Defining a Drought

In Mexico, there is no standard definition for agricultural drought. However, the Comisión Nacional del Agua (CNA; i.e., National Water Commission), which is a federal agency responsible for making water policies, has coined its own definition for drought. This agency determines whether a particular region has been affected by drought, by studying rainfall records

collected from the national climatic network. The national climatic network is spread throughout the country and is managed by the Servicio Meteorológico Nacional (SMN; i.e., National Meteorological Services). The CNA determines, for a municipal region, if the rainfall is equal to or less than one standard deviation from the long-term mean over a time period of two or more consecutive months. If it is, then the secretary of state declares drought for the region. Based on such a definition, drought was declared in 60 municipalities during 2000-01 and in 50 municipalities during 2001-02, out of 67 municipalities in the state of Chihuahua. If a municipality is declared drought-affected, it qualifies for federal funds for drought mitigation.

Table 10.1 The distribution of irrigated and rainfed area in selected states of Mexico

State

Irrigated Area (I)

Rain-fed Area (R)

Area Ratio (R/I)

(ha)

(%)

(ha)

(%)

Aguascalientes

35,252

5.5

94,884

4.3

2.7

Coahuila

122,484

19.1

53,765

2.4

0.4

Chihuahua

265,410

41.3

634,129

28.6

2.4

Durango

98,762

15.4

508,880

22.9

5.2

Zacatecas

120,253

18.7

928,559

41.8

7.7

Total/Average

642,161

100

2,220,217

100

3.5

Insurance companies have adopted a different definition of drought for the purpose of payments to farmers during drought periods. These companies define an agricultural drought as a state of insufficient water or rainfall availability such that plants are damaged due to any of the following problems: rickets, dehydration, permanent withering, total or partial desiccation of the reproductive fruit organs or grains, irregular pollination during the embryo formation, or plant death.

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