Exercise 11

The majority of the papers on a particular mega aquifer reporting a value of mean groundwater recharge do not specify how this estimate has been derived. This raises questions regarding the reliability and accuracy of the reported estimate. Outline ideas and steps that can help evaluate the plausibility of the reported value.

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Exercise 12

Non-renewability of groundwater resources under present-day conditions may have different causes. List three such causes, and give examples among the mega aquifer systems or the aquifers they include.

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Exercise 13

Are water quantity policies and management for non-renewable groundwater similar to or fundamentally different from those for renewable groundwater? Please explain.

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Exercise 14

When groundwater abstraction records are not available for a large aquifer system of concern, it may be possible to produce a reasonable estimate of abstraction by disaggregating national groundwater abstraction statistics under the assumption that abstraction is strongly correlated with population size and groundwater-irrigated area. Box 3 shows the approach in practice, with the Paris Basin as an example. As an exercise, use this approach to estimate abstraction for one of the other mega aquifer systems, for example, the Maranhão basin or the Ganges-Brahmaputra Basin. It is convenient to consult Margat and Van der Gun (2013), Siebert and others (2010, Supplement S2), and the internet for statistics on national groundwater abstraction, areas equipped for groundwater irrigation, and population, respectively. Compare your outcomes with the values listed in Table 7 and comment on the differences.

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Exercise 15

Methodological flaws and inadequate data may explain (at least partly) the often significant divergence of storage depletion trend estimates for the same mega aquifer system, as listed in Table 8. Identify the main flaws and data deficiencies commonly encountered when applying method 1 (multiplying water level changes by storativity and integrating over the aquifer area); method 2 (evaluating gravity changes over time using GRACE data); and method 3 (using a calibrated flow model).

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Exercise 16

Among the mega aquifer systems with renewable groundwater resources, several systems are facing exceptional water quantity sustainability challenges, in response to intensive groundwater development. Select five such stressed systems and consult a few relevant papers on each of the selected systems (the Reference Section will help you identify potential papers). What are the main impacts observed or anticipated in each of them? What options exist to control the related problems to some extent?

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