| Title | Relevance of inflows on the thermodynamic structure and on the modeling of a deep subalpine lake (Lake Maggiore, Northern Italy/Southern Switzerland) |
| Abstract | Atmospheric exchanges largely dominate the heat budget of deep lakes in temperate regions. Heat import and export by through-flows is of much lower entity and has been neglected or simplified in many numerical thermodynamic models of lakes. This is often due either to the unavailability of data for inflows and outflows, or to the difficulties in forecasting the evolution of their discharge and temperature in climate change studies. While disregarding through-flows may seem correct, riverine intrusions can bring warmer water than the deep hypolimnetic one to the lower metalimnion and upper hypolimnion, where sunlight does not penetrate and mixing is poor. For holomictic lakes with significant inflow contributions, this can affect the thermal structure at intermediate depths, hampering any numerical model which neglects through-flows. This study focuses on a relevant basin under such aspect, Lake Maggiore (Northern Italy/Southern Switzerland), which drains the rainiest watershed of the Southern Alps. First, we quantify to what extent a one-dimensional fixed-level model ignoring through-flows is able to predict the observed evolution of the thermal structure of the lake and the improvements resulting from reproducing the main inflows and outflows. Then, we directly discuss the influence of through-flows on the thermodynamic structure of Lake Maggiore. The General Lake Model (GLM) was here adopted, reproducing the 1998-2014 period, spanning years with different meteorological and hydrological features. Results show that a calibrated enclosed-lake model can give satisfactory results only if it employs an unrealistically low light extinction coefficient to allow heating of the deep metalimnion and hypolimnion, whose real warming strongly depends on interflows. |
| Source | Limnologica (Jena) 63 (-), pp. 42–56 |
| Keywords | 1D thermodynamic model; Heat budget; Inflow; River intrusion; Lake Maggiore; Enclosed-lake model |
| Journal | Limnologica (Jena) |
| Editor | Elsevier, München, Germania |
| Year | 2017 |
| Type | Articolo in rivista |
| DOI | 10.1016/j.limno.2017.01.006 |
| Authors | Fenocchi A.; Rogora M.; Sibilla S.; Dresti C. |
| Text | 381408 2017 10.1016/j.limno.2017.01.006 Scopus 2 s2.0 85013159181 ISI Web of Science WOS 000401209800007 1D thermodynamic model; Heat budget; Inflow; River intrusion; Lake Maggiore; Enclosed lake model Relevance of inflows on the thermodynamic structure and on the modeling of a deep subalpine lake Lake Maggiore, Northern Italy/Southern Switzerland Fenocchi A.; Rogora M.; Sibilla S.; Dresti C. Department of Civil Engineering and Architecture, University of Pavia, Via Ferrata 3, Pavia, 27100, , Italy; CNR Institute of Ecosystem Study, Largo Tonolli 50, Verbania Pallanza, 28922, , Italy Atmospheric exchanges largely dominate the heat budget of deep lakes in temperate regions. Heat import and export by through flows is of much lower entity and has been neglected or simplified in many numerical thermodynamic models of lakes. This is often due either to the unavailability of data for inflows and outflows, or to the difficulties in forecasting the evolution of their discharge and temperature in climate change studies. While disregarding through flows may seem correct, riverine intrusions can bring warmer water than the deep hypolimnetic one to the lower metalimnion and upper hypolimnion, where sunlight does not penetrate and mixing is poor. For holomictic lakes with significant inflow contributions, this can affect the thermal structure at intermediate depths, hampering any numerical model which neglects through flows. This study focuses on a relevant basin under such aspect, Lake Maggiore Northern Italy/Southern Switzerland , which drains the rainiest watershed of the Southern Alps. First, we quantify to what extent a one dimensional fixed level model ignoring through flows is able to predict the observed evolution of the thermal structure of the lake and the improvements resulting from reproducing the main inflows and outflows. Then, we directly discuss the influence of through flows on the thermodynamic structure of Lake Maggiore. The General Lake Model GLM was here adopted, reproducing the 1998 2014 period, spanning years with different meteorological and hydrological features. Results show that a calibrated enclosed lake model can give satisfactory results only if it employs an unrealistically low light extinction coefficient to allow heating of the deep metalimnion and hypolimnion, whose real warming strongly depends on interflows. 63 Published version http //www.scopus.com/record/display.url eid=2 s2.0 85013159181 origin=inward Fenocchi et al. 2017 Fenocchi et al 2017.pdf Articolo in rivista Elsevier 0075 9511 Limnologica Jena Limnologica Jena Limnologica Jena Limnologica. Jena Limnologica Munchen. Print Jena claudia.dresti DRESTI CLAUDIA michela.rogora ROGORA MICHELA |
