Agricultural Drought in North-Central Mexico - Monitoring and Predicting Agricultural Drought: A Global Study - page 138

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Table 10.2 Basic statistics showing the variation in bean and maize yields in the five
north-central states of Mexico
Bean (tons/ha) Maize (tons/ha)

State Min Max Mean Std. dev. Min Max Mean Std. dev.

Aguascalientes 0.06 0.36 0.17 0.07 0.17 0.93 0.36 0.18

Coahuila 0.20 0.60 0.40 0.09 0.33 0.91 0.62 0.14

Ch ihuahua 0.20 0.73 0.40 0.12 0.13 1.15 0.75 0.24

Durango 0.17 0.67 0.40 0.16 0.38 0.95 0.64 0.14

Zacatecas 0.14 0.57 0.39 0.12 0.50 1.02 0.68 0.13

National 0.32 0.57 0.47 0.07 1.39 2.05 1.68 0.16

ca rry out correlation analysis between regional yields and corresponding
SP I values. Another reason for poor relationship is that SPI depends only
on rainfall, which is just one of the several variables that affect a crop yield.
Th ough a simple indicator, SPI cannot be used to satisfactorily predict
cr op yield and therefore cannot be used for quantitative assessment of
ag ricultural droughts in Mexico. There is a need to develop an agricultural
dr ought index that can be used to predict agricultural drought by predicting
yi elds of major crops.

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Drought Research Needs

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D ensity of Weather Stations

During the last two decades, there has been a tendency to reduce the to-
tal number of weather stations. In 1980, there were about 2000 stations,
whereas in 2002 only 800 remained. Also, the gauging network is unevenly
distributed, with a higher density in the central states of Mexico and a
lower density in the northern (or arid) part of the country. This uneven dis-
tribution is understandable considering a more mountainous terrain, more
urban centers, and greater population in the south. However, the northern
states need more weather stations for better monitoring of droughts. Re-
cent efforts by the CNA and the SMN are focused on bridging the gap by
installing automatic weather stations in areas that have difficult terrain.

A utomation
Another issue for drought monitoring is transferring the database updating
process, from the manual climatic stations to the SMN's main data collec-
tion and analysis center. Although there are about 800 weather stations in
the nation, only about 160 stations send the daily climatic report to the
SMN's analysis center. Therefore, there is an urgent need to expedite this