Leaky Sewers Hydraulically Disconnect from Groundwater: A Proof-of-Concept

Area of Science:

• Environmental science
• Hydrogeology
• Urban infrastructure

Background:

• Aging sewer and stormwater pipes leak, degrading groundwater quality and altering urban water balances.
• Quantifying leakage flux is challenging due to complex interactions between pipes, soil, and groundwater.
• Existing models may inaccurately estimate leakage by overlooking threshold behaviors.

Purpose of the Study:

• To investigate the phenomenon of hydraulic disconnection between leaky pipes and groundwater.
• To demonstrate this disconnection using numerical modeling and analyze influencing factors.
• To provide a proof-of-concept for this mechanism in sewer-groundwater systems.

Main Methods:

• Numerical modeling of a hypothetical leaky pipe-groundwater system.
• Analysis of leakage flux under declining groundwater levels.
• Sensitivity analysis of hydraulic parameters and aquifer properties.

Main Results:

• Leaky pipes can become hydraulically disconnected from groundwater, similar to river-groundwater systems.
• Leakage flux initially increases with falling groundwater but becomes constant after hydraulic disconnection.
• Disconnection depth varies with aquifer material (e.g., 0.89m in sand, 4.00m in sandy loam).

Conclusions:

• Hydraulic disconnection is a critical threshold behavior in leaky pipe systems.
• Once disconnected, leakage flux is independent of groundwater level fluctuations.
• This finding is crucial for accurate leakage modeling and urban water management.