{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,9]],"date-time":"2026-04-09T18:46:10Z","timestamp":1775760370409,"version":"3.50.1"},"reference-count":47,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2026,2,2]],"date-time":"2026-02-02T00:00:00Z","timestamp":1769990400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"FCT-Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia"},{"name":"European Commission\u2019s Recovery and Resilience Facility","award":["UID\/04423\/2025"],"award-info":[{"award-number":["UID\/04423\/2025"]}]},{"name":"European Commission\u2019s Recovery and Resilience Facility","award":["UID\/PRR\/04423\/2025"],"award-info":[{"award-number":["UID\/PRR\/04423\/2025"]}]},{"name":"European Commission\u2019s Recovery and Resilience Facility","award":["LA\/P\/0101\/2020"],"award-info":[{"award-number":["LA\/P\/0101\/2020"]}]},{"name":"national funds through the Foundation for Science and Technology"},{"name":"European funds","award":["COMPETE2030 (COMPETE2030-FEDER-0691700)"],"award-info":[{"award-number":["COMPETE2030 (COMPETE2030-FEDER-0691700)"]}]},{"name":"Associate Laboratory ARNET","award":["LA\/P\/0069\/2020"],"award-info":[{"award-number":["LA\/P\/0069\/2020"]}]},{"name":"Contrato-Programa","award":["UID\/04050\/2025"],"award-info":[{"award-number":["UID\/04050\/2025"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Monitoring water quality in large reservoirs is essential yet challenging, particularly in regions with limited in situ coverage. This study presents a robust methodology for integrating a decade-long in situ dataset (2014\u20132022) with Sentinel-2 multispectral imagery to develop and validate localized algorithms for water quality assessment in the Alqueva Reservoir, the largest artificial lake in Western Europe. Three atmospheric correction algorithms (C2RCC, C2X, C2X-COMPLEX) were evaluated, with C2RCC-COMPLEX identified as the most suitable for capturing the reservoir\u2019s optical complexity, yielding the lowest RMSE for Total Suspended Solids (TSS: 2.4 g\/m3) and Secchi Disk Depth (SDD: 0.85 m). Empirical models using Sentinel-2 bands 7 (783 nm), 6 (740 nm), and 8A (865 nm) demonstrated strong correlations (R2 \u2248 0.69\u20130.71) for Chlorophyll-a (Chl-a) with a range data of 0.1\u201365 mg\/m3, TSS with a range data of 2\u201313.1 g\/m3, and SDD with a range data of 0.4\u20138 m. Spatially explicit water quality maps illustrate the models\u2019 capacity to capture distinct gradients and seasonal dynamics, e.g., elevated Chl-a (&gt;30 mg\/m3) and TSS (&gt;7.5 g\/m3) in the reservoir\u2019s nutrient-rich northern section during drought (August 2022), and more uniform conditions following winter recovery (March 2019), with SDD exceeding 2 m near the dam. These results underscore the utility of Sentinel-2 for resolving spatial and temporal variability in optically complex inland waters. The proposed workflow offers a transferable, cost-effective framework for monitoring eutrophication risks and sediment dynamics under increasing hydrological variability.<\/jats:p>","DOI":"10.3390\/rs18030469","type":"journal-article","created":{"date-parts":[[2026,2,2]],"date-time":"2026-02-02T14:12:46Z","timestamp":1770041566000},"page":"469","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Development and Calibration of Sentinel-2 Spectral Indices for Water Quality Parameter Estimation in Alqueva Reservoir, Southern Portugal"],"prefix":"10.3390","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-3798-730X","authenticated-orcid":false,"given":"V\u00edtor H.","family":"Neves","sequence":"first","affiliation":[{"name":"ICBAS, School of Medicine and Biomedical Sciences, University of Porto, Rua de Jorge Viterbo Ferreira, 228, 4050-313 Porto, Portugal"},{"name":"CIIMAR\/CIMAR LA, Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Terminal de Cruzeiros do Porto de Leix\u00f5es, 4450-208 Matosinhos, Portugal"},{"name":"Department of Biology, Faculty of Sciences, University of Porto, Rua do Campo Alegre S\/N, 4169-007 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0009-0000-1315-4234","authenticated-orcid":false,"given":"Lisette","family":"S\u00e1nchez-P\u00e9rez","sequence":"additional","affiliation":[{"name":"Image Processing Laboratory, Universitat de Val\u00e8ncia, C\/Catedr\u00e1tico Jos\u00e9 Beltr\u00e1n Mart\u00ednez, 2, 46980 Val\u00e8ncia, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6686-9919","authenticated-orcid":false,"given":"Sara C.","family":"Antunes","sequence":"additional","affiliation":[{"name":"CIIMAR\/CIMAR LA, Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Terminal de Cruzeiros do Porto de Leix\u00f5es, 4450-208 Matosinhos, Portugal"},{"name":"Department of Biology, Faculty of Sciences, University of Porto, Rua do Campo Alegre S\/N, 4169-007 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4231-5644","authenticated-orcid":false,"given":"Giorgio","family":"Pace","sequence":"additional","affiliation":[{"name":"Centre of Molecular and Environmental Biology (CBMA)\/Aquatic Research Network (ARNET) Associate Laboratory, Department of Biology, University of Minho, 4710-057 Braga, Portugal"},{"name":"Institute of Science and Innovation for Bio-Sustainability (IB-S), University of Minho, Rua da Universidade, 4710-057 Braga, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8080-5826","authenticated-orcid":false,"given":"Xavier","family":"S\u00f2ria-Perpiny\u00e0","sequence":"additional","affiliation":[{"name":"Image Processing Laboratory, Universitat de Val\u00e8ncia, C\/Catedr\u00e1tico Jos\u00e9 Beltr\u00e1n Mart\u00ednez, 2, 46980 Val\u00e8ncia, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2819-6979","authenticated-orcid":false,"given":"Jes\u00fas","family":"Delegido","sequence":"additional","affiliation":[{"name":"Image Processing Laboratory, Universitat de Val\u00e8ncia, C\/Catedr\u00e1tico Jos\u00e9 Beltr\u00e1n Mart\u00ednez, 2, 46980 Val\u00e8ncia, Spain"}]}],"member":"1968","published-online":{"date-parts":[[2026,2,2]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Rodrigues, G., Potes, M., Costa, M.J., Novais, M.H., Marcha, A., Salgado, R., and Morais, M. 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