HR: 0800h
AN: H41D-0431    [Abstracts]
TI: Basin-scale Impact of Irrigation and Precipitation on Potential Evapotranspiration in the Krishna Basin, Southern India
AU: * Biggs, T W
EM: t.biggs@cgiar.org
AF: International Water Management Institute, ICRISAT/IWMI, Patancheru, AP 502-324 India
AU: Scott, C
EM: c.scott@cgiar.org
AF: International Water Management Institute, ICRISAT/IWMI, Patancheru, AP 502-324 India
AU: Turral, H
EM: h.turral@cgiar.org
AF: International Water Management Institute, ICRISAT/IWMI, Patancheru, AP 502-324 India
AB: Irrigation has expanded over the past century in large basins of southern India, resulting in poorly understood changes in basin-scale water balance and hydroclimate. Here we document an inverse relationship between potential evapotranspiration (Ep) and both precipitation and irrigation development in the Krishna River Basin, India (258,912 km2). Irrigated agriculture in the basin expanded to 44,000 km2 by 2002, and from 1950 to 2000 annual basin runoff decreased by 36 km3. During the monsoon (June to October), precipitation explains most of the inter-annual variability in temperature, relative humidity and Ep. Anthropogenic effects are most prominent in the post-monsoon (December - April), when temperatures decrease, relative humidity increases, and Ep decreases by 0.2-0.7 mm/day in areas with the most intensive irrigation development. By contrast, parts of the basin with little or no irrigation development show higher temperatures and an increase in Ep of 0.2-0.8 mm/day. Higher water availability and higher actual evapotranspiration result in a net decrease of potential ET during strong monsoons, and as basins develop irrigation.
DE: 1803 Anthropogenic effects (4802, 4902)
DE: 1818 Evapotranspiration
DE: 1834 Human impacts
DE: 1843 Land/atmosphere interactions (1218, 1631, 3322)
SC: Hydrology [H]
MN: Fall Meeting 2005