Assessment of the WRF-Hydro uncoupled hydro-meteorological model on flashy watersheds of the Grande Terre tropical island of New Caledonia (South-West Pacific)
Abstract
Study region: Six watersheds of the main island of New Caledonia.
Study focus: In the context of a projected reduction of extreme precipitation events by ~ 20% by
2100 combined to large land cover variability, a distributed hydrological approach was adopted
over New Caledonia. The WRF-Hydro model was implemented using a one-way WRF meteorological
forcing, with rainfall being spatially interpolated from rain gauge observations using the
Thiessen polygon and IDEW methods. The Dynamically Dimensioned Search algorithm was
applied for calibration on three contrasted flash-floods. Two-year validation allowed the dynamics
of the watersheds to be studied and compared.
New hydrological insights for the region: Good results in terms of Nash-Sutcliffe efficiency were
reached on all watersheds (NSE ≥ 0.6). WRF-Hydro showed consistent water budget components
for two flash-floods with 90% correlation between simulated and observed runoff coefficients of
all basins. Adjusted physical parameters matched known watershed morphological and hydrological
features. Both methods of rainfall interpolation produced similar NSE but strongly
different water distributions, with simulated soil moisture changes varying by up to 60% during
flash-floods. Spatial patterns of soil moisture and flood decomposition led to improved understanding
of watershed behavior and to a revision of infiltration properties for one of them.
Overall, WRF-Hydro proved to be a suitable framework to better understand hydrological processes
and efficiently handle prospective modifications of New Caledonia’s land cover and climate
regimes.
Domains
Hydrology
Origin : Publisher files allowed on an open archive
