Agricultural Drought Warning System

Although there are numerous departments that routinely collect data relevant to drought monitoring, there is no integrated system for drought monitoring or early warning at national level. Recently, the Ministry of Agriculture and Cooperative has taken an initiative and has proposed an early warning system for agricultural drought based on a better coordination among different departments and organizations. The proposed system operates in two modes: time-warning mode and event-warning mode, as illustrated in figure 25.2.

The time-warning mode is a long-term drought warning system based on meteorological and physical data. The Department of Meteorology provides weather information throughout the year. Particularly in the dry season, the department predicts drought for different parts of the country. The Department of Land Development provides the information on current land use, land use changes, and soil types. This mode evaluates the seasonal as well as monthly weather conditions during the hot and dry season and helps identify the potential drought-prone areas and their drought sever-

Table 25.2 Input variables to compute drought severity classes for the rain-fed areas of Thailand



Score and the corresponding range of variable

Meteorological data


3, [if 05ET > P]

Monthly rainfall, P (mm)

2, [if P > 0.5ET]

Evapotranspiration, ET

1, [if P > ET]

Ground water


3, 5-10m3/h

2, 10-20m3/h

1, 20-50m3/h

Land use


3, sugarcane (high water requirement)

2, rice (moderate water requirement)

1, other crops (low water requirement)

Soil water holding capacity


3, sand

2, loam

1, clay



3, >5%

2, 2-5%

1, <2%

Density of river


3, <0.5 km/km2

2, 0.5-1.0 km/km2

1, >1.0 km/km2

Size of basin


3, >3000 km2

2, 1000-3000 km2

1, <1000 km2

Source: Eiumnoh (2000).

Source: Eiumnoh (2000).

ity levels. In this mode the system basically predicts the time of drought occurrence to help farmers plan preventive measures to minimize losses.

In the case of the event mode, the farmers and agricultural extension officers at district and subdistrict levels report drought information (area of drought occurrence, pest and disease cases, rainfall amount, types of crops, etc.) to the Warning Center established in the Office of Agriculture Economics (figure 25.2). The raw data are supplied to Warning Center by different departments (irrigation, forestry, agriculture, livestock, fisheries). The information is stored and analyzed in a Geographic Information System (GIS) to plan for drought mitigation. The output of analysis is disseminated to the target areas, such as the Agricultural Technology Transfer Station (ATTS) located in each district, the Executive Information System (EIS), mass media, and the provincial government offices.

The ATTS is the lowest level administrative unit run by locally elected officials. The general public, including farmers, can access the agricultural and other related information from the ATTS. The EIS is the highest-level body that plans measures to combat drought and other disasters. Finally, based on the output, response actions in regard to drought mitigation can be planned.

The Warning Center's structure and manpower consists of three sections: system development, data analysis, and estimation of damage and

Event Warning


Figure 25.2 Proposed drought warning system for Thailand.

public relations. The system development section is responsible for setting up the computer system, network connection, operation, and maintenance of hardware and software and data reception and update. The data analysis section is responsible for data analysis and display of the information to the affected areas. The damage estimation and public relations section is responsible for maintaining up-to-date statistical records and performing economic analysis of the drought and reporting the outcome to the EIS and making it available to public and the media.

To perform the above task, the Warning Center is equipped, in addition to required personnel support, with the following: Remote sensing and GIS hardware and software and their specialists, relevant equipment to establish an on-line linkage with the ATTS, and public relations office. The manpower in the center is pooled from existing government organizations and consists of one director, two system engineers, two system officers, four agricultural officers, two geographers, two hydrologists, three statisticians, three economists, and two public relations officers.

Use of Satellite Data

The National Oceanic and Atmospheric Administration's (NOAA) Advanced Very High Resolution Radiometer (AVHRR) ( and Moderate Imaging Scatterometer (MODIS) ( are suggested for drought monitoring. At this stage, the remote sensing data are suggested to generate current land-use information as required in the proposed early warning system. After the potential drought areas are identified, the use of satellite data with higher spatial resolution remote sensing data is suggested to study detailed land-use types in the identified areas.

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