Understanding Niger Delta Rainfall Variability and Trend Using Parametric and Non-parametric Statistics

Understanding Niger Delta Rainfall Variability and Trend Using Parametric and Non-parametric Statistics | 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 Understanding Niger Delta Rainfall Variability and Trend Using Parametric and Non-parametric Statistics Chinago Budnukaeku Alexander This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9023969/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 8 You are reading this latest preprint version Abstract This study investigates the variability and long-term trends of annual rainfall in the Niger Delta region of Nigeria over a 41-year period (1981‒2021). Annual rainfall data from five key meteorological stations—Benin, Calabar, Port Harcourt (PH), Uyo, and Warri—were analyzed using both parametric (Linear Regression) and non-parametric (Mann-Kendall and Sen’s Slope Estimator) statistical techniques. Descriptive statistics revealed high mean annual rainfall across the region, with Uyo exhibiting the highest variability (CV of 28.71%). The Mann-Kendall test indicated a statistically significant increasing trend in annual rainfall only at the Calabar station (Z = 1.988, p 0.05) with a magnitude of 7.56 mm/year, just below the significance threshold. The remaining stations (Port Harcourt, Uyo, and Warri) showed no statistically significant trend. The Rainfall Anomaly Index (RAI) for the region highlighted periods of severe wet and dry years, with the most pronounced positive anomalies occurring in the early 2000s and the most severe negative anomalies in the late 1980s. These findings are crucial for water resource management, agricultural planning, and flood mitigation strategies in the vulnerable coastal environment of the Niger Delta. Earth and environmental sciences/Climate sciences Earth and environmental sciences/Environmental sciences Earth and environmental sciences/Hydrology Rainfall Variability Trend Analysis Mann-Kendall Test Sen’s Slope Niger Delta Climate Change Nigeria Full Text Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Reviews received at journal 27 Apr, 2026 Reviewers agreed at journal 31 Mar, 2026 Reviewers agreed at journal 30 Mar, 2026 Reviewers invited by journal 29 Mar, 2026 Editor assigned by journal 29 Mar, 2026 Editor invited by journal 24 Mar, 2026 Submission checks completed at journal 14 Mar, 2026 First submitted to journal 14 Mar, 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. 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-9023969","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":615028094,"identity":"e2aee828-7de2-4a86-b40d-bfb720aa3211","order_by":0,"name":"Chinago Budnukaeku Alexander","email":"data:image/png;base64,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","orcid":"","institution":"Captain Elechi Amadi Polytechnic","correspondingAuthor":true,"prefix":"","firstName":"Chinago","middleName":"Budnukaeku","lastName":"Alexander","suffix":""}],"badges":[],"createdAt":"2026-03-03 22:23:05","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9023969/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9023969/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":106093298,"identity":"64a16c23-10a5-463f-bf7b-5a64b157ecb6","added_by":"auto","created_at":"2026-04-03 11:36:30","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":826163,"visible":true,"origin":"","legend":"","description":"","filename":"RevisedManuscrWPSOffice.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9023969/v1_covered_83b70eaa-4f9f-4d75-9553-4429dd88c4c6.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Understanding Niger Delta Rainfall Variability and Trend Using Parametric and Non-parametric Statistics","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":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Rainfall Variability, Trend Analysis, Mann-Kendall Test, Sen’s Slope, Niger Delta, Climate Change, Nigeria","lastPublishedDoi":"10.21203/rs.3.rs-9023969/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9023969/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study investigates the variability and long-term trends of annual rainfall in the Niger Delta region of Nigeria over a 41-year period (1981‒2021). Annual rainfall data from five key meteorological stations\u0026mdash;Benin, Calabar, Port Harcourt (PH), Uyo, and Warri\u0026mdash;were analyzed using both parametric (Linear Regression) and non-parametric (Mann-Kendall and Sen\u0026rsquo;s Slope Estimator) statistical techniques. Descriptive statistics revealed high mean annual rainfall across the region, with Uyo exhibiting the highest variability (CV of 28.71%). The Mann-Kendall test indicated a statistically significant increasing trend in annual rainfall only at the Calabar station (Z\u0026thinsp;=\u0026thinsp;1.988, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05), with a magnitude of 12.52 mm/year as estimated by Sen\u0026rsquo;s Slope. Benin showed a strong increasing tendency (Z\u0026thinsp;=\u0026thinsp;1.898, p\u0026thinsp;\u0026gt;\u0026thinsp;0.05) with a magnitude of 7.56 mm/year, just below the significance threshold. The remaining stations (Port Harcourt, Uyo, and Warri) showed no statistically significant trend. The Rainfall Anomaly Index (RAI) for the region highlighted periods of severe wet and dry years, with the most pronounced positive anomalies occurring in the early 2000s and the most severe negative anomalies in the late 1980s. These findings are crucial for water resource management, agricultural planning, and flood mitigation strategies in the vulnerable coastal environment of the Niger Delta.\u003c/p\u003e","manuscriptTitle":"Understanding Niger Delta Rainfall Variability and Trend Using Parametric and Non-parametric Statistics","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-01 20:19:38","doi":"10.21203/rs.3.rs-9023969/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"editorInvitedReview","content":"","date":"2026-04-27T15:24:35+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"323407940997168016366709481165827124785","date":"2026-03-31T06:17:16+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"249488862174384134306877045946667409204","date":"2026-03-30T11:16:42+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-03-30T02:13:12+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-03-30T02:12:38+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2026-03-24T06:21:39+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-03-14T21:07:52+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2026-03-14T21:03:02+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"88ec2152-02de-4d10-a95d-e7ae15d9a54c","owner":[],"postedDate":"April 1st, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":65441684,"name":"Earth and environmental sciences/Climate sciences"},{"id":65441685,"name":"Earth and environmental sciences/Environmental sciences"},{"id":65441686,"name":"Earth and environmental sciences/Hydrology"}],"tags":[],"updatedAt":"2026-04-01T20:19:38+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-01 20:19:38","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9023969","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9023969","identity":"rs-9023969","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}