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Manipulation of Normalized Difference Vegetation Index (NDVI) for Delineating Drought Vulnerable Areas
The new scientific technologies of remote sensing, satellite imaging, geographical information systems (GIS) and geographical positioning system (GPS) can be put to effective use in forecasting and monitoring drought. GIS/SRS if incorporated in drought mitigation and research process exhibits two principal advantages. First, the technology allows long-term time-series studies and storage of the information, which may prove invaluable in future situations. Secondly, GIS/RS improves information accessibility. Remote sensing platforms can provide large amounts of data quickly and inexpensively, relative to other means of collection, and GIS can bring together vast amounts of information from a wide variety of sources and make the information quickly visible and applicable in emergency situations (Verstappeen, 1995).
Satellite data processed into Normalized Difference Vegetation Indices (NDVI) can be used to indicate deficiencies in rainfall and portray meteorological and/or agricultural drought patterns both timely and spatially, thus serving as an indicator of regional drought patterns. NDVI is a measure or estimate of the amount of radiation being absorbed by plants. The amount of radiation absorbed is directly related to evapotranspiration, since the plant must cool primarily by evaporating water. The evapotranspiration is constrained by the amount of water in the soil. And for relatively low rainfall amounts, the amount of water in the soil is constrained by rainfall. Hence NDVI correlates with rainfall (Rowland et al. 1996). Drought will continue to occur, but the application of NDVI as a tool for decision making will allow better integration and more timely planning of methods to promote food security. Drought in Balochistan in 1999 is said to be the worst drought in Pakistan’s history. For the development of the Action Plan for mitigation of drought and development of adaptation strategies systematic zoning of Balochistan province indicating the relative drought risk of various zones is required. This information will be helpful in selecting the interventions for the proposed Action plan and formulation of projects accordingly (Ahmad, 2000). The aim of present research work was to integrate Satellite Remote Sensing and Geographic Information System for delineating drought vulnerable areas and the objectives were:
2.1 Study Area The study area for the present research work was Sindh and major part of Balochistan province (Figure 2.1). Sindh province is located in south east part of Pakistan. It lies between 23º-40' and 28º-29' north latitudes and 66º-40' and 71º-05' east longitudes. It is bordered by the provinces of Balochistan on the west and north, Punjab on the north east, the Indian states of Rajastan and Gujrat on the east, and the Arabian Sea in the south. The total area of the province is 140914 square kilometers. Indus is the main and only river that flows in the province. The climate of Sindh is reminiscent of the Sahara type and of that prevailing in the tropical region of low and dry lowlands. The scanty rainfall, the province gets is often due to cyclonic storms, caused by eastern and western disturbances, particularly the former. The annual rainfall is about 200mm in the Lower Sindh and less than 100 in the Upper Sindh. The average annual rainfall is hardly 125mm. 
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