Monsoons and groundwater irrigation are the primary sources of water for the rice, millets and pulses crops for the state of Tamil Nadu in southern India. Identification of water-stressed areas where there is below average rainfall is one of the first steps toward minimizing harm for the region’s crop production. In Gumma et al, 2015, the study is performed at the river basin level, as it is impacted by rainfall throughout the study area. During the time periods of the study, 2000 to 2001 and 2010 to 2011, three different major land use changes occurred, resulting in a decrease of 30 to 40 percent of irrigated land. The consequence of decreased irrigated land was vegetation loss and decreased crop output.
Remote sensing products and analysis techniques are used in this study to determine areas that are susceptible to water-stress. The authors calculated Normalized Difference Vegetation Index (NDVI) values from the red and near-infrared bands of the 8-day Moderate Resolution Imaging Spectroradiometer (MODIS) surface reflectance (MOD09A1) product. This 500-meter resolution product is comprised of the best possible pixel observation over an 8-day period. NDVI shows the relative health of the vegetation to a specified area. The images below are a true-color composite showing a portion of the study area that highlights water-stressed land compared to the same area with healthy vegetation.
Land surface elevation data from the Shuttle Radar Topography Mission (SRTM) are used in the study as a secondary dataset to provide surface slope, catchment boundaries and stream network identification for the study area. Ground survey data is used to confirm the accuracy of the study’s datasets.
The authors found that alternative cropping patterns, water management practices and encouraging varieties of drought-tolerant crops can help promote better food security and sustain livelihoods.
Gumma, M.K., Kajisa, K., Mohammed, I.A., Whitbread, A.M., Nelson, A., Rala, A., and Palanisami, K., 2015, Temporal change in land use by irrigation source in Tamil Nadu and management implications: Environmental Monitoring and Assessment, v.187, n. 187, at http://dx.doi.org/10.1007/s10661-014-4155-1
Material written by: Jonathan Walkes1, Lindsey Harriman1, and Danielle Golon2
1 Stinger Ghaffarian Technologies, contractor to the U.S. Geological Survey, Earth Resources Observation and Science (EROS) Center, Sioux Falls, South Dakota, USA. Work performed under USGS contract G10PC00044 for LP DAAC3.
2 Innovate!, Inc., contractor to the U.S. Geological Survey, Earth Resources Observation and Science (EROS) Center, Sioux Falls, South Dakota, USA. Work performed under USGS contract G10PC00044 for LP DAAC3.
3 LP DAAC Work performed under NASA contract NNG14HH33I.