ABSTRACT
Variation in normal sediments transported in rivers and watercourses, primarily due to excessive utilisation and rapid land use changes in the basin, may threaten sensitive receiving wetlands and lakes. Loss of operational volumes as a result of reductions in supply and disruptions in the performance of wetlands in terms of quality and ecosystem are some of the resulting adverse impacts amongst many. A toolbox has been designed here to address the issue based on sustainability criteria. The toolbox comprises an estimating engine for the sediment transport, namely the SWAT model, a powerful GIS tool and a Multi Criteria Decision Making (MCDM) tool. Flow variations as well as nitrate concentrations would also be investigated alongside sediment quantities for various potential scenarios. Ranking of individual and combined scenarios may be obtained based on decision makers’ priorities while the toolbox has the capability to incorporate various desired sustainability criteria. The toolbox has been utilised for the case of Zarineh-Rud river basin feeding Lake Urmia. Lake Urmia, one of the largest saltwater lakes on earth and a highly endangered ecosystem, is on the brink of a major environmental disaster similar to the catastrophic death of the Aral Sea. Once with a surface area of approximately half a million hectares, Lake Urmia’s shoreline has been receding severely with no sign of recovery, leading to a significant shrinkage in the lake’s surface area currently decreased by around 88%. Lake Urmia is fed by a total of 60 (21 seasonal or permanent, and 39 periodic) rivers with the Zarrine-Rud being the main input, reckoned to provide around 37% of the total inflow into the lake. Evidently sediment transport conditions in Zarine-Rud will have grate impacts both on the morphology of the river course and the sensitive conditions of Lake Urmia. Results obtained using the toolbox indicates that impacts of erosion and sedimentation in river basins and receiving lakes and wetlands may be effectively investigated under various development scenarios thereby providing a decision support tool for operation and planning.
