What does 'infiltration' refer to in the context of water systems?

Infiltration, in the context of water systems, specifically refers to the process by which groundwater or surface water enters the sewer system, typically through cracks or openings in the pipes and infrastructure. This extraneous water can contribute to increased flow in the sewer system, which can lead to overflows or increased treatment costs at wastewater facilities. Understanding infiltration is crucial for effective sewer system design and management, as it helps engineers ensure that systems are capable of handling both the intended wastewater flow and any unintentional inputs.

The other options revolve around different aspects of water management or collection, but they do not accurately capture the definition of infiltration. For example, while drainage may involve moving water away from a site, it does not imply the unplanned entry of water into sewage systems. Stormwater management typically addresses surface water runoff and its handling, and rainwater collection focuses on harvesting precipitation, neither of which encompass the concept of infiltration into sewer systems.