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Article

Assessment of SWAT Model Performance in Simulating Daily Streamflow under Rainfall Data Scarcity in Pacific Island Watersheds

1
Water Resources Research Center, University of Hawaii at Manoa, Honolulu, HI 96822, USA
2
Department of Geology and Geophysics, University of Hawaii at Manoa, Honolulu, HI 96822, USA
3
Department of Soil Science and Water Resources, University of Kufa, Najaf 54003, Iraq
*
Author to whom correspondence should be addressed.
Water 2018, 10(11), 1533; https://doi.org/10.3390/w10111533
Received: 8 September 2018 / Revised: 22 October 2018 / Accepted: 25 October 2018 / Published: 27 October 2018
(This article belongs to the Section Hydrology)
Evaluating the performance of watershed models is essential for a reliable assessment of water resources, particularly in Pacific island watersheds, where modeling efforts are challenging due to their unique features. Such watersheds are characterized by low water residence time, highly permeable volcanic rock outcrops, high topographic and rainfall spatial variability, and lack of hydrological data. The Soil and Water Assessment Tool (SWAT) model was used for hydrological modeling of the Nuuanu area watershed (NAW) and Heeia watershed on the Island of Oahu (Hawaii). The NAW, which had well-distributed rainfall gauging stations within the watershed, was used for comparison with the Heeia watershed that lacked recoded rainfall data within the watershed. For the latter watershed, daily rain gauge data from the neighboring watersheds and spatially interpolated 250 m resolution rainfall data were used. The objectives were to critically evaluate the performance of SWAT under rain gauge data scarce conditions for small-scale watersheds that experience high rainfall spatial variability over short distances and to determine if spatially interpolated gridded rainfall data can be used as a remedy in such conditions. The model performance was evaluated by using the Nash–Sutcliffe efficiency (NSE), the percent bias (PBIAS), and the coefficient of determination (R2), including model prediction uncertainty at 95% confidence interval (95PCI). Overall, the daily observed streamflow hydrographs were well-represented by SWAT when well-distributed rain gauge data were used for NAW, yielding NSE and R2 values of > 0.5 and bracketing > 70% of observed streamflows at 95PCI. However, the model showed an overall low performance (NSE and R2 ≤ 0.5) for the Heeia watershed compared to the NAW’s results. Although the model showed low performance for Heeia, the gridded rainfall data generally outperformed the rain gauge data that were used from outside of the watershed. Thus, it was concluded that finer resolution gridded rainfall data can be used as a surrogate for watersheds that lack recorded rainfall data in small-scale Pacific island watersheds. View Full-Text
Keywords: Hawaii; Heeia and Nuuanu watersheds; rainfall; streamflow; SWAT Hawaii; Heeia and Nuuanu watersheds; rainfall; streamflow; SWAT
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MDPI and ACS Style

Leta, O.T.; El-Kadi, A.I.; Dulai, H.; Ghazal, K.A. Assessment of SWAT Model Performance in Simulating Daily Streamflow under Rainfall Data Scarcity in Pacific Island Watersheds. Water 2018, 10, 1533. https://doi.org/10.3390/w10111533

AMA Style

Leta OT, El-Kadi AI, Dulai H, Ghazal KA. Assessment of SWAT Model Performance in Simulating Daily Streamflow under Rainfall Data Scarcity in Pacific Island Watersheds. Water. 2018; 10(11):1533. https://doi.org/10.3390/w10111533

Chicago/Turabian Style

Leta, Olkeba T., Aly I. El-Kadi, Henrietta Dulai, and Kariem A. Ghazal 2018. "Assessment of SWAT Model Performance in Simulating Daily Streamflow under Rainfall Data Scarcity in Pacific Island Watersheds" Water 10, no. 11: 1533. https://doi.org/10.3390/w10111533

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