Analysis of Model and Parameter Uncertainty in Simple Phytoplankton Models for Lake Balaton

Straten, G. van (1980). Analysis of Model and Parameter Uncertainty in Simple Phytoplankton Models for Lake Balaton. IIASA Working Paper. IIASA, Laxenburg, Austria: WP-80-139

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Abstract

The principal aim of the investigation is to analyze the major modes of phosphorus exchange between water and sediment from uncertain data of phosphorus fractions in the water. Based on a priori knowledge two relatively simple models have been postulated. State variables are winter and summer algae phosphorus, detritus phosphorus and orthophosphate phosphorus. Most parameters of the model were estimated or inferred from data from independent measurements. Several sensitive parameters, most of them related to the sediment-water interaction processes remain unknown. In the first model coprecipitation of phosphorus with biogenic lime, sedimentation of detritus and release of orthophosphate from the sediment is accounted for. This model predicts a rise in orthophosphate after the spring and autumn blooms not observed in the data. In the second model a mechanism of adsorption/desorption of phosphate to the sediment or suspended particles is postulated, to account for the remarkable stability of orthophosphate over the year. A Monte Carlo simulation is run to find areas in the parameter space where the model produces results fully within specified boundaries drawn around the data to account for the data uncertainty. Data and forcings from 1977 are used for this purpose. Several parameter combinations were found, and the results were analyzed in terms of the model processes. It is concluded that an adsorption/desorption mechanism is likely to occur, but that various modifications of the postulated model would be desirable. Further analysis using 1976 data is needed. The results suggest that it is worthwhile to perform additional field experiments with lake water and sediments in order to confirm or reject the sorption hypothesis.

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