Korea is a land-limited country and large-scale polder projects have been practiced to dike, drain, and reclaim coastal tidelands to develop additional agricultural land and water resources during the last decades in Korean peninsula. After closure of the dikes, much pollutant loads from the watershed has been transported by streams and ditches to the estuarine reservoir, and most estuarine reservoirsaresufferingfromeutrophicationinKorea.