Spain
In Spain, most of the larger-scale experiences were built on an experimental basis, with few large-scale operational devices located in Castilla y León and Catalonia. The amount of water artificially recharged to the aquifers ranges, depending on the sources, from 50 hm³/year (IGME 2000) to 350 hm³/year (LBAE, MIMAM, 2000), 380 hm³/year (DINA-MAR, 2010), figures that, even in the largest of cases, represent a volume on the order of 10 times lower than that of Central Europe. These figures exceed 60 hm³/year,[7] when considering the devices located in forest areas for palliative water management (generally lamination and recharge dams) and in urban areas, although it remains to include the infiltration that takes place at the bottom of large dams, which in Spain exceed 1,400 in number. In this way it is possible to realistically estimate an "artificial" recharge volume, intentional or not, of up to 800 hm³/year, a figure far from the volume published in the LBAE 2000.
Of all the possible points of view and perspectives to promote the MAR technique, the economic one takes precedence. A preliminary analysis has been carried out, as there is a fairly limited volume of information, which concludes that the water from aquifer recharge management (MAR) has costs slightly lower than the average cost of desalinated water and less than half that of water impounded in dams and ponds. This is because recharge devices are much less expensive than large hydraulic works and offer especially positive results in those areas where it is not feasible to apply other complementary water management techniques.
The indicator adopted has been the ratio between the construction cost and the volume of water stored for documented cases. Some subsequent studies have considered amortization costs, cost/benefit ratio, average life of structures and other long-term calculations (Fernández et al, 2014). Even so, there is a lack of sufficient information to estimate the cost of water for MAR devices given the youth and heterogeneity of most of the MAR experiences in Spain.
Information has been obtained regarding eight dams, all of them from Castilla y León and La Rioja "La Rioja (Spain)"). The average resulting ratio is €1.25/m³.
The cost of water in RAA devices (=MAR) varies within broader limits, depending on the nature of the device, age, years in operation, etc. All cases for which information has been accessible have also been analyzed:
By analyzing the data, we can establish some first approximations to the economic reality of each technique (average values of the relationships, 2008 situation):
These data, although they lack the rigor of a very complete economic analysis, allow us to affirm that the costs of water from MAR operations are somewhat lower than the average cost of desalinated water and less than half of that impounded in dams and ponds.
Based on these results, it can be seen that water costs are affordable and decreasing as the level of knowledge of the MAR technique advances and investments are amortized, especially since the design of deep recharge devices has been improved, generally injection wells, whose design has been progressively improved, with good experiences in Barcelona, Madrid, Ciudad Real, Palma de Mallorca, etc.
To the economic advantage we must add the one linked to the occupation of the land (almost zero), its high landscape value, its high contingent value compared to structural works. It is also worth highlighting its progressive acceptance as a technique that allows us to combat "frontally" some of the effects that climate change is causing on water resources, generally in the form of extreme events or prolonged periods of water scarcity and drought.
The devices inventoried in Spain exceed 32, although not all of them are currently operational. Many of them correspond to experiences carried out by the IGME (in ITGE, 2000) that have not been continued.
In Catalonia, infiltration devices through wells and drillings in the alluvial rivers, scarification of the bed and deep infiltration drillings predominate. In the rest of the Mediterranean arc and the Balearic Islands, passive systems predominate (they do not require electricity) such as wells, galleries and infiltration ponds, with abundant retention dikes and manholes in the Levant. In Palma de Mallorca, intermittent schemes (Crestatx) and recharge through deep drillings have been tested, an active system that requires electrical consumption.
In the plateau areas, surface artificial recharge devices promoted by the MAPA predominate through infiltration ponds (known as recharge pools in several South American countries), canals and ditches (Segovia), in addition to a series of installations with wells in the alluvial rivers (Valladolid, La Rioja "La Rioja (Spain)"), etc.
In Madrid and Castilla-La Mancha the most notable experiences have been carried out through deep drilling, wells combined with drilling and ditches.
In Central Andalusia there are irrigation ditch systems (a pioneering system of artificial recharge in Spain and surely in Europe, with written chronicles dating back to at least the century, DINA-MAR, 2010), mine drainage and boreholes; while in the Occidental wells and ponds predominate as induced infiltration devices. There are also advanced experiences in the Las Cruces copper mine in Seville using active injection systems.
Conclusions
Artificial aquifer recharge (MAR) is a water management technique with great potential and very little used in Spain. There is great skepticism about its value and little diffusion to date. Likewise, it continues to be barely considered by the country's water managers, although its degree of implementation is increasing and continuous experiences are yielding positive results.
The sociopolitical circumstances, as well as the legal framework that regulates the activity, are suitable at the current time to include this type of devices in the new water management schemes. Although the economical ones are not desirable despite being low-cost devices and the cost/benefit ratio increases as the state of the art progresses.
The economic analysis and the environmental dimension of the RAA (or MAR) technique confirm its effectiveness, its convenience and its good adaptation to the Spanish water reality of the 20th century. This technique should not be understood as a tool to control the environment, but as an instrument to act on the consequences of poorly planned activities in the past and/or plan others for the future that are more in line with sustainable development.
Despite its excessively ecological appearance, it is a structural measure, perhaps more “elegant” than the construction of a dam or a pond, although it allows a much greater margin of maneuver, by enabling the occupation of the land above the aquifer used for artificial recharge, it is cheaper, more real, safer and more viable. Furthermore, there are those who advocate for the greater contingent value of the associated elements with respect to large hydraulic works.
The technique must be incorporated into complex joint use topological schemes, since, by itself, it can hardly cover a strong guarantee of supply in multi-year periods.
In Spain there are great possibilities of installing new artificial aquifer recharge devices (according to provisional calculations, approximately 16% of the national territory is susceptible to RAA operations, DINA-MAR, 2010). The most prone basin is the Duero, followed by the Balearic, and the least prone are those in the north.
Regarding quantitative aspects, in the current water situation it is considered possible and appropriate to “invest” volumes from rivers for the regeneration of spaces of environmental interest, although it is questionable whether this activity can be maintained over time if the current drought continues, aggravated by global problems such as desertification, climate change, the economic crisis, etc.
The technique has become a way to face "head-on" the adverse effects of climate change and allow the storage of water as a strategic resource to face situations of water scarcity and drought, in addition to allowing volumes to be derived to recharge from extreme climatic events due to excess (floods, floods).
The use of water resources for environmental purposes will undoubtedly raise controversial debates in the immediate future.