Droughts are common occurrences in mainland Portugal. During the 1976-2002 periods, severe droughts occurred during 1980-81, 1982-83, 1991-92, 1994-95, and 1997.
Between September 1991 and May 1992, the absence of rainfall caused a long drought that directly affected winter cereals and pastures. This agricultural year was classified as extremely dry in the whole territory (Report on Climate Conditions, 1992).
Between September 1994 and October 1995, a severe drought occurred; this period was classified as extremely dry, especially in the southern region of Portugal. These conditions caused serious damage to winter cereals (Report on Climate Conditions, 1995).
The meteorological drought event of 1997 was so intense that, within three months, it gave rise to a severe agricultural drought. In these three months (February, March, and April) it did not rain at all and the temperature was well above the average, which caused dryness of the soil that affected winter cereals. In Alentejo, 70% of the cereal production was lost, and a state of crop calamity was declared (Report on Climate Conditions, 1997).
Figure 14.2 shows the variation in wheat yields for Portugal for the 197099 period. A higher average yield with higher variability can be observed for the second half of the period. From 1977 to 1979, too much rainfall caused a very low yield for wheat, as well as for other crops. Yield losses from 1981 to 1983 were caused by a prolonged and severe drought. In 1992 and 1995 also, drought caused significant yield losses. The low yields in 1997 and 1998 were caused by irregular rainfall distribution (i.e., surplus in autumn and in the beginning of winter, but deficit in February and March) and untimely heat during critical growing phases (GPPAA, 1999).
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