numerical groundwater model construction.
• Coarse discretization offers benefits like reduced data needs and computational cost but risks output bias.

Purpose of the Study:

• To investigate the impact of vertical discretization on decision-relevant simulated outputs in groundwater modeling.
• To assess whether model simplification through coarse discretization leads to biases affecting resource management.

Main Methods:

• Employed a paired complex-simple model analysis approach.
• Utilized a Bayesian framework and decision analysis.
• Examined two case studies: a synthetic unsaturated/surface/groundwater model and a real-world surface/groundwater nitrate transport model.

Main Results:

• Coarse vertical discretization can induce significant bias in certain decision-relevant outputs, such as streamflow characteristics and nitrate concentrations/loads.
• These biases may lead to flawed resource management actions.
• For some outputs, coarse discretization had minimal impact on decision-making.

Conclusions:

• The choice of vertical discretization significantly influences the reliability of groundwater model outputs for decision-making.
• Practitioners must carefully consider the trade-offs between model simplicity and potential biases.
• Overly coarse discretization can compromise the accuracy of environmental resource management strategies.