### Basuki Widodo : *Determining of Pollutant Sources Location At The Confluence of Two Rivers*

Prof. Dr. Basuki Widodo M.Sc.

Abstract

River is a natural water source which is kept from the influence of waste and pollutant. Therefore, the water quality must be maintained in order to not be affected by the pollutants. In a river system, confluence is a very important issued. This is due to the confluence could affect the morphology and hydraulics in upstream and downstream. Nowadays, many discharge of waste from factories to the river which give many negative effects. Coming from the problem, we want to find the coordinate of potentially pollutant in the confluence of two rivers using discretization method, that is MLPG (Meshless Local Petrov Galerkin) method in order that we can get the best result which like the real condition in fact. These result are then simulated using Matlab 7.1. The parameter used are COD, BOD, and the velocity of water flow that is obtained from Perum Jasa Tirta I in Kali Surabaya. The results showed that the spread of pollutant is changed on the value of the velocity and the concentration, because of the difference in location. There are 3 factories which discharged some pollutants in the river. Using MLPG method, we can conclude that there are two factories which is very optimal to give any dangerous pollutants than others.