Abstract
Alternatives in irrigation management can lead to the creation of irrigation lands that are more efficient and more respectful towards the environment. The objective of this work is to analyze the evolution of the agro-environmental impact in a traditional irrigation land of the middle Ebro Valley (Spain) which has experienced changes in its management. For such, water, salt and nitrate balances were accomplished in a hydrological basin (95 ha) in 2001, 2005, 2006 and 2007. The drought of 2005 caused more intensive water use (86%), increasing in 33% the irrigation efficiency when compared to 2001 (53%), even though a high hydric deficit (24%) was caused. Changes in the flood irrigation system management (from rotation to ondemand), maximum allocations of irrigation water, billing for the volume of irrigation water consumed and the expansion of crops with lower water and fertilization needs made it possible to achieve irrigation efficiencies of approximately 73% (an increase of 20%) and to halve salt (1.3 Mg ha-1 year-1) and nitrate (25 kg NO3--N ha-1 year-1) loads exported in the drainage. The evaluated management changes have been efficient, but nevertheless, crops still suffer certain hydric stress and since 2005 a slight but worrying negative agro-environmental tendency has been observed and should be reversed.
Highlights
Increment in food needs and the development of new technologies oriented towards the use of biofuels result in an increase in the land area destined for irrigation in the world (FAO, 2006)
The annual water balances accomplished in the drainage basin D-XIX-6 were satisfactory, in the hydrological years of 2006 and 2007, when the groundwater inflows into the basin and the water stored in the system between the initial and final moment of the balances were taken into consideration
The inadequate irrigation management executed in 2001 caused low irrigation efficiency (IE = 53%) it led to a low hydric deficit in crops (HD = 1%)
Summary
Increment in food needs and the development of new technologies oriented towards the use of biofuels result in an increase in the land area destined for irrigation in the world (FAO, 2006). High volumes of water are destined for agriculture, not all water is well used; a significant percentage returns to the natural environment, contaminated either in a greater or lesser degree. The contamination of aquatic ecosystems that receive irrigation return flows is an increasing problem due to the introduction of more areas dedicated to irrigated agriculture. Contamination originating from agrarian nitrogen deserves a special mention, as the World Health Organization classified the presence of nitrates derived from nitrogenous fertilization in surface water and groundwater (WHO, 2004) as a very important problem
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