25 Apr 2022
25 Apr 2022
Status: this preprint is currently under review for the journal HESS.

On the importance of phenology in the Miombo ecosystem: Evaluation of open-source satellite evaporation models

Henry Zimba1,2, Miriam Coenders-Gerrits1, Kawawa Banda3, Petra Hulsman4, Nick van de Giesen1, Imasiku Nyambe3, and Hubert Savenije1 Henry Zimba et al.
  • 1Delft University of Technology, Water Resources Section, Building 23 (Faculty of Civil Engineering and Geosciences) 2628 CN Delft, P.O Box 5048 2600 GA Delft, The Netherlands
  • 2Ministry of Agriculture, Department of Agriculture, P.O Box 50595, Mulungushi House, Independence Avenue, Lusaka, Zambia
  • 3University of Zambia, Integrated Water Resources Management Centre, Department of Geology, School of Mines, Great East Road Campus, Lusaka, Zambia
  • 4Ghent University, Hydro-Climate Extremes Lab (H-CEL), Coupure links 653, 9000 Ghent, Belgium

Abstract. Accurate spatial-temporal information on evaporation is needed for use in many sectors including hydrology, agriculture and climate studies. This would require a dense observation network, which is practically impossible. Over the past decades, remotely sensed evaporation models to estimate spatially continuous evaporation have been developed. However, deciding which model to use is a challenge as these models vary in complexity and accuracy across the different global ecosystems. It is even more challenging for complex African ecosystems that have very few, or none at all, flux tower observations. In this study, we used the general water balance evaporation (Ewb) as reference to which we compared six models that determine evaporation, i.e., FLEXTopoWB, TerraClimate (TMCWB), GLEAM, MOD16, SSEBop and WaPOR, in the Luangwa Basin, a semi-arid catchment in the Miombo ecosystem in southern Africa. FLEXTopoWB and TMCWB models are calibrated on discharge, while GLEAM, MOD16, SSEBop and WaPOR have been validated on evaporation data from flux tower observations. Key focus is on inter-model performance comparison in the Miombo ecosystem across phenophases and land cover types. Results show that major spatial-temporal discrepancies in model performance occur in the forest and open water body land surfaces during the dormant and green-up phenophases in the dry season. Compared to Ewb, annually WaPOR consistently overestimated evaporation while GLEAM consistently underestimated evaporation. The rest of the models showed biases within the GLEAM and WaPOR boundaries. With reference to bias, SSEBop and WaPOR showed lowest aggregated 2009–2020 bias in terms of estimating long-term average annual evaporation. It appears that correct understanding of the Miombo vegetation phenology associated moisture feedbacks and incorporating these in model structure is likely to improve evaporation estimates in the Luangwa Basin and Miombo Woodland ecosystem as a whole.

Henry Zimba et al.

Status: open (until 20 Oct 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on hess-2022-114', Anonymous Referee #1, 30 May 2022 reply
    • AC1: 'Reply on RC1', Henry Musonda Zimba, 31 May 2022 reply
    • AC2: 'Reply on RC1', Henry Musonda Zimba, 02 Jun 2022 reply

Henry Zimba et al.

Data sets

ZAMSECUR Project Field Data Mpika, Zambia Henry Zimba, Miriam Coenders

Henry Zimba et al.


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Latest update: 28 Sep 2022
Short summary
We compare performance of evaporation models in the Luangwa Basin located in a semi-arid and complex Miombo ecosystem in Africa. Miombo plants changes colour, drop off leaves and acquire new leaves during the dry season. In addition, the plant roots go deep in the soil and appear to access groundwater. Results show that evaporation models with structure and process that do not capture this unique plant structure and behaviour appears to have difficulties to correctly estimating evaporation.