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Lookup NU author(s): Dr Greg O'Donnell, Professor Claire Walsh
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
© 2024 by the authors. Non-point sources of pollution (NPSPs) originating from runoff from contaminated agricultural and populated areas are becoming a growing concern in developing countries, endangering the environment and public health. This requires systematic investigation, including modelling the likely impact using an appropriate hydrological model. This study quantified the spatiotemporal variation of the NPSP and prioritised the most vulnerable sub-watersheds for intervention planning. We investigated the effects of land use and cover (LULC) conversion on runoff generation and NPSP loads in terms of sediment, phosphate, total nitrogen, total phosphorus, and nitrate loading using the SWAT model. The principal source of data utilised to assess the change in NPSP loads was the 2003 and 2023 LULC. The analysis of the results showed that grassland and shrubland substantially changed, with 96.7% and 74.4% reductions, respectively, while the increase in agricultural land was 147.3% and that of built-up areas increased by 80.14%. The mean yearly increase in sediment yield ranges from 25.46 to 27,298.75 t, while the mean yearly increase in surface runoff ranges from 183.1 mm to 487.9 mm. The minimum recorded runoff was 10.69 mm (5.1%) in WS03, while the highest was 123.3 mm (66.5%) in WS02. The NO3− load increased from 127.6 to 20,739.7 kg, and the PO43− load increased from 3.12 to 2459.7 kg. The TN load increased from 4465.5 to 482,014.5 kg, and the TP load increased from 1383.5 to 133,641.3 kg. The monthly analysis of nitrate loading revealed that the “Belg” season has the highest nitrate load than the rainy season, probably due to nitrification. The findings clearly showed that the inputs applied to the farms were not effectively utilised for the intended purpose. Hence, efforts must be made to ensure that nutrients remain in the catchment through an appropriate land management intervention.
Author(s): Assegide E, Alamirew T, O'Donnell G, Dessie BK, Walsh CL, Zeleke G
Publication type: Article
Publication status: Published
Journal: Water
Year: 2024
Volume: 16
Issue: 23
Online publication date: 29/11/2024
Acceptance date: 30/10/2024
Date deposited: 06/01/2025
ISSN (electronic): 2073-4441
Publisher: MDPI
URL: https://doi.org/10.3390/w16233447
DOI: 10.3390/w16233447
Data Access Statement: The original contributions presented in the study are included in the article; further inquiries can be directed to the corresponding author.
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