Page 1 8 th International Perspective on Water Resources and the Environment Sri Lanka, 4-6 January, 2016 PHOSPHORUS MODELS FOR HATIRJHEEL LAKE Islam, M. M. 1* , Siddika, A. 2 , Afrin, S. 3 & Rahman, M. M. 4 1* Md. Maksimul Islam, Lecturer, Department of Civil Engineering, Bangladesh University of Engineering and Technology (BUET), Dhaka-1000, Bangladesh; PH: +8801712225389; FAX: +88029665639; email: maksimulislam075@gmail.com 2 Afsana Siddika, Student, Department of Civil Engineering, BUET, Dhaka-1000, Bangladesh; PH: +8801687026496; email: afsana_jui41@yahoo.com 3 Sadia Afrin, Lecturer, Department of Civil Engineering, BUET, Dhaka-1000, Bangladesh; PH: +8801915213462; FAX: +88029665639; email: sadiaafrinbuet@gmail.com 4 Md. Mujibur Rahman, Professor, Department of Civil Engineering, BUET, Dhaka-1000, Bangladesh; PH: +8801755655424; FAX: +88029665639; email: mmujib4@gmail.com ABSTRACT This paper aims at simulating two Phosphorus models to assess their suitability to use for Hatirjheel which is one of the largest lakes of Dhaka City, the capital of Bangladesh. Two empirical models- the Reckhow model and the Vollenweider model were used in this study which are based on the contribution of Phosphorus resulting from different land patterns. Various land patterns within the catchment of the lake were identified and digitized using geographic information system. Maximum likelihood supervised classification system was used to classify different land uses and determine contributing areas. To validate the model results several samples were collected from different locations of the lake in two separate time periods and Phosphorus concentration of those samples were evaluated in the laboratory. The average Phosphorus concentration was found to be close to those obtained from the models. This suggests that Reckhow and Vollenweider models could be used for Phosphorus modelling for the lakes in Bangladesh. This is important as study related to Phosphorous modelling of lakes has not been accomplished in the country yet. Moreover, the outcome of the study was used further to assess tropic condition of Hatirjheel Lake as Phosphorus is considered as a key element to accelerate eutrophication process. The Hatirjheel Lake can be termed as hyper-eutrophic based on its high Phosphorus content indicating excessive biological productivity within the lake probably due to extreme human