Preprints
https://doi.org/10.5194/hess-2022-185
https://doi.org/10.5194/hess-2022-185
 
20 May 2022
20 May 2022
Status: this preprint is currently under review for the journal HESS.

How useful are gridded water resources reanalysis and evapotranspiration products for assessing water security in ungauged basins?

Elias Nkiaka1, Robert G. Bryant1, Joshua Ntalja2,3, and Eliézer Biao4 Elias Nkiaka et al.
  • 1Department of Geography, University of Sheffield, Sheffield, S10 2TN, UK
  • 2Department of Geography, University of Bonn, 53115 Bonn, Germany
  • 3Center for Development Research, University of Bonn, 53113 Bonn, Germany
  • 4Laboratory of Applied Hydrology, University of Abomey-Calavi (UAC), Cotonou, Benin

Abstract. Achieving water security in ungauged basins is critically hindered by a lack of in situ hydrometeorological data to assess past, current and future evolution of water resources in those areas. To overcome this challenge, there has been a shift toward the use of freely available satellite and reanalysis hydrometerological products. However, due to inherent bias and uncertainty, these secondary sources require careful evaluation to ascertain their performance before being applied in ungauged basins. The objectives of this study were to evaluate the performance of nine gridded water resources reanalysis (WRR), and eight evapotranspiration (ET) products and to estimate the relative uncertainties in monthly basin-scale water balance evapotranspiration (ETWB) in eight river basins located in Central-West Africa. Evaluation results highlight strengths and weaknesses of the different WRR and ET products in simulating discharge dynamics and ET estimates respectively across the basins. Analyses further revealed that the relative uncertainties in monthly ETWB range from 4–25 % with a significant increase in magnitude during the rainy season while river discharge is the dominant source of uncertainty. Our results further revealed that the performance of land surface models (LSMs) and global hydrological models (GHM) in simulating river discharge is strongly influenced by the model structure, input data and spatial resolution. Differences in ET estimates from the different ET products may be attributed to model structure and the input data used in driving the models. Results from this study suggest that gridded WRR and ET products are a useful source of data for assessing water security in ungauged basins. However, given the plethora of products available, it is imperative to evaluate their performance in representative gauged basins to identify products that can be applied in each region.

Elias Nkiaka et al.

Status: open (until 15 Jul 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on hess-2022-185', Anonymous Referee #1, 17 Jun 2022 reply

Elias Nkiaka et al.

Elias Nkiaka et al.

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Short summary
Achieving water security in ungauged regions is hindered by a lack of in situ hydrometeorological data. In this study we validated nine existing gridded water resources reanalysis and eight evapotranspiration products in eight representative gauged basins in Central-West Africa. Our results show the strengths and and weaknesses of the existing products and that these products can be used to assess water security in ungauged basins. However, it is imperative to validate these products.