who moniters the quantity and quality of groundwater
Answers
In general, groundwater is not used as extensively as surface water [1]. This is primarily due to the lack of understanding and knowledge of groundwater. In addition, there are two main areas of concern with groundwater usage: maintaining quality and ensuring a sustainable quantity.
Groundwater Quality Issues
Just like surface water, groundwater quality can be diminished due to the effects of human use. Groundwater quality can be diminished from contamination of chemicals seeping into the ground, sewage contamination leaching into aquifers or from saltwater infiltration where saline water enters a freshwater aquifer.
Contamination
Water quality is a major concern for groundwater wells because contamination can come from a variety of sources. It is common for run-off from agricultural lands to percolate into the ground. This water may contain high concentrations of chemicals, including arsenic, ammonia, acids or nutrients like nitrates and phosphates from pesticides and fertilizers.
The amount of pesticides in groundwater in Alberta is of increasing concern[2]. In general, in order to produce the same amount of crops from year to year, farmers must use a higher dose of pesticide to have the same effect that it did a few years prior (also known as the law of diminishing returns) meaning the amount of chemicals reaching groundwater is increasing [3]. In Canada there are strict water quality regulations that determine the maximum allowable concentration of a compound in potable water. If the well is producing water with concentrations higher than the regulated amount of any chemical, then the well can no longer be used without treatment. Sophisticated filtration or purification systems are needed to make the well water potable. Fortunately, for the most part, pesticide content in Alberta has been below the maximum allowable concentration for drinking water [4].
Sewage Contamination
In areas with older septic tanks, sewage waste can leach into the aquifer rendering nearby wells useless. Leaching of these contaminants is not limited to unconfined aquifers near the surface as contaminants can percolate deep into confined aquifers. If a water source becomes contaminated, it must undergo a remediation process in order to be usable. Remediation is a process of removing contaminants and making the source of water clean. Remediation of aquifers is more difficult than remediation of surface water sources, and the deeper the aquifer the more difficult the process becomes.
Saline Infiltration
Saline infiltration is another complication that can negatively affect aquifer quality. Although saline infiltration is most often a concern with deeper aquifers, it can also be problematic in aquifers at the surface. Saline infiltration can occur when an aquifer is being pumped too intensely, resulting in a low pressure zone forming very close to the deepest part of the aquifer. This low pressure zone draws water from the surrounding area and if the unit below the aquifer contains saline water, this is what will be drawn into the pumping well. Once saline water infiltrates the producing aquifer, the well is no longer useable.
Groundwater Quantity Concerns
Another concern for groundwater users is maintaining a usable quantity of groundwater. It is important to note that when water loses its quality, the overall quantity of useable water is decreased however; water quantity can be impacted directly through withdrawing groundwater.
Extensive groundwater withdrawal can result in overdrafts. Once a well begins to be pumped, a cone of depression is formed around it. When two wells are near each other their cones of depression can intersect and form an interference zone. In regions where overdrafts are widespread, land subsidence can occur.