Trend detection in water-quality and load time-series from agricultural catchments of Yläneenjoki and Pyhäjoki, SW Finland

• Published in: Boreal environment research 2016-04, Vol.21 (1-2), p.166
• Main Authors: Gonzales-Inca, C A, Lepistö, A, Huttula, T
• Format: Article
• Language: English
• ISSN: 1239-6095; 1797-2469

Long-term water quality (WQ) and load trends were studied in the catchments of Yläneenjoki and Pyhäjoki in SW Finland, where agricultural water protection measures have been implemented since the mid-1990s. A univariate Mann-Kendall (MK) trend test, a multivariate Mann-Kendall (MMK) trend test, and a multivariate Mann-Kendall trend test applied to the WQ data flow-normalized by a semi-parametric model (FN-MMK) were used. The results of all methods were similar when the nutrient concentration data were used, but they differed when using the nutrient load data. The FN-MMK test was intended to detect trends caused by anthropogenic impact. In the clay-soil-dominated catchment of Yläneenjoki there were increasing trends in the concentrations and loads of total nitrogen, nitrate-nitrogen, dissolved reactive phosphorus, and a decreasing trend in suspended solid concentrations. However, no increasing or decreasing trends were detected for the majority of the concentrations or loads in sand-soil-dominated catchment of Pyhäjoki. This suggests different responses to comparable environmental and anthropogenic pressures in these two river basins.