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Chemical and biological characteristics of the Pühajõgi and Kunda catchments were determined in 1995, 2000 During last ten years the concentration of total nitrogen in the samples of the river water from the Pühajõgi catchment has decreased on the average almost 90% since four mines were closed. The concentrations of total nitrogen in the water samples of the Kunda catchment decreased on the average ca 20% during these ten years. The conductivity values of the river water samples of the Pühajõgi catchment between 800 and 1800 µS cm -1 indicated a significant amount of ionic species in the river water. The water was microbiologically unpolluted according to the results of the analysis in 2005.

We determined the incoming fluxes of total organic carbon (TOC), dissolved inorganic (DIC) and organic carbon (DOC), nitrogen, phosphorus, and silicon via four main inflows into Lake Võrtsjärv and compared these with the outgoing fluxes from the lake during 2008-2009. The discharge and loads of the studied substances from the four main rivers alone were higher than the amounts carried out of the lake in 2008. In 2009, the outflow of water exceeded the inflows and this was the case with the amounts of TOC, DIC, and DOC as well. However, the incoming load of nutrients was continuously higher than the outgoing load. The lake accumulated nutrients (nitrogen, phosphorus, and silicon) irrespective of whether water retention was positive or negative, but the balance between carbon accumulation and carbon emission depended on the lake's water budget.