Der Einfluss von Bodennutzung, Kulturart und Abfluss auf die Wasserqualität von Vorflutern

Wien

1988

S. 189-202

2 Abb., 11 Lit. Ang.

Unselbständiges Werk

200005044

The relationship between run-off from catchment areas characterized by different types of vegetation and land use, on the one hand, and the amount of run-off, on the other, has been the subject of numerous studies. The impact of the type of soll, land-use und crop as well as of the amount of run-off from precipitations on the quality of the draining stream has been studied - in the course of extensive series of measurement - in the framework of a project entitled "The Impact of erosion of nutrients and soll particles on the eutrophication of waters". The relevant publication is part of the cited project. The eroded nutrients and soil particles are part of the total nutrient load of stagnant waters. Within the context of the restoration of the quality of lakes, the magnitude of that factor has become a matter of interest. The removal of substances from a catchment area occurs in three different ways: - leaching of dissolved substances out of the soil and into the ground water; removal of substances deposited on the ground (animal excretions, waste materiais of all kinds, liquid manure, sludges from cesspools, mineral fertilizers, waste waters); - erosion of solid soll particles. The following rates of erosion of nutrients have been determined for particular catchment areas: uncultivated catchment areas (forests, waste lands, swamps): 0,06 kg p total /ha.year, - catchment areas under various types of cultivation 0,20 kg P total/ha.year . In the course of singular events like snow meltings and heavy rainfalls, however, substantially higher amounts of nutrients are carried away: on frozen ground with spreaded manure: up to 3 kg/ha per event; average erosion in the course of snow melting and heavy rainfall: 7 kg/ha.year. The nutrient removal of up to 3,2 kg/ha.year which was determined downstream of a swamp drained in great depth (Bleistätter Moor, Carinthia), constitutes rather an exceptional case. The most significant factors influencing the removal of nutrients are: - type of soll; - type of land-use (type of cultivation and fertilization); - type of crop (vegetation); - precepitation and run-off. Whereas the loss of phosphorus is very small in comparison with that of nitrates when leaching into the underground takes place, the loss of phosphorus becomes significant when erosion and removal occurs on the ground surface, particularly, when the top soll layer has been enriched with phosphorus and made more erodible due to cultivation practices. The significance of the type of crop is demonstrated by the fact that the removal of substances and the rate of run-off are highest on fallow land. The amount of precipitation is of greatest importance in the removal of substances because of its effect of surface erosion and transport; infact, surface run-off and consequently nutrient loads in the streams increase with the magitude of heavy rainfalls.