Pohjavesiovat

Pohjavesiovat are groundwater reservoirs located in the subsurface that store and transmit groundwater in permeable rock or sediments. The term is used in Finnish hydrology to describe discrete groundwater bodies that can be tapped for use, rather than a single uniform groundwater resource. Pohjavesiovat can be confined or unconfined, depending on the surrounding geology, and their boundaries are often defined by less permeable layers such as aquitards.

Formation and characteristics: Pohjavesiovat form in porous rocks or sediments with sufficient permeability, including fractured crystalline bedrock, sand and gravel deposits, or glacial tills with permeable lenses. Porosity and hydraulic conductivity determine the storage capacity and the rate at which groundwater can move through the unit. Recharge occurs primarily through precipitation and surface water infiltration, while discharge takes place at springs, seeps, or pumped wells. Groundwater quality is influenced by mineral content, rock type, and human activity in the recharge and discharge areas.

Occurrence and use in Finland: In Finland, pohjavesiovat are important sources of drinking water for many municipalities. They occur in regions with crystalline bedrock as well as in glaciofluvial and glacially deposited sediments. Mapping and assessment of pohjavesiovat support management of yields and protection of water quality. Protecting recharge zones, preventing contamination from land use, and monitoring groundwater levels and pollutants are central to sustainable use.

Management and protection: Groundwater resources are managed under environmental and water legislation. Sustainable abstraction, contamination prevention, and ongoing monitoring are standard practices. Climate change can affect recharge patterns and the availability of pohjavesiovat.

See also: pohjavesi, aquifer, hydrogeology, groundwater protection.