This section is mainly taken from an invited paper presented by Llamas and Pérez Picazo in the 2001 Stockholm World Water Week. The term 'hydrosolidarity' has been coined mainly by professors Falkenmark and Lundquist who were the organizers of this water week.
The Segura catchment is located in south-eastern Spain. Its main features are: (i) surface area 19,000 km2; (ii) average annual precipitation: 400 mm, ranging from 800 mm in the headwater to 200 mm in the coastal plain; (iii) annual potential evapotranspiration: 800-900 mm; (iv) average streamflow: 1000 million cubic metres. The relief is abrupt with mountains that reach an altitude of 2000 m. The geology is complex with numerous faults and thrusts. Calcareous aquifers cover about 40% of the catchment's surface. Natural groundwater recharge is estimated at about 600 million cubic metres per year (about 60% of the total stream flow). The climate is typical of Mediterranean regions: hot summers, frequent flash floods and long droughts.
As much as 60% of the Segura River basin is within the Murcia Autonomous Region and the remaining 40% divided between the autonomous regions of Valencia and Castilla-La Mancha. The mild climate and the important base flow (typical of a karstic catchment) of the Segura River encouraged the development of an important agricultural economy in the region. It was based on an irrigation network on the flood plains of the middle and lower part of the catchment area, which dates as far back as the Muslim occupation 1200 years ago. Vegetables, citrus and other fruits have been cultivated in the region for many centuries. Agro-industry (food processing) has also been significant at least since the beginning of the 20th century. Collective systems to manage surface irrigation were implemented several centuries ago.
Until recently, agriculture was the main revenue-generating activity in the Segura catchment area. Murcia was considered the orchard of Spain. Since the integration of Spain in the EU (1986), the demand for its agricultural products increased significantly. The scarcity and/or variability in the availability of surface water resources have motivated the construction of 24 reservoirs that provide total storage of about 1000 million cubic metres. Although good at preventing floods, they have not satisfied the farmers' water demands for irrigation at a nominal price. Politicians and engineers who have advocated for the transfer of water resources from 'humid' Spain to 'dry' Spain have backed the old paradigm, with intense reliance on subsidies. In 1933, the first formal proposal to transfer water from the Tagus River headwaters (in central Spain) to the Segura River was formally made, but became operative only in 1979.
In the 1950s and 1960s, the Spanish Ministry of Agriculture launched a significant effort to promote groundwater irrigation in Spain. This promotion can be said to be totally independent of the National Water Policy that, as mentioned earlier, was driven by the corps of civil engineers of the Ministry of Public Works. This initial activity, heavily subsidized with public funds, soon became a catalyst that promoted intensive water well drilling by many private farmers in many regions of Spain. The most active region in this respect was the Segura catchment area. There were several reasons for the special development of groundwater abstraction in this region: (i) the area had a long tradition of irrigation with surface water and a traditional capacity to market high-value crops in Spain and abroad; (ii) many farmers had the expectation that these groundwater-irrigated areas would have some kind of preference in the allocation of surface water coming from the Segura reservoirs, from the Tagus River water transfer or from the future Ebro River water transfer project. In 1976, several years before the arrival of the first Tagus water, the new areas irrigated with groundwater required more water than the total theoretical volume to be transferred to the Segura catchment in the 1980s.
In Spain, according to the Water Law of 1879, groundwater was private-owned. The landowner could drill a water well in his or her land and pump as much groundwater as he or she wished, unless a third person was affected. Nevertheless, in the 1950s special regulations were enacted by the government that theoretically made groundwater a part of the public domain in the Vegas del Segura (Segura flood plains). The lack of experts in hydrogeology in the Segura Water Authority made this regulation difficult to enforce.
Even after the enactment of the 1985 Water Act the control of the old and new water wells in the Segura catchment area is rather scarce. The situation can accurately be described as one of administrative and legal 'chaos' (see Llamas and Pérez Picazo, 2001). For example, the official White Paper on Spain's Water (MIMAM, 2000, p. 343) admits that in this region only about 2500 water wells out of more than 20,000 drilled are legally inventoried by the Segura Water Authority.
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