Irrigation water requirement (CLIM 033) - Assessment published Nov 2012
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Climate change (Primary topic)
Typology: Descriptive indicator (Type A – What is happening to the environment and to humans?)
- CLIM 033
Key policy question: How is climate change affecting the water requirement of agricultural crops and water availability for irrigation across Europe?
- In the Iberian Peninsula and Italy, an increase in the volume of water required for irrigation from 1975 to 2010 has been estimated, whereas parts of south-eastern Europe have recorded a decrease.
- The projected increases in temperature will lead to increased evapotranspiration rates, thereby increasing crop water requirements across Europe.
- The impact of increasing water requirements is expected to be most acute in southern Europe, where the suitability for rain-fed agriculture is projected to decrease and irrigation requirements are projected to increase.
Rate of change of the meteorological water balance
Note: This figure shows the rate of change of the ‘water balance’. The map provides an estimate increase (red in map) or decrease (blue in map) of the volume of water required from irrigation assuming that all other factors are unchanged and given that there is an irrigation demand.
- Rate of change of frost-free period map for Europe provided by Geo network - open source
Projected change in water availability for irrigation in the Mediterranean region
Note: This figure shows the relative change in water availability for irrigation as projected under the A1B emission scenario by the HIRHAM (DMI) regional climate model for 2071-2100 relative to 1961-1990. Light yellow areas indicate no change in water availability.
- Regional Assessment of Climate Change in the Mediterranean provided by Euro-Mediterranean Centre on Climate Change (CMMC)
Consistent observations of water demand for agriculture do not currently exist for Europe but past trends can be estimated on the basis of meteorological data. Figure 1 estimates the change in the water balance, which is the difference between a reference evapotranspiration and the rainfall. This indicator provides only a rough proxy for changes in irrigation demand, because actual irrigation demand is determined by the crops grown, the type of irrigation applied and the local soil conditions. In the period considered (1975–2010), the Iberian Peninsula and Italy experienced an increase in the volume of water required for irrigation, if yields of irrigated crops were to be maintained, whereas parts of south-eastern Europe have experienced a decrease.
No projections of changes in irrigation demand are available for Europe. Many climate change projections show a consistent increase in the number of dry days in spring and summer in much of southern and central Europe [i]. In some of the severe climate change scenarios the increase in the number of dry days in summer even extends far into northern Europe. The increasing temperatures will increase the evaporative demand, which would be further increased if the higher frequency of dry days leads to lower relative humidity and reduced cloud cover. These effects will only be partly compensated by the reduced crop transpiration under higher CO2 concentrations [ii].
The expected increasing evapotranspiration will put pressure on the use of irrigation in drought-prone areas. Irrigation in Europe is currently concentrated along the Mediterranean, where some countries use more than 80 % of total freshwater abstraction for agricultural purposes [iii]. The increasing demand for irrigation will therefore increase the competition for water, in particular where total water availability declines due to reduced precipitation. Assuming that urban water demands would have preference over agricultural purposes, the proportional reduction of water availability for irrigation in many European basins is larger than the reduction in annual run-off (Figure 2) [iv]. Projections for the Mediterranean region show a considerable decline in water availability, which in some areas makes current irrigation practices impossible in the future.
[i] M. Trnka et al., „Agroclimatic Conditions in Europe Under Climate Change“, Global Change Biology 17, Nr. 7 (Juli 1, 2011): 2298–2318, doi:10.1111/j.1365-2486.2011.02396.x.
[ii] J. E. Olesen et al., „Uncertainties in projected impacts of climate change on European agriculture and terrestrial ecosystems based on scenarios from regional climate models“, Climatic Change 81 (März 17, 2007): 123–143, doi:10.1007/s10584-006-9216-1.
[iii] EEA, Water resources across Europe — confronting water scarcity and drought EEA Report (Copenhagen: European Environment Agency, 2009), http://www.eea.europa.eu/publications/water-resources-across-europe.
[iv] A. Iglesias et al., „Water and people: Assessing policy priorities for climate change adaptation in the Mediterranean“, in Regional Assessment of Climate Change in the Mediterranean (RACCM) (Springer, 2012), in press.
Regional Assessment of Climate Change in the Mediterranean
provided by Euro-Mediterranean Centre on Climate Change (CMMC)
Monitoring Agricultural ResourceS (MARS)
provided by Joint Research Centre (JRC)
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