bypassflöden

Bypassflöden, or bypass flows, describe portions of fluid movement that propagate through a system via pathways that bypass the main pore network or primary flow channel. In hydrology, soil science and environmental engineering, they refer to water and dissolved substances that move through preferential routes—such as macropores, fractures, root channels, or specially designed bypass channels—that circumvent the bulk of the porous medium or treatment stage.

In soils and natural systems, bypass flows occur when rainfall or irrigation exploits discontinuities in the medium, allowing rapid infiltration or drainage along coarse conduits. This can lead to short residence times for water and solutes, reducing contact with sorption surfaces and altering transport and fate predictions for nutrients, pesticides, or contaminants. Similar processes can operate in engineered drainage, groundwater recharge, or canal systems where portions of flow circumvent traditional treatment or circulation paths.

Measurement and modeling of bypass flows rely on tracer tests, dye tracing, and observation of rapid breakthrough compared with matrix flow. In modeling terms, bypass flows are commonly represented with dual-porosity or dual-permeability frameworks that separate matrix flow from preferential pathways, or with models that include parameters for macropore conductance and fracture networks.

Implications of bypass flows are broad: they can accelerate contaminant transport, decrease apparent sorption and retardation, complicate groundwater recharge estimates, and affect the design and evaluation of drainage, treatment, and irrigation systems. Understanding bypass flows is important for accurate hydrological modeling, risk assessment, and the development of management practices that account for preferential transport pathways.