Droughts have far reaching social, economic, and political implications. With limited hydrometeorological data available in Mexico, simple drought indicators such as the deviation from the mean rainfall are more suitable than a sophisticated indicator such as Palmer drought severity index. The standardized precipitation index, which depends only on precipitation, appears to be a qualitative tool for drought monitoring, but this index was not suitable for quantitative assessment of agricultural droughts at small scales. The correlation between maize and bean yields with SPI ranged from 0.26 to 0.54. However, the relationship was better in the case of bean than maize. Additional factors that influence crop yields were not analyzed. Low yields of maize and high probabilities of drought occurrence in the north-central states tend to discourage maize farming in these areas. However, bean is a less drought-resistant crop and therefore is more favorable for the region.

Drought research in Mexico is a relatively new but is catching up fast. New models and methodologies are being attempted to better understand the climatic processes responsible for drought occurrence. Currently, methodologies can estimate length, severity (intensity), and spatial distribution

Figure 10.4 Correlations of dryland bean and maize yields (t/ha) with seasonal standardized precipitation index (SPI-3) for the five states.

th-1 = ton/ha of droughts on annual and seasonal bases. But there is a need for installing additional weather stations and expediting the process of data transfer from manual stations to the central data analysis center to improve drought monitoring. Installing automatic weather stations should also be considered for arid and desertic regions of Mexico. Also, there is a need to perform this analysis on a daily basis for better monitoring and predicting of droughts in Mexico.

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