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National Agricultural Drought Assessment and Monitoring System (NADAMS)
Drought differs from other natural hazards in many respects - most complex and least understood of all disasters. While it is difficult to demarcate the onset and end of drought but the effects of drought accumulate for a considerable period of time. Agricultural drought is a situation when rainfall and soil moisture are inadequate during the crop growing season to support healthy crop growth to maturity, causing crop stress and wilting. Monitoring and assessment of drought conditions at different scales and timely dissemination of information constitute the most vital part of drought management system. Therefore, a sound, operationally feasible, objective and economically viable system for drought monitoring and decision support would enable efficient management of this hydro-meteorological disaster. Along with a robust monitoring system, a mechanism for rainfall prediction and drought early warning brings out total solutions for drought management. In India, National Agricultural Drought Assessment and Monitoring System (NADAMS) was initiated towards the end of 1986, with the participation of National Remote Sensing Agency, Dept. of Space, Government of India, as nodal agency for execution, with the support of India Meteorological Department (IMD) and various state departments of agriculture. NADAMS was made operational in 1990 and has been providing agricultural drought information in terms of prevalence, severity and persistence at state, district and sub-district level. In the early years of the project, drought assessment was largely dependent on only one satellite derived index i.e., NDVI and IMD rainfall data at district and sub-division (Thiruvangadachari, 1990 and Jhonson et al. 1993). The satellite data adopted was also coarse in resolution i.e, 1 km.
The drought assessment was restricted to aggregated level i.e., district or regional. Biweekly drought bulletins were issued from June to October every year. Over a period of time, NADAMS project has undergone many methodological improvements such as use of moderate spatial resolution data for disaggregated level assessment, use of multiple indices for drought assessment, augmentation of ground data bases, achieving synergy between ground observations and satellite based interpretation, providing user friendly information, enhanced frequency of information etc. The developments in the projects in terms of satellite data employed and derived indices are indicated in Table . NADAMS now covers 13 agriculturally important and drought vulnerable states of the country and provides information on prevalence, spatial extent and intensity of agricultural drought at state, district and sub-district level. The project Monitoring of agricultural drought is carried out for the kharif season (June-Oct/November) as this season is agriculturally more important and rainfall dependent. Drought assessment is carried out on fortnightly basis and reporting of information to the User departments is done on monthly basis. Resourcesat 1/ Resourcesat 2 AWiFS based sub-district level agricultural drought assessment is carried-out in 4 states namely Andhra Pradesh, Karnataka, Maharashtra and Haryana. AVHRR/MODIS based district level assessment is carried out in 9 states namely Bihar, Chhattisgarh, Gujarat, Madhya Pradesh, Orissa, Rajasthan, Uttar Pradesh, Jharkhand and Tamil Nadu. From the year 2012, the NADAMS project is being carried out at Mahalanobis National Crop Forecast Centre (MNCFC), Ministry of Agriculture (GOI), with the technical support of NRSC. The detailed methodology, execution plans and databases of NADAMS project have been transferred to MNCFC by NRSC in 2012. Approach: The methodology of NADAMS project essentially reflects the integration of satellite derived crop condition / surface wetness indices and their anomalies with ground collected rainfall and crop area progression to evolve decision rules on the prevalence, intensity and persistence of agricultural drought situation. Agricultural drought assessment with multiple indices as indicated below; Shortwave Angle Slope Index (SASI) Normalized Difference Wetness Index Normalized Difference Vegetation Index Soil Moisture Index (derived from soil water balance approach) IMD Rainfall data – rainfall deviation, number of dry weeks Resourcesat AWiFS data is being used for sub-district level assessment in four states. The coarse resolution NDVI from Oceansat 2 OCM, NOAA AVHRR and Terra MODIS are being used to detect crop condition and wetness anomalies respectively for detecting drought intensity at district / state level.
The AMSR-E soil moisture resampled to 25 km resolution is useful to corroborate the NDVI / NDWI based interpretation. CPC rainfall forecasts are useful to foresee the rainfall events in immediate future and interpret the expected change in the agricultural situation. SASI variations in the season which represent dynamics of surface moisture were used for assessing the Area Favourable for Crop Sowing (AFCS) from time to time. General threshold values of SASI specific to soil texture, that indicate favourable situation for crop sowings were identified. Based on SASI thresholds, discrimination of the Area Favourable Crop Sowing (AFCS) was done on weekly basis for each state. The AFCS weekly values are useful to assess the intensity of early season/sowing period agricultural drought intensity in terms of timeliness in the commencement of sowings, extent of delay or reduction in crop sowings. The Area Favourable for Crop Sowing (AFCS), was found to be 87 M ha out of 108 M ha of potential kharif area of the nation. District-wise analysis in 13 states by the end of July indicated “Normal” agricultural situation in 132 districts. The agricultural situation is categorized as “Watch” in 148 districts and as “Alert” in 119 districts. “Alert” category districts are characterised by either delayed sowing time or reduced crop sown area or poor greenness of agricultural vegetation or lack of adequate irrigation infra-structure or all of them. There may not be improvement to the extent of normal agricultural situation in these districts.“Watch” category districts are characterised by slightly reduced crop sown area or slightly reduced greenness of crops, with scope for significant improvement in subsequent fortnights. The number of districts under “Alert” class has increased to 119 in July from 94 in June, thereby indicating continued intense agricultural drought conditions in Rajasthan, Bihar, Uttar Pradesh and Gujarat, Haryana, Maharashtra, Karnataka, Andhra Pradesh and Tamil Nadu states. Drought Reports Monthly drought reports of NADAMS project are disseminated to the Ministry of Agriculture, Government of India, and respective state departments of Agriculture and Relief. The reports are also being sent to IMD, Central Water Commission and other scientific organizations. Utilization The feedback on drought reports, from Ministry of Agriculture, Govt. of India and departments of Agriculture/Relief of various states from time to time is encouraging and indicates the effective end use of information. The drought information is used in the crop review meetings and contingency planning during the season.
At the end of the season, the drought information is used as input in the drought declaration process. NRSC team makes special presentation to the MoA and to the States upon their intent. Way forward: Research activities related to improvement of agricultural drought assessment are carried out at NRSC from time to time. In addition to new operational products in the project, a number of research publications have resulted from these activities. With the operational component of NADAMS project is being carried out at “ Mahalanobis National Crop Forecast Centre (MNCCF)” from kharif 2012, NRSC team now enhanced the time spent on Research activities for enhanced products. These activities include development of an integrated approach using multiple parameters, development of methodology for crop sown area estimation, agricultural drought vulnerability assessment, soil water balance analysis, use of Standardized Precipitation Index (SPI), use of SWIR based indices for crop stress detection, drought impact assessment, drought early warning etc.