An artesian aquifer is a confined aquifer containing groundwater that is under pressure. This causes the water level i a well to rise to a point where hydrostatic equilibrium has been reached.
A well drilled into such an aquifer is call an artesian well. If water reaches the ground surface under the natural pressure of the aquifer, the well is a flowing artesian well.
An artesian well is a well that taps into a confined aquifer (see above). Under artesian pressure, water in the well rises above the top of the aquifer, but does not necessarily reach the land surface. A flowing artesian well is one that has been drilled into an aquifer where the pressure within the aquifer forces the groundwater to rise above the land surface naturally without using a pump. Flowing artesian wells can flow on an intermittent or continuous basis and originate from aquifers occurring in the either unconsolidated materials such as sand and gravels or bedrock, at depths ranging from a few meters to several thousand meters. All flowing wells are artesian but not all artesian wells are flowing wells.
Flow from artesian wells should be controlled to prevent wasting groundwater. For instance, an uncontrolled artesian well flowing at 10USgpm (55m3/day) wastes 14,400 US gallons (2.0*104m3) per year. An uncontrolled flow of 1 USgpm wastes enough water to supply four homes. Wasting water may lower the confining pressure in teh aquifer so that the well no longer flows of flows at a reduced rate and affects the yield of neighbouring wells and springs.
The provincial regulatory requirements for controlling flowing artesian wells are outlined in section 77 of the Water Act. If artesian conditions are encountered when constructing or supervising construction of a well, the qualified well driller or qualified professional must ensure the artesian flow is or will be stopped or controlled and advise the well owner (and the land owner if applicable) of the steps taken to do so. It is also good practice to advise of any potential hazards associated with uncontrolled flow not being controlled(e.g., erosion, flooding, subsidence) and any associated costs. Agreement on these issues prior to drilling can help prevent or minimize misunderstandings. For example, some issues can be addressed in a contract. If the qualified well driller or qualified professional fails to stop or control the flow, it is the well owner's responsibility to hire another qualified professional of qualified well driller to ensure that the flow is stopped or controlled. If the ownership of the well is not known, the land owner is responsible to have this done. If the flow cannot be controlled, the person responsible for drilling the well should advise the Ministry of Environment's regional hydrogeologist and must comply with any direction given.
A flowing artesian well must have a securely attached cap to provide access to the well, prevent entry of vermin and contaminants, and to prevent flow escaping from the well.
A flowing artesian well is considered "under control" when the entire flow is through the production casing to the wellhead and the flow can be stopped indefinitely without leaking on the surface of the ground and with no leakage into any other aquifer penetrated by the well.
The BC Ministry of the Environment has more information on flowing artesian wells.
Artesian well-head changeover.
Drilling an artesian well
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