Water Balance in Spain

Spain on average has sufficient water to meet water demands, but these resources are very unevenly distributed. According to the "White Paper on Water in Spain" (Ministerio de Medio Ambiente, 2000), natural water resources are estimated at 111 billion m3 per year, distributed as shown in Figure 3.

The total amount of natural water resources is not available for abstractions.* Two limitations are usually considered: (1) a precautionary reserve of 20% of the natural resources for environmental requirements, and (2) the minimum water volume that must be maintained along the Spanish-Portuguese border, per the Albufeira Treaty.

Annual freshwater abstraction by sector is shown in Table 3 (Ministerio de Medio Ambiente, 2000). To illustrate the possibilities of reusing water, we obtain the consumptive

Global Water Balance
Figure 3 Natural annual water resources in Spain (mm). (From Ministerio de Medio Ambiente, 2000.)

fraction of the water demand that cannot be reused, by applying different percentages: 20% for urban use, 80% for irrigation, 20% for industrial use, and 5% for energy use.

With the percentages for reusing water and data obtained from the basin hydrological plans, the distribution of the total water demand in Spain is shown in Figure 4.

Once maps of potential water resource supply and demand have been drawn up, they can be compared to identify existing imbalance and its territorial location (see Figure 5).

* EUROSTAT (Statistical Office of the European Communities) defines water abstraction as "water removed from any source, either permanently or temporarily." In Europe, water abstraction is equivalent to water withdrawal. Water demand is defined as the "volume of water requested by users to satisfy their needs." According to EUROSTAT, water use is "water actually used by end users for a specific purpose within a territory, such as for domestic use, irrigation or industrial processing."

Table 3 Annual Freshwater Abstraction in Spain, by Sector

Urban Water Demand

Consumptive Urban Water Demand

Agricultural Water Demand (Irrigation)

Consumptive Agricultural Water Demand (Irrigation)

Industry

Water Demand*

5,393 1,079 27,863 22,290 1,920

5,393 1,079 27,863 22,290 1,920

Consumptive Industrial Water Demand

Energy Water Demand

Consumptive Energy Water Demand

Total Water Demand

Total Consumptive Water Demand

Returned Water

5,679

40,855

24,037

16,818

Note: All figures are in millions of cubic meters per year. Source: Ministerio de Medio Ambiente (2000).

1-250 250-500

□ 500-750 750-1000 1000-1250 1250-1500

2000-2250 2250-2500 2500-2750 2750-3000 3000-3200 3200-3500 >3500

Figure 4 Total water demand in Spain (mm). (From Ministerio de Medio Ambiente, 2000.)

l_i 0 1-200 200-400 400-600 600-800 800-1000 □ 1000-1200 cu 1200-1400

1400-1600 □ 1600-1800 1 800-2000 2000-2200 2200-2400 2400-2600 2600-2800 □ >2800

Figure 5 Territorial distribution of water deficits (mm). (From Ministerio de Medio Ambiente, 2000.)

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