Uncovering Key Drivers of Colorado River Flow Uncertainty with High-Resolution Models

Uncovering Key Drivers of Colorado River Flow Uncertainty with High-Resolution Models | 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 Article Uncovering Key Drivers of Colorado River Flow Uncertainty with High-Resolution Models Yujia You This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7511560/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted You are reading this latest preprint version Abstract The Colorado River is a critical water source for the arid and semi-arid American Southwest, yet its future remains highly uncertain because climate models struggle to represent the complex hydroclimate of its mountainous headwaters. By analyzing a suite of global climate models with grid resolutions from ~250 km to ~25 km, we demonstrate that high-resolution models with improved representation of fine-scale topography provide a much more realistic simulation of upper-elevation snowpack. This snowpack functions as a hydrological buffer, storing precipitation that would otherwise be lost to evapotranspiration and releasing it months later as runoff. In high-elevation terrain, snowpack and runoff are primarily modulated by precipitation rather than temperature. However, as climate warming pushes winter temperatures close to and above the melting threshold, snowpack becomes increasingly sensitive to temperature, shifting precipitation partitioning toward evapotranspiration at the expense of runoff. Coarse-resolution models fail to simulate these key processes. Consequently, the dominant source of uncertainty in future runoff is not the wide inter-model spread in precipitation projections but rather the misrepresentation of snowpack and the resulting biases in runoff sensitivity to warming. Our findings suggest that future declines in Colorado River flow might be more severe than current projections indicate. Earth and environmental sciences/Climate sciences/Climate change/Projection and prediction Earth and environmental sciences/Climate sciences/Hydrology Full Text Additional Declarations There is NO Competing Interest. Supplementary Files SI.docx Supplementary information Cite Share Download PDF Status: Under Review Version 1 posted 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. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-7511560","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":512107002,"identity":"0bec3919-461f-40e8-a892-cfff42ea5980","order_by":0,"name":"Yujia You","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA9ElEQVRIiWNgGAWjYHCChAMMFRaMDWB2AQODATOIwUZIyxkJqBYD4rQwMDC2IWthIKDF4EbCwwM/50nI9rM3MH74YHA42pyd+QHDh7LD+LQkHOzdJmE8s+cAs+QMg8O5O5vZDBhnnMOv5QDvNonEDTcS2Jh5gFo2HAZ6h7eNgC1/50gk7kdoYf/A/JeAlsO8DUBbJOBaeAyYGfFokTzzIOGwzDEJ4xlnDjYD/ZIO9AtPwcGec+k4tfAdz0n++KbGRra/vfnghw8V1rnb+Y9vfPCjzBqnFoUDPAlQJjRqQOAATvVAIN/Ajld+FIyCUTAKRgEDAwD8YF6Ws13o8AAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0000-0002-3494-2456","institution":"Atmospheric and Oceanic Sciences Program, Princeton University, NJ, USA","correspondingAuthor":true,"prefix":"","firstName":"Yujia","middleName":"","lastName":"You","suffix":""}],"badges":[],"createdAt":"2025-09-01 21:15:09","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7511560/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7511560/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":91465323,"identity":"c63e9523-2275-49ad-9d6e-d7cea3dd6adb","added_by":"auto","created_at":"2025-09-16 18:34:17","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1079047,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7511560/v1_covered_6bfbb21d-c035-46b1-9ef7-2b61566193c6.pdf"},{"id":91464289,"identity":"f94abb3c-fba9-434c-99c8-79a98b474d61","added_by":"auto","created_at":"2025-09-16 18:18:15","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":8043254,"visible":true,"origin":"","legend":"Supplementary information","description":"","filename":"SI.docx","url":"https://assets-eu.researchsquare.com/files/rs-7511560/v1/5962b5ff028971d8151561d1.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Uncovering Key Drivers of Colorado River Flow Uncertainty with High-Resolution Models","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"nature-portfolio","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"","title":"Nature Portfolio","twitterHandle":"","acdcEnabled":false,"dfaEnabled":false,"editorialSystem":"ejp","reportingPortfolio":"","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-7511560/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7511560/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"The Colorado River is a critical water source for the arid and semi-arid American Southwest, yet its future remains highly uncertain because climate models struggle to represent the complex hydroclimate of its mountainous headwaters. By analyzing a suite of global climate models with grid resolutions from ~250 km to ~25 km, we demonstrate that high-resolution models with improved representation of fine-scale topography provide a much more realistic simulation of upper-elevation snowpack. This snowpack functions as a hydrological buffer, storing precipitation that would otherwise be lost to evapotranspiration and releasing it months later as runoff. In high-elevation terrain, snowpack and runoff are primarily modulated by precipitation rather than temperature. However, as climate warming pushes winter temperatures close to and above the melting threshold, snowpack becomes increasingly sensitive to temperature, shifting precipitation partitioning toward evapotranspiration at the expense of runoff. Coarse-resolution models fail to simulate these key processes. Consequently, the dominant source of uncertainty in future runoff is not the wide inter-model spread in precipitation projections but rather the misrepresentation of snowpack and the resulting biases in runoff sensitivity to warming. Our findings suggest that future declines in Colorado River flow might be more severe than current projections indicate.","manuscriptTitle":"Uncovering Key Drivers of Colorado River Flow Uncertainty with High-Resolution Models","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-16 18:18:10","doi":"10.21203/rs.3.rs-7511560/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"communications-earth-and-environment","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"commsenv","sideBox":"Learn more about [Communications Earth and Environment](https://www.nature.com/commsenv/)","snPcode":"","submissionUrl":"","title":"Communications Earth \u0026 Environment","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Communications Series","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"bafda98f-6496-45c7-9406-d4e458817c7a","owner":[],"postedDate":"September 16th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":54392972,"name":"Earth and environmental sciences/Climate sciences/Climate change/Projection and prediction"},{"id":54392973,"name":"Earth and environmental sciences/Climate sciences/Hydrology"}],"tags":[],"updatedAt":"2026-04-17T07:01:50+00:00","versionOfRecord":[],"versionCreatedAt":"2025-09-16 18:18:10","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7511560","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7511560","identity":"rs-7511560","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}