Crop-specific seasonal estimates of irrigation-water demand in South Asia
Date
2016-05
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Publisher
Copernicus Publications on behalf of the European Geosciences Union
Abstract
Especially in the Himalayan headwaters of the main rivers in South Asia, shifts in runoff are expected as a result of a rapidly changing climate. In recent years, our insight into these shifts and their impact on water availability has increased. However, a similar detailed understanding of the seasonal pattern in water demand is surprisingly absent.This hampers a proper assessment of water stress and ways to cope and adapt. In this study, the seasonal pattern of irrigation-water demand resulting from the typical practice of multiple cropping in South Asia was accounted for by introducing double cropping with monsoon-dependent planting dates in a hydrology and vegetation model. Crop yields were calibrated to the latest state-level statistics of India, Pakistan, Bangladesh and Nepal. The improvements in seasonal land use and cropping periods lead to lower estimates of irrigation-water demand compared to previous model-based studies, despite the net irrigated area being higher. Crop irrigation-water demand differs sharply between seasons and regions; in Pakistan, winter (rabi) and monsoon summer (kharif) irrigation demands are almost equal, whereas in Bangladesh the rabi demand is 100 times higher. Moreover, the relative importance of irrigation supply versus rain
decreases sharply from west to east. Given the size and importance of South Asia improved regional estimates of food production and its irrigation-water demand will also affect global estimates. In models used for global water resources and food-security assessments, processes like multiple cropping and monsoon-dependent planting dates should not be ignored.
Description
This work was carried out by the Himalayan Adaptation, Water and Resilience (HI-AWARE) consortium under the Collaborative Adaptation Research Initiative in Africa and Asia (CARIAA), with financial support from the UK Government’s Department for International Development and the International Development Research Centre, Ottawa, Canada. We acknowledge the Potsdam Institute for Climate Impact Research for their support in using the LPJmL model and computational facilities.
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Journal Article (peer-reviewed)
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Keywords
CROP SPECIFIC SEASONAL ESTIMATES OF WATER DEMAND, TWO MAIN SOUTH ASIAN CROPPING PERIODS, KHARIF AND RABI, ZONE-SPECIFIC, MONSOON-ONSET-DETERMINED PLANTING DATES, INDIA, PAKISTAN, NEPAL, BANGLADESH, LUND-POTSDAM-JENA MANAGED LAND (LPJmL) MODEL, IRRIGATION, AGRICULTURE, CLIMATE CHANGE, ADAPTATION, BASINS, SOUTH ASIA
Citation
Biemans, H. et al., Crop-specific seasonal estimates of irrigation-water demand in South Asia, Hydrology and Earth System Sciences, 20, 1971-1982, 2016. doi:10.5194/hess-20-1971-2016