Management of Aquifers - Hydrogeology: Objectives, Methods, Applications - page 207

C HAPTER C4
Management of Aquifers
1 DEFINITION
In traditional societies where water is scarce, its management generally
follows strict rules. In oases in the Sahara, foggara systems have traditionally
enabled exploitation of the aquifer with the help of gravity, thanks to
drainage galleries feeding irrigation ditches equipped with a distribution
system allowing each individual the amount of water allotted by customary
rights. Management of the resource occurs in this case at the exit from the
system. It is impossible to take more than what the system can provide. The
appearance of wells and boreholes where the quantity of water extracted is
determined by the nature and power of the material poses the problem of
managing the resource itself. Water must be taken in accordance with the
capacity of the pumping system and of the aquifer, but also with the needs
of society. Otherwise, it puts an entire social system at risk.
The same is true in France, where advances in exploitation technology
combined with increases in extraction and dumping are prompting the
emergence of qualitative or quantitative problems that can affect all or part
of society. For example in Bretagne, the spreading of liquid pig manure
produces more than 200,000 tons of nitrogen per year, and agricultors
add another 200,000 tons of nitrified mineral fertilizers. The nitrate
concentrations in groundwater often exceeds 50 mg·L -1 and the water is
therefore no longer potable.
The management of aquifers includes all of the actions enabling the
optimal use of the resource they contain, in order to answer to socitey's
needs. Management can be both quantitative and qualitative.
Water management can therefore be studied on several levels:
￿ at the level of the catchment system (see chap. C2): what must the
system's characteristics (well, borehole, gallery, well) be in order to
adapt to the possibilities of the resource?
￿ at the level of the aquifer: how to manage exploitation in order to most
benefi t from the resource?