Extreme precipitation events induce high fluxes of groundwater and associated nutrients to coastal ocean

Abstract

Abstract. Current studies of submarine groundwater discharge (SGD) are commonly conducted under aquifer baseflow conditions, neglecting the influence of episodic events that can significantly increase the supply of nutrients and water. This limits our understanding of the social, biogeochemical, and ecological impacts of SGD. In this study, we evaluated the influence of an extreme precipitation event (EPE) on the magnitude of SGD. To do so, three seawater sampling campaigns were performed at a Mediterranean ephemeral stream-dominated basin after an EPE (∼ 90 mm in few hours) and in baseflow conditions. Results indicate that the groundwater flows after the EPE were 1 order of magnitude higher than those in baseflow conditions. The SGD induced by EPEs, which only take place a few days per year, represented up to one third of the annual discharge of groundwater and associated nutrients at the study site. This work accentuates the need to account for episodic increases in the supply of water and nutrients when aiming to provide reliable annual SGD estimates, particularly in the current context of climate change, since the occurrence of such events is expected to increase worldwide.

Impacts of Extratropical Cyclone Fiona on a sensitive coastal lagoon ecosystem

“…4d) arises from the time required for the recharged meteoric water to mobilize root‐zone nitrate into the rivers via interflow and shallow groundwater, and to push out deeper “old” nitrate‐rich water from the aquifer (Paradis et al 2018). The sustained loading, which is due to the transport through the groundwater system, indicates that extratropical cyclones can trigger elevated nutrient loading that persists much longer than the surface effects of high flows, as has been recently reported elsewhere (Diego‐Feliu et al 2022; Pavlovskii et al 2023), with the timing likely related to the shallow and deep nitrate transport pathways. Given that nitrate loading is the primary driver of eutrophication in Basin Head and in many other coastal waters worldwide (González‐De Zayas et al 2021), such sustained nutrient loading may trigger sustained coastal ecosystem eutrophication, at least when storms occur in summer or early fall when the water is warm.…”

Challenge to Lake Ecosystems: Changes in Thermal Structure Triggered by Climate Change

“…Precipitation resulting from these storms leads to dilution effects, influx of organic matter, and decreased turbidity, which can cause changes in stratification [66] and increased greenhouse gas emissions under flood conditions [67]. Extreme precipitation events can transport organic components between land and water via runoff [68,69], Increased runoff volume can limit the development of thermal stratification [70]. Additionally, extreme precipitation and occasional wind events are important factors affecting thermal stratification [71,72].…”

Physical and chemical characterization of remote coastal aquifers and submarine groundwater discharge from a glacierized watershed

“…Climate‐mediated changes are expected to impact groundwater resources negatively (Kundzewicz & Doell, 2009; Michael et al, 2013; Richardson et al, 2024), particularly at high latitudes (Guimond et al, 2022) and in mountain environments (Somers & McKenzie, 2020). Extreme rainfall events have been observed to induce high SGD rates and increase nutrient delivery to coastal waters (Diego‐Feliu et al, 2022). Degradation of the cryosphere coincides with radical land cover changes (Lane et al, 2017), which may significantly alter groundwater recharge zones and storage (Bouraoui et al, 1999; Mackay et al, 2020).…”