Current water supplies are not enough to support increased food production for a larger future population, according to new research conducted in collaboration with IIASA by Wageningen UR researcher Hester Biemans, who defends her PhD thesis on 5 October.
Global agricultural production will have to more than double in this century in order to meet growing food demand of a larger population. That means that croplands will have to expand, and farmers will need even more water to irrigate the new fields, and that future crop production will be even more reliant on irrigation. In her PhD thesis, Biemans investigated whether enough water resources are available to sustain a higher agricultural production and which regions are expected to face the largest scarcity. Biemans also looked at potential solutions to the problem.
As a first step, the researchers investigated which water sources are available for irrigated agriculture. But tracking down water is no simple task – water moves around the earth and atmosphere in a complicated cycle involving weather, climate, plants and trees, animals, and people. To pull in the many processes related to water Biemans used a global hydrology and crop model, in order to understand the complex interplay between climate change, land use change, population growth and economic development that are all influencing water availability and demand.
The thesis, which has already been published in part in several journal articles, therefore provides a broad assessment of the effects of future socio-economic changes and climate change on future water supply for agriculture.
Biemans found that almost a fifth of total irrigation water worldwide is currently supplied directly from reservoirs. Therefore reservoirs play a very important role in global food production. However, the study showed that with current reservoir capacity and inefficient irrigation in large parts of the world, not enough water can be supplied to sustain an increased food production. Worldwide, irrigated food production could be reduced as much as 20% because of water limitations. In some basins of Southern Africa and South Asia, irrigated crop production could be reduced by as much as 50%. Meanwhile, the effects of climate change are likely to have large effects on water supply and demand at the local level.
This means that either much more land is needed to achieve the production needed, or that water use efficiency and water storage will need to increase. In another study, Biemans looked at potential solutions to the water shortage. Focusing on 5 rivers in Asia, she showed that adaptation measures like improving irrigation efficiency and increasing reservoir size could help make up the shortfall. However, the study also showed that the best solution may be different in each basin, emphasizing the need for more detailed analysis.
Biemans will present her research at Wageningen University on Friday, 5 October. On the same day, IIASA Director and CEO Pavel Kabat will speak at a seminar on water and food production, along with researchers Dieter Gerten of the Potsdam Institute for Climate Change, Arjen Hoekstra of the University of Twente, and Charles Vörösmarty of the City University of New York.
Biemans, H., L. Speelman, F. Ludwig, E. Moors, A.J. Wiltshire, P. Kumar, D. Gerten, P. Kabat (in revision). Climate change impacts on water availability in five South Asian river basins and potential of adaptation options – a modelling study. Science of the Total Environment
Biemans, H., I. Haddeland, P. Kabat, F. Ludwig, R. W. A. Hutjes, J. Heinke, W. von Bloh, and D. Gerten (2011), Impact of reservoirs on river discharge and irrigation water supply during the 20th century, Water Resour. Res., 47, W03509, doi:10.1029/2009WR008929
Gerten, D., J. Heinke, H. Hoff, H. Biemans, M. Fader, K. Waha (2011). Global water availability and requirements for future food production. Journal of Hydrometeorology.
Biemans, H., R.W.A. Hutjes, P. Kabat, B. Strengers, D. Gerten, S. Rost (2009). Impacts of precipitation uncertainty on discharge calculations for main river basins. Journal of Hydrometeorology.