Changes in nutrients in the Dotnuvele and Smilga streams

Abstract

Due to the intensifying agricultural activity, the leaching of nitrogen and phosphorus compounds from the soil to water has been increasing each year. According to the data of Helsinki Commission, the largest river in Lithuania – Nemunas, which Nevezis flows into, is considered to be one of the nutrient suppliers to the Baltic Sea. The tributaries of the Nevezis River - Smilga and Dotnuvele, collect the water saturated with nutrients from agricultural land, thus degrading the quality of the water of Nevezis, Nemunas and the Baltic Sea. Research data from 2013-2017 has shown that the average Ntotal and NO3-N concentrations in Dotnuvele and Smilga streams’ water in March (12.6 mg l-1, 11 mg l-1 as well as 8.5 mg l-1 and 8.7 mg l-1, respectively), May (11 mg l-1, 9.1 mg l-1 as well as 5.4 mg l-1 and 4.6 mg l-1, respectively), and November (4.5 mg l-1, 8.7 mg l-1 as well as 3.5 mg l-1 and 7.4 mg l-1, respectively) mostly corresponded to a very bad and poor ecological status, and only in August they corresponded to a good and very good water ecological status (2.4 mg l-1, 3.2 mg l-1 as well as 1.1 mg l-1 and 1.3 mg l-1, respectively). Ptotal and PO4-P concentrations in the researched streams’ water were usually low (0.04 – 0.08 mg l-1 and 0.02 – 0.05 mg l-1 in Dotnuvele, 0.03 – 0.08 mg l-1 and 0.01 – 0.03 mg l-1 in Smilga, respectively) and corresponded to a very good ecological status of water bodies, except in August, when the water quality in Dotnuvele was found to be average (0.19 and 0.14 mg l-1).