title: Changes in nutrient emissions, fluxes and retention in a north-eastern European lowland drainage basin.
abstract: Despite dramatic reductions in the 1990s of N and P emissions in the drainage basin, Lake Peipsi/Chudskoe (Estonia/Russia) is still suffering from algal blooms, probably caused by low N:P ratios of the lake water. To quantify the sources and changes of N and P inputs to the lake as a result of economic changes, we modelled emissions, transfer and in-stream retention using a GIS model. The model was calibrated using river monitoring data from the 1985-1989 period, and used to simulate emissions and loads for five future scenarios for 2015-2019. During the 1985-1999 period, diffuse P emissions decreased relatively more than N diffuse emissions, but this was not reflected in the loads to the lake. P loads decreased relatively less than N loads, which caused a decrease in the N:P ratio of the rivers. About 30-45% of diffuse N emissions and only 3-10% of diffuse P emissions reaches the river network. In-stream retention reduces N and P loads to the lake by about 62% and 72%, respectively. Point sources contribute negligibly to the N load to the lake, but form about one-third of the P load. A target/fast development scenario is the most likely scenario for the 2015-2019 period, resulting in higher nutrient loads than in recent years. We conclude that effective load reductions can be achieved by focussing on diffuse N and P emissions close (< 50 km2) to the lake and by upgrading P removal capacity in wastewater treatment plants of towns.
authors.affiliation: Department of Physical Geography, Faculty of Geosciences, Utrecht University, PO Box 80115, 3508 TC, Utrecht, The Netherlands. d.mourad@geo.uu.nl
authors.forename: Daniel S J
authors.initials: DS
authors.lastname: Mourad
authors.forename: Marcel
authors.initials: M
authors.lastname: Van Der Perk
authors.forename: Kristjan
authors.initials: K
authors.lastname: Piirimäe
mesh_terms: D004957:Estonia; D005068:Eutrophication; D009584:Nitrogen / Q000032:analysis; D010758:Phosphorus / Q000032:analysis; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D014874:Water Pollutants, Chemical; D010758:Phosphorus; D009584:Nitrogen