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Desertification Indicator System for Mediterranean Europe


1. Definition

Name GROUNDWATER DEPTH (CHANGE IN)
Brief definition The change in the depth of groundwater levels
Unit of measure m
Spatial scale  
Temporal scale  

2. Position within the logical framework DPSIR

Type of Indicator Impact indicator

3. Target and political pertinence

Objective The objective if this indicator is to measure the impact that land uses are putting on a natural resource, groundwater.
Importance with respect to desertification

There are natural changes in groundwater levels because of climate change (drought, pluvial episodes), but the main changes are due to human extraction. Land use evolution needs to increase the water consumption, when changing towards more water-demanding activities (such as irrigation farming, recreational activities or urban sprawl). Often this is achieved, as in times of drought, by increasing the groundwater exploitation. The result is that the groundwater level decreases, and more effort is necessary to extract the water. If the pressure on the resource is too strong it can run out (or be too difficult to obtain) and then socio-economic problems emerge. Groundwater over-exploitation occurs when groundwater extraction exceeds recharge and leads to a lowering of the groundwater table.

At the parcel level, when the cost of getting water is too high (the deeper the water, is the more expensive it is to extract) land use changes or the land is just abandoned.

International Conventions and agreements The UNCCD emphasizes that combating desertification must be tackled within the general framework of actions to promote sustainable development.
Secondary objectives of the indicator Contribution to the definition and mapping of ESAs and assessment of the desertification risk in an area. To assess the pressure that agricultural and other activities (recreational, domestic consumption) put on the environment.

4. Methodological description and basic definitions

Definitions and basic concepts The change in groundwater level is a very good indicator of the pressure put on the resource. Groundwater is, sometimes, the most easily available water that farmers and other land users can obtain, sometimes it is the only source. Hence it is the most likely to be exploited first, especially in times of drought. The relationship between the natural recharge of groundwater and the extraction rate will show if reserves are increasing or decreasing. An indirect but efficient way of measuring this is by assessing the change in level of the groundwater table. This can be done using the wells or boreholes already in existence and will give information about the sustainable or unsustainable use of the aquifer. By knowing the capacity of the aquifer it is possible to assess the consumption and the time remaining until the resource is depleted. It is necessary to know the natural dynamics of each aquifer in order to distinguish between natural variations and effects of human withdrawal.
Benchmarks Indication of the values/ranges of value Benchmarks depend on the individual characteristics of the aquifer. The change in groundwater depth has a different importance in each aquifer, so information about the aquifer is necessary.
Methods of measurement By measuring depth of water in wells used to pump up water from the aquifer. The minimum frequency of measurement is at monthly intervals in order to reflect seasonal as well as annual changes. The state of fossil aquifers should be assessed at about 5 year intervals.
Limits of the indicator Complementary information about the aquifer is necessary. If it is not available this indicator only shows that the recharge is less than the extraction, but not the degree of severity of the process or the real impact of the extraction. Water levels need to be measured both seasonally and annually over decades to determine overall trends.
Linkages with other indicators Water availability, Drought, Drought index, Infiltration capacity, Land use evolution, Urban sprawl, Water scarcity, Aquifer over-exploitation, Irrigation intensity and seawater intrusion, Water use policy/law

5. Evaluation of data needs and availability

Data required to calculate the indicator Depth of pumping from wells in one area. Hydro geological maps (aquifer distribution and limits)
Data sources Necessary data are usually available and accessible and the cost/benefit ratio is reasonable.
Availability of data from national and international sources Data can be obtained from various regional, national or international institutions involved in the collection and the analysis of geological data.

6. Institutions that have participated in developing the indicator

Main institutions responsible University of Murcia (Spain)
Other contributing organizations Agricultural University of Athens. Universities of Lisbon, Basilicata, Amsterdam, Leeds

7. Additional information

Bibliography

Burdon, D.J., 1997: The flow of fossil groundwater. Quarterly J.of Eng Geology, 10: 97-124

Estrela T., Marcuello C.and Iglesias A. 1996. Water resources. Problems in Southern Europe. An overview report. European Topic Centre on Inland Waters. European Environment Agency

Gleick, P., 1993: Water in crisis: a guide to the world´s fresh water resources. Oxford University Press. 493 pp

Poland, J.F. (Ed), 1985: Guidebook to studies of land subsidence due t ground-water withdrawal. Studies and Reports in Hydrology, 40. UNESCO. Paris

Rockwell, D.L., 2002: The influence of Groundwater on Surface Flow Erosion Processes During a Rainstorm. Earth Surface Processes and Landsforms, Vol.27 No 5:495-514

Other references

Collin, J.J.; Margat, J., 1993: Overexplotaition of water resources: overreaction or an economic reality? Hydroplus, No 36: 26-37

Custodio, E., 1992: Hydrogeological and hydrochemical aspects of aquifer overexplotaition. In Selected Papers in Hydrogeology. International Association of Hydrogeologits. Heise, Hannover, Vol.3: 3-28

Custodio, E., 2000: The complex concep of overexploited aquifer. Papeles del Proyecto Aguas Subterráneas. Serie A, No 2. Fundación Marcelino Botín. Madrid, 62 pp

Cruces de Abia, J., Martinez Corina, L., 2000: La Mancha Húmeda. Explotación intensiva de las aguas subterráneas en la cuenca del río Guadiana. Papeles del Proyecto Aguas Subterráneas. Serie A, No 3. Fundación Marcelino Botín. Madrid, 66 pp.

Foster, S., 2003: Integrated groundwater resources management. Key Technical Concepts and Institutional Provisions. In A.Pulido y A. Vallejos (Eds): Gestión y contaminación de recursos hídricos. Publicaciones de la Universidad de Almería .Almería, 55-70

Llamas, M.R., 1992: ¿La Sobreexplotación de Aguas Subterráneas: Bendición, Maldición o Entelequia? Tecnología del Agua, 91: 54-68

Llamas, M.R., 192: La surexploitation des aquifères: aspects techniques et institutionnels. Hydrogéologie, Orléans No 4: 139-144

Llamas, M.R.; Hernández-Mora, N.; Martinez Cortina, L., 2000: El uso sostenible de las aguas subterráneas. Papeles del Proyecto Aguas Subterráneas. Serie A, No 1. Fundación Marcelino Botín. Madrid., 54 pp.

Llamas, M.R.,2003: El Proyecto Aguas Subterráneas: Resumen, resultados y conclusiones. Papeles del Proyecto Aguas Subterráneas, No 13. Fundación Marcelino Botín. Madrid,101 pp.

Pulido, A.; Castillo, A.; Padilla,A, (Eds), 1990: La sobreexplotación de acuíferos. Instituto Tecnológico Geominero de España. Madrid, 156 pp

Valdés, J.B. & Maddock,T., 2003: Water resources management in Semi-Arid Regions: The United States Southwest. In A. Pulido y A. Vallejos (Eds): Gestión y contaminación de recursos hídricos. Publicaciones de la Universidad de Almería. Almería, 37-54

Contacts Name and address University of Murcia
Jorge García Gómez jorgegg@um.es
Pr. Francisco López Bermúdez lopber@um.es