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CHAPTER 2

STUDIES ON DROUGHT ASSESSMENT

2.1 GENERAL

History of any concept will give an idea about the aspects which

are not yet covered, present requirements and a future direction for research.

It will throw light on the state of the art of knowledge and enlighten the future

course of study. In the case of droughts, several studies were completed the

world over in tropical as well as humid countries. Drought is fundamentally

the resultant of an extended period of reduced precipitation. It is viewed

through its impacts such as soil moisture, streamflow, crop yields, etc. As

such, the question of predictability of drought must extend to those quantities

as well. Nevertheless, in developing an understanding of drought and its

predictability, it is useful to first consider the physical mechanisms that cause

precipitation deficits and how they vary by time scale.

Availability of varied definitions of drought reflects the complexity

of the natural disaster cum hydrologic extreme. Studies were conducted on

drought assessments using different techniques (conventional such as

estimation of relevant hydrologic parameters and advanced such as Remote

Sensing technique, GIS software, etc.) in varied domains of dry land

agriculture, rural / urban contexts, etc. There is a need to analyse the drought

implications in an irrigated agriculture with inputs from Participatory

irrigation management. The following sections cover a review of literature

that are relevant to the objectives of this study.

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2.2 ESTIMATION OF CROP WATER REQUIREMENT

Information on crop water requirements is imperative in the planning

and operation of soil and water management strategies. Water used by the

crops is predominantly lost by transpiration (T) but there are also evaporative

(E) losses from the soil and plant surfaces. The amount of water used by

plants together with water losses through evaporation is called

evapotranspiration (ET). Other potential areas of water loss are due to many

meteorological factors such as humidity, wind speed, temperature etc.

Estimating evapotranspiration in a locality is a difficult task because it

involves equipments which are considered to be quite costly. A lot of research

has been undertaken to estimate a kind of reference ET from meteorological

data and convert this to the actual ET. There are various methods to calculate

ET such as directly using lysimeters, indirect methods of meteorological

factors and pan evaporation data.

A study sponsored by the United Nations indicates that irrigated

agriculture will need to provide 70% of the world’s increased food

requirements in future (Report of United Nations, 2005). Postel (1999)

indicates that food production levels needed in 2025 could require upto 2,000

cubic kilometers of additional water for irrigation. Water management and

crop yields can be improved by means of increased use of reliable methods

for estimating crop evapotranspiration (ET). More than a score of methods

have been proposed and used over the past 50 years. Selection of the preferred

ETo method should be based on the time step required, site aridity, equipment

costs and operation and maintenance requirements, quality of the weather data

available and the required simplicity of computations.

Where equipment cost is a consideration, where data quality is

questionable or where historical data are missing, both the reduced set FAO-

PM and the Hargreaves (Hargreaves and Allen, 2003) methods are

16

recommended, since the two methods are surprisingly equivalent over a wide

range of climates. When the weather data site is not located within a large and

well-watered area, the Hargreaves method will generally have less aridity-bias

impact in the estimate of ETo as compared to the combination equations.

Daily estimates by the Hargreaves equations are subject to error caused by the

influence of the temperature range caused by the movement of weather fronts

and by large variations in wind speed or cloud cover. Therefore, the

Hargreaves methods are recommended for use with five-day or longer time

steps.

Allen et al (2005) report that the measurement of evaporation in the

initial stage of the crop by semi theoretical integrated function to predict the

average Kc ini representing the initial period of a growing season when the

soil is mostly bare. This incorporates factors like wetting frequency,

evaporative demand and water-holding capacity of the upper soil layer. The

procedure can be used to produce graphical figures similar to that introduced

in FAO-24 for Kc ini. The model is based on a two stage evaporation process,

where evaporation during the second stage is predicted in proportion to

cumulative evaporation depth during the second stage. The model served as

the basis for figures in FAO-56. The Kc max value has been shown by several

studies to range from 1 to 1.3 for grass reference ETo, so that this value can

be predicted with relatively small error in evaporation estimates.

Singh and Irmak (2009) presented a modified approach towards

estimating Kc values from remotely sensed data. The surface energy balance

algorithm for land model was used for estimating the spatial distribution of

ETc. Land use map was used for sampling and profiling the Kc values from

the satellite overpass. Finally, a regression model was developed to establish

the relationship between the normalized difference vegetation index (NDVI)

and the ETr based crop coefficients Kcr. There was a good correlation

17

between the NDVI estimated Kcr and the Bowen ratio energy balance system

based Kcr with a R2 of 0.74 and a low root mean square difference of 0.21.

This can be a very useful tool for a large watershed or regional scale

estimation of evapotranspiration using the crop coefficient and reference

evapotranspiration approach.

Sabziparvar and Tabari (2010) used digital elevation model (DEM )

and GIS assisted methods to generate a regional distribution of monthly ETo

using the best performed model and multiple linear regressions. The

comparison of model results showed that the HG model presented the best

performance for estimation of monthly ETo values in arid and semiarid

regions northeast of Iran. Besides, the input variables are available at all of

the meteorological stations in the study area. These suggest that the model can

be a good candidate for prediction of monthly ETo in arid and semiarid

regions, where comprehensive measurements of meteorological data are not

available. The statistical analyses showed that the mean air temperature was

well correlated with altitude and latitude. When the correlations averaged over

all 12 months, a reasonable coefficient of determination 0.76 was obtained.

The maximum and minimum temperatures were also affected by altitude and

latitude of the region. The predicted ETo values showed both temporal and

spatial variations in the region. The estimated monthly ETo increased

southward because of drier climate in the south. Though PMF-56

evapotranspiration model was considered as the reference, standard method

for validating the predicted ETo data, the use of field lysimeter data can

improve the model estimates.

Murali and Prasad (2011) have done a study which is especially

relevant in a changing climate where there is a need to see how changes occur

in croplands, their implications on water use and strategies for adaptability to

ensure food security. The outcome of this research highlights the value of

18

using time-series data and advanced methods like spectral matching

techniques in the study of agricultural cropland changes in large river basins.

Ram Karan and Pawar (2011) conclude that by giving due importance to both

criteria’s viz. R2 based analysis and statistical indicators (RMSD, MBE and t-

statistics) based analysis, that Priestley-Taylor and FAO 24 Blaney-Criddle

method can be used for ETo predictions under wide range of climatic

conditions when limited data is available or reliability of data is in question.

Nandagiri and Kovoor (2012) provide guidance on the choice of the

most appropriate ETo equation to be adopted in a particular Indian climate

when input data are insufficient to apply the preferred FAO-56 PM method,

alternative ETo methods were ranked on the basis of SEE, STDEV, R2 and

also on the basis of an overall rank that considered all the performance

statistics.

2.3 DROUGHT ASSESSMENT

Agricultural drought occurs when soil moisture and rainfall are

inadequate during the growing season to support healthy crop growth to

maturity and cause extreme crop stress and wilt. Agricultural drought can be

estimated directly using conventional demand supply gap or indirectly using a

few approaches such as Remote Sensing.

Rama Prasad (1990) tried to quantify the water deficiency during a

drought and the method considers the soil moisture in the form of an

Antecedent Precipitation Index (API). The difference between the actual API

on a given time period and the API value necessary (crop water requirement

for the time period) to ensure that the crop water demand is fully met is

defined as the deficit for the day. The cumulative value of the deficits in a

water year is calculated as total deficit. The total deficit for each water year is

plotted with the crop yield data and a straight line is fitted. The drought

19

severity classification is made based on the normalised yield values that were

noted from the plotted line against the corresponding deficit for each year.

Byun (1999) analyzed the common weaknesses of current drought

indices. First, most of the current indices are not precise enough in detecting

the onset, end and accumulated stress of drought. Second, they do not

effectively take into account the aggravating effects of runoff and

evapotranspiration, which build up with time. Third, they have a limited

usefulness in monitoring ongoing drought because they are based on a

monthly time step. Fourth, most of them fail to differentiate the effects of

drought on surface and subsurface water supply. A new series of indices are

proposed to solve these weaknesses and to improve drought monitoring. New

quantified definitions on drought and its onset, end and duration are proposed.

Wilhite (1991 and 1994) focuses on the definition of drought and

the quantification of its intensity and duration. Most drought indices are based

on meteorological or hydrological data. They include indices developed by

Palmer (1965), McKee et al (1993) and Subramanyam (1964). Of all the

indices, the Palmer Drought Severity Index is still the most widely used and

recognized index on an operational bases.

Panu and Sharma (2002) studied the challenges in drought research.

Major challenge of drought research is to develop suitable methods and

techniques for forecasting the onset and termination points of droughts. An

equally challenging task is the dissemination of drought research results for

practical usage and wider applications. The statistical and mathematical

algorithms of forecasting are reasonably well developed, whereas the

phenomenal and causative aspects are far from satisfactory. One major

application of drought forecasting is in the planning of measures to mitigate

the impacts of drought by governments and related agencies. The spatial

coverage of drought duration, severity and/or intensity is of significant

20

importance in planning measures towards mitigating impacts of droughts.

Drought impacts should be handled using the risk-based approach rather than

the crisis-based approach, as is the practice today in most countries.

Svoboda (2000) focuses on discussion about the drought plans

which normally contain three basic components: monitoring & early warning,

risk assessment & mitigation and response. A 10-step drought planning

process illustrates how these components of a plan are addressed during plan

development. An example of a new climate monitoring product, the Drought

Monitor, is presented to illustrate how climate parameters and indices are

being used in the United States to produce a weekly comprehensive

assessment of drought conditions and severity levels. A critical component of

planning for drought is the provision of timely and reliable climate

information, including seasonal forecasts, that aids decision makers at all

levels in making critical management decisions. This information, if properly

applied, can reduce the impacts of drought and other extreme climate events.

Drought differs from other natural hazards in several ways. First,

since the effects of drought often accumulate slowly over a considerable

period of time and may linger for years after the termination of the event, the

onset and end of drought is difficult to determine. Because of this, drought is

often referred to as a creeping phenomenon (Tannehill 1947). Although

Tannehill first used this terminology more than fifty years ago, climatologists

continue to struggle with recognizing the onset of drought and scientists and

policy makers continue to debate the basis (i.e., criteria) for declaring an end

to a drought. Second, the absence of a precise and universally accepted

definition of drought adds to the confusion about whether or not a drought

exists and, if it does, its degree of severity. Realistically, definitions of

drought must be region and application (or impact) specific. Third, drought

impacts are nonstructural, in contrast to, the impacts of floods, hurricanes and

21

most other natural hazards. These characteristics of drought have hindered the

development of accurate, reliable and timely estimates of severity and impacts

and, ultimately, the formulation of drought contingency plans by most

governments.

Drought severity is dependent not only on the duration, intensity,

and spatial extent of a specific drought episode, but also on the demands made

by human activities and vegetation on a region’s water supplies. The

characteristics of drought, along with its far-reaching impacts, make its effects

on society, economy, and environment difficult to identify and quantify.

Improved understanding of a region’s drought climatology will provide

critical information on the frequency and intensity of historical events.

Identifying the factors that explain who and what is at risk and why (i.e., the

underlying factors behind the vulnerability) can lead to the development and

implementation of a wide variety of mitigation actions and programs to

reduce impacts from future drought events.

Droughts differ from one another in three essential characteristics:

intensity, duration, and spatial coverage. Intensity refers to the degree of the

precipitation shortfall and/or the severity of impacts associated with the

shortfall. It is generally measured by the departure of some climatic index

from normal and is closely linked to duration in the determination of impact.

Many indices of drought are in widespread use today, such as the decile

approach (Gibbs and Maher 1967) used in Australia, the Palmer Drought

Severity Index and Crop Moisture Index (Palmer 1965, Alley 1984) in the

United States and the Yield Moisture Index in the Philippines and elsewhere.

A relatively new index that is gaining increasing popularity in the United

States and worldwide is the Standardized Precipitation Index (SPI), developed

by McKee et al. (1993).

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Another distinguishing feature of drought is its duration. Droughts

usually require a minimum of two to three months to become established but

then can continue for months or years. The magnitude of drought impacts is

closely related to the timing of the onset of the precipitation shortage, its

intensity and the duration of the event. Droughts also differ in terms of their

spatial characteristics. The areas affected by severe drought evolve gradually

and regions of maximum intensity shift from season to season.

Ray Motha (2000), dealt with establishing an effective national

drought information delivery system, a coordinated effort must be undertaken

to bring more systematic data networks to rural and tribal areas. A

comprehensive information gateway must be established to provide users with

free and open access to observational network data and drought monitoring,

prediction, impact, assessment, preparedness and mitigation measures. The

key elements of an effective national drought policy include planning,

proactive mitigation, risk management, resource stewardship and public

education. All of these elements require detailed knowledge of observational

data and research products that form the foundation for efforts to reduce

drought impacts on society.

Sinha Ray (2000) have dealt with monsoon variability and the

impact of global and regional scale parameters on summer monsoon rainfall

and the prediction of summer monsoon rainfall through numerical models.

The advisories regularly issued by the India Meteorological Department

(IMD) and the National Centre for Medium Range Weather Forecasting

(NCMRWF) can be made more user oriented and a better feedback

mechanism may evolve. Proper validation of remotely sensed data in

coordination with IMD scientists, scientists from other agencies, and policy

makers for proper and timely monitoring of drought in smaller areas has been

emphasized. Better communication between farmers, policy makers, and

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researchers to improve the nature and quality of information provided to the

users also has been stressed.

To assess the utility and impact of operational weather services to

farmers, feedback can be obtained through conferences, workshops of

forecasters, agrometeorologists, agriculturists, extension workers and farmers.

Feedback is obtained by various means, such as questionnaires. The

questionnaires usually include (1) general information (e.g., name of unit,

main crops and main cultural operations), (2) information regarding farmers’

awareness of meteorological forecasts and agromet advisories, and (3)

information regarding the language of advisories (e.g., whether the language

is easy or difficult to follow), reliability of forecasts and usefulness of

warnings. Regular surveys for this feedback information are essential for the

improvement of our forecasting at such a level, so that the user community

can correctly interpret the advisories to their best advantage.

Studies by Smith (1978) and Singh and Kriplani (1987) have shown

that the 30-50 day mode has strong interannual variability, which may in turn

affect the variability of the monsoon season rainfall through active-break

monsoon episodes. They prepared a time series of the drought area index.

They defined the moisture index as the ratio of departure of rainfall from the

monthly mean and standard deviation of monthly rainfall. The epochal

behavior of drought has been discussed by Joseph (1978).

Appa Rao (1981 & 1987) classified the drought-prone areas and

chronically drought-affected areas. Most of the drought-prone areas identified

above are in either arid or semiarid regions where droughts occur more

frequently. Sinha Ray and shewale (2001) have shown a decreasing trend in

the area affected by drought in India. They made a detailed study of the

variability of drought incidence over districts of Maharashtra. Shewale (2001)

have determined the probability of occurrence of drought on the basis of

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summer monsoon rainfall data for the period 1875-1999. Probability of

occurrence of severe drought was found to be greatest in Saurashtra and

Kutch, followed by Gujarat and West Rajasthan. He also studied the effects of

El NiZo on summer monsoon rainfall of various subdivisions of India.

The National Natural Resource Management System (Jeyaseelan

2002) has been set up to monitor the progress of remote sensing applications

to natural resources management in the country. To pursue and guide remote

sensing application development in the agriculture sector, the Standing

Committee on Agriculture and Soils (SC-AS) has been created. The SC-AS is

entrusted with the responsibility of examining the role of remote sensing

technology in addressing various issues related to management of agricultural

resources. They are assessing the present and future capabilities of that

technology to develop procedures to retrieve agromet parameters from space

borne systems and disseminate agromet information for farmers’ advisory

services. Recent efforts to combat drought through policies formulated by

governmental agencies include: 1. Crop weather watch groups at the national

and state level, 2. Food security through buffer stocks, 3. Priority to the most

seriously affected areas for “food for work”/National Rural Employment, 4.

Project and other programs, 5. High priority to food production in the most

favorable/irrigated areas as compensatory, 6. Programs, 7. Optimum input

use, 8. Rural godowns to avoid crash sales, and 8. Crop insurance schemes.

The space-based National Agricultural Drought Assessment and

Monitoring System (Jeyaseelan 2002), which has been operational since 1989

under India’s Department of Agriculture, provides scientific information at

the district level for most of the states and sub district levels in a few states.

The NADAMS program needs to be strengthened with interdepartmental

support. The Drought Prone Area Development Programme (DPAP) and

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Desert Development Programme (DDP) should use the action plans prepared

on the basis of integrated resource estimation from remote sensing data.

Premier government institutions like the Central Arid Zone

Research Institute (CAZRI),Jodhpur; Indian Grassland and Fodder Research

Institute (IGFRI), Jhansi; Central Soil Salinity Research Institute (CSSRI),

Karnal; and research stations of the Ministry of Agriculture in various states

have developed some ameliorative measures. These practices are region

specific, and after proper implementation, they have the potential of bringing

forth productive green cover on otherwise marginal degraded lands.

2.4 DROUGHT STUDIES USING REMOTE SENSING AND GIS

National Remote Sensing Agency of India (Thiruvengadachary,

1988) has assessed the drought based on the analysis of vegetation index map

and the greenness map as well as vegetation index statistics for bimonthly

periods for each taluk. The satellite based drought assessment and monitoring

methodology was developed based on the relationship obtained between

previous years Normalized Difference Vegetation Index (NDVI) profiles with

the corresponding agricultural performance available at district level and their

relative difference in the current year. The National Agricultural Drought

Assessment and Monitoring System (NADAMS) in a view of the whole

country coverage, envisages the use of data from NOAA satellites with

1.1 km resolution, for generation of weekly composited Normalized

Difference Vegetation Index (NDVI) maps of country. The NDVI is a

transformation of reflected radiation in the visible and near infrared bands of

NOAA AVHRR and is a function of green leaf and biomass.

The various approaches presented above have not tried to quantify

the water deficiency during an agricultural drought, which is relevant from the

water resources engineering point of view. Rama Prasad (1990) tried to

26

quantity the water deficiency during an agricultural drought and the method

considers the soil moisture in the form of an Antecedent Precipitation Index

(API).

Krishnaveni (1993) reported that in case of drought assessment, the

important parameters that may be influencing drought are rainfall,

groundwater levels, stream flows, soils, land use etc. These parameters

possess temporal and spatial characteristics. Geographic Information System

software provides tools to incorporate spatial and temporal variations.

Therefore, GIS can be advantageously used for the analysis of drought.

Tiruvengadachari et al (1987) in their case study in Tadipatri taluk

of Anantapur District in Andhra Pradesh, India, reported that the NDVI

response over the taluk was compared between two years, supported by

ground reports on agricultural conditions. NDVI comparisons over specific

sites around rain gauges and anomalous areas provided an improved

understanding of the NDVI response specially as applied to taluk level

drought assessment. It is suggested that in addition to total vegetated area, the

NDVI response averaged over the total geographic area of the taluk or the

product of vegetated area and NDVI response could be significantly used as

drought indicators. They were found to be more effective than the mean

NDVI response over vegetated areas.

Chanzetal (2003) developed the procedure to form the image to

express the unavailability of water during periods of drought for a selected

drainage basin. Based on the method of truncation level, truncated values of

precipitation and stream flows were estimated at each gauging station. These

truncation levels were used to reflect the levels of drought severity. The

stream flow image from precipitation was subtracted to obtain drought

severity at each level. These were done on a cell by cell basis to create new

attribute values for the new image to represent the unavailability of water at

27

each level of drought severity. He discusses the future perspective of the

applications of GIS technology for agricultural resources management. Land

use suitability analysis is carried out as a part of the study and land use

classification is given. The drought mitigation and management and spatial

variation of drought conditions are explained. It offers in-depth analyses of

regional drought conditions.

Mongkolsawat et al (2000) modeled the drought risk area with a set

of themes using remotely sensed data and GIS. The underlining concept of the

paper is that the severity of drought can be considered as being a function of

rainfall, hydrology and physical aspect of landscape. Each theme of the

drought consists of a set of logically related geographic features and attributes

are used as data input for analysis. The matrix overlay operation of the

drought risk layers was performed. They are then classified into 4 drought

classes of drought risk: very mild, mild, moderate and severe.

Nagarajan and Subrata Mahapatra (2000) developed the Land

Based Information System for drought to store information of past, compared

it with the current data and to assess the vulnerability of an area using orbital

temporal remotely sensed and ancillary data in understanding the situation

and decided on the mitigation planning. This study provides an overall

picture about drought information requirement for decision makers. This

study highlights the land information based system developed for this purpose

for the drought prone Marathwada region.

Wilhelmi (2002) explains the agro-climatological factors of

vulnerability to agricultural drought. Evapotranspiration (ET) values were

estimated based on the relationship between ET, water use efficiency and crop

yield. Probability values were assigned by spatial interpolation and classified

using GIS. The classifications included low, moderate, high and very high

probability of seasonal crop moisture deficiency. The results of this study

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formed the basis for a comprehensive, GIS-based agricultural drought

vulnerability assessment for Nebraska.

Ajay and Baldev Sahai (1986) have described the role of remote

sensing in drought detection and its quantification. Different types of drought

have been discussed. It is stated that the steady rise in temperature, absence or

the deficiency of rainfall over a fairly long period form the basic characteristic

of drought. In addition, the study provides the information on useful spectral

bands and indices used for the assessment of drought like NDVI, Stress Degree

Day, Temperature Stress Days and Crop Water Stress Index. The study

concluded that the problem of drought/crop condition assessment may use a

hybrid approach which uses both comparatively high resolution earth resources

satellite data together with coarse resolution meteorological satellite data.

Thiruvengadachari and Gopalakrishna (1993) developed an

Integrated Data base Environment for Assessment of Drought (IDEA),

primarily meant to provide operational assistance to the National Agricultural

Drought Assessment and Monitoring System (NADAMS) in the analyses and

interpretation of NDVI data derived from the NOAA AVHRR satellite sensor.

IDEA has been used to derive two indices namely Seasonal Vegetation Index

(SVI) and Peak Vegetation Index (PVI) that are used in tandem to

characterize the drought prone taluks of the Karnataka State. A weighting

model was used to show relative drought proneness of the Karnataka taluks.

The ground variables taken into account were, percentage irrigation support,

percentage forested area, percentage rainfed area and normal seasonal rainfall

for each taluk.

Bora et al (1995) studied the integrated resource survey using

remote sensing to combat drought in a part of Nagaur district of Rajasthan

State, India using False Colour Composite (FCC) of IRS-1A LISS-II of

October 1988 and January 1989. Based on visual interpretation, it is

29

concluded that remote sensing technique is a useful tool for inventory of

resources of any area and the integration of database of resources led to

scientific planning and alternate land uses for combating drought menace.

Tripathy et al (1996) attempted to evaluate the indicators of

desertification process in semi-arid lands of Shahapur and Shorapur taluks of

Gulbarga district of Karnataka State, India by making use of temporal satellite

information (Landsat-4 MSS 1984 & 1985 and IRS-1A LISS-II 1988 & 1991)

along with the surface and statistical data with the aid of GIS. A

desertification severity map was produced by integrating meteorological,

hydrological and biological indicators. The study concludes that the average

severity of desertification is moderate and aggravated by human activity.

A study for monitoring the regional drought of South American

continent using AVHRR data was carried out by Liu and Kogan (1996).

Drought areas are delineated with certain threshold values of NDVI and

Vegetation Condition Index (VCI). It has been reported that drought patterns

delineated by NDVI and VCI agreed quite well with rainfall anomalies

observed from rainfall map. The results showed that NDVI images provided a

useful tool to study large scale climatic variability, while VCI images

provided a useful tool to analyse the temporal and spatial evolution of

regional drought as well as to estimate the crop production qualitatively.

Seiler et al (1998) carried out a study on AVHRR based Vegetation

and Temperature Condition indices for drought detection and impact

assessment on agricultural yields in Cordoba province of Argentina. It is

concluded that the VCI and TCI are useful to assess the spatial characteristics,

the duration and severity of drought, and were in a good agreement with

precipitation patterns.

30

Bayarjargal Yu et al (2000) carried out a study on drought and

vegetation monitoring in the arid and semi arid regions of the Mongolia using

NOAA/AVHRR satellite data. Drought affected regions were detected by

calculating the Normalised Difference Vegetation Index (NDVI) and Land

Surface Temperature (LST) values of the drought and wet years. Due to

moisture stress on the vegetation, NDVI (LST) value recorded in the dry

years should be lower (higher) than those values recorded in a normal year. It

is concluded that the AVHRR based NDVI and LST can provide valuable

information for operational drought detecting and monitoring.

Hostert et al (2001), made a study on monitoring and assessment of

desertification using remote sensing and GIS. The study provides the

additional value that can often be added through integrating remote sensing

derived information with auxiliary data through GIS approach. The study

outlined the importance of integrating socio-economic boundary conditions

and anthropogenic influences. The study further highlights the perspectives of

future developments and their likely implications on Remote Sensing and GIS

based desertification research.

Jayaseelan (2002) has described the recent trends in remote sensing

applications to drought assessment and monitoring with a case study on

National Agricultural Drought Assessment and Monitoring System

(NADAMAS). After the country wide drought in 1987, the emphasis on using

space technology for drought monitoring grew and in 1989, NADAMAS was

set up at National Remote Sensing Agency (NRSA), India. Organizations

involved in the functioning of NADAMS are National Remote Sensing

Agency (NRSA), India Meteorological Department (IMD), Central Water

Commission (CWC) and State Agricultural Departments. The project covers

14 agriculturally important and drought vulnerable states of the country,

which include Tamil Nadu State. NADAMS monitors drought during June to

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October, the main cropping season in the country. The NADAMS uses

NOAA AVHRR data to monitor country level vegetation dynamics. Bi-

weekly NDVI time series is used to monitor the vegetation phenology through

out the season. For regional drought monitoring (State level), NADAMS uses

Wide image Field Sensor (WiFS) data of IRS-1C/1D and IRS-P3.

Singh Ramesh et al (2003) carried out a study on monitoring

drought over India by studying VCI and TCI of NOAA AVHRR data. Time

series of satellite data during 1985-1996 over various Indian regions have

been used for mapping vegetation cover and classification employing NDVI.

The VCI quantifies weather component which varies from 0 to 100,

corresponding to changes in vegetation condition from extremely

unfavourable to optimal. The study has reported that VCI and TCI can be

used for drought detection and mapping. The TCI alone can not be used alone

to predict drought due to stressed vegetation and wetting of land. The VCI

coupled with TCI may be employed as a tool to monitor both drought and

excessive wetness.

Lei and Peters (2003) presented a study for assessing the vegetation

response to drought in Northern Great Plains using AVHRR data during 1989

to 2000. The derived vegetation condition and moisture availability for the

grassland crop land in the Northern Great Plains fits very well with the

predicted and observed NDVI values in most cases. It is concluded that the

NDVI is a good indicator of moisture condition and can be an important data

source when used for detecting and monitoring the drought. However,

seasonality may be an important factor for decision makers to consider.

Wan et al (2004) carried out studies for drought monitoring in

Southern Great Plains, USA. The NDVI derived from Terra Moderate

Resolution Imaging Spectroradiometer (MODIS) of 2001 and Land Surface

Temperature (LST) has been used in this study. These two are called

32

Vegetation Temperature Condition Index (VTCI) which ranges from 0 to 1.

Lower the value, higher is the occurrence of drought. The study concluded

that VTCI is physically interpreted as the ratio of LST differences among the

specific NDVI values in an area large enough to provide wide ranges of

NDVI and soil moisture at surface layers. Drought monitoring approach by

VTCI integrates the remotely sensed land surface reflectance and thermal

properties and gives the emphasis on changes in both LST and NDVI over a

region. VTCI is time dependant and usually region specific and is useful

during plant growing seasons.

Symeonakis and Drake (2004) studied the monitoring

desertification and land degradation over sub-Saharan Africa using AVHRR

data of 1996. This study emphasized the role of soil erosion that has resulted

due to natural processes, such as drought and human activities, such as

irrigation, agriculture, deforestation and urbanization. The regional land

degradation is assessed by the estimation of vegetation cover which is linearly

related with NDVI. Soil erosion, the chief indicator is estimated using a

model parameterized over land flow, vegetation cover, the digital soil map

and a digital elevation model. The most susceptible degraded land is

highlighted by combining the effects of all the four indicators.

Bhuiyan (2004) used multi-sensors data to deduce surface and

meteorological parameters (vegetation index, temperature, evapotranspiration)

of Aravalli region for the years 1984-2000 together with actual ground data

(rainfall, temperature, ground water level) for detailed drought analysis. The

Standardised Precipitation Index (SPI) has been used to quantify the

precipitation deficit. A standardized Water-level Index (SWI) has been

developed to assess groundwater recharge deficit. Vegetation drought index

has been calculated using NDVI values obtained from Global Vegetation

Index (GVI) of NOAA AVHRR data. Spatial and temporal variations in

33

meteorological, hydrological and vegetative droughts in the Aravalli terrain

have been analysed and correlated for monsoon and non-monsoon seasons

during the years 1984-2000. Based on the results, it is concluded that, none of

the drought indices follow any particular spatial and temporal pattern in this

region. The analysis reveals that meteorological, hydrological and vegetative

droughts are not linearly inter-related and suggests that combination of

various indices offer better understanding and monitoring of drought

conditions for hilly and semi-arid terrains such as Aravalli of Western India.

Nageswara Rao et al (2005) used METEOSAT-5 thermal infrared

(TIR) data for assessing the spatial and temporal distribution of rainfall and

impact of successive agricultural droughts in the state of Karnataka. It is

emphasized that there is a need for an independent system that can provide

the severity, duration and aerial extent of drought and its impact on the actual

condition of the crops/vegetation so that the authorities concerned can take

appropriate relief measures. A comparison of NDVI for the years 2000, 2001

and 2002 has been made. Districts having permanent vegetation, like forests

and agricultural land under irrigation did not show much variation between a

normal year (2000), drought year (2001) and a severe drought year (2002). It

is concluded that the NDVI is a good indicator of agricultural drought but the

reduction in green cover due to drought may be inferred and interpreted

carefully by comparing the NDVI values of the year under study with a

normal year.

Wipop and Sirirat (2006) carried out a study on drought risk area

analysis in Bandanlanhoi district, Sukhothai province based on stepwise

regression model from spatial data. QUICKBIRD satellite images were used

for creation of spatial data. Geographic Information System was applied to

simulation spatial data such as rainfall, rainy days, relative humidity,

temperature, groundwater potential, distance from water body, elevation and

34

soil drainage data. The model showed that the well soil drainage and rainfall

are important parameters for the determination drought risk area. The drought

risk area was divided into four classes viz., No risk, low risk, moderate risk

and high risk. The study concluded that, though the result was shown quite

low accuracy, the technique is good enough for using with GIS.

Rasheed and Venugopal (2009) attempted to map the agro-

ecological units for Vellore district of Tamil Nadu and derive the crop-zone

map for the four corps namely, paddy, sugarcane, groundnut and millets. The

study has demonstrated the application of agro-ecological units for

sustainable land use planning of a region. The basic theory of FAO

framework for land evaluation was adopted to define the suitability of crops.

Land quality details like terrain, soil and climatic characteristics are necessary

for evaluating agro-land suitability of crops and for delineating the agro-

ecological units. Agro-ecological units map was generated by overlaying the

agro-edaphic and agro-climatic map layers in GIS. The agro-land suitability

map was generated by matching the crop requirement details with the land

qualities. The results of the suitability evaluation, when compared with the

current land use statistics of these crops showed that area cultivated is less

than the area suitable for these crops.

2.5 IRRIGATED AGRICULTURE AND PARTICIPATORY

IRRIGATION MANAGEMENT

Agriculture is closely linked to water resource management issues.

Worldwide, 70% of water use is related to agriculture, climbing to 95% in

several developing countries. It is estimated that freshwater usage for

agricultural purposes will increase 14% over the next 30 years to meet the

growing food demands of an increasing population (Report of UN, 2005).

35

Irrigated agriculture, of which 58% of the world‘s total is in Asia,

inevitably comes under intense pressure to improve efficiency of water use in

response to scarce water resources. To promote the efficiency of water use,

there needs to be a focus on enhanced governance and capacity building at all

levels that integrates the basic principles of transparency, subsidiary, and

equity. Decentralizing water governance in agriculture and developing

equitable cost-sharing mechanisms within irrigation systems assists in

achieving more effective use of water.

Irrigation has been the primary engine for the agricultural growth of

developing nations such as India. Notwithstanding the massive public

expenditures, under performance of irrigation systems are a major concern for

such nations. Ineffective irrigation management is due to the non participation

of farmers from the process of planning and implementation. Often, lack of

social and political commitments are identified as the main reasons for the

slow progress in irrigation management. To address the issue, concepts of

Participatory Irrigation Management (PIM) involving the farmers in various

levels of decision making processes has been attempted in various

countries.PIM is a process for improving productivity and sustainability of

irrigation systems. It was during the late 1970’s and early 1980’s, India began

to focus, initiate and support programmes that would later lead to PIM. But,

this has happened after several other countries have examined with it and

became wiser in the use of it.

There are several studies carried out in past by several researchers

on Participatory Management of Irrigation system all over the world. The first

and the best-documented nation-wide programme to build participation in

irrigation management, as a corner stone of irrigation policy, occurred in

Philippines (Bagadion, 1988). The process of institutionalizing this approach

entailed workshops, training programmes, and information dissemination

36

within the agency and the farming community. This learning process was

carried out with the help of outside consultants, academic researchers and

donors, but initiative came from within agency (Bagadion and Korten, 1985).

Participatory Irrigation Management (PIM) is one approach to improve water

allocation, and effective water use being tested within agriculture systems that

are striving to be more sustainable. PIM refers to the participation of water

users at all phases of irrigation management, such as the planning, operation,

maintenance, monitoring, and evaluation of the system. The common

problems of irrigation, including inequitable water distribution, poor irrigation

system maintenance, inadequate water availability, and lack of incentives for

saving water, can be considered through a PIM approach. However,

employing PIM simply by decentralization and transfer of authority to local

water user organizations (WUOs) does not guarantee automatic success.

Institutional capacity building needs to be done step by step.

In Sri Lanka, reports have shown that out of 30 percent of increase in

the flow of water to the downstream, half of the Minipe scheme within the

first year of introducing a farmer’s organization (Uphoff, 1998). In Thailand,

in Norway scheme the farmer’s organization reportedly raised cropping

intensity from 50percent to 90 percent in two years. In Philippines, when a

participatory approach was taken to expand the Buhi-Lalo scheme, engineers

with farmers advised that concurrence would be rendered to the planned

length of field channel by 12 percent, thereby saving substantial costs. The

construction work by farmers was completed four months ahead of schedule

and the project engineer judged the quality of work as good.

In Malaysia, Muda Irrigation Scheme has lined tertiary channels

which have been constructed at government expenses to avoid field to field

irrigation and at the same time group farming has been encouraged and

37

farmers cooperatives have been formed to handle subsidized agricultural

inputs (Report of IIMI,1994).

Robert Chambers’ (1994) participatory action research (PAR) has

been parallel and overlapping with participatory research, and has had strong

associations with industry and agriculture (Whyte, 1991).Participatory Rural

Appraisal (PRA) describes a growing family of approaches and methods to

enable local people to share enhance and analyze their knowledge of life and

conditions, to plan and to act. PRA has sources in activist participatory

research, agro ecosystem analysis, applied anthropology, field research on

farming systems, and rapid rural appraisal (RRA). In RRA information is

more elicited and extracted by outsiders; in PRA it is more shared and owned

by local people. Participatory methods include mapping and modeling,

transect walks, matrix scoring, seasonal calendars, trend and change analysis,

well-being and wealth ranking and grouping, and analytical diagramming.

PRA applications include natural resources management, agriculture, poverty

and social programs, and health and food security. Dominant behavior by

outsiders may explain why it has taken until the 1990s for the analytical

capabilities of local people to be better recognized and for PRA to emerge,

grow and spread.

Ruth Meinzen-Dick (2002) identifies factors affecting organization

and collective action among water users in major canal irrigation systems in

India. Policies of devolving management of resources generally assume that

users will organize and take on the necessary management tasks. Water users’

organizations increase the likelihood of collective maintenance work by

farmers, but do not affect the likelihood of collective representation, or

lobbying activities, which seem to happen more spontaneously. The

devolution of responsibility and control over natural resources from

government agencies to user groups has become a widespread policy trend

38

that cuts across countries and natural resource sectors, encompassing water

(especially irrigation), forests, rangelands, fisheries and wildlife. One such

programs go by a range of names (e.g., Community-based Natural Resource

Management, co management, or management transfer), and range from those

that simply try to increase users’ involvement in management as a supplement

to state management (participatory management or co management), to those

that transfer full responsibility and control over resources to organized users.

A common feature, however, is the emphasis on increasing the participation

of resource users in the management of the resources.

Iskandar Abdullaev (2009) reports that the formation of the UWU has

improved the transparency of water management, helped to improve

responsiveness of water managers to the water users’ complaints, generated

support on canal de-silting, helped to reduce illegal water withdrawals from

the canal and WUAs have seen UWU as their advocate organization.

Establishment of UWUs provided a higher platform for the representation of

water users than common WUAs at the on-farm, secondary canal level. The

results of the water users’ surveys before and after UWU has been formed

have not shown a considerable improvement on water distribution. This will

bring long expected sustainability to irrigation water management. The

inclusion of water users will also engender more transparent practices and as a

result reduce the transaction costs of water management. The implementation

of the above approach on a basin scale will require a huge effort to mobilize

water users and re-organize the irrigation water management structure. Water

allocation approaches should also be revised with more inclusion of water

users’ voice in the process. This requires goodwill from state agencies, which

has to be emphasized and managed as a key element in the process.

United Nations Development Programme Report (Report of UN,

2005) captures the global water crisis in the following way: Unlike wars and

39

natural disasters, the global crisis in water does not make media headlines.

Nor does it galvanize concerted international action. Like hunger, deprivation

in access to water is a silent crisis experienced by the poor and tolerated by

those with the resources, the technology and the political power to end it. Yet

this is a crisis that is holding back human progress, consigning large segments

of humanity to lives of poverty, vulnerability and insecurity.

Accounting for 60% of the world‘s population, Asia currently

experiences the acute pressure of inadequate regional water resources supplies

because it only possesses 36% of global water resources. By 2025, nearly two

billion people will be living in countries or regions with absolute water

scarcity, and two-thirds of the world population could be under what the UN

terms stress conditions. Coming to terms with this water crisis will be one

of the greatest two challenges faced by every nation on the earth during early

21st century (Report of UN, 2005).

2.6 DROUGHT MONITORING AND VULNERABILITY

ASSESSMENT

Droughts are periods of time when natural or managed water

systems do not provide enough water to meet established human and

environmental uses because of natural shortfalls in precipitation or stream

flow. Drought management is a subset of water supply planning. The

distinction between a “drought” problem and a “water supply” problem is

essentially defined by the nature. Attempts to understand and address the

failings of water management during drought would be unsuccessful unless

shortcomings in the larger context of water management are also understood

and addressed. This was also one of the conclusions drawn by the Corps of

Engineers in the first year of the National Drought Study (William, 1994).

40

The purpose of assessing vulnerability is to identify appropriate

actions that can be taken to reduce vulnerability before the potential for

damage is realized. The need for vulnerability assessment is noted in the

scientific literature (Anderson, 1994; Hewitt, 1997; Keenan and Krannich,

1997; Downing and Bakker, 2000). However, because of the complexity of

the issue of vulnerability, assessments are commonly subjective and vary

between regions and hazards. Mapping vulnerability to drought is a

challenging task, because drought is also a very complex and the least

understood phenomenon, which lacks universal definition and onset criteria.

Wilhelmi and Wilhite (2002) presented a method spatial,

Geographic Information Systems-based assessment of agricultural drought

vulnerability in Nebraska. It was hypothesized that the key biophysical and

social factors that define agricultural drought vulnerability were climate, soils,

land use, and access to irrigation. The framework for derivation of an

agricultural drought vulnerability map was created through development of a

numerical weighting scheme to evaluate the drought potential of the classes

within each factor. The results indicate that the most vulnerable areas to

agricultural drought were non-irrigated cropland and rangeland on sandy

soils, located in areas with a very high probability of seasonal crop moisture

deficiency.

The spatial characteristics of agricultural drought vulnerability in

China were investigated using a GIS-based agricultural drought vulnerability

assessment model, which was constructed by selecting three agricultural

drought vulnerability factors,( Wu et al, 2002). Seasonal crop water

deficiency, available soil water-holding capacity and irrigation were identified

as the main indicators of agricultural drought vulnerability in China. The

study showed that the distribution of seasonal crop moisture deficiency

showed significant differentiation in both north–south and east–west

41

directions, and the agricultural drought vulnerability presented a similar trend.

At a regional scale, southern and eastern China typically has a low- and

moderate-vulnerability to drought, while high and very high vulnerability to

agricultural drought is observed in northern and western China.

Kiumars et al (2012) assessed drought vulnerability across three

drought intensities (very high, extremely high, and critical) areas in Western

Iran for the case of wheat farmers in Western Iran. A survey study was

applied and 370 wheat farmers who all experienced drought during 2007–

2009 were selected through a multi-stage stratified random sampling method.

Face to face interviews were used to collect data on vulnerability indices from

the farmers. Me-Bar and Valdez's vulnerability formula was applied to assess

the vulnerability of wheat farmers during drought. Results revealed that the

farmers' vulnerability is influenced mainly by economic, socio-cultural,

psychological, technical, and infrastructural factors. The results also indicated

that the farmers in Sarpole-Zahab township were most vulnerable compared

to those in the Kermanshah township as the least vulnerable.

IMD’s long-range forecasts should be available on a smaller spatial

and temporal scale, which will be helpful for sustainable agriculture. Agromet

parameters estimated from remote sensing data need to be validated with

ground based observation and turned into a usable product. Agrometeorology

of ICAR and IMD should have a linkage with the NADAMS project of the

Department of Space to provide periodic crop/pest/disease information at

subdistrict to national levels. The Agromet advisory service issued from

NCMRWF and AGRIMET of IMD should coordinate the space-based

program on NADAMS and use the spatial maps for strengthening the present

advisory services on crop pest/disease monitoring. The Drought Prone Area

Programme (DPAP) and the Desert Development Programme (DDP) require

improved management of land and water resources to avoid land degradation

42

like salinity, alkalinity, and water logging. Each state should be equipped with

a drought management system, linking district administration with state and

national departments that provide services. Agromet information for farmers’

advisory services should be made more user-oriented, and frequent feedback

may be obtained from farmers for further improvement. Use of the Internet

may be exploited for more efficient feedback (Sinha Ray, 2000).

Sivakumar et al (2011) calls for pro-active future actions to cope

with droughts. National governments must adopt policies that engender

cooperation and coordination at all levels of governments in order to increase

their capacity to cope with extended periods of water shortages due to

drought. Despite the repeated occurrences of droughts throughout human

history and the large impacts on different socio-economic sectors, no

concerted efforts have ever been made to initiate a dialogue on the

formulation and adoption of national drought policies. The time is ripe for

nations to move forward with the development of a pro-active, risk-based

national drought policy. Without a coordinated, national drought policy that

includes effective monitoring and early warning systems to deliver timely

information to decision makers, effective impact assessment procedures, pro-

active risk management measures, preparedness plans aimed at increasing the

coping capacity, and effective emergency response programs directed at

reducing the impacts of drought, nations will continue to respond to drought

in a reactive, crisis management mode.

According to Bryant (1991), drought ranks first among all natural

hazards who ranked natural hazard events based on various characteristics,

such as severity, duration, spatial extent, loss of life, economic loss, social

effect, and long-term impact. Drought produces a large number of socio-

economic impacts as water is integral to produce goods and provide certain

services. The socio-economic impacts of droughts may arise from the

43

interaction between natural conditions and human factors, such as changes in

land use and land cover, water demand and use. Excessive water withdrawals

can exacerbate the impact of drought. Some direct impacts of drought are

reduced crop, rangeland, and forest productivity; reduced water levels;

increased fire hazard; increased livestock and wildlife death rates; and

damage to wildlife and fish habitat. A reduction in crop productivity usually

results in less income for farmers, increased prices for food, unemployment,

and migration. There is growing evidence that the frequency and extent of

drought has increased as a result of global warming.

The fraction of land surface area experiencing drought conditions

has risen from 10-15 percent in the early 1970s to more than 30 percent by

early 2000 (Dai et al 2004). A global analysis has shown that abrupt changes

in rainfall are more likely to occur in the arid and semi-arid regions, and that

this susceptibility is possibly linked to strong positive feedbacks between

vegetation and climate interactions (Narisma et al 2007).

Ray Motha (2000) depicts the key elements of a drought plan, which

include 1) Monitoring, Assessment and Prediction, 2) Preparedness and

Mitigation, 3) Response and 4) Communications. From the public hearings,

more than one hundred people testified on behalf of urban and rural water

associations, tribes, federal agencies, state and county governments,

municipalities, livestock producers and farmer associations, and conservation

groups. A clear assessment of the findings became very conclusive from all

sectors of society affected by drought. Preparedness, including drought

planning, plan implementation, proactive mitigation, risk management,

resource stewardship, consideration of environmental concerns, and public

education must become the cornerstone of a national drought policy. To

ensure preparedness, there must be fundamental principles of a national

drought policy. There must be an adequate national observation network to

44

provide the basis for an effective drought monitoring program. A national

drought information “gateway” needs to be accessible to the entire user

community. The benefits of high quality research must be focused on

information and technology that are fundamental to drought preparedness,

with research results as well as the transfer of technology more effectively

implemented in drought programs.

Zuqiang Zhang (2011) says that effective and efficient drought risk

management is difficult to accomplish without the comprehensive

involvement of stakeholders and the public. Non-governmental organization

and volunteers are encouraged to join the efforts of drought management. The

agriculture insurance services have been proved to be a useful approach of

risk transfer for drought relief and recovery. Charities also play an active role

in drought relief, and the government has adopted measures, in terms of the

preferential taxation system, to encourage public donations. Capacity building

in self-reliance of the public from the drought impact has recently received

more attentions from the government. Relevant training opportunities and

financial assistances are offered to the public to enhance their self-reliant

capability in alleviating the impact of drought. The agricultural sector will

evaluate the possible impact of drought on the crop growth and production

and then prepare some tailored measures for the drought risk management.

Philippe Roudier and Gil Mahe (2010) conducted Study on Bani

River (Niger basin, Mali) about water stress and droughts with indicators

using daily data water deficit (drought) was logically addressed using the

Standardized Precipitation Index at a 10 days time step. The inadequacies in

the Standardized Precipitation Index while estimating water deficit within the

basin based on technical issues result in the usage of the Effective Drought

Index (EDI). Vulnerability is a very wide concept, with several definitions

(Füssel and Klein, 2006), that demand several dataset, if satisfactory

45

assessment of a region vulnerability to climate change is to be attained. This

is evident in Water Poverty Index computation (and its evolution: Climate

Vulnerability Index) by Sullivan and Meigh (2005). Precipitation threshold

parameter is highly useful due to its practical application while studying

drought event and while addressing issues relating to irrigation water

management. The structure of the precipitation threshold map is similar to

annual isohyets, especially for the extreme drought values.

Todisco et al (2009), allows a new classification of the drought

phenomenon on the seasonal time scale a distinction is made between

potential and actual agricultural drought on the inter-seasonal time scale a

distinction is made between agricultural drought and agricultural aridity.

Janki Jiwan (2012) reports that Sustainable Drought Management

implies reconciliation of short term and long term strategies. Long term

strategy entails drought preparedness, prevention and management of natural

resources in watershed framework with active participation of the people.

Short term strategy is contingent upon timely government initiatives in the

form of relief measures in drought affected areas Monitoring and declaration

are the primary tasks to agricultural drought management. Central and State

Weather-Crops Watch Group (CWCWG and SWCWG) keeps vigil on

drought like condition across the country based on data supplied by

specialized agencies like India Meteorological Department (IMD), National

Agricultural Drought Assessment and Monitoring System (NADAMS) and

National Centre For Medium Range Weather Forecasting (NCFMRF)

(National Disaster Management Authority, NDMA 2010).

Traditionally, response to drought throughout the world has been

through a reactive, crisis management approach. This approach to drought

management responds to the impacts of drought once they occur in an attempt

to speed the recovery process. This crisis management approach has been

46

noted to be costly, largely untimely, poorly coordinated, and often results in

resources or assistance being misdirected. Drought impacts illustrate the

vulnerability of societies to drought and programs that provide assistance to

those affected by drought are essentially treating the symptoms of

vulnerability rather than the causes. Many assistance programs, in fact, result

in increased vulnerability to future drought events by making individuals and

societies more reliant on government programs or assistance from donor

organizations. As a consequence of an increased frequency of drought and

societal vulnerability to extended period of water shortages, the economic,

social and environmental impacts of droughts have increased significantly

worldwide. Because of their long-term socio-economic and environmental

impacts, droughts are by far the most damaging of all natural disasters.

The Intergovernmental Panel on Climate Change Fourth

Assessment Report (Concept Note, 2011) states that the world indeed has

become more drought-prone during the past 25 years, and that climate

projections for the 21st century indicate increased frequency of severe

droughts in many parts of the world. Whether due to natural climate

variability or climate change, there is an urgent need to improve drought

management strategies that will lead to improved coping capacity. These

strategies must be science based and directed at managing the risks and

mitigate the effects of drought.

Drought Management Centre for Southeastern Europe (Report of

DMCSEE, 2006) lists out some its objectives for effective drought

management as (i) to assess the data available for effective drought

monitoring and early warning system; (ii) to evaluate and select the most

effective and reliable indices and indicators for drought assessment; (iii) to

conduct a drought risk assessment; (iv) to identify the specific training needs;

(v) to develop and implement a data and information delivery system on

47

drought management; (vi) to develop a comprehensive network of experts and

institutions to assist the Drought Management Centre; (vii) to ensure

communication and user feedback and (viii) to establish the permanent

drought management centre and ensure its sustainable functioning and

operations.

2.7 SUMMARY

The different classifications, definitions and the various

methodologies for meteorological, hydrological, agricultural drought

assessments and forecasting were reviewed. The above review has given a

much greater understanding of the drought and its characteristics. It also

helped to have information and to perceive importance of the present scenario

of the drought problem to be analysed in detail. Existing methods of drought

analysis either have qualitative assessments or use only a few drought causing

parameters and data intensive.

From literature review, it is understood that the use of GIS

technique might enhance the spatial analysis of drought distribution across the

study area. Understanding the drought occurrences in various parts of the

study area, it is proposed to analyse the vulnerability of different areas for

agricultural drought in an irrigated area.