{"paper_id":"0182be62-e0ff-45ac-8c65-0a7a23b89dcb","body_text":"Rainwater Harvesting from Bitumen Roof for Managed Aquifer Recharge: First Flush Characterization and the Organic Carbon Challenge | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Rainwater Harvesting from Bitumen Roof for Managed Aquifer Recharge: First Flush Characterization and the Organic Carbon Challenge Lior Netzer, Guy Gasser, Sharona Henig, Itzhak Katra, Daniel Kurtzman, and 5 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9611742/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 11 You are reading this latest preprint version Abstract Urbanization critically reduces groundwater recharge and elevates flood risks, making rainwater harvesting from rooftops (RWHR) for managed aquifer recharge (MAR) an essential strategy. While the technical implementation of MAR is well-established, our understanding of RWHR water quality and its subsequent impact on the hydrochemical status of groundwater remains ambiguous. A primary concern is the 'first flush' – the initial, often contaminated runoff after dry periods. This study defines the first flush and evaluates roof rainwater quality from bitumen-sheet covered flat roofs. In this research, we continuously monitored roof rainwater from three bitumen roofs in Israel, sampled groundwater, and conducted controlled rain simulator experiments on sun-exposed and shaded bitumen samples, analyzing the release of major ions, total organic carbon (TOC), total nitrogen (TN), trace elements, and electrical conductivity (EC). The results show strong EC-inorganic solute correlations, enabling effective first flush identification. The first flush defined as the initial 10 mm of cumulative rainfall, and beyond this threshold, most pollutant concentrations significantly decrease, making 'subsequent flow' water suitable for MAR. Critically, TOC behaves differently; despite substantial reduction in subsequent flow, its concentrations remain two orders of magnitude higher than typical groundwater concentrations. Rain simulator tests confirmed high TOC release from sun-exposed bitumen, with low biodegradability, indicating TOC as a persistent concern Managed Aquifer Recharge Roof Rainwater Harvesting Water Quality First Flush Dissolved Organic Matter Full Text Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Reviews received at journal 13 May, 2026 Reviewers agreed at journal 13 May, 2026 Reviewers agreed at journal 12 May, 2026 Reviewers agreed at journal 09 May, 2026 Reviewers agreed at journal 08 May, 2026 Reviewers agreed at journal 07 May, 2026 Reviewers agreed at journal 07 May, 2026 Reviewers invited by journal 06 May, 2026 Editor assigned by journal 05 May, 2026 Submission checks completed at journal 05 May, 2026 First submitted to journal 04 May, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {\"props\":{\"pageProps\":{\"initialData\":{\"identity\":\"rs-9611742\",\"acceptedTermsAndConditions\":true,\"allowDirectSubmit\":false,\"archivedVersions\":[],\"articleType\":\"Research Article\",\"associatedPublications\":[],\"authors\":[{\"id\":639759054,\"identity\":\"43cfa2cc-ecab-4f21-9626-0e9e372c4840\",\"order_by\":0,\"name\":\"Lior Netzer\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"Israeli Water Authority\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Lior\",\"middleName\":\"\",\"lastName\":\"Netzer\",\"suffix\":\"\"},{\"id\":639759055,\"identity\":\"33d67368-38d2-4823-af9d-67f71d16fda4\",\"order_by\":1,\"name\":\"Guy 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