Källor i Stockholms län - Inventering och underlag ... - Länsstyrelserna

Summary
An inventory of coldwater springs in Stockholm County:
a basis for environmental quality monitoring of groundwater
The County Administrative Board of Stockholm carried out an inventory of
coldwater springs in Stockholm County from October 2002 to January 2003.
The inventory was part of the regional environmental monitoring
programme, which is run by the County Administrative Board and receives
financial support from the Swedish Environmental Protection Agency.
The aim of the inventory was to increase knowledge about coldwater
springs in the county and to determine whether the springs were suitable
objects for long-term monitoring of groundwater quality. One advantage of
springs is that methods such as drilling or observation pipes are not required
for environmental monitoring, and natural hydrological processes are thus
not disturbed. Another advantage is that the water quality and flow are
representative of a larger area, namely the entire drainage area of the
springs.
The inventory includes a compilation of information from earlier inventories
of springs in the county, a field survey of about 70 springs and analyses of
water chemistry in 19 springs. The springs that were chosen for the water
analyses represent different geological environments and different levels of
exposure to pollutants.
Most of the springs were located in the direct vicinity of large glaciofluvial
deposits (eskers), but some headsprings emerged from glacial till or seeped
directly from bedrock, and some headsprings emerged from layers of sand
and gravel under clay.
The field survey documented the type of spring, the water flow, the geological
conditions in the drainage area of the springs, and the soil characteristics
in the vicinity. The data that were gathered during the survey were
stored in a Geographical Information Systems (GIS) database that includes
photographs of the springs.
The field survey was conducted during late autumn and winter, which is the
best season for identifying permanent groundwater springs. At other times
of the year, it is difficult to distinguish permanent springs from temporary
flows of surface water. The disadvantage of winter fieldwork was that it was
not possible to survey the flora and fauna. The field survey should therefore
be supplemented with a biological survey, in order to gain a complete
picture of the environmental conditions in the vicinity of the springs.
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