Articles | Volume 21, issue 2
Research article
14 Feb 2017
Research article |  | 14 Feb 2017

Using satellite-based evapotranspiration estimates to improve the structure of a simple conceptual rainfall–runoff model

Tirthankar Roy, Hoshin V. Gupta, Aleix Serrat-Capdevila, and Juan B. Valdes

Abstract. Daily, quasi-global (50° N–S and 180° W–E), satellite-based estimates of actual evapotranspiration at 0.25° spatial resolution have recently become available, generated by the Global Land Evaporation Amsterdam Model (GLEAM). We investigate the use of these data to improve the performance of a simple lumped catchment-scale hydrologic model driven by satellite-based precipitation estimates to generate streamflow simulations for a poorly gauged basin in Africa. In one approach, we use GLEAM to constrain the evapotranspiration estimates generated by the model, thereby modifying daily water balance and improving model performance. In an alternative approach, we instead change the structure of the model to improve its ability to simulate actual evapotranspiration (as estimated by GLEAM). Finally, we test whether the GLEAM product is able to further improve the performance of the structurally modified model. Results indicate that while both approaches can provide improved simulations of streamflow, the second approach also improves the simulation of actual evapotranspiration significantly, which substantiates the importance of making diagnostic structural improvements to hydrologic models whenever possible.

Short summary
This study presents and compares two different approaches to using satellite-derived estimates of actual evapotranspiration (ET) to improve the performance of a conceptual rainfall–runoff model. In the first approach, the ET process within the model is constrained using the satellite ET estimates, while in the second one, the model structure is altered. Results indicate that both the approaches improve streamflow forecasting, while the second one also improves the ET simulations significantly.