Modelling physical and ecological processes in medium-to-large deep European perialpine lakes: a review

Abstract

In this paper we review a significant sample of the modelling studies carried out on medium-to-large deep European perialpine lakes (MLDEPLs). The reviewed bibliographic corpus was obtained querying Elsevier’s Scopus® database with a tailored search string on 8 January 2021. Results were filtered, accepting only journal papers written in English dealing with natural lakes having surface area > 10 km2. A list of 75 works was obtained, published between 1986 and 2021. Most studies have been carried out on Swiss lakes (44 out of 75 papers), Lake Geneva being the most investigated environment. A significant positive correlation was found between lake surface area and volume and the number of dedicated papers, suggesting that scientific attention is higher for environments characterised by large dimensions and relevant socio-economic interests. Both the number of papers and their citation count have experienced an exponential growth in time, pointing to a rising interest in quantitative modelling applications, but also to the increasing availability and ease of use of numerical modelling tools. Among the 75 selected papers, 55 employ a hydrodynamic driver, used alone or coupled with an ecological module, while the remnant 20 works adopt an ecological-only model. Among the papers employing hydrodynamic models, the use of three-dimensional (3D) drivers is surprisingly slightly more frequent (28 papers) than that of one-dimensional (1D) ones (26 papers), with most 3D applications having been published in the last 2011-2020 decade (24 papers). This reflects the interest on the hydrodynamic processes leading to the observed spatial heterogeneities in the biochemical properties of the MLDEPLs. However, coupling of ecological modules with 3D hydrodynamic drivers, to directly simulate these phenomena, is still restricted (2 papers) compared to that of 1D hydrodynamic drivers (8 papers), due to calibration and computational difficulties, which could be strongly reduced by future research achievements. Nevertheless, 1D models allow performing long-term prognoses considering multiple climate change and watershed management scenarios, due to their much smaller computational burden. The largest group of works dealing with ecological-only models (6 papers) is dedicated to applications of phosphorus budget models, which can above all be used to forecast variations in lake productivity in response to changes in the availability of the limiting nutrient. Graphical abstract

A crisis of lake hypoxia in the Anthropocene: The long-term effects of climate and nutrients

“…We selected Lake Geneva to apply our methodology because of its representativeness as it is one of the most studied and well-known lakes in the world, with a rich high-quality monitoring database spanning over 60 years. In addition, since the 1950s, it has experienced a history of anthropogenic eutrophication followed by re-oligotrophication similar to that of several other lakes over about the same time period 11 . And like other lakes, Lake Geneva faces the ongoing effects of climate change with signi cant warming trends and strengthening thermal strati cation 25 .…”

“…Although other processes such as differential cooling or riverine under ow push towards the use of 3D models (or in some cases 2D models) in large deep lakes because hydro-meteorological conditions are heterogeneous over extensive water surface areas, 1D models can be su cient to represent long-term dynamics and provide a good compromise between accuracy and computational cost, which facilitates model implementation, calibration and simulation, especially at high spatial resolution 19 . Notably, 1D models have proved to be a viable compromise of the representation of physics being able to reproduce the thermal regime with reasonable accuracy in perialpine lakes 11 . Particularly for Lake Geneva, 1D models have been found to be applicable beyond investigations solely of physical processes, but they are su cient to attempt effects-oriented modelling for issues such as water quality in a changing climate 40 .…”

“…This water body, one of the most thoroughly monitored and well-known lake in the world, with a rich highquality database of monitoring data for over 60 years, has experienced a distinct history of changing phosphorus input over the last century similar to that of several other lakes worldwide 11 (see "Methods"). Model forcing data, applied to iconic Lake Geneva, consist of (a) climatic models of air temperature, shortwave radiation, and wind speed derived from the ISIMIP framework 12 comprising a historical period (1850-2014) and future simulations (2015-2100) of three projections based on socioeconomic pathways and forcing levels of the representative greenhouse gas concentration pathways (SSP1-RCP2.6, SSP3-RCP7.0, and SSP5-RCP8.5 12 ); (b) eld measurements of discharge, temperature, and nutrients collected in the main tributary of the lake (Rhone River) over 47 years (1974-2020 13 ); (c) paleolimnological proxies, i.e., preserved Daphnia subfossils (Cladoceran) extracted from well-dated sediment cores that allow the development of a Daphnia-based transfer function to predict volumeaveraged total phosphorus (TP) concentration in the lake water from 1850 to 2018 based on their strong relationship, also referred to as Daphnia-inferred TP 14 ; and d) lake-speci c hypsography 15 .…”

Integration of Water Quantity/Quality Needs with Socio-Economical Issues: A Focus on Monitoring and Modelling

“…Healthy freshwater ecosystems are also necessary for the protection of biodiversity [2]. A global water crisis is currently affecting our planet [3], with impacts even in regions considered rich in water, such as the subalpine areas north and south of the Alps [4,5]. Climate change is also exerting direct and indirect impacts on both water availability and biogeochemical cycles [6,7].…”