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Disaster management
Drought
Drought is the single most important weather- related
natural disaster often aggravated by human action. Drought's beginning is
subtle, its progress is insidious and its effects can be devastating.
Drought may start any time, last indefinitely and attain many degrees of
severity. Since it affects very large areas for months and years it has a
serious impact on economy, destruction of ecological resources, food
shortages and starvation of millions of people. During 1967-1991, droughts
have affected 50 percent of the 2.8 billion people who suffered from all
natural disasters and killed 35 percent of the 3.5 million people who lost
their lives due to natural disasters. Owing to abnormalities in the
monsoon precipitation, in terms of spatial and temporal variation
especially on the late on set of monsoon, prolonged break and early
withdrawal of monsoon, drought is a frequent phenomenon over many parts of
India. In India, thirty three percent of the area receives less than 750mm
rainfall and is chronically drought-prone, and thirty five percent of the
area with 750-1125mm rainfall is also subject to drought once in four to
five years. Thus, 68 percent of the total sown area covering about 142
million hectares are vulnerable to drought conditions. India has faced
three major droughts in this century- 1904-1905,1965-66 and 1986-87. The
1987 drought had a lasting impact on one-third of the country. The role of
space technology in drought mitigation is enumerated hereunder:
Drought Preparedness
Drought mitigation involves three phases, namely, preparedness phase, prevention phase and relief phase. In case of drought preparedness,
identification of drought prone areas information on land use and land cover, waste lands, forest cover and soils is a pre- requisite. Space-borne multi
spectral measurements hold a great promise in providing such information.
Drought Prediction
Remote sensing data provide major input to all the three types rainfall predictions; namely such as long-term seasonal predictions, medium
range predictions and short-term predictions. Global and regional atmospheric, land and ocean parameters (temperature, pressure, wind, snow, El-Nino, etc.)
required for long-term prediction, could be generated from observations made by geo-stationary and polar orbiting weather satellites such as INSAT and NOAA
. In the medium range weather prediction, the National Centre Medium Range Weather Forecasting (NCMRWF) uses satellite-based sea surface temperature
, normalised difference vegetation index, snow covered area and depth, surface temperature, altitude, roughness, soil moisture at surface level and vertical
sounding and radio sonde data on water vapor, pressure and temperature, and vertical profile data in the T86/NMC model. In the short-range rainfall
prediction also INSAT-based visible and thermal data are being used.
Drought Monitoring
Drought monitoring mechanisms exists in most of the countries using ground-based information on drought- related parameters such as rainfall, weather,
crops condition and water availability, etc. Conventional methods of drought monitoring in the various States in India suffer from limitations with regard to
timeliness, objectivity, reliability and adequacy (Jeyaseelan and Thiruvengadachari, 1986). Further, the assessment is generally, influenced by local
compulsions. In order to overcome the above limitations, -sponsored a project titled 'National Agricultural Drought Assessment and Monitoring System
(NADAMS)' and sponsored by the Dept. of Agriculture and Cooperation and Dept. of Space Dept. of Space (DOS) was taken up by the National Remote
Sensing Agency in collaboration with the India Meteorological Department (IMD), Central Water Commission (CWC) and concerned State
Government agencies. The focus has been on the assessment of agricultural drought conditions in terms of prevalence, relative severity level and
persistence through the season. Satellite-derived Vegetation Index (VI) which is sensitive to vegetation stress is being used as a surrogate measure to
continuously monitor the drought conditions on a real -time basis. Such an exercise helps the decision makers in initiating strategies for recovery by
changing cropping patterns and practices. Initially, NDVI derived from NOAA-AVHRR data was used for drought monitoring biweekly drought bulletins
have been issued between 1989 to 1991, and reports on monthly detailed crop and seasonal condition during kharif season (June to October) have been
brought out since 1992 at district level (Fig.2). The project covers eleven agriculturally important and drought-vulnerable States of Andhra Pradesh, Bihar,
Gujarat, Haryana, Karnataka, Maharashtra, Madhya Pradesh, Orissa, Rajasthan, Tamil Nadu and Uttar Pradesh.
With the availability of Indian Remote Sensing satellite (IRS) WiFS data with 188m spatial resolution, the methodology is being updated to provide
quantitative information on sowings, surface water spread, and taluk / mandal /block level crop condition assessment along with spatial variation in
terms of maps (Fig.2). The IRS WiFS -based detailed monitoring has been opertionalised for Andhra Pradesh State in 1998, and subsequently
extended to Orissa and Karnataka.
Drought Relief
The State Governments are primarily responsible for both short -term and long- term relief management. The NADAMS provide detailed
assessment of drought conditions for providing short -term relief.
Long-term management:
Several chronically drought-affected districts in India experience acute shortage of
drinking and irrigation water. To address this issue, a nationwide project titled 'Integrated Mission for Sustainable Development (IMSD)' was taken
up in collaboration with other DOS centres and State Remote Sensing Applications Centres. The project essentially aims at generating locale-specific
action plan for development of land and water resources on a micro watershed basis in drought- prone areas of the country using IRS data. In the first phase,
175 districts covering 84 million ha has been covered (Rao,1998).
For providing safe drinking water to rural masses, a nationwide project titled "National Drinking Water Technology Mission", was launched by Department
of Space (DOS) in collaboration with other State Remote Sensing Applications Centres, and Central Ground Water Board and State Ground water
Departments. Ground water potential maps showing ground water prospect at 1:250,000 scale have been prepared for entire country.
The success rate achieved by drilling wells through the use of remote sensing data has been found to be much better than those achieved by
conventional means. Furthermore, as a follow-up large scale (1:50,000) mapping of ground water prospects for Rajasthan, Madhya Pradesh,
Andhra Pradesh, Karnataka and Kerela under Rajiv Gandhi National Drinking Water Mission is in progress.
Cyclone
The intense tropical storms are known in different part of the world by different names. In the Pacific ocean, they are called 'typhoons', in the Indian
ocean they are called 'cyclones' and over North Atlantic, they are called 'hurricane'. Among various natural calamaties, tropical cyclones are known
to claim a higher share of deaths and distruction world over. Records show that about 80 tropical cyclones form over the globe every year. India has
a vast coast line which is frequently affected by tropical cyclones causing heavy loss of human lives and property. Cyclones occurs usually between April
and May (called pre-monsoon cyclonic storms) and between October and December (called post-monsoon cyclonic storms). While cyclonic storms can't
be prevented, the loss of lives and damage to the properties can be mitigated if prompt action is taken after receiving timely warnings.
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