Sources and transport of phosphorus in the Vltava River Basin (Czech Republic)

Export and sources of P in the Vltava basin (subbasin of upper Elbe: total area - 28,093 km(2); population density - 115 km(-2); forests - 35%, farmland - 51%) were evaluated during 1972-1993. Annual export rates of total P from the basin to the river Elbe ranged between 38 and 68 kg km(-2) a(-1). Reservoirs with hydraulic retention times longer than 15 days were efficient traps for phosphorus retaining 20 to 30% of total P loading into the watercourses. Point sources (municipal wastewaters) were most important throughout the period and their share varied from approximately 60% in wet years to more than 90% in dry years. Export from diffuse sources (dominated by output from farmland) was highly dependent on discharge and fluctuaded between 5 and 40 kg km(-2) a(-1) in dry and wet years, respectively. Only about 2% of the P input into the basin from the fertilisation of farmland and from the atmospheric deposition was exported to the watercourses. Copyright (C) 1996 IAWQ.