Review of water, crop production and system modelling approaches for food security studies in the Eastern Gangetic Plains

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Kirby, Mac; Ahmad, Mobin ORCID ID icon; Poulton, Perry; Zhu, Zili; Lee, Geoffrey ORCID ID icon; Mainuddin, Mohammed ORCID ID icon



75 pp

Executive summary too long for this box... Our aim in this study is to describe the current state of water resources and cropping systems in the Eastern Gangetic Plains, the likely future challenges resulting from changes such as population increase and climate change, and to identify gaps in knowledge in the assessment. We approached the task partly by reviewing the literature and data, and partly by some preliminary modelling. The Eastern Gangetic Plains has a humid sub-tropical climate, with a distinct wet summer season and a cooler dry season. Rivers likewise have a distinct high flow period and frequent flooding in the wet season and lower flows in the dry season. The region is mostly underlain by a large aquifer system which receives considerable recharge from rain and the rivers during the wet season and contributes to dry season river flows. Groundwater is extensively used for irrigation, particularly in northwest Bangladesh where dry season irrigation using groundwater provides for the high yielding and highly productive dry season rice crop. In parts of northwest Bangladesh, groundwater use is probably unsustainable. Elsewhere, it appears that groundwater could be used more, and there are calls for greater use of groundwater to boost food production in West Bengal. However, there are few studies of how much groundwater can be sustainably used, in part because of a lack of models. Aside from issues of groundwater quantity, groundwater must be used with care because of natural contamination with arsenic and other water quality issues. The population of the region is likely to increase to one and a half times the present population by 2050, and food demand is likely to increase by between one and a half and two times. The increased demand for food will in turn lead to increased demand for water, to perhaps as much as twice the current demand by 2050. Satisfying this increased demand will be a challenge, and will likely involve more use of groundwater. Climate change is projected to lead to an increase in rainfall in the wet season and also an increase in extreme rainfall which, if realised, would lead to greater flooding. However, rainfall projections are uncertain and the impact on water resources, particularly on groundwater, is uncertain and the changes not necessarily large. Crop production in the Eastern Gangetic Plains is dominated by rice in the wet season; in the dry season wheat dominates in Bihar while rice dominates in West Bengal and northwest Bangladesh , the latter relying on extensive groundwater irrigation. In Bihar and West Bengal, increased crop production to meet the greater demand in the future may come from both increased use of irrigation and from improved varieties, management and other factors. In northwest Bangladesh, on the other hand, irrigation is already intensively used, and increased production will depend more on the technical factors of improved varieties, management and so on. Systems models are useful in understanding constraints and opportunities in crop production for food security. Furthermore, considerable understanding is derived from linking models from the plot or farm scale to the regional scale. At the farm scale we use the APSIM crop production modeling system. Remote sensing modeling provides assessments of the spatial variability of crop performance and water use. At the regional scale, we use a dynamic regional water balance. Assessments at these three scales together show how much yield may be improved (and how this varies through years of varying climate), where yield may be improved, and how this adds up to an increase in production at a regional scale given constraints on how much water may be sustainably used. The systems modelling approach applied to northwest Bangladesh shows that there is potential for improving yields and optimising water use through improved irrigation and fertiliser application, both in the curren



Agricultural Hydrology (Drainage, Flooding, Irrigation, Quality, etc.)

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Kirby, Mac; Ahmad, Mobin; Poulton, Perry; Zhu, Zili; Lee, Geoffrey; Mainuddin, Mohammed. Review of water, crop production and system modelling approaches for food security studies in the Eastern Gangetic Plains. Canberra: CSIRO; 2013. csiro:EP134291.

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