Effect of upslope runoff on crop functioning under Mediterranean conditions: an analysis based on a modelling approach

Mediterranean hilly landscapes, surface runoff is one of the main hydrological processes that redistributes water from upslope to downslope. In agricultural catchments, surface runoff causes rainfall water to transfer from upstream plots to downstream plots due to hydrological connectivity. The water thus redistributed can then infiltrate into the soil of the downstream plot, depending on the soil's infiltration capacity, thereby increasing water availability in the root zone. While the impact of hydrological connectivity on hydrological processes such as streamflow generation is well recognized, few studies evaluate its effect on crop functioning. In general, crop functioning is studied using multilocal methods that assume hydrological independence between plots, overlooking the influence of hydrological connectivity. In the development of catchment agro-hydrological models, the coupling between the crop model and the hydrological model is partly conditioned by the effect of hydrological connectivity.

The objective is to study the effect of water redistribution through runoff on crop functioning in the context of Mediterranean rainfed annual crops, using a modelling approach. A numerical experiment using the AquaCrop model was performed, considering two hydrologically connected plots. The experiment explored a range of agro-pedo-climatic conditions upstream and downstream: crop type, soil texture and depth, climate forcing, and the size of the upstream plot. Data collected over the past 25 years from the OMERE Environmental Research Observatory in northeastern Tunisia (Molénat et al., 2018) were used, along with data from the literature. The Aquacrop model was previously parametrised and validated for the soil, crop and climate conditions of this in northeastern Tunisia site (Dhouib et al., 2022).

Results show that annual crop production under semi-arid and subhumid climatic conditions can be increased due to hydrological processe in a moderate number of cases (16% for wheat and 33% for faba bean on average for above-ground biomass and yield) (Dhouib et al., 2024). Positive impacts are mainly observed for higher soil water retention capacity and under semi-arid and dry subhumid climate conditions, with a significant effect of the intra-annual distribution of rainfall in relation to crop phenology.

 

Dhouib M., Zitouna-Chebbi R., Prevot L., Molénat J., Mekki I., Jacob F. (2022). Multicriteria evaluation of the AquaCrop crop model in a hilly rainfed Mediterranean agrosystem. Agricultural Water Management, 273, 107912, https://dx.doi.org/10.1016/j.agwat.2022.107912

Dhouib M, Molénat J., Prevot L., Mekki M, Zitouna-Chebbi, C et Jacob F.. Numerical exploration of the impact of hydrological connectivity on rainfed annual crops in Mediterranean hilly landscapes. Agronomy for Sustainable Development, 2024, 44 (6), 51 p. ⟨10.1007/s13593-024-00981-5⟩. ⟨hal-04752688⟩

Molénat J., Raclot D., Zitouna R., et al., 2018. OMERE, a long-term observatory of soil and water resources in interaction with agricultural and land management in Mediterranean hilly areas. Vadose Zone journal, 17(1), doi:10.2136/vzj2018.04.0086