Impact of hydrological connectivity on rainfed annual crops in Mediterranean hilly landscapes: a numerical exploration

Abstract

Abstract Within hilly agricultural landscapes, topography induces lateral transfers of runoff water, so-called interplot hydrological connectivity. Runoff water generated in upstream plots can infiltrate downstream plots, thus influencing the water content in the root zone that drives crop functioning. As the impact of runoff on crop functioning in the context of Mediterranean rainfed annual crops has been understudied thus far, the current study aims to comprehensively investigate this effect. To quantify how the downstream infiltration of upstream runoff affects crop functioning, we conduct a numerical experiment using the AquaCrop crop model and consider two hydrologically connected plots. The experiment explores a range of upstream and downstream agro-pedo-climatic conditions: crop type, soil texture and depth, climate forcing, and the area of the upstream plot. The experiment relies on data collected over the last 25 years within the Kamech catchment, an environment research observatory in northeastern Tunisia. Overall, the results show that the downstream infiltration of upstream runoff has a positive impact on crop functioning in a moderate number of situations, ranging from 16% (wheat) to 33% (faba bean) as the average across aboveground biomass and yield. This positive impact is mostly found for soils with higher available water capacity and under semiarid and dry subhumid climate conditions, with a significant impact of rainfall intra-annual distribution in relation to crop phenology. These results need to be deepened by considering both a wider range of crops and future climate conditions, for which larger occurrences of semiarid climate conditions are expected.