Groundwater quantity, groundwater quality, deforestation
Oddelek za biologijo, Biotehniška fakulteta, Univerza v Ljubljani, p.p. 2995, 1001 Ljubljana, Slovenia
(i.e. Phragmites) have been successfully used in small
Deforestation has often been mentioned as a constituent of purifying plants and some trees (Alnus) have been shown to be
"landscape alteration". In fact, it has a many-sided influence successful in removing nitrates from the interstitial water
on groundwater bodies. First of all, the protection of a forested (Labroue & Pinay 1986). Similar might be possibilities in
area means the protection of an area where all doors for filling shallow karst streams. In this context, the forest is not merely
up the underground reservoirs stay open - contrary to the conserving the land; it plays an active role in the protection of
situation in urbanised areas. Beside preserving the natural groundwater quality.
access to groundwater bodies, the forest produces and The extent of forests on the Earth and the degree of forest
maintains a spongeous upper soil layer which may capture a loss are well known (IUCN/UNEP/WWF 1991). However, to
great part of the precipitation (Dengler 1980), store some calculate its impacts on the groundwater quantity and quality
water, and gradually release it to deeper layers. In such a way, during the Millennium, very detailed studies would be
some quantity of the surface runoff is diverted underground, necessary, involving the mechanisms of the possible
which diminishes loss of water and erosion; the latter would purification processes as well as statistics of the local
also influence hydrological conditions. In eroded areas the forest/groundwater-type relations.
outflow of water by surface and underground is faster,
immediate, and therefore episodic, it may go beyond the References
instantaneous capacity of the aquifer. However, already at this IUCN/UNEP/WWF. (1991) Caring for the Earth. Gland.
point the relation between the forest and the groundwater is Foerster, P. (1988) Zeitliche und vertikale
equivocal. The forest may extract a high quantity of water Nitratverteilung in der ungesaettigten und gesaettigten
from underground reservoirs and distribute a part of it into the Bodenzone grundwassernaher Sandboeden
atmosphere. The somehow unfavourable influence of the Nordwestdeutschlands. Journal of Agronomy & Crop
forest to the groundwater is most obvious in the tropics, where Science 161: 238-248
climatic conditions and the gradual, dispersed fall of leaves Labroue, L. and Pinay, G. (1986) Epuration naturelle des
prevent building of a humus layer, and where the nitrates des eaux souterraines: possibilités d'application
evapotranspiration is high all the year round. It is possible to au reaménagement des lacs de gravières. Annls Limnol.
regulate the loss of water by thinning the forest to a degree, 22(1): 83-88.
which may still prevent the erosion. Sket, B. (1977) Gegenseitige Beeinflussung der
Less equivocal is the relation between the forest and the Wasserpollution und des Hoehlenmilieus. Proceedings
quality of groundwaters. The organically polluted stream can 6th International Congr. Speleology, Olomouc 1973, 5:
be quite efficiently purified during its underground course – 253-262.
but only to the level of nitrates (Sket 1977). Since green plants Trémolières, M. (2001) Functioning of interfaces surface
were absent, the nitrate concentration has been augmenting water/groundwater/forest ecosystems in a fluvial
hydrosystem: the case of the Rhône floodplain. In:
along a ca 10-km long cave corridor. A high amount of Groundwater Ecology, eds. C. Griebler, D.L.
nitrates is contributed to the groundwater, interstitial waters in Danielopol, J. Gibert, H.P. Nachtnebel, & J.
particular, by excessive agricultural fertilisation (Foerster Notenboom, pp. 143-164. EC
1988). The interrelations between the groundwater and the
vegetal cover of an alluvial plain are very complex
(Tremolieres 2001). The forest plays an important role in
purifying the groundwater of nutrients as well as of some other
unwanted substances. The purifying activity of the deeply
penetrating tree root systems with associated fungi and
bacteria has not yet been studied in detail. Some marsh plants