Aquifer Overexploitation And Groundwater Mining

1. Aquifer Overexploitation And Groundwater Mining Vladimir STAVRIC

2. Contents • Definitions of safe yield, aquifer overexploitation and groundwater mining • Undesirable effects of overexploitation • Benefits of groundwater exploitation • Management of aquifers' utilization • Alternatives to groundwater mining • Conclusions

3. LIMITS • The limits how much water can be extracted from a finite groundwater aquifer are economic and environmental • When water is pumped out faster than it is recharged by the natural processes, the water level in the aquifer drops, and the distance the water must be raised to the surface increases. Eventually, either the energy costs rise to the point that exceeds the value of the water, or the water quality falls bellow acceptable levels. At this point pumping must cease

4. TERMINOLOGY • What is overexploitation ? overpumping ? overdraft? overdevelopment ? • groundwater mining ?

5. Dilemma • two main questions: (a) How should we assess whether an aquifer is being overexploited, or predict If this may happen as a result of planned new exploitation? According to what criteria?; and (b) Is the overexploitation of an aquifer always undesirable, "bad management" that should be prohibited and prevented, or is it permissible or even advantageous under certain situations, and what impact should be anticipated and compensated for?

6. Safe yield VS Overexploitation • concept of safe yield: sustainable economic output when there is excessive groundwater withdrawal; • overexploitation is largely point of view referring to the consequences of intensive groundwater use, as perceived by environmentalists, sociologists, news media and public in general, and places more emphasis on the adverse or detrimental aspects, sometimes even with apocalyptic undertones

7. Safe yield “amount of water which can be taken from the aquifer indefinitely without producing an undesirable result “ • Hydrological point of view: maximum safe yield is equal to the long-term mean annual recharge (basin’s natural baseflow): • potentially exploitable groundwater resources which represent a maximum close to the live storage, • actually exploitable groundwater resources are governed by technical, environmental and legal requirements on the minimum baseflow and/or minimum groundwater level. • Safe yield, called also sustainable yield, is considered as the upper limit of exploitation.

8. Overexploitation • To evaluate a situation that can be termed overexploitation, not only hydrological aspects have to be taken into account, but also economic, social and political ones, as well as the point of view of the stakeholders and all persons involved • Overexploitation is term oftenly used when the rate of abstraction exceeds the so-called 'safe yield' (or sustainable yield) with formation of overdraft areas. • In another interpretation, undesirable results occur when the groundwater storage cannot be replenished by a natural recharge in a reasonable period of time

9. Aquifer overexploitation • Effects of aquifer exploitation, do not only depend on the volume being abstracted, but also on the distribution of withdrawals and the well pattern • Thus, the safe yield of an aquifer is a complex function that changes with time. It cannot be considered as a fixed value for an aquifer. The problem is complicated with changes in natural recharge due to land-use modifications and different forms of artificial recharge.

10. Assessment of overexploitation • depending on the the resource-management objectives: • maintaining conservative conditions for exploitation at a given stage of development; • searching for ways to develop the use of resource by intensifying exploitation (either long-term, and therefore limiting the use to renewable resources, or by temporarily withdrawing part of the non-renewable resource); or • minimising detrimental impacts on the users of surface waters or the occupants of the land, • relative criteria for assessment of overexploitation may be applied

11. Assessment of overexploitation • Criteria: • purely physical and quantitative: depletion of resource, non-equilibrium etc.; • qualitative: degradation of water quality; • economic: non competitivnes, or more broadly - the all direct costs and external costs greater than collective advantages; • social: conflicts of use between unequal developers with detrimental effect suffered by third parties; • environmental: damage to the natural environment, especially to sensitive aquatic ecosystems.

12. Assessment of overexploitation • To evaluate possible aquifer overexploitation, not only detrimental (negative) effects have to be considered, but also beneficial (positive) ones. • Otherwise a biased assessment may be reached. • In some extreme cases of severe water shortage beneficial aspects may dominate over detrimental ones.

13. Groundwater mining • The term groundwater mining is used when conscious and planned abstraction rate greatly exceeds aquifer recharge (UN, 1992). • In some arid and desert areas there are enormous quantities of groundwater stored in aquifers infiltrated long before present day. They are often described as 'fossil waters'. Exploitation of these waters, as well as connate and juvenile waters, considering that the replenishment is negligible or non-existent, is analogous to that of any other non-renewable mineral resource, and for this reason is referred to as groundwater mining.

14. Groundwater mining “continuous water table lowering due to groundwater abstraction greatly exceeding recharge “ • fresh groundwater in the aquifer is not beneficial to anyone, except to sustain some environmental conditions, • in principle there is no objection to 'mine' the reserves for beneficial use if environmental values and the rights of future generations are duly considered

15. Groundwater mining • Well planned'groundwater mining' is not to be considered 'overexploitation' if things go as planned, even if the effects are the same. • It can be termed ‘overexploitation’ only • when there are serious deviations from what was planned or • when there is no planning at all.

16. UNDESIRABLE EFFECTS OF OVEREXPLOITATION • (a)    groundwater level deepening; • (b)  spring and river flow diminution or/and wetland surface reduction; • (c)  degradation of groundwater quality, either salinity increase or the increase of certain undesirable constituents; • (d)   land surface changes in the form of generalized or local land subsidence, or ground collapse.

17. UNDESIRABLE EFFECTS OF OVEREXPLOITATION • These changes produce a series of undesirable results with the following aspects: • hydrological aspects; • water quality aspects; • economic aspects; • environmental aspects; • morphological and geotechnical; • legal aspects; • social aspects.

18. UNDESIRABLE EFFECTS OF OVEREXPLOITATION • Perhaps, the most detrimental cause of overexploitation is the ignoranceof what is happening and the negligence in getting the needed data to correctly evaluate the hydrogeological and economical situation. In the long run, a balance will somehow be reached or the overexploitation will finally be abandoned, but meanwhile a major investment in money, effort, and in hope, will be lost ; • Another detrimental effect of overexploitation, is the irresponsible overreacting of water authorities, especially when they are poorly informed or lack the scientific technical skills to evaluate the physical problem. the aquifer may be underexploited, losing large quantities of water since the first by law have installations that do not allow correct exploitation of aquifer resources .

19. BENEFITS OF GROUNDWATER EXPLOITATION • development in simple stages. This allows for a better fit between demand and supply, progressive financing and the payment of works from revenues of the project already finished; • little surface area; • local manpower can be used, maintenance cost are low and may be solved locally & contribute to the development of the area; • water resources availability increased by evaporation reduction; • the lowering of groundwater levels allow for valuable utilization of shallow groundwater, less evaporation; • groundwater is in most instances suitable for human consumption and safe without or with only simple treatment; • water close to user, thus saving costlywater lines; and • complex and sometimes unfair subsidizing can be avoided.

20. BENEFITS OF GROUNDWATER EXPLOITATION • These benefits are not absolute and have to be weighed against other alternatives, case by case taking into account local physical, human, economic, environmental and legal circumstances. • Groundwater allows the temporary solution of acute problems; • Possibility to avoid megaprojects; • However, aquifer, than, have to be studied and monitored, undesirable effects corrected to the maximum, and provisions have to be made to cope with reserve depletion and ecologic impacts.

21. BENEFITS OF GROUNDWATER EXPLOITATION • Overexploitation is an acceptable policy only if planned with specific aims and as long as negative consequences have been technically evaluated by decision makers and they are economically and socially acceptable. • This is the case if groundwater mining is used to induce a cycle of economic development, which will give way to substitution of more expensive water at a later date or to new technology improving the water use. Even so, the issue of intergenerational equity can arise and it has to be considered with due seriousness.

22. MANAGEMENT OF AQUIFERS' UTILIZATION • a complex interaction between human society and the physical environment; and • an extremely difficult problem of policy design. • economist's preferred criterion: maximum net return (rate of abstraction that gives the maximum Present Net Benefit). • If externalities are included in the analysis, represented by 'damage functions', an optimal level of abstraction is similar, but even more restricted, yielding even smaller rate of abstraction. • A successful method of managing aquifer exploitation, as a part of regional water resources management, should have the capability of balancing competing demands so that actual operating policies optimize the net benefit to the region .

23. MANAGEMENT OF AQUIFERS' UTILIZATION • Three exploitation strategies, are conceivable and practicable: • a strategy of maximum and lasting exploitation of the renewable resources, in a regime of dynamic equilibrium, with average abstraction greater than average recharge • a strategy of repeated exploitation of the storage in a prolonged unbalanced regime, In this case, the depletion of the reserve contributes largely, in second phase of possible re- equilibration, the reserve may be either: • stabilized, on average, bringing abstraction close to recharge; or • in part restored, by reducing abstraction bellow recharge, by artificially increasing recharge, and than stabilising, in this new condition. • a strategy of mining or exhaustion exploitation, with abstraction from the start much greater than the average recharge.

24. MANAGEMENT OF AQUIFERS' UTILIZATION • Several criteria are appropriate for assessing management strategies : • economic efficiency; • equity; • security: satisfaction of minimum human needs; • liberty: ability to act freely as long as it doesn't interfere with others; • avoiding harm; • Secondary criteria are: • local control and popular participation; • orderly conflict resolution processes; • information intensity; • ease of monitoring and enforcement; • social considerations;

25. MANAGEMENT OF AQUIFERS' UTILIZATION Approaches in management of overexploited aquifers: • Structural approaches generally involve developing some alternative source of water supply, whether • conventional (reservoir/conveyance schemes, conjunctive use of surface and groundwater) or • unconventional (desalination, weather modification through cloud seeding etc.). • Nonstructural approaches are policies of demand management. • cognitive methods to modify human behaviour; • institutional arrangements to coordinate activities of individual water users; • administrative organizations as a necessary element of institutional arrangements .

26. MANAGEMENT OF AQUIFERS' UTILIZATION Incentive and sanction system can influence individual pumper behaviour. Two general types of incentive-based strategies can be employed in an overexploited aquifer: • financial incentives, both positive and negative: • pumping charges or taxes, subsidies; • quantity-control approaches: • permits, • pumping quotas, • transferable pumping entitlements, • use of water-rights markets; • monitoring and enforcing pumping controls.

27. ALTERNATIVES TO GROUNDWATER MINING • Artificial recharge of aquifers • Artificial recharge and conjunctive use of surface and groundwaters • Reclamation and reuse of wastewater • Desalination • Weather modification • Demand modification • measures include an array of technical, administrative, legal, political and operational instruments Alternatives to groundwater overexploitation are neither simple nor easy. Those mentioned are the major ones, yet not exclusive.

28. CONCLUSIONS • Non-equilibrium or an unbalanced regime of an aquifer can not simply be identified as overexploitation. • The assessment of overexploitation is relative to the criteria used, which are themselves linked to the resource-management objectives: • Purely physical and quantitative: • Qualitative • Economic • Social • Environmental

29. CONCLUSIONS • Depending on the exploitation strategies, various methods of use (of management) of the reserve of an aquifer are conceivable and practicable, and they should be assessed for various criteria. • We can distinguish two basically different approaches in management of overexploited aquifers: • structural (conventional and non-conventional alternatives to overexploitation and mining) and • non-structural, comprising policies of demand management.

30. CONCLUSIONS • To evaluate possible aquifer overexploitation, not only detrimental (negative) effects have to be considered, but also beneficial (positive) ones. Otherwise a biased assessment may be reached. In some extreme cases of severe water shortage beneficial aspects may dominate over detrimental ones. • Overexploitation may even be an acceptable policy if planned with specific aims and as long as negative consequences have been technically evaluated by decision makers and they are economically and socially acceptable.

31. Aquifer Overexploitation And Groundwater Mining Vladimir STAVRIC