Application of a process-based, distributed, hydrological and material transport model to assess water resources and pollute transport in malwathu oya basin, sri lanka

Abstract

The Water and Energy transfer Processes Model – WEP Model is a distributed, physically based hydrologic model that has been coupled with a material transport component. The model uses meteorological, geographical, hydrological data and, data relevant to anthropogenic activities and water quality simulation processes, as inputs. The model is capable of providing time series values of water and heat balance as well as water quality/material transport results for each grid, as outputs. It has been successfully applied to river basins in Japan, China, Korea and elsewhere to study the water resources management options and pollution caused by dissolved and particulate pollutants including the dispersal of excess Nitrogen and Phosphorous introduced by industrial effluents and chemical fertilizers. The present study incorporates a detailed modelling approach to the Nachchaduwa sub-catchment (598.74 km2) of the Malwathu Oya river basin, to study the water resources management options under the effect of varying rainfall patterns and impending climate change impacts. The model can be extended to study the fate and behaviour of the elements (Nitrogen and Phosphorous) which are added to the waterways as a result of the extensive use of agrochemicals in paddy lands in the upstream catchment area. This paper reviews the current state of the catchment as well as the suitability of applying the proposed model to Sri Lanka to assess this basin, which is seasonally stressed due mainly to over exploitation and water pollution. Apart from the water resources management, a quantitative analysis on the fate of excess amounts of agrochemicals used can also be concluded by studying the dispersal and accumulation behaviour of these elements after they have been added to the crop fields and waterways. The findings of the research study will be useful in identifying possible better water management scenarios and managing the fertilizer/agrochemical usage of this catchment in a more pragmatic manner. This study will set the baseline for commencing and continuing quantitative studies regarding studying the behaviour of the pollutants including their conveyance and spatial and temporal accumulation patterns after they have been added to the waterways, in the North Central Province of Sri Lanka