Rain that infiltrates the waste body generates leachate at a rate given by the standard water-balance method used to size real landfill sumps:
Q_gen = I · A · C
I = rainfall intensity (m/day)
A = landfill footprint area (m²)
C = infiltration coefficient (0–1)
Leachate collects above the composite liner and its head h rises or falls with the balance between what arrives, what the pump removes, and — if the liner is imperfect — what leaks through it. The sump is modelled as a simple reservoir:
dh/dt = (Q_gen − Q_pump − Q_leak) / A_sump
A liner is never a perfect barrier: pinholes, seams and punctures let water through at a rate that grows with both the defect fraction and the hydraulic head pushing on it — a Darcy-law leak:
Q_leak = k · (1 − integrity) · A_liner · h
k = liner leakage coefficient
integrity = fraction of the liner still intact (0–1)
Note: the original 3D build of this simulator multiplied Q_leak by an extra undocumented ×1000 that appears nowhere in the formula it displays — the effect was that a mere 10% liner defect fully drained the sump and leaked hundreds of m³/day even under ordinary rainfall, making "liner integrity" behave as an almost binary switch instead of the gradual Darcy relationship the text describes. This build's constant (k below) is recalibrated so Q_leak sits on the same order of magnitude as Q_gen and Q_pump, matching the formula exactly as written above — verified numerically before shipping.
- Rainfall intensity and infiltration coefficient set how fast Q_gen fills the sump — a storm event spikes both instantly.
- Liner integrity — drop it below 100% and any standing head starts driving water through the liner into the aquifer layer below; watch the plume appear.
- Pump capacity — the collection system's maximum daily draw-down; if Q_gen ever exceeds it, head keeps climbing no matter how good the liner is.
- The risk bar tracks a smoothed function of current leak rate and head — real landfill designs keep head under ~30 cm and integrity near 100% specifically to hold this near zero.
- Drag the cross-section left/right and scroll to zoom; the strip chart below tracks head and leak rate over the last two simulated minutes.