Groundwater

The county of Alicante is pioneer in using subterranean water resources, indeed in wide zones of its geography constitute the main supply source. The volume of subterranean water used for urban purposes, including the supply to those industries connected to the municipal network and the supply to seasonal population, sums up to 100 hm³/year (60% of total) allowing supply to 79 % of boroughs with an actual population of 600,000 people, (50%) and a seasonal population of 1,900,000 people (53%). In the month of maximum demand they are catered to 1,300,000 people with a volume of 13hm³.

Aquifer or groundwater reservoirs can be defined as the geological formation able to store and transmit water, susceptible to be exploited to obtain resources. The province of Alicante, framed geologically within the Cordillera Bética, has a very rugged and highly complex geological structure, which causes its 163 aquifers to have small to medium dimensions. The complex orography of the province, results in high groundwater depths, generally above 100m. However there is a wide variation range, from the upwellings on the surface (springs) to the depths higher than 500m in some overexploited aquifers.

From north to south of the province there is a clear variation of the different aquifers’ characteristics based on geology :

– In the northern area, where high-permeability materials abounds (highly fractured limestone and dolomites), aquifers have optimal features for exploitation (Almudaina-Segaria, Albuerca-Mustalla, Carrascal-Bernia, Solana. Pinar de Camus, Aitana).

– Southward, more impermeable materials (with the presence of marl and clay) and greater structural complexity results in small-scale aquifer and less optimal hydrogeological characteristics (Anticlines of Orcheta, Monnegre, Ventós-Castellar, Albabor, etc.).

In the areas of “Vega Baja”, “Bajo Vinalopó” and “Alicante”, the aquifer formations consist of sandy materials and fragile limestone with few resources and quality.

The average net recharge in permeable outcrops in Alicante is 197mm/year, but shows very pronounced oscillations, from hardly 10mm/year in heavy clay aquifers, as in the “Valle del Serpis” or “Racó” ones, to values higher than 300mm/year, as in some aquifers in the south Albuerca Mustalla, Mediodía o Vergel. The total groundwater resources of the county aquifers have been estimated to be ca. 454 hm³.

Overall, the groundwater resources quality is good and even excellent in large areas of “Marinas”, “Comarca de Alcoy”, “Hoya de Castalla” and “Alto Vinalopó”. The worst quality corresponds to the southern half of the province and some aquifers in connection with the sea that are experiencing saltwater intrusion phenomena.

Vulnerability to contamination of aquifers: Water quality is the set of physical, chemical and biological water features that makes it suitable or unsuitable for a particular use.

Groundwater is generally better protected from pollution than surface water. However, once a pollutant is incorporated into the groundwater flow, its treatment is very costly. The best measure to maintain good water status, and especially groundwater, is to avoid contamination. For this reason, it is essential to know the degree of vulnerability to contamination of the different aquifers in Alicante and use this knowledge to define land use policies and establish measures to mitigate as much as possible the potential impacts.

The provincial council of Alicante has promoted and posted the Map of Aquifers Vulnerability to Contamination for the province, using the DRASTIC method, which assesses the groundwater vulnerability to contamination based on a series of factors: Depth of the water table, net recharge, aquifer media characteristics, soil characteristics, topography, impact of the vadose zone and aquifer hydraulic conductivity.

This map is an example of the interest of Alicante’s society by having water resources that meet their needs without giving up a healthy environment.