Computationally Efficient Multivariate Calibration and Validation of a Grid-Based Hydrologic Model in Sparsely Gauged West African River Basins

Thomas Poméon,Bernd Diekkrüger,Rohini Kumar

doi:10.3390/w10101418

Abstract

The prediction of freshwater resources remains a challenging task in West Africa, where the decline of in situ measurements has a detrimental effect on the quality of estimates. In this study, we establish a series of modeling routines for the grid-based mesoscale Hydrologic Model (mHM) using Multiscale Parameter Regionalization (MPR). We provide a computationally efficient application of mHM-MPR across a diverse range of data-scarce basins using in situ observations, remote sensing, and reanalysis inputs. Model performance was first screened for four precipitation datasets and three evapotranspiration calculation methods. Subsequently, we developed a modeling framework in which the pre-screened model is first calibrated using discharge as the observed variable (mHM Q), and next calibrated using a combination of discharge and actual evapotranspiration data (mHM Q/ET). Both model setups were validated in a multi-variable evaluation framework using discharge, actual evapotranspiration, soil moisture and total water storage data. The model performed reasonably well, with mean discharge KGE values of 0.53 (mHM Q) and 0.49 (mHM Q/ET) for the calibration; and 0.23 (mHM Q) and 0.13 (mHM Q/ET) for the validation. Other tested variables were also within a good predictive range. This further confirmed the robustness and well-represented spatial distribution of the hydrologic predictions. Using MPR, the calibrated model can then be scaled to produce outputs at much smaller resolutions. Overall, our analysis highlights the worth of utilizing additional hydrologic variables (together with discharge) for the reliable application of a distributed hydrologic model in sparsely gauged West African river basins.

Highlights

Due to economic conditions in many West African countries, between 50 and 60% of the labor force works in the agricultural sector, mostly as self-sustaining farmers generating income by selling surpluses and cash-crops not intended for local consumption [1,2,3]
The runs were validated against discharge, MODerate-resolution Imaging Spectroradiometer (MODIS) derived potential (ETP) and actual (ETA) evapotranspiration, as well as GRACE ∆TWS without calibration of free parameters
It is apparent that the aspect-driven correction (ASP) method produces the worst Kling-Gupta Efficiency (KGE) results regarding

Summary

Introduction

Due to economic conditions in many West African countries, between 50 and 60% of the labor force works in the agricultural sector, mostly as self-sustaining farmers generating income by selling surpluses and cash-crops not intended for local consumption [1,2,3]. The estimation of available water resources using hydrologic modeling provides important information for planners and policy makers to mitigate problems arising due to water shortages. The subject of performing hydrologic predictions in sparsely gauged West African river basins has been well covered in recent years [4,5,6,7,8,9,10,11]. Water 2018, 10, 1418 model [14,15,16] for several West African river basins in a previous study [11]. While multi-objective validation of streamflow, actual evapotranspiration, soil moisture dynamics, and total water storage revealed the model to provide robust results, the applied scale was coarse due to computational constrains, with the smallest areas of fully distributed estimations, called subbasins in SWAT, being at least 500 km large

Methods

Results

Conclusion