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ANALYSIS OF LONG-TERM AND SEASONAL RIVER WATER QUALITY CHANGES IN LATVIA
Citation:
Tsirkunov, V., A. Nikanorov, M. Laznik, AND D. Zhu. ANALYSIS OF LONG-TERM AND SEASONAL RIVER WATER QUALITY CHANGES IN LATVIA. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-92/331.
Description:
An analysis of long-term historical records of the concentrations of major ions, TDS and-nutrients for 20 river sites in Latvia is reported. eriods of water quality observations ranged from 15 to 43 years A study of the quarterly adjusted time series showed that characteristic features of the data are non-normal distributions, seasonality, serial correlatIon and presence of significant trends that are mostly positive. The application of state-of-the-art software, based on non-parametric statistics such as the Seasonal Kendall slop.e estimator and the Seasonal Hodges-Lehmann estimator, made it possible to investigate these water quality records more accurately than other methods allow. ypical seasonal variations and concentration-discharge relationships were analyzed for different constituents. t was shown that fertilizer application and marsh land reclamation can cause widespread and intensive river water quality. changes. Concentration increases of as much as 5-10 times that of background values were detected for N03, C1-, Na+ + K+ and S02-4. The main water quality changes took place in the 1960s and the early 1970s when fertilizer applications and reclamation works increased. fter that, concentration increases for constituents other than N03 and S02-4 were statistically insignificant. he significant increases for N03 and SOB-' were probably due to the additional impact of increased atmospheric deposition. he results of long-term changes in river loads entering the Baltic sea and the Gulf of Riga from Latvian territory are examined.