Unravelling the contribution of potential evaporation formulation to uncertainty under climate change

Abstract

Abstract. The increasing air temperature in a changing climate will impact actual evaporation and have consequences for water resources management in energy-limited regions. In many hydrological models, evaporation is assessed by a preliminary computation of potential evaporation (PE) representing the evaporative demand of the atmosphere. Therefore, in impact studies the quantification of uncertainties related to PE estimation, which can arise from different sources, is crucial. Indeed, a myriad of PE formulations exist and the uncertainties related to climate variables cascade into PE computation. So far, no consensus has emerged on the main source of uncertainty in the PE modelling chain for hydrological studies. In this study, we address this issue by setting up a multi-model and multi-scenario approach. We used seven different PE formulations and a set of 30 climate projections to calculate changes in PE. To estimate the uncertainties related to each step of the PE calculation process (namely Representative Concentration Pathways, General Circulation Models, Regional Climate Models and PE formulations), an analysis of variance decomposition (ANOVA) was used. Results show that PE would increase across France by the end of the century, from +40 to +130 mm/year. In ascending order, uncertainty contributions by the end of the century are explained by: PE formulations (below 10 %), then RCPs (above 20 %), RCMs (30–40 %) and GCMs (30–40 %). Finally, all PE formulations show similar future trends since climatic variables are co-dependent to temperature. While no PE formulation stands out from the others, in hydrological impact studies the Penman-Monteith formulation may be preferred as it is representative of the PE formulations ensemble mean and allows accounting for climate and environmental drivers co-evolution.

Evapotranspiration in hydrological models under rising CO2: a jump into the unknown

“…The differences are obvious under the RCP 8.5 but also present under the RCP 4.5 scenario. It is noteworthy that the different trends (and sign of the trend) are highly variable compared to differences of changes in PE when considering different PE formulations (Lemaitre-Basset et al 2021), showing that the uncertainties in projections of CO 2 concentrations might be translated to large uncertainties in PE (and simulated runoff). While the use of the Budyko framework highlights moderate-to-important impacts of taking into account CO 2 in PE formulations, how this could reflect on hydrological projections made with rainfall-runoff hydrological models might not be straightforward.…”

Hydraulic Issues Concerning Injection of Harvested Rainwater to the Subsurface Through Drywells: Insight From Numerical Simulations of Flow in a Realistic Combined Vadose Zone‐Groundwater Flow System

“…In some water markets, Managed aquifer recharge (MAR) operations have become a significant component of the water supply system (Kurtzman & Guttman, 2020). For the Mediterranean climate zone, practically all climate change researches predict a significant increase in surface temperatures during the 21st century (Alpert et al., 2008; Garc'ıa‐Ruiz et al., 2011; Spinoni et al., 2017; Vogel et al., 2021), which, in turn, will lead to rise in potential evapotranspiration (PET) (Lemaitre‐basset et al., 2022). Climate models predict a decline in annual precipitation (P) at the same time (Alpert et al., 2008), hence, the ratio of P/PET, which is a measure of aridity, is expected to decline (Le Houérou, 1996).…”

Evaporation in Hydrological Models Under Rising CO2: A Jump into The Unknown

“…The differences are obvious under the RCP 8.5 but also present under the RCP 4.5 scenario. It is noteworthy that the different trends (and sign of the trend) are highly variable compared to differences of changes in PE when considering different PE formulations(Lemaitre-Basset et al 2021), showing that the uncertainties in projections of CO2 concentrations might be translated to large uncertainties in PE (and simulated runoff).…”