Forecasting leachate generation from pilot woodchip stockpiles using a three-dimensional transient flow model.

Area of Science:

• Environmental Science
• Hydrology
• Soil Science

Background:

• Leachate from woodchip piles poses risks to aquatic ecosystems.
• Accurate simulation of leachate requires understanding material hydraulic properties.
• Numerical modeling is increasingly used for predicting leachate generation.

Purpose of the Study:

• To simulate leachate generation from woodchip piles using HYDRUS-3D.
• To optimize hydraulic parameters for single (SPM) and dual (DPM) pore flow models using DREAM_ZS.
• To assess the suitability of SPM and DPM for predicting woodchip leachate.

Main Methods:

• Experimental setup of three 30 m³ woodchip piles (coarse and fine ground).
• Continuous leachate collection over six months.
• Numerical simulation with HYDRUS-3D and Bayesian calibration with DREAM_ZS.

Main Results:

• Leachate generation was similar across all woodchip piles.
• Optimized flow parameters did not differ between coarse and fine woodchips.
• Both SPM and DPM showed good agreement with field data (Nash-Sutcliffe efficiency > 0.6).
• Leachate was under-predicted during heavy rainfall events (1-27%).

Conclusions:

• The simpler single pore model (SPM) is adequate for field-scale leachate predictions.
• Optimized models can aid in developing woodchip pile management strategies.
• Further model refinement is needed for heavy rainfall event prediction.