Environmental Engineering Reference
In-Depth Information
l
It was necessary to develop a more complex description of the sediment water
exchange than applied initially (Jørgensen et al. 1982).
l
It was necessary to apply a two-step production sub-model of the phytoplankton
involving initial and subsequent uptake and a determination of actual growth by
intracellular mineral nutrient concentrations.
l
A simple Monod kinetics (in analogy to the form frequently used for enzymatic
catalysis) was tested but failed in the verification and calibration phase.
l
The presence of various functional types of zooplankton, herbivores, detrivores
and omnivores was tested and found not to be important.
It was necessary to apply a carrying capacity and threshold values for grazing of
zooplankton.
l
While the initial model was able to simulate the correct level in each compart-
ment, the temporal pattern was not sufficiently met. An additional, intensive
measuring program was set up for a short period covering the spring bloom in
order to calibrate the model involving identification of a proper maximum growth
rate and temperature dependency of the phytoplankton. While temporal density of
data input can be important, it is not recommended to use a temporal resolution
that is too low, as it increases the noise of predictions. In a couple of studies the
model was found to perform relatively well even on other lakes, such as Lake
Balaton and also to perform well when compared with other models (Costanza and
Sklar 1985).
19.3 Further Elaboration of Modelling Techniques Departing
from the Lake Glumsø Model
The Lake Glumsø model served as a blueprint for other lake models. Several model
descriptions were inspired or advanced by pioneering work done at this lake (see
Jørgensen and Bendoricchio 2001). A list of other case studies based on the Lake
Glumsø model is shown in Table
19.1
.
The many applications that have been possible illustrate that the framework is
robust. However, for each case it was necessary to elaborate which additional state
variables and processes were of importance and therefore needed to be incorporated
in order to simulate the system under consideration.
In addition to its function as a basis for advancement in lake modelling, the case
also served as an example to develop new modelling techniques and improve model-
ling approaches. Some of the developments are briefly described in the following.
19.3.1 Discussing the Model Structure
The observed applicability of the model for a broad number of cases sparked a
considerable discussion on what aspects of the lake dynamics were the most
