 Water
 GROUND WATER
QUALITY
Groundwater forms one constituent in the
overall water cycle, hence, deterioration of groundwater quality
brings along deterioration of the other environmental components
with future consequences difficult to predict. Groundwater is not
but a natural resource - it is also a vital component of the overall
environment. Therefore, respective protection measures should not be
limited in scope to caring for drinking water only.
Groundwater is considerably cleaner than
surface water, however, quality problems exist. For the most part,
problems arise with groundwater that is virtually unshielded against
pollution. This happens in cases where there is a thin aeration
layer containing earth permeable to water. Water table contamination
can occur both at a smaller local level (around one particular
contamination source - a petrol station, a waste dump, and the like)
or at a regional level (in a city or town, on certain agricultural
lands). In practice, groundwater is polluted to a lesser or greater
extent all over the city, reaching excessive levels in some
particular places, for example, in the territory of waste disposal
site Getlini or in the territories of former Soviet military bases.
At the Milgravis petroleum lubricant plant, free phase product in
the water table is 1m thick.
QUANTITATIVE CHANGES
IN GROUNDWATER
Because of prolonged, uncontrolled and unbalanced utilisation of groundwater
during sixties and seventies, a groundwater cone of
depression has formed in the central part of the country with its
centre in Riga (the Greater Riga depression). In the
territory of Riga, reduced levels of groundwater have been
registered in all aquifers.
This kind of hydrodynamic change in the
subterranean hydrosphere disrupts the hydrodynamic balance that, in
its turn, engenders hydro chemical changes. These processes are
truly complex and, in majority of cases, irreversible too.
Furthermore, abrupt fall in the groundwater level and its pressure
brings about changes in the isostatic pressure, which could alter
also the geotechnical conditions. Occasionally, sinking of the
ground and other processes has been noticed. The hydrological
conditions are affected.
In the cones of depression, contaminated
groundwater can infiltrate into the horizons of artesian waters.
Similarly, deeper mineralised water can inject into the above-lying
horizons carrying drinking water. This is a phenomenon common to
Riga and its adjacent territories.
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