Irrigation water use and its effective efficiency in Portugal

Abstract

The 2007 report of the Intergovernmental Panel on Climate Change (IPCC) projected with high confidence that the conditions (drought and high temperatures) in the Southern Europe will worsen. It stated that this region that includes Portugal is already vulnerable and will experience a reduction in water availability, hydropower potential and crop yield and productivity. The evidence of such conditions have already struck Portugal when during the 2004-2005 hydrological year experienced one of its worst droughts in decades. Between June to September 2005, the whole country was classified as experiencing sever to extreme drought according to the Palmer Drought Severity Index (PDSI). At the same time, Portugal was developing its new Water Law based on the requirements of the so called Water Framework Directive of the European Union. Its Article 11 states that one of the basic and required measures is to promote efficient and sustainable use of water. As a consequence of these two factors, the Portuguese Government adopted a series of adaptation measures, one of them being a ten year National Program for Efficient Use of Water. This paper will present this program in its irrigation water use, analyse its effective efficiency and discuss advantages and disadvantages of the portfolio of measures that are being considered. Until recently, classical efficiency defined as the ratio of the beneficial output to input was mostly used to calculate irrigation water efficiency. But in this study, the effective efficiency (EE) indicator was used which is defined as the ratio of beneficial output to the effective demand. Beneficial output is essentially net evapotranspiration. The preliminary results show an EE of about 60% corresponding to an effective water demand of about 6.6 billion cubic meter per year. This quantity of water is more than 85% of total water demand in Portugal. The cost of supplying this amount of water is estimated to be about half a billion Euros per year resulting in about 200 millions of Euros of losses. Some specific results of two river basins namely the international Douro River Basin will be presented in this paper. The Program sets a goal of improving the EE to 65% to be achieved in 10 years by 2015. Four areas of intervention were proposed to achieve this goal: information and education, training and technical help, legislation and normalisation, and Measurement and conversion of equipments of water use.