Agricultural Drought Indices - US Department of Agriculture

Series of mean SPI 36 over peninsular Spain
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Figure 12. SPI series for a time scale of 36 months for all of peninsular Spain. The drought intensity
of 1991-95 can be compared with that of the first part of the 1980s.
This persistent meteorological drought led to a severe hydrological drought, which in turn caused
adverse impacts because the precipitation deficit was mainly concentrated in the winter period,
when rainfall is more effective in producing surface runoff. The water resources stored in some big
Atlantic Spanish basins such as Tajo, Guadiana, and Guadalquivir fell below 10% of total capacity
at the end of the long drought spell, in September 1995.
Because water supply was so limited for such a long period, various productive sectors
experienced a number of direct impacts. The main impacts were the following:
• Domestic water supply problems: Most urban areas of the southwestern corner of Spain
suffered shortages in domestic water supply, and at the beginning of autumn 1995, about
15% of the Spanish population experienced water shortages and another 15% faced
reduced water supply.
• Overexploitation of aquifers: The shortage of water resources in 1995 forced a greater
exploitation of hydrogeological resources, especially for agricultural users, causing a
depletion of groundwater levels. This resulted in the draining of wetlands in some parts of
central Spain and increasing salinisation by marine intrusion in some coastal aquifers of
southeast Spain.
• Reduction of irrigated land surface: Strong restrictions were placed on irrigation in this
period, and this seriously affected irrigated herbaceous crops, reducing the total land area
in these crops by 18% between 1992 and 1993. During the 1992-1995 period, the average
area in corn was reduced by 30% (compared with the previous five years), the area in
cotton was reduced by 51%, and the area in rice was reduced by 33%.
• Decrease of hydroelectric energy production: The average production of hydroelectric
energy for the four hydrological years 1991-92 to 1994-95 was 14.5% less than the
average during the five-year period 1986-1991; in 1992-93 the reduction was 30%.
Electrical companies had to increase thermal energy production by 7% to compensate for
this deficit.
The water shortages were centered in certain areas and crops of the southern half of Spain, but
the growing diversification of the Spanish agrarian sector tended to limit the magnitude of the
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