Kaveri River - drainage areas in Karnataka and Tamil Nadu

This video shows how I computed sub-basin areas for the Kaveri river in the Indian states of Karnataka (KA) and Tamil Nadu (TN). Data for drainage areas came from AQUASTAT and was processed in QGIS open source software. I then created this video using Flashback Express 5 screen recording software.



Process:

• Intersect layers for administrative boundaries and sub-basin areas to obtain sub-basin areas by state
• Extract sub-basin areas by state layers into two separate layers (KA and TN) 
• Dissolve the two layers to get total area by state

The values I computed for drainage areas: 35462 sq km (KA) and 44422 sq km (TN) India Water Resource Information System (India-WRIS) provides these values for drainage areas: 36240 sq km (KA) and 48730 km2 (TN)

#India: areas under irrigation map

After being unhappy with the maps in Brahma Chellaney’s book Water: Asia's New Battleground, I decided to create my own map of areas under irrigation in India.

For this map, I used irrigation data from the global map of irrigation areas from AQUASTAT, the FAO's global information system on water and agriculture.  Data shows the percentage of irrigated land per 5 arcmin cell, which is approximately 8547 hectares: someone check my calculations!

Source: Stefan Siebert, Petra Döll, Sebastian Feick, Jippe Hoogeveen and Karen Frenken (2007) Global Map of Irrigation Areas version 4.0.1. Johann Wolfgang Goethe University, Frankfurt am Main, Germany / Food and Agriculture Organization of the United Nations, Rome, Italy

The number of cells in the AQUASTAT data set is huge: 4320 columns x 1260 rows = 5,443,200 cells.  To bring this down to size, I clipped the map to the area of India.  Even so, I had more data than ArcMap could handle (max: 10,000 items) in computing equal percentage intervals (see the map legend).  Nonetheless, the resulting map corresponded well to the Global Map of Irrigated Ares.  The Ganges River basin is the most irrigated area in the world.

You may download the map of irrigated areas in India in JPEG format or the map of irrigated areas of India in PDF format. Alternatively, if you would like to muck around with the map itself, download the ArcMap document showing irrigated areas of India.