Irrigation

In Spain, as in many arid and semiarid countries, the main groundwater use is for agriculture. Although few studies have looked at the role that groundwater plays in irrigation, those that do exist point to a higher socio-economic productivity of irrigated agriculture using groundwater than that using surface water. A 1998 study of Andalusia (south Spain) showed that irrigated agriculture using groundwater is significantly more productive than agriculture using surface water, per volume of water used (Hernández-Mora et al., 2001). Table 13.2 shows the main results of the Andalusia study. It is important to note that these results were based on the average water volumes applied in each irrigation unit (or group of fields). The water losses from the source to the fields were not estimated, but are sig nificant in surface water irrigation. Other studies have calculated the volumes used in surface water irrigation as the water actually taken from the reservoirs. For example, the White Paper of Water in Spain (MIMAM, 2000) estimated an average use of 6700 m3/ha/year and 6500 m3/ha/year for the two catchments that are the subject of the Andalusia study without differentiating between surface and groundwater irrigation. Using these new figures and the volumes given for irrigation with groundwater in the Andalusia study, a more realistic average volume used for irrigation with surface water of 7400 m3/ha/year can be estimated. Table 13.2 shows that productivity of groundwater irrigation is five times greater than irrigation using surface water and generates more than three times the employment per cubic metre used. It could be argued that the greater socio-economic productivity of groundwater irrigation in Andalusia can be attributed to the excellent climatic conditions that occur in the coastal areas. While good climatic conditions may influence the results, the situation is similar in other continental regions of Spain (Hernández-Mora and Llamas, 2001). The updated data presented by Vives (2003) about the Andalusian irrigation confirm the previous assessment about the greater social and economic efficiency of groundwater irrigation.

Table 13.3 provides an overview of Spanish irrigation, indicating the water sources and irrigation technologies. In general, drip irrigation and sprinkler systems are more common in the regions where groundwater is used more intensively.

When examining this section it is important to keep in mind the uncertainties of hydrologic data. However, the results are indicative of the greater productivity of irrigation using groundwater. This should not be attributed to any intrinsic quality of groundwater. Rather, causes should be found in the greater control and supply guarantee that groundwater provides mainly during droughts (see Llamas, 2000), and the greater dynamism that has characterized the farmers who have sought their own sources of water and bear the full (direct) costs of drilling, pumping and distribution (Hernández-Mora and Llamas, 2001).

Table 13.2. Comparison of irrigation using surface and groundwaters in Andalusia. (From Hernández-Mora et al., 2001.)

Origin of irrigation water

Indicator for irrigation

Surface

Groundwater water Total

Relation groundwater/ surface water

Irrigated surface (103 ha) Average use at origin

210 4000

600 810 7400 6500

Water productivity (€/m3) Employment generated (EAJ/106 m3)b a

2.16

bEAJ ~= equivalent annual job, which is the work of one person working full-time for 1 year.

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