Non point source pollution modelling in the watershed managed by Integrated Conctructed Wetlands: A GIS approach.

Abstract

The non-point source pollution has been recognised as main cause of eutrophication in Ireland (EPA Ireland, 2001). Integrated Constructed Wetland (ICW) is a management practice adopted in Annestown stream watershed, located in the south county of Waterford in Ireland, used to cleanse farmyard runoff. Present study forms the annual pollution budget for the Annestown stream watershed. The amount of pollution from non-point sources flowing into the stream was simulated by using GIS techniques; using rainfall, land use and soil data. The product of runoff and concentration gives expected pollutant loading from that area. Two hydrological models, rational method and SCS-CN method were used to simulate annual runoff and literature based pollutant concentration values were used to estimate annual pollution load. Total nitrogen and total phosphorus were simulated by using this method.

The rational method gave good estimation of annual runoff. The reduction in TP load due to presence of ICW system was found to be 53.59 ton/year. Annual runoff contribution of ICW and associated farms was in proportion with their aerial contribution. The study presents simple methods to model annual runoff and pollutant load in ungauged catchments.