INTEGRATING IMPACT OF LAND-USE CHANGES INTO CATCHMENT-WIDE NUTRIENT MODELING

摘要

Non point source nutrient pollution remains a major problem within sustainable coastal catchment management. The aim of this study is to provide a decision support tool which can predict the impact of land use changes on water quality in coastal waters. A linked modelling approach was used to integrate land use changes with a water quality model, based on the QUAL2E standard, and the 2D numerical hydrodynamic model HEMAT. The linked model was adapted to conditions in estuarine and coastal waters and applied to the catchments of Carmarthen Bay in West Wales, UK. This approach took into account the assessment of nutrient production rates in the catchment for dry and wet weather conditions, as well as the reactions of constituents passing from the catchment into the coastal basin. A catchment modelling tool was developed, in addition to the coastal model, and with the catchment modeling tool using detailed geographical and hydrological information. The predominant types of land use in the catchment were arable land, improved grassland, rough grazing and woodland. Nutrient loads from these areas were estimated by geographical data (GIS) and export coefficients, which characterize the amount of nutrient losses. Furthermore, economical and ecological effects of land use changes were integrated using an input-output analysis approach. A range of scenarios were simulated involving different river discharges, and reduced nutrient input rates resulting from appropriate measures for land use changes. The quality of the receiving waters was analysed, with the aim being to reduce the environmental risks related to eutrophication. Quantification of the pollutant sources, pathways and sinks into estuarine and coastal waters are likely to assist in minimising these problems.