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Irrigated agriculture impacts the quality of water bodies receiving irrigation return flows. The leaching of salts and nitrate from Lerma Basin (7.38 km 2 ), a newly-implemented pressurized irrigated area in the Ebro Basin (Spain), was assessed in this study for the hydrological years 2004–2013, covering years before (2004–2005), during (2006–2008) and after (2009–2013) the implementation of irrigation. The concentration of salts and nitrate were measured for all the components of the water balance and the amounts of these pollutants coming from the irrigated surface (352 ha) were estimated. Besides, salt and nitrate contamination indices were computed. Under unirrigated conditions, the studied area exported 1.89 Mg ha −1 year −1 and 11.4 kg ha −1 year −1 of salts and nitrate-nitrogen, respectively. These amounts increased to 3.51 Mg ha −1 year −1 for salts and 30.8 kg ha −1 year −1 for nitrate-nitrogen after the implementation of irrigation. Salt and nitrate contamination indices (SCI and NCI, respectively) increased by a factor of three from unirrigated to irrigated conditions, reaching values of 0.96 [Mg ha −1 year −1 ]/[dS m −1 ] and 0.12, respectively. Despite these values being well under the threshold considered for more sustainable irrigated areas (SCI < 2.0 [Mg ha −1 year −1 ]/[dS m −1 ] and NCI < 0.2), it would be advisable to improve irrigation management to increase water use and decrease leaching. Complementary measures such as adjusting fertilization rates to temporal crop necessities or the use of catch crops may prove to be useful. [ABSTRACT FROM AUTHOR]

Irrigation practice has increased considerably recently and will continue to increase to feed a growing population and provide better life standards worldwide. Numerous studies deal with the hydrological impacts of irrigation, but little is known about the temporal evolution of the affected variables. This work assesses the effects on a gully after irrigation was implemented in its hydrological basin (7.38 km2). Flow, electrical conductivity, nitrate concentration and exported loads of salts and nitrates were recorded in Lerma gully (Zaragoza, Spain) for eight hydrological years (2004–2011), covering the periods before, during and after implementation of irrigation. Non-parametric statistical analysis was applied to understand relationships and trends. The results showed the correlation of irrigation with flow and the load of salts and nitrates exported, although no significant relationship with precipitation was detected. The implementation of irrigation introduced annual trends in flow (3.2 L s-1, +23%), salinity (–0.38 mS cm-1, –9%), and nitrate concentration (5.4 mg L-1, +8%) in the gully. In addition, the annual loads of contaminants exported increased (salts and nitrates, 27.3 Mg km-2year-1, +19%, and 263 kg NO3–-N km-2year-1, +27%, respectively). The trends presented a strong seasonal pattern, with higher and more significant trends for the irrigation season. The changes observed were different from those of larger irrigation districts or regional basins, due to the differences in land use and irrigation management. It is important to understand these changes in order to achieve an adequate management of the environment and water resources. EditorZ.W. Kundzewicz CitationMerchán, D., Causapé, J., and Abrahão, R., 2013. Impact of irrigation implementation on hydrology and water quality in a small agricultural basin in Spain.Hydrological Sciences Journal, 58 (7), 1400–1413. [ABSTRACT FROM AUTHOR]

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Evaluation of water management has been progressively more necessary to determine the availability of water resources, especially in the Mediterranean environment where competition for these resources is maximum. This work evaluates the irrigation management and evolution of hydric needs for the main crops implemented in the Ebro basin (Spain), through the monitoring of a pilot experimental basin between 1998 and 2012. This 15-year period comprehends changes in irrigation implemented by the Irrigation District as well as climate and agronomic variabilities of the region. Changes in water management (implementation of an on-demand irrigation system with annual water allowances and payment per surface and consumption, in opposition to an irrigation system in shifts) and crops contributed to reduce irrigation by 40% and drainage by 72%. This occurred due to better adjustments between the water volumes applied and the hydric needs of the crops, achieving flood irrigation efficiencies of 80%. However, small negative trends were detected in the water deficit evolution of corn and sunflower, which should be addressed and improved. Improvements in water management by farmers have enabled the increase of irrigation efficiency up to values found in pressurized irrigation systems, especially in initial stages of the irrigation campaigns. However, specific water deficit episodes were detected that should be remediated. [ABSTRACT FROM AUTHOR]