Figure 11: Map of average precipitation in Castilla-La Mancha.
As was previously mentioned, the principal irrigated areas are associated with aquifers that are overexploited or are at risk of being so. The uncoordinated exploitation of groundwater has resulted in the continuous degradation of certain areas, with the following results:
• Decrease in the piezometric levels, and an increase in the pumping costs and drying of wetlands.
• Deterioration of groundwater quality, of which a high percentage of the population centres are supplied.
• Natural spaces of special ecological value have undergone alterations that can be irreversible.
Subsequently, the situation of the three main Hydrological Units of the region are detailed, which as a whole, constitute more than 50% of the irrigated land area.
The HU 08.29 Mancha Oriental is managed by the Hydrographie Confederation of the Júcar (Confederación Hidrográfica del Júcar, CHJ). The HU 08.29 includes the set of surface as well as groundwater resources, located in the geographic area that is shown in Fig. 2. Of these resources, the Júcar River and the groundwater of aquifer 08.29 have special importance.
The 08.29 aquifer has a surface area of approximately 8,500 km2 and constitutes one of the most important underground water reserves in Spain. One study estimates its total reserves at 100,000 hm3 and those available at 20,000 hm3 (IGME, 1980). After the intense process of exploitation that has progressed since the decade of the 1970's, in great excess of natural recharge, useful reserves of the aquifer are considered to be lower than that previously specified (Martín de Santa Olalla and de Juan, 2001). The natural recharge of the aquifer is estimated at 377 hm3/year (CHJ, 2004). The volume assigned by the CHJ to the irrigable areas of UH 08.29, for the purposes of guaranteeing sustainability, is 320 hm3/year (CHJ, 1998).
The extension in the area of irrigation from 1975 until the end of the 1990's has been notable, constituting an important source of development. This development has resulted in a pronounced increase in water consumption (Figure 12).
1975 1980 1985 1990 1995 2 00 0 2003 Year
1975 1980 1985 1990 1995 2 00 0 2003 Year
Figure 12: Irrigated area and volume for irrigation demand evolution of HU 08.29 Mancha Oriental (ITAP, 2004).
Water consumption in the last fifteen years has been in excess of natural recharge, which has caused an average reduction of the piezometric levels by 1.5 m/year (López Fuster, 2000). During this period, demand has increased from less than 300 hm3, to surpass 480 hm3 in 2005, due to the conditions of drought that year. It is necessary to indicate that the total volume of water utilized in the irrigation of the zone does not proceed entirely from the 08.29 aquifer. The total employed surface water used has increased to 70 hm3 year-1 (45 hm3 year-1 of traditional irrigated lands and 25 hm3 year-1 of groundwater replacement), which means an average volume of groundwater extraction from the aquifer around 390 hm3 year-1 (Domínguez, 2004).
In order to achieve sustainability of the aquifer, the Hydrological Plan of the Júcar river basin established the construction of necessary infrastructure to substitute groundwater dedicated to irrigation, by surface waters, of up to 80 hm3 year-1. Currently, the total volume that it is able to replenish is lower than 40 hm3 year-1. Due to situations of drought, the volume is even lower due to a lack of surface water resources. Thus, in 2006 only 23 hm3 were replaced (JCRMO, 2007). The absence of guaranteed water supply for irrigation, greater control by the Hydrographic Confederation, and the lack of knowledge of farmers in terms of water costs in the future, is the main reasons that the measure is not heartily accepted by farmers.
In 2005, the entire 111,178 ha of UH 08.29, were irrigated with approximate consumption of 482 hm3; 89% of this area utilized groundwater. The main crops of this zone are cereals. Maize, barley and wheat constitute almost 50% of the total of the area of irrigated land. Other important crops are garlic and onion, which do not require great amounts of water, but generate a high level of income for farmers. Set-aside land, approximating 12,000 ha, is voluntary on the part of farmers and is compulsory to the obtainment of aids from the CAP (ITAP, 2006).
The Hydrogeological Units 04.04 Mancha Occidental and 04.06 Campo de Montiel
Of the different zones that the Guadiana river basin is divided into, the upstream river basin is the one of greatest interest to CLM. This territory equates to 25% of the area of CLM, with 19,147 km2, and boasts a population of 500,000 inhabitants. Agricultural activity is the main source of income, with farmers having made important efforts in recent years to modernize farms and adjust crops to market demands.
This area is constituted of a central plain, where the aquifer of 04.04 Mancha Occidental is located. It has a surface area of 5,126 km2, and acts as a geologic drain to the Guadiana River. Into this plain spills the waters of the drainage network of the Campo de Montiel through to the Lagunas de Ruidera and waters from other rivers of lesser importance. A great proportion of the contributions infiltrate into the aquifer of Mancha Occidental, which also discharge into wetlands, of greatest importance being the Tablas de Daimiel, declared a National Park in 1973. In the decade of the 1960's, this wetland maintained 6,000 flooded hectares, however, at the onset of the 1990's this figure was reduced to less than 1,000 ha. Also important are the Lagunas de Ruidera, which accumulate the water of the aquifer 04.06. Since 1980, these lagoons have been protected as a Natural Park (R.D. 13/7/79). These wetlands were designated as a Biosphere Reserve by UNESCO in 1981.
Vineyards, cereals (chiefly barley and wheat), and lesser water consuming horticultural cultivations, such as melon, garlic, and pepper, and with a high impact in labor, are the current trend. This tendency arranges traditional agriculture of rainfed land with irrigated land, being a key element that helps the economic viability of the farms. This new agriculture is displacing that which was established in the decades of the 1970's and 1980's, which boasted crops of high water consumption such as maize, and alfalfa, etc.
In the Manchega Plain, a supply of groundwater for agricultural uses has traditionally existed. It is estimated that at the beginning of the 1960's, in the Aquifer 04.04 Mancha Occidental, 20,000 ha of irrigation existed with water-wheels, that extracted between 50 and 100 hm3 of water annually. From different agricultural development plans, irrigated land area has increased remarkably, from 30,000 ha in 1974 to more than 125,000 ha in 1987. Similarly, extractions have reached 550 hm3 year-1. This amount greatly exceeds the renewable resources of the aquifer, considered to be 320 hm3 year-1 (PHG, 1999). As a result, the aquifer of Mancha Occidental was declared overexploited in December of 1994 by the Hydrographic Confederation of the Guadiana (Confederación Hidrográfica del Guadiana, CHG).
In June of 1989, the aquifer of 04.06 Campo de Montiel was declared overexploited, due to the fact that the irrigated area reached 8,000 ha. The overexploitation of this aquifer became evident when water from the aquifer no longer reached the Lagunas de Ruidera, also affecting other traditional irrigated lands of the area, and the urban supplying of some villages (CES, 2006).
According to the data collected in Table 11, the HU 04.04 and HU 04.06 are obviously overexploited. Not only do they consume their own resources but they also use the transfer that is produced from a peripheral HU. HU 04.06 is an aquifer with a pronounced flow and discharge to adjacent aquifers, where the decrease of piezometric levels produces a drying in the highest lagoons of the Lagunas de Ruidera, being an aquifer with limited capacity of permanent water storage and highly dependent on rain.
Table 11: Description of the hydrological planning in the Hydrogeological Units of the
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