|
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 |
|
