Non-renewable groundwater resources: a ... - unesdoc - Unesco

CHAPTER 1 ■ CONCEPT AND IMPORTANCE OF NON-RENEWABLE RESOURCESThe way in which the utilisation of non-renewable groundwater arises can be conveniently classified(Foster and Kemper, 2002-04) into :● planned schemes, in which mining of aquifer reserves is contemplated from the outset, usuallyfor a specific development project in an arid area with little contemporary groundwaterrecharge (eg. Figure 3)● an unplanned basis with incidental depletion of aquifer reserves, as a result of intensivegroundwater abstraction in areas with some contemporary recharge but where this provessmall or where there is limited hydraulic continuity between deep aquifers and theirrecharge area (e.g. Figure 4).Unplanned depletion of non-renewable groundwater reserves can undermine, and potentiallyerode, the economic and social vitality of the traditional groundwater-dependent community– and instances of the collapse of such rural communities are known. Hence, there is need toplan the exploitation of non-renewable groundwater resources, and guide their utilisation witha view to making communities better prepared socio-economically to cope with increasingwater stress as aquifer storage is depleted.Unplanned depletion of non-renewable groundwater reserves can undermine, and potentiallyerode, the economic and social vitality of the traditional groundwater-dependent community– and instances of the collapse of such rural communities are known. Hence, there isneed to plan the exploitation of non-renewable groundwater resources, and guide their utilisationwith a view to making communities better prepared socio-economically to cope withincreasing water stress as aquifer storage is depleted.Figure 3Planned mining of essentially non-renewable groundwater resourcesin the southern Kalahari of Botswana (Foster et al., 1982)Hhydrogeological conditions in area where Middle Ecca (Karroo) Sandstone was discovered to form an excellentaquifer readily capable of supplying a wellfield yielding the 5 M m3/a required for development of a major miningcomplex and regional centre - the question of physical and social sustainability of the proposed groundwater extractionarose in the 1980s before the development took place, since detailed investigations revealed that most of thegroundwater extraction would be non-renewable because deep rainfall infiltration to the aquifer was very limited– however worst-case predictions for aquifer drawdown (at the expected mine life of 20 years), generated by aquifernumerical modeling, were such that they would not prejudice long-term use of the aquifer for town water-supply andtraditional ranching activity, and post-development monitoring has proved this to be the case.21