Reduce groundwater extraction

Reduce groundwater extraction

Category 01. Water flow quantity improvement

General description

Implementing groundwater management and protection measures needs quantitative appraisal of aquifer evolution and effects based on detailed multidisciplinary studies, which have to be supported by reliable data (Custodio, 2002). Social and environmental constraints and the implication of skateholders should be taken into account to choose the restoration or mitigation measures. Some management options that could be studied as alternatives are the following:

• Water rights should be properly defined and distributed so they are managed more efficiently and extractions decrease.

• The quantity of water that can be extracted from each sector of the aquifer has to be defined according to the rate of recharge and discharge, the available stock, and water demand. But negative effects doesn´t necessary occur only when discharge is greater than recharge. They may be simply due to well interferences and the long transient period that follow changes in the aquifer water balance. Groundwater storage is depleted to some extent during the transient period after abstraction is increased (Custodio et al., 2001).

• Water pricing is an appropriate tool to stimulate efficient water use: groundwater price understimates water value, and the environmental costs of its depletion. The internalisation of the negative as well as positive externalities on stock quality and quantity in the price of groundwater is particularly significant if the recharge of groundwater is large compared to stock size (Hellegers et al., 2001).

• Improve water use efficiency (modernization of distribution infrastructures to reduce water losses, better irrigation practices, close-cycle systems and water recycling, etc).

• Limit the expansion of irrigation surface and the construction of new wells.

• Transformation of irrigated land into rain-fed crops or natural land, land acquisition.

• Payment for Environmental Services and encouraging Best Management Practices to improve natural recharge and storage of water (terracing, creek management, reduction in planting phreatophyte forest areas).

Applicability

In areas highly dependent on groundwater resources, where environmental uses compete with agricultural, urban or industrial uses of water, it may be difficult to come to an agreement among skateholders. Public participation is essential in the selection of the measure´scope, so it has social acceptance.

Expected effect of measure on (including literature citations):

• HYMO (general and specified per HYMO element)

Rivers supplied primarily by underground water would seen increased their average flow. The groundwater level would rise and so the discharge into water courses would be increased partially restoring their natural flow regime. Temporal and permanent wetlands would recover their natural hydroperiod (Custodio et al. 2006,Manzano et al.,2001)

• physico � chemical parameters

Maintenance or improvement of groundwater levels in aquifers near the coast helps to keep the regulatory effect and prevent seawater intrusion maintaining physical and chemical parameters of water quality. In marshes and wetlands the level of salinity and nutrients depends on freshwater input and therefore the rising of the water table would contribute to restore their natural balance.

• Biota (general and specified per Biological quality elements)

The effect would be especially positive for those ecosystems dependent on the proximity of the water table (wetlands, riparian forests). The resilience and regeneration of the vegetation would be improved. Fish communities would be benefited by the maintenance of water quality and the base flow on dry periods.

BQE	Macroinvertebrates	Fish	Macrophytes	Phytoplankton
Effect	+	+	+	o

Temporal and spatial response

Immediately after a modification in recharge, or abstraction, the aquifer-system discharge does not change. For large, low-diffusivity aquifers the response is so slow that storage depletion and water-quality changes will continue well beyond any reasonable planning horizon (Custodio, 2002)

Pressures that can be addressed by this measure

• Groundwater abstractions

Case studies where this measure has been applied

• Bouxweerd - Artificial pool

Useful references

Custodio, E. 2002. Aquifer overexploitation: what does it mean? Hydrogeology Journal 10:254–277

Custodio, E., M. Manzano y J. Dolz (2006). El agua en Doñana: una perspectiva general. Informe Técnico

Hellegers P., D. Zilberman and E. van Ierland. 2001. Dynamics of agricultural groundwater extraction. Selected for presentation at the annual meeting of the American Agricultural Economics Association in Chicago, August 5-8, 2001

Manzano, M. (2001). Los humedales de Doñana y su relación con el agua subterránea. I Reunión Internacional de Expertos sobre la Regeneración Hídrica de Doñana-Proyecto Doñana 2005. 161–167.

Manzano, M. y Custodio, E. 2005. El acuífero de Doñana y su relación con el medio natural. Doñana: Agua y Biosfera (Eds. R. García Novo y C. Marín Cabrera). Doñana 2005 Confederación Hidrográfica del Guadalquivir. Ministerio de Medio Ambiente. Madrid. 133–142; 163–164.

Manzano, M., Custodio, E. y Colomines, M. (2005). El fondo hidroquímico natural del acuífero de Doñana (SO España). V Congreso Ibérico de Geoquímica. IX Congreso de Geoquímica de España. Soria. 1–13.