Impacts of fully coupling land surface and flood models on large
wetland’s water dynamics: the case of the Inner Niger Delta
Abstract
It is known that representing wetland dynamics in land surface modeling
improves models’ capacity to reproduce fluxes and land surface boundary
conditions for atmospheric modeling in general circulation models. This
study presents the development of the full coupling between the Noah-MP
land surface model (LSM) and the HyMAP flood model in the NASA Land
Information System and its application over the Inner Niger Delta (IND),
a well-known hot-spot of strong land surface-atmosphere interactions in
West Africa. Here, we define two experiments at 0.02º spatial resolution
over the 2002-2018 period to quantify the impacts of the proposed
developments on IND dynamics. One represents the one-way approach for
simulating land surface and flooding processes (1-WAY), i.e., Noah-MP
neglects surface water availability, and the proposed two-way coupling
(2-WAY), where Noah-MP takes surface water availability into account in
the vertical water and energy balance. Results show that accounting for
two-way interactions between Noah-MP and HyMAP over IND improves all
selected hydrological variables. Compared to 1-WAY, evapotranspiration
derived from 2-WAY over flooding zones doubles, increased by 0.8mm/day,
resulting in an additional water loss rate of
~18,900km3/year, ~40%
drop of wetland extent during wet seasons and major improvement in water
level variability at multiple locations. Significant soil moisture
increase and surface temperature drop were also observed. Wetland
outflows decreased by 35%, resulting in a substantial a Nash-Sutcliffe
coefficient improvement, from -0.73 to 0.79. It is anticipated that
future developments in global water monitoring and water‐related
disaster warning systems will considerably benefit from these findings.