do Nascimento Thiago Victor Medeiros, de Oliveira Rodrigo Proença, Condesso de Melo Maria Teresa
CERIS - Civil Engineering Research and Innovation for Sustainability, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal.
CERIS - Civil Engineering Research and Innovation for Sustainability, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal.
Sci Total Environ. 2024 Jan 10;907:168151. doi: 10.1016/j.scitotenv.2023.168151. Epub 2023 Oct 26.
This research aims to analyze the impacts of the large-scale Alqueva Irrigation System (AIS) on the water cycle in selected sub-basins and the underlying Gabros de Beja aquifer system (GBAS) in Southern Portugal. The Alqueva reservoir and irrigation project is one of the largest strategic water reservoirs in Western Europe and the AIS's primary source. The closure of the dam in 2002 resulted in significant changes to the region's land use and agricultural practices, shifting from predominantly rainfed dry cereals to intensively irrigated olive and almond orchards. Therefore, this study used SWAT+ to simulate water flows from 1934 to 2021 and examined the evolution of groundwater quality and its correlation with irrigation, using data from about 50 wells from 2002 to 2021. Kriging spatial interpolation, Mann-Kendal and Sen's trend tests and the correlation technique were used. The findings revealed several noteworthy trends. First, there was a significant historical decrease in precipitation, which can be attributed to climate change. The simulation indicated a decrease in runoff and recharge, along with an increase in actual evapotranspiration due to irrigation. Furthermore, the hydrogeostatiscal analysis showed that the aquifer experienced significant salinization after the AIS implementation. In contrast, a preponderant decreasing trend in nitrate concentration was observed, which may be attributed to (a) a decrease in fertilizer use, (b) dilution effects and (c) alteration in nitrates pathways due to changes in crop types. Finally, the correlation analysis suggested that nitrates and chlorides were highly correlated to actual evapotranspiration and precipitation evolution, which may be associated to irrigation. In conclusion, the large-scale irrigation implementation and climate change significantly altered the water cycle of the study region. Overall, these findings addressed existing knowledge gaps and provided valuable insights that can be extrapolated to draw conclusions and generalize climate change and irrigation's effects on fluvial ecosystems.
本研究旨在分析大规模的阿尔克瓦灌溉系统（AIS）对葡萄牙南部选定子流域的水循环以及下伏的贝雅辉长岩含水层系统（GBAS）的影响。阿尔克瓦水库和灌溉项目是西欧最大的战略水库之一，也是AIS的主要水源。2002年大坝的建成导致该地区土地利用和农业实践发生了重大变化，从主要依赖雨养的旱作谷物转变为集约灌溉的橄榄园和杏仁园。因此，本研究使用SWAT+模拟了1934年至2021年的水流，并利用2002年至2021年约50口井的数据，研究了地下水水质的演变及其与灌溉的相关性。采用了克里金空间插值、曼-肯德尔和森趋势检验以及相关技术。研究结果揭示了几个值得注意的趋势。首先，降水量在历史上显著下降，这可归因于气候变化。模拟结果表明径流和补给减少，同时由于灌溉实际蒸散量增加。此外，水文地质统计学分析表明，AIS实施后含水层经历了显著的盐渍化。相反，观察到硝酸盐浓度呈主要下降趋势，这可能归因于：（a）化肥使用减少；（b）稀释效应；（c）作物类型变化导致硝酸盐路径改变。最后，相关分析表明，硝酸盐和氯化物与实际蒸散量和降水演变高度相关，这可能与灌溉有关。总之，大规模灌溉的实施和气候变化显著改变了研究区域的水循环。总体而言，这些研究结果填补了现有知识空白，并提供了有价值的见解，可用于推断气候变化和灌溉对河流生态系统的影响并得出结论。
