Robustness of a parsimonious subsurface drainage model at the French national scale

Abstract

Abstract. Drainage systems are currently implemented on agricultural plots subjected to temporary or permanent waterlogging issues. Drained plots account for 9 % of all arable soils in France. As such, the need for accurate hydrological modeling is crucial, especially in an unstable future context affected by climate change. The aim of this paper is to assess the capacity of the SIDRA-RU hydrological drainage model to represent the variability in pedoclimatic conditions within French metropolitan areas and to demonstrate the utility of this model as a long-term management tool. The model is initially calibrated using the KGE′ criterion as an objective function (OF) on a large and unique database encompassing 22 plots spread across France and classified according to three main soil textures (silty, silty–clay, and clayey). The performance of SIDRA-RU is evaluated by monitoring both the set of KGE′ calibration values and the quality of simulations on each plot with respect to high and low discharges, as well as the annual drained water balance. Next, the temporal robustness of the model is assessed by conducting, on selected plots, the split-sample test capable of satisfying the data requirements. Results show that the SIDRA-RU model accurately simulates drainage discharge, especially on silty soils. The performance on clayey soils is slightly weaker than that on silty soils yet remains acceptable. Similarly, the split-sample test indicates that SIDRA-RU is temporally robust on all three soil textures. Consequently, the SIDRA-RU model closely replicates the diversity of French drained soil and could be used for its long-term management potential.

Drainage assessment of irrigation districts: on the precision and accuracy of four parsimonious models

“…Where SIDS (mm) is the intense drainage season reservoir level (Jeantet et al, 2021). Note that RU is not spatialized, implying that a single simulation is performed for AB1 and AB2 separately with average forcings and parameters.…”

“…KGE (Q 0.5 ) is the KGE calculated from the squared roots of simulated and observed drainage, allowing the weights between high and low flows to be more balanced. Following Jeantet et al (2021), we consider simulations as "excellent" 345 when KGE (Q 0.5 ) is larger than 0.8, "very good" when it is larger than 0.7, "good" when it is larger than 0.6, "acceptable" when it is between 0.5 and 0.6, and "unsatisfactory" when it is below 0.5. Furthermore, to get a reference in mind, a KGE of -0.41 is equivalent to having a simulation performance equal to the average of the observed data (Knoben et al, 2019).…”

Effects of Climate Change on Hydrological Indicators of Subsurface Drainage for a Representative French Drainage Site

“…The four calibrated parameters are K, µ, S inter and S max . In this study, their values were extracted from the analysis of Jeantet et al (2021). Unlike most current subsurface drainage models, the SIDRA-RU model use strong assumptions, such neglecting current crop to simulate CET.…”

“…This assumption is based on the fact that, despite being managed by the two-year crop rotation winter wheat/maize and the absence/presence of cover crops, the water balance of the studied site is not affected by current crop (Henine et al, 2022). A more detailed description of the SIDRA-RU model is provided by Henine et al (2022) and Jeantet et al (2021).…”

“…We use 30 Euro-Cordex future climate projections distributed over three RCPs: RCP2.6, RCP4.5 and RCP8.5. These climate projections feed the subsurface drainage model SIDRA-RU (Henine et al, 2022), a lumped and parsimonious model which has demonstrated good performance and temporal robustness in simulating subsurface drainage fluxes in France (Jeantet et al, 2021). The SIDRA-RU model provides subsurface drainage discharges, which then allow us to calculate 17 hydrological indicators specific to subsurface drainage, which constitute a uniquely large range of complementary indicators and give a comprehensive view of the subsurface drainage response.…”