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Proceedings of the International Association of Hydrological Sciences An open-access publication for refereed proceedings in hydrology

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Proc. IAHS, 373, 45-49, 2016
https://doi.org/10.5194/piahs-373-45-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
 
12 May 2016
Reservoir impacts downstream in highly regulated river basins: the Ebro delta and the Guadalquivir estuary in Spain
María J. Polo1, Albert Rovira2, Darío García-Contreras1, Eva Contreras1, Agustín Millares3, Cristina Aguilar3, and Miguel A. Losada3 1Andalusian Institute of Earth System Research, University of Cordoba, Córdoba, Spain
2Aquatic Ecosystems, IRTA, Sant Carles de la Rápita, Tarragona, Spain
3Andalusian Institute of Earth System Research, University of Granada, Granada, Spain
Abstract. Regulation by reservoirs affects both the freshwater regime and the sediment delivery at the area downstream, and may have a significant impact on water quality in the final transitional water bodies. Spain is one the countries with more water storage capacity by reservoirs in the world. Dense reservoir networks can be found in most of the hydrographic basins, especially in the central and southern regions. The spatial redistribution of the seasonal and annual water storage in reservoirs for irrigation and urban supply, mainly, has resulted in significant changes of water flow and sediment load regimes, together with a fostered development of soil and water uses, with environmental impacts downstream and higher vulnerability of these areas to the sea level rise and drought occurrence. This work shows these effects in the Guadalquivir and the Ebro River basins, two of the largest regulated areas in Spain. The results show a 71 % decrease of the annual freshwater input to the Guadalquivir River estuary during 1930–2014, an increase of 420 % of the irrigated area upstream the estuary, and suspended sediment loads up to 1000 % the initial levels. In the Ebro River delta, the annual water yield has decreased over a 30 % but, on the contrary, the big reservoirs are located in the main stream, and the sediment load has decreased a 99 %, resulting in a delta coastal regression up to 10 m per year and the massive presence of macrophytes in the lower river. Adaptive actions proposed to face these impacts in a sea level rise scenario are also analyzed.

Citation: Polo, M. J., Rovira, A., García-Contreras, D., Contreras, E., Millares, A., Aguilar, C., and Losada, M. A.: Reservoir impacts downstream in highly regulated river basins: the Ebro delta and the Guadalquivir estuary in Spain, Proc. IAHS, 373, 45-49, https://doi.org/10.5194/piahs-373-45-2016, 2016.
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Regulation by reservoirs affects both the freshwater regime and the sediment delivery downstream. Spain is one the countries with more water storage capacity by reservoirs in the world. The spatial redistribution of the seasonal and annual water storage in reservoirs mainly for irrigation and urban supply has resulted in significant environmental impacts downstream. This work shows these effects in the Guadalquivir and the Ebro River basins, two of the largest regulated areas in Spain.
Regulation by reservoirs affects both the freshwater regime and the sediment delivery...
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