The need to feed an increasing population while limiting the environmental impact of agriculture is currently one of the greatest challenges relating to the food chain. One of the key factors involved in doing this is irrigation, which has a downstream impact that can be minimised if nutrient and water management are efficiently undertaken. The objective of this study was to determine which irrigation management improvements can be done at field scale in modern irrigated areas to reduce its irrigation return flow impact. The study was conducted in the Noguera Ribagorçana River basin, in NE Spain, where almost 6000 ha of land were brought into irrigation from 2000 to 2009. We based our study on a water quality dataset, measured in four different sites along a 29 km stretch of the river over a period of 20 years. Our results show an increase in nitrate (from 1.7 mg·L to 10.5 mg·L) and salt concentrations (electrical conductivity from 297 to 675 µS·m) in the downstream course of the river compared to the most upstream monitoring site. That was exclusively associated with the irrigation return flows from the newly irrigated area. The highest nitrate and salt concentrations are found during the non-irrigation season which corresponds to the local rainy season. To reduce this impact, better irrigation management is required. Autumn leaching could be lowered by reducing irrigation volume applied during the final weeks of crop cycles in order to allow the soil to retain the volume of water received from rainfall. To deal with this issue, we propose a methodology based on soil moisture to determine the end of the irrigation season. In this way, the impact on ecosystems located further downstream would be reduced while crop yields and productivity in the area could be maintained.

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评估灌溉对水质条件的影响：诺格拉·里巴戈尔萨纳河（西班牙东北部）的案例研究

满足不断增长的人口的需要，同时限制农业对环境的影响，是目前与食物链相关的最大挑战之一。实现这一目标的关键因素之一是灌溉，如果有效地进行养分和水管理，灌溉对下游的影响可以最小化。本研究的目的是确定现代灌溉地区可以在田间规模上进行哪些灌溉管理改进，以减少灌溉回流的影响。这项研究在西班牙东北部的 Noguera Ribagorçana 河流域进行，从 2000 年到 2009 年，这里有近 6000 公顷的土地被用于灌溉。我们的研究基于水质数据集，在 29 公里长的四个不同地点进行了测量这条河长达20年的历史。我们的结果显示，与最上游监测点相比，下游河道的硝酸盐浓度（从 1.7 mg·L 增加到 10.5 mg·L）和盐浓度（电导率从 297 µS·m 增加到 675 µS·m）。这完全与新灌溉地区的灌溉回流有关。硝酸盐和盐浓度最高出现在非灌溉季节，即当地雨季。为了减少这种影响，需要更好的灌溉管理。可以通过减少作物周期最后几周的灌溉量来减少秋季淋滤，以使土壤保留从降雨中获得的水量。为了解决这个问题，我们提出了一种基于土壤湿度来确定灌溉季节结束的方法。这样，对下游生态系统的影响将减少，同时该地区的作物产量和生产力得以维持。