In natural lakes, where thermal stratification hinders complete mixing, the theoretical value T 0 of the water renewal time provides a low-order approximation to the time T 37 when 37% of the original water is still present within the lake; this time could be operatively regarded as the actual value of the water renewal time. In this paper, we present a simple nonparametric model to estimate the age distribution of water within stratified natural lakes, taking into account fundamental aspects of its mass exchange and ther- mal evolution. This distribution provides a straightforward way to compute T 37 . The model is presented as a system of ordinary differential equations along with a MATLAB script for its numerical solution, so that it can be easily applied to lakes where a minimum of limnological data are available, without the need of extensive meteorological data set and modeling expertise that an hydrodynamic model would require to the same purpose. The case of a deep oligomictic Italian prealpine lake (Lake Iseo) is considered: after a pos- itive comparison with the results obtained using a 1-D lake hydrodynamic model, the reiterated application to the available time series allows to approximate the water age probability distribution. This distribution is used to compute the actual value of the water renewal time, that resulted T 37 5 1.6T 0 .
A simple approach to the evaluation of the actual water renewal time of natural stratified lakes
PILOTTI, Marco;VALERIO, Giulia
2014-01-01
Abstract
In natural lakes, where thermal stratification hinders complete mixing, the theoretical value T 0 of the water renewal time provides a low-order approximation to the time T 37 when 37% of the original water is still present within the lake; this time could be operatively regarded as the actual value of the water renewal time. In this paper, we present a simple nonparametric model to estimate the age distribution of water within stratified natural lakes, taking into account fundamental aspects of its mass exchange and ther- mal evolution. This distribution provides a straightforward way to compute T 37 . The model is presented as a system of ordinary differential equations along with a MATLAB script for its numerical solution, so that it can be easily applied to lakes where a minimum of limnological data are available, without the need of extensive meteorological data set and modeling expertise that an hydrodynamic model would require to the same purpose. The case of a deep oligomictic Italian prealpine lake (Lake Iseo) is considered: after a pos- itive comparison with the results obtained using a 1-D lake hydrodynamic model, the reiterated application to the available time series allows to approximate the water age probability distribution. This distribution is used to compute the actual value of the water renewal time, that resulted T 37 5 1.6T 0 .File | Dimensione | Formato | |
---|---|---|---|
WRR_2014.pdf
solo utenti autorizzati
Tipologia:
Full Text
Licenza:
DRM non definito
Dimensione
4.25 MB
Formato
Adobe PDF
|
4.25 MB | Adobe PDF | Visualizza/Apri Richiedi una copia |
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.