Kondratyev S.A., Briukhanov A.Yu., Ignatyeva N.V., Shmakova M.V., Oblomkova N.S.,
Korobchenkova K.D.
The article presents the results of the assessment of the phosphorus load on the largest European transboundary water body — Lake Chudsko-Pskovskoye under the conditions of the minimum flow rate typical for the dry period of 2010–2015. The external phosphorus load was calculated using the nutrient load model ILLM (Institute of Limnology Load Model) developed at the Institute of Limnology of the Russian Academy of Sciences and taking into account the contribution of point and non-point sources. Phosphorous losses from agricultural fields were determined based on the Ptot content in the arable soil layer, application rates of mineral and organic fertilisers, and nutrient uptake by crops. Free-access satellite imagery data was used to estimate the current areas of various types of land cover, which were the input data for modeling. The internal phosphorus load on the lake ecosystem due to the secondary phosphorus release from bottom sediments was calculated by the data from field observations in the water area. The study applied the methodology developed at the Institute of Limnology RAS and based on balance estimates of the main fluxes of phosphorus, such as sedimentation, burial, and release into the water from bottom sediments, in the “water–bottom” boundary zone. The study demonstrated that under the conditions of the considered low-water period, the internal phosphorus load exceeded the external one, having an adverse effect on the lake eutrophication.
