Water requirement (CLIM 033) - Assessment published Sep 2008

Key policy question: ..

Meteorological water balance in selected parts of Europe 1975-2007

Note: Surplus means positive values of meteorological water balance.

Data source:

Genovese, G. (ed.), 2004a. Methodology of the MARS Crop Yield Forecasting System. Vol. 1 to Vol. 4, EUR-report 21291 EN.
Genovese, G., 2004b. Methodology of the MARS Crop Yield Forecasting System. EUR 21291 EN/14. http://mars.jrc. it/marsstat/Crop_Yield_Forecasting/METAMP/.

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Rate of change of the meteorological water balance 1975-2007

Note: The rate of change of the 'meteorological water balance', expressed in m3 ha-1 y-1 The map provides an estimate of the increase (red in the map) or decrease (blue in the map) of the volume of water required from irrigation in order to ensure that crop growth is not limited by water stress.

Data source:

Genovese, G. (ed.), 2004a. Methodology of the MARS Crop Yield Forecasting System. Vol. 1 to Vol. 4, EUR-report 21291 EN.
Genovese, G., 2004b. Methodology of the MARS Crop Yield Forecasting System. EUR 21291 EN/14. http://mars.jrc. it/marsstat/Crop_Yield_Forecasting/METAMP/.

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Key assessment

Past trends

Systematic observations of water demand for agriculture do not exist at the European scale, however local trends can be reconstructed by using meteorological data. On average, the rate of increase in water demand is around 50 m³/ha/year, but in some cases (Italy, Greece, Maghreb, central Spain, southern France and Germany) it is more than 150-200 m³/ha/year. Areas with upward trends in the water balance (due mainly to an increase in rainfall), have been observed in the Balkan Peninsula, the Alpine region, Scandinavia, Scotland, Benelux, the Czech Republic, Slovakia, Poland and Hungary, as well as in many Turkish areas. In the Mediterranean area, a worsening meteorological water deficit (declining water balance) has been observed over the past 32 years.

Projections

No quantitative projections of irrigation demand are available. Many climatic projections for Europe (IPCC, 2007) foresee a very likely precipitation increase in the north and a decrease in the south, especially during the summer. Also the extremes of daily precipitation are projected to increase in the north and the annual number of rainy days to decrease in the Mediterranean.
The risk of summer drought is therefore likely to increase in central Europe and in the Mediterranean area. Agricultural crops will be affected, among other factors, in positive and negative ways by changes in the length and timing of the vegetative cycle. Crop management will have to be adapted in order to try to avoid crucial development stages sensitive to water-stress (flowering, grain filling, etc.) occurring during generally dry periods.