Impact of Natural Processes and Human Activities on Groundwater Quality in the Negombo-Muthurajawela Region in Sri Lanka

Abstract

Groundwater is an essential and finite resource in the world. Numerous knowledge gaps remain in the understanding of groundwater resources in Sri Lanka, mainly due to the lack of accurate data. The purpose of this study is to assess the water quality in groundwater and its spatial distribution in Negombo-Muthurajawela area in Sri Lanka. The data collection was conducted at the beginning and at the end of south west monsoon (May and September, respectively) in 2013. A pilot survey was carried out using 116 dug wells. A total of thirty-one dug wells were selected for physiochemical analysis. In situ field testing of electrical conductivity (EC), salinity, and pH were carried out and laboratory tests were performed for HCO₃⁻, Na⁺, K⁺, Ca²⁺, Cl⁻, SO₄²⁻, Mg²⁻, PO₄³⁻, NO₃⁻, and total hardness (TH). Principal component analysis (PCA) was performed to assess water quality and interpolation technique in ArcGIS was performed to analyze and prepare spatial distribution maps of water. Sri Lankan standards for drinking water were used to determine the threshold levels of physiochemical parameters. The results of the PCA reveal that thirty-one observation wells can be classified under three main components: the first based on the impact on EC, HCO₃⁻, Na⁻, K⁺, Cl⁻, Mg²⁻, and TH; the second component considering the pH, HCO₃, Ca²⁺, SO₄²⁻, PO₄³⁻, and TH; and the third component based on NO₃⁻. These three components evidence the role of salt water intrusion, the influence of Muthurajawela wetlands, and the anthropogenic discharges on groundwater quality in the Negombo-Muthurajawela area.

Keywords:

• groundwater
• human and natural impacts

Funding

This study was funded by the Higher Education for Twenty First Century (HETC), 2011 project, Sri Lanka, and the School of Environment, Science and Engineering, Southern Cross University, Australia.

Additional information

Notes on contributors

C.M. Kanchana N. K. Chandrasekara

C. M. KANCHANA N. K. CHANDRASEKARA is a Lecturer in the Department of Geography, University of Colombo, Colombo-03, Sri Lanka. E-mail: [email protected]. Research interests include biogeography, land use and land cover change, water pollution, GIS, and remote sensing.

K. D. N. Weerasinghe

K. D. N. WEERASINGHE is Professor in the Department of Agricultural Engineering, Faculty of Agriculture, University of Ruhuna, Mapalana, Kamburupitiya, Sri Lanka. E-mail: [email protected]. His research interests include natural resource management, disaster risk reduction, and climate change adaptation.

Sumith Pathirana

SUMITH PATHIRANA is Associate Professor in the Department of Biological and Environmental Sciences, College of Arts and Sciences, Qatar University, PO Box 2713, Doha, Qatar. E-mail: [email protected]. His research interests include the application of GIS and remote sensing in vulnerability and hazard studies, particularly related to coastal environments.

Ranjana U. K. Piyadasa

RANJANA U. K. PIYADASA is Professor in the Department of Geography, University of Colombo, Colombo-03, Sri Lanka. E-mail: [email protected]. His research interests include water-related research studies, climate change, and groundwater.