Hydrological regime shifts and functional river typologies in South-Western Nigeria

نوع مقاله : پژوهشی

نویسندگان

1 PhD of Department of Civil Engineering, Federal University of Technology, Akure, Nigeria

2 Professor, Department of Civil Engineering, Federal University of Technology, Akure, Nigeria

3 Associate Professor, Department of Civil Engineering, Federal University of Technology, Akure, Nigeria

4 Associate Professor, Department of Remote sensing and Geo-informatics, Federal University of Technology, Akure, Nigeria

چکیده

Rivers in tropical regions and specifically West Africa are experiencing core hydrological changes under the twin-impacts of climate variability and intense land use change. This study analysed daily discharge for six rivers in South-Western Nigeria (Oba, Ogbese, Ogun, Osun, Owena, Yewa) over 1983–2023 (~14,600 observations per river). Methods combined Mann–Kendall with Sen’s slope (annual means), flow-duration curves (Q10/Q50/Q90 and log-slope), descriptive statistics, percentile-based extremes (Q95/Q5), Weibull flood-frequency, Colwell’s predictability (P, C, M), and PCA–k-means clustering. No river showed a significant monotonic trend (p > 0.05), yet variability was large (CV range ≈ 1.03–2.10). Ogun carried the largest high flows (Q10 = 488 m³ s⁻¹) and, with Yewa (CV ≈ 1.03), exhibited more baseflow support; Oba and Ogbese were flashy (CV = 2.10 and 1.37). Predictability was low across basins (P ≤ 0.246; C = 0), indicating unstable seasonality. Extremes were frequent: each river recorded ~296–749 flood days and a similar number of drought days over the record; 100-year peaks in Ogun exceeded 3,000 m³ s⁻¹. PCA–k- means separated Ogun from the other five rivers, supporting a functional typology for management. These findings argue for regime-oriented, nonstationary planning: linking operations, urban green infrastructure, and monitoring to variability, thresholds, and detected shifts rather than historical means.

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مدل سازی و مدیریت آب و خاک
دوره 5، شماره 4
آبان 1404
صفحه 143-158

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  • تاریخ دریافت: 19 مرداد 1404
  • تاریخ بازنگری: 30 شهریور 1404
  • تاریخ پذیرش: 21 مهر 1404

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