University of Oulu

Panditharathne R, Gunathilake MB, Chathuranika IM, Rathnayake U, Babel MS, Jha MK. Trends and Variabilities in Rainfall and Streamflow: A Case Study of the Nilwala River Basin in Sri Lanka. Hydrology. 2023; 10(1):8.

Trends and variabilities in rainfall and streamflow : a case study of the Nilwala River Basin in Sri Lanka

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Author: Panditharathne, Ravindu1,2; Gunathilake, Miyuru B.3,4; Chathuranika, Imiya M.1;
Organizations: 1Department of Civil Engineering, Faculty of Engineering, Sri Lanka Institute of Information Technology, New Kandy Road, Malabe 10115, Sri Lanka
2Faculty of Technology, Wayamba University of Sri Lanka, Kuliyapitiya 27411, Sri Lanka
3Hydrology and Aquatic Environment, Division of Environment and Natural Resources, Norwegian Institute of Bioeconomy and Research, 1430 Ås, Norway
4Water, Energy and Environmental Engineering, Faculty of Technology, University of Oulu, 90570 Oulu, Finland
5Water Engineering and Management, Asian Institute of Technology, Pathumthani 12120, Thailand
6Civil, Architectural and Environmental Engineering, 456 McNair Hall, North Carolina Agricultural and Technical State University, Greensboro, NC 27411, USA
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 1.6 MB)
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Language: English
Published: Multidisciplinary Digital Publishing Institute, 2022
Publish Date: 2023-08-24


Rainfall is one of the dominating climatic parameters that affect water availability. Trend analysis is of paramount significance to understand the behavior of hydrological and climatic variables over a long timescale. The main aim of the present study was to identify trends and analyze existing linkages between rainfall and streamflow in the Nilwala River Basin (NRB) of Southern Sri Lanka. An investigation of the trends, detection of change points and streamflow alteration, and linkage between rainfall and streamflow were carried out using the Mann–Kendall test, Sen’s slope test, Pettitt’s test, indicators of hydrological alteration (IHA), and Pearson’s correlation test. Selected rainfall-related extreme climatic indices, namely, CDD, CWD, PRCPTOT, R25, and Rx5, were calculated using the RClimdex software. Trend analysis of rainfall data and extreme rainfall indices demonstrated few statistically significant trends at the monthly, seasonal, and annual scales, while streamflow data showed non-significant trends, except for December. Pettitt’s test showed that Dampahala had a higher number of statistically significant change points among the six rainfall stations. The Pearson coefficient correlation showed a strong-to–very-strong positive relationship between rainfall and streamflow. Generally, both rainfall and streamflow showed non-significant trend patterns in the NRB, suggesting that rainfall had a higher impact on streamflow patterns in the basin. The historical trends of extreme climatic indices suggested that the NRB did not experience extreme climates. The results of the present study will provide valuable information for water resource planning, flood and disaster mitigation, agricultural operations planning, and hydropower generation in the NRB.

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Series: Hydrology
ISSN: 2306-5338
ISSN-E: 2306-5338
ISSN-L: 2306-5338
Volume: 10
Issue: 1
Article number: 8
DOI: 10.3390/hydrology10010008
Type of Publication: A1 Journal article – refereed
Field of Science: 218 Environmental engineering
Funding: This research was carried out under the financial support of a SLIIT Research Grant: FGSR/RG/FE/2022/02.
Copyright information: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (