In CLM there are more than 90 reservoirs, with a total capacity in excess of 6,741 hm3, with approximately 60 of them having a very limited capacity i.e. less than 5 hm3. Among the reservoirs, emphasized are those of "Entepeñas and Buendía", in the Tajo river basin, which can store more than 2,440 hm3. These reservoirs are well known, as from them originates the Tajo-Segura Aqueduct (Acueducto Tajo-Segura, ATS). Other important reservoirs are those of Alarcón and Contreras, in the river basin of the Júcar, with capacities of 1,112 and 884 hm3 respectively. The reservoir of the Cenajo in the Segura river basin has a capacity of 437 hm3.

In relation to the number of Hydrogeological Units (HU) in the region, 55 HU are recorded, less than half belonging to the Júcar and Segura river basins. The total surface area occupied by the CLM aquifer systems is 50,807 km2 (CES, 2006), with reserves around 65,000 hm3 (Table 2). The aquifers with greater water volume and greater operation level are: the 08.29 Mancha Oriental of the Júcar river basin with renewable resources around 377 hm3 year-1 (CHJ, 2004a), the 04.04 Mancha Occidental and 04.06 Campo de Montiel of the Guadiana river basin, with renewable resources around 329 and 86 hm3year-1 respectively (CHG, 1999 and 2004). It is in these aquifers where problems related to overexploitation are most pressing; between them, they support more than 50% of irrigable area according to the National Irrigation Plan (Plan Nacional de Regadíos; PNR, 2000) (Figure 2).

Figure 2: Distribution of the irrigated lands in Castilla-La Mancha (PNR, 2000).

Although the regulated surface and groundwater resources, that average 6,330 hm3 year-1 for CLM, would satisfy demands amply, this is not the case because:

• Parts of the resource are generated at the boundary with other regions, as is the case of the Tajo and Guadiana. Resources are also available at the boundary with Extremadura, which prevents its possibility of use in this region.

• A great part of the regulated water in CLM is "committed" for use in other territories. This occurs at the source of the Tajo, its resources are used in some provinces of Andalucía, Región de Murcia and Comunidad Valenciana by the ATS. The water resources of the high river basin of Segura are mainly designated for use in Murcia, and the resources of the Júcar river basin are appropriated in great extent to uses in the Comunidad Valenciana (Figure 1).

• There is no physical or administrative agreement between the existence of resources and the location of the demands.

2.1.2 The Water Demand and Allocation of Resources by the Hydrographie Confederations

The population of CLM is estimated to be approximately 1,850,000 (INE, 2004) to which must be added another 500,000 transitory inhabitants. Of the 915 municipalities that constitute this region, 69% have less than 1,000 inhabitants registered, which is 11% of the population. On the other hand, although the percentage of municipalities greater than 5,000 inhabitants represents 7% of the total, within them 60% of the population is found.

The nuclear power plants of "José Cabrera" and "Trillo", and the thermal power stations of "Aceca" and "Puertollano", use an important percentage of the total water assigned to the region; they constitute the second sector in importance after agriculture. However, the consumptive use of water resources due to these activities is reduced, by approximately 5% (EEA, 2003), as a great part of the used water is returned to the environment after purification processes.

The agricultural sector utilizes and consumes the greatest volume of water in CLM. The transformation of great zones of the region into irrigated land, mainly during the decades of the 70's and 80's, has permitted an increase in the level of income of the population and has allowed for a large percentage of the population to remain in the countryside.

Table 3 illustrates the assigned volumes by the different Hydrological Plans (HP) to cover the previous demands.

Table 3: Established allocations in the Hydrological Plans of river basin for water use in

CLM grouped by sectors (CES, 2006)

Table 3: Established allocations in the Hydrological Plans of river basin for water use in

CLM grouped by sectors (CES, 2006)

River Basin

Supplying (hm3 year-1)

Irrigated land (hm3 year-1)

Industry &

energy (hm3 year-1)

Total (hm3 year-1)


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