Transmissivity

Transmissivity is a hydrogeological parameter describing a material's capacity to transmit groundwater. It quantifies the rate at which water of a specific kinematic viscosity can move through a unit width of an aquifer under a hydraulic gradient. This property is essential for understanding groundwater flow patterns, aquifer storage capacity, and predicting the impact of pumping wells or contaminant transport. The standard units are typically m²/day or ft²/day, reflecting the volume of water transmitted per unit time across a vertical section of the aquifer with unit width under a hydraulic gradient of unity.

Transmissivity meaning with examples

• During a field study, the high transmissivity of a gravel aquifer was found to facilitate rapid groundwater flow. This allowed for quick recharge but also increased the risk of rapid contaminant spread from a nearby landfill. Understanding this parameter was critical for proper environmental management and long-term planning for the region.
• Numerical models simulating groundwater flow rely heavily on accurate transmissivity values. In this case, the model's calibration was greatly improved when higher transmissivity readings were recorded from the regional test wells, representing the known geology in the area.
• Dewatering projects, such as those in a construction site, are often assessed with transmissivity values, as a higher transmissivity means that more water can be removed and that the area can remain dry for the construction to commence.
• Water resource managers use transmissivity maps, which can indicate regions that may be affected by the over-extraction of water. Knowing the transmissivity of an aquifer informs the ability to predict how wells interact and to avoid groundwater depletion.