The drying of the Deccan
This panel of 12 images shows the change that takes place in a region of the Deccan. Each image shows what is called a Normalised Difference Vegetation Index (NDVI) for the region. This is a rolling eight-day series computed daily using imagery from the Terra/MODIS system and viewed using the NASA Worldview website.
The colours (green and brown shades, whitish shades) show us the vegetation health with deep green being better than light green, dark brown being better than light brown. The index is also used to signal where areas are beginning to experience arid and water-scarce conditions.
The region is the west-central Deccan – the Karnataka Plateau – corresponds to the Vijayapur (Bijapur) district of north Karnataka with parts of Bagalkot district and is part of the central Indian semi-arid bioclimatic zone.
The pictures in the panel show the vegetation extent and health (NDVI) calculated on that day for an eight-day period. Each picture is a fortnight apart, and this series starts on 4 November 2016 (bottom right) and ends on 7 April 2017 (top left). The retreat of the green is seen clearly from one fortnight to the next.
Of interest in this region is the Almatti dam and reservoir, in the Krishna river basin, which is visible in the lower centre of each picture. On 13 April there was no water in Almatti, which has a full capacity of 3.105 billion cubic metres (bcm). For the week ending 30 March it had 0.015 bcm of water, the week ending 6 April 0.001 bcm.
For the week ending 3 November 2016, which is when the panel of pictures begins, Almatti had 2.588 bcm of water. The reservoir water runs a hydroelectric power plant, of 240 MW, and which needs flowing water to turn the turbines.
When the reservoir is full, the hydel plant produces about 175 million units of electricity. But on 13 March the Central Electricity Authority’s daily report showed that Almatti could produce only 3.02 million units. On 10 April, this had plunged to 0.04 million units, but the hydel plant had produced no power since 1 April.