Case study on water quality modelling of Dianchi lake, Yunnan Province, South West China

The main aim of this work was to construct and validate a mathematical wate r quality model of the Dianchi lake, so that by altering input total phosph ate (TP) loads the projected changes in the lake water TP concentrations co uld be estimated. Historical information had indicated deteriorating lake w ater quality with increasing TP concentrations. The model was based on a si mple annual mass balance, relying on 3 years (wet, average and dry) data wi th all TP loads quantified, 7 years of lake water quality, and 36 years of flow data. AU lake processes were considered within a single variable, R. P lanning TP removal at STWs and within fertilizer plants, coupled with inter ventions to reduce non-point TP loads from all land run-off by 50%, suggest ed future lake water TP concentrations could be stabilised at about 0.3 mg TP/1, i.e. the estimated limit for producing algal concentrations that woul d cause major problems in water treatment plants. The TP load reductions en visaged as realistic would only stabilise the lake water quality by about t he year 2008; interventions, unfortunately, could not return the lake to it s former pristine condition. The accuracy of the predictions was;+/- 0.1 mg TP/1, so collection of better data was needed. (C) 1999 IAWQ Published by Elsevier Science Ltd. All rights reserved.