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The Upper Bhima River Basin is facing both episodic and chronic water shortages due to intensive irrigation development. The main objective of this study was to characterize the hydrologic processes of the Upper Bhima River Basin and assess crop water productivity using the distributed hydrologic model, SWAT. Rainfall within the basin varies from 450 to 5000 mm in a period of 3-4 months. The basin has an average rainfall of 711 mm (32 400 Mm 3 (million cubic metres)) in a normal year, of which 12.8% (4150 Mm ) ruissellent, et le reste (63%) est prélevé pour l'évapotranspiration. La productivité de l'eau agricole dans le bassin pour la canne à sucre, le sorgho et le mil ont été estimés à 2.90, 0.51 et 0.30 kg m¯3, ce qui est significativement plus faible que le potentiel maximal habituellement rencontré dans le monde. Il y a donc des marges de progrès qu'il convient d'explorer. Différents scénarios impliquant différents itinéraires techniques ont été testés dans le but d'accroître la valeur économique de la productivité de l'eau dans le système d'irrigation d'Ujjani. L'analyse suggère que la maximisation de la superficie grâce à la fourniture d'irrigation d'appoint pour les zones pluviales, ainsi que le recours à des pratiques agricoles de gestion plus économes en eau, peuvent offrir des possibilités pour améliorer la productivité de l'eau.

[1] Changes in both land cover and the atmosphere have impacted the heat fluxes of south Asia in ways that may have altered the timing and magnitude of the monsoon. Century-long budgets of water and energy in the Krishna Basin (258,948 km 2 ) in southern India demonstrate that irrigation impacted the sensible heat flux of the land surface (H) as much as or more than did the atmospheric brown cloud (ABC) over 1960-2005. Annual discharge of the Krishna River fell from 226 mm during pre-irrigation land cover to 64 mm by 1990-2005, when 14-20% of the basin area was irrigated. Over the same period, annual evaporation increased by 166 ± 32 mm (+28%) causing H to decrease by 12.7 ± 2 W m À2 (À18%) compared to a decrease of 11.2 ± 1.8 W m À2 caused by the atmospheric brown cloud (ABC). The rate of change in H during irrigation expansion ; this decrease was more than offset by irrigation, resulting in a net increase in the latent heat flux of 12.9 W m À2 . The maximum surface air temperature (Tmax) either decreased or remained the same in areas experiencing irrigation expansion but increased in a majority of unirrigated areas during the post-monsoon season. The results provide observational evidence that irrigation changed both the basin-scale sensible heat flux and surface air temperatures.Citation: Biggs, T. W., C. A. Scott, A. Gaur, J.-P. Venot, T. Chase, and E. Lee (2008), Impacts of irrigation and anthropogenic aerosols on the water balance, heat fluxes, and surface temperature in a river basin, Water Resour. Res.,

In many river basins, upstream development and interannual variations in rainfall can cause both episodic and chronic shortages in water supplies downstream. Continued rapid development of surface and groundwater throughout the Krishna Basin in southern India resulted in historically low inflows to the main canals of the Nagarjuna Sagar irrigation project ͑8,955 km 2 ͒ during a recent drought ͑2002-2004͒. This paper presents an integrated approach to assess how cropping patterns and the spatial equity of canal flow changed with water supply shocks in the left canal command area ͑3,592 km 2 ͒ of Nagarjuna Sagar. We combined 3 years ͑2000-2003͒ of canal release data with census statistics and high temporal resolution ͑8-10 days͒ moderate resolution imaging spectrometer ͑MODIS͒ 500-m resolution satellite imagery. The impact of water scarcity on land use pattern, delineated by MODIS images with moderate spatial resolution, was comparable with the census statistics, while the MODIS data also identified areas with changes and delays in the rice crop area, which is critical in assessing the impact of canal operations. A 60% reduction in water availability during the drought resulted in 40% land being fallowed in the left-bank canal command area. The results suggest that head reach areas receiving high supply rates during a normal year experienced the highest risks of fluctuations in water supply and cropped area during a water short year compared to downstream areas, which had chronically low water supply, and better adaptive responses by farmers. Contrary to expectations, the spatial distribution of canal flows among the three major zones of the command area was more equitable during low-flow years due to decreased flow at the head reach of the canal and relatively smaller decreases in tail-end areas. The findings suggested that equitable allocations could be achieved by improving the water distribution efficiency of the canal network during normal years and by crop diversification and introduction of alternative water sources during water shortage years. The study identified areas susceptible to decreases in water supplies by using modern techniques, which can help in decision-making processes for equitable water allocation and distribution and in developing strategies to mitigate the effects of water supply shocks on cropping patterns and rural livelihoods.