Management of Aquifers - Hydrogeology: Objectives, Methods, Applications - page 218

Basins must therefore be regularly maintained. In order to limit
clogging, water is generally decanted and fi ltered, and chemicals are added
to encourage fl occulation of clay particles or discourage the proliferation
of algae and bacteria. Finally, the oxygenation of water, through waterfalls,
helps the elimination of suspended organic material by bacteria. Infi ltration
basins can also be equipped with liners or geotextiles which are then
regularly cleaned and changed. In some cases, a lawn can be planted at
the bottom of the basin, but this solution allows only short recharge times,
under a thin layer of water.
In infi ltration basins, the alternation of aquifer recharge phases with
dry phases generally limits clogging effects (Figure 112).
Figure 112 Clogging avoidance by alternating wet and dry phases (from Detay, 1997).
3.2 Qualitative action
The fi rst step is to avoid contaminating the aquifer. French regulations
require the emplacement of protection zones around water catchment points
(see chap. C3-4 ) and the law passed in 1992 clearly details the prohibitions
and restrictions intended to protect surface and groundwater quality.
As in coastal aquifers, contamination through intrusion of polluted
water can be limited with the emplacement of a hydrauic barrier with
artifi cial groundwater recharge (Figure 113).
The aquifer can nevertheless be accidentally contaminated or, due to the
age of its contamination, require processing. Humans can also intervene in
the quality control of an aquifer by acting on the reactive properties of the