Title: | Assessment of SWAT model performance in simulating daily streamflow under rainfall data scarcity in Pacific Island watersheds |
Authors: | Leta, O.T, A.I. El-Kadi, H. Dulai and K.A. Ghazal |
Year: | 2018 |
Journal: | Water |
Volume (Issue): | 10(11) |
Pages: | |
Article ID: | 1533 |
DOI: | 10.3390/w10111533 |
URL (non-DOI journals): | |
Model: | SWAT |
Broad Application Category: | hydrologic only |
Primary Application Category: | climate data effects |
Secondary Application Category: | calibration, sensitivity, and/or uncertainty analysis |
Watershed Description: | 11.5 km^2 Heeia River and 100 km^2 Nuuanu River, located in the southeast part of the Island of Oahu in the State of Hawaii, U.S. |
Calibration Summary: | |
Validation Summary: | |
General Comments: | |
Abstract: | 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. |
Language: | English |
Keywords: | Hawaii; Heeia and Nuuanu watersheds; rainfall; streamflow; SWAT |