Management of Aquifers - Hydrogeology: Objectives, Methods, Applications - page 214

in the basins thus created. Examples are numerous in desert zones, such
as in southern Tunisia, where a massive development campaign along the
path of wadis has been under way for several years. This technique offers
the additional advantage of supplying water to arable land, and therefore
of allowing cultivation. On the Island of Malta, hillside retaining walls
were emplaced on wadis in order to encourage infi ltration, with the goal
of limiting the saltwater intrusion caused by pumping.
The lowering of the level of the Var (Alpes-Maritimes) alluvial aquifer,
which forced truck farmers and water exploiters to lower the level of their
wells, was limited by the construction of several retaining basins along the
length of the river. Nevertheless, these basins were progressively silted up,
limiting the infi ltration possibilities. Silting up is the principal problem in
recharge systems. The creation of a sinuous path can be considered in order
to slow circulation and favor infi ltration along riverbanks.
Agriculture can also play a role in the recharge of aquifers. In Spain, in
the Alpujara, irrigation channels from Roman times (Sabovik, 1973) divert
water from rivers in order to feed the aquifer. In France, Lacroix & Blavoux
(1994) thus highlighted the benefi cial role of irrigation on the Lower Durance
aquifer, the level of which peaks in July-August. Inversely, studies can be
undertaken to favor infi ltration in agricultural zones, in order to limit the
harmful effects of runoff: soil erosion, transport of solids, and contribution
to fl ood discharge.
Stormwater runoff from urban impermeable surfaces can also be
directed towards infi ltration setups. This system offers the double advantage
of relieving the infi ltration defi cit caused by the impermeabilisation of
surfaces and of avoiding the negative effects of runoff. 80% of the runoff
from Valence-Lautegne (Drome) are directed in such a manner towards
three infi ltration basins with a total volume of 70,000 m 3 over a surface of
4.1 ha. In karst zones, runoff can be directed into natural cavities, as long
as it is of acceptable quality, since the environment provides only a reduced
level of natural purifi cation.
b) Allochthonous input from river diversions
Surface water from rivers can be diverted in order to recharge an aquifer.
karst environments, thanks to their rapid recharge properties, can give rise
to interesting situations, as is the case in the West Bank of Jordan, where
the Yarqon-Taninim aquifer (Cenomano-Turonian carbonate formation),
exploited at a rate of 400·10 6 m 3 per year, receives a complement of
approximately 100·10 6 m 3 per year through infi ltration of surface water
from the Jordan river.