Aquatic Sciences Meeting, Albuquerque 2001

SS40 Long-Term Research Programs in the Twenty-first Century (Spatial and Temporal Connections)

Date: Thursday, February 15, 2001, Time: 10:45:00 AM

Location: Ruidoso/Pecos

Zobrist, J, , Swiss Federal Institute for Environmental Science and Technology (EAWAG), Duebendorf, Switzerland, zobrist@eawag.ch

Hari, R, , Swiss Federal Institute for Environmental Science and Technology (EAWAG), , Duebendorf, Switzerland, hari@eawag.ch

Schoenenberger, U, , Swiss Federal Institute for Environmental Science and Technology (EAWAG), , Duebendorf, Switzerland, uschoene@eawag.ch

Sigg, L, , Swiss Federal Institute for Environmental Science and Technology (EAWAG), , Duebendorf, Switzerland, sigg@eawag.ch

TRENDS IN CHEMICAL PARAMETERS OVER 25 YEARS IN SWISS RIVERS

Analysis of the data set gained by the national long-term monitoring program revealed changes in concentrations and fluxes caused by natural processes or/and anthropogenic factors. Concentrations of most water constituents reveal a marked annual periodicity and exhibit often a better correlation to water temperature than to water discharge. A slight (except P), but statistically significant increase in water temperature, Mg and K and a decrease in Ca and P concentrations is estimated at all 15 stations. The weathering rates in alpine watersheds (mainly calcareous rocks with some gypsum and silicates) remain constant. In rivers downstream from the lakes bordering the Alpes, alkalinity, total hardness and SO4 concentration stay constant, but their fluxes decrease due to diminishing water discharge. Concentrations of H4SiO4 also decrease due to re-oligotrophication of the lakes. The distinct reduction in P loads reflects the P-ban in household detergents and the improved P-removal in wastewater treatment. In contrast, measures taken recently in agricultural practices only show a flattening of the earlier observed increasing trend in NO3 concentrations and loads.

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Aquatic Sciences Meeting, Albuquerque 2001

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