Spatial-temporal variability of algal bloom in the Dnipro Reservoirs

Abstract

Using the remote sensing data, first of all, the data of Terra and Aqua satellites, the spatial-temporal patterns of algal bloom in the Dnipro Reservoirs were established. The greatest growth of algae is observed in the Kremenchuts’ke, the smallest — in the Kyivske reservoirs. The reasons for these patterns are formulated. In particular, the growth of algae in the Kyivske Reservoir, primarily in its northern part, is restricted with the significant water colour, the inflow of solid runoff and the relatively low water temperature. A smallest algal bloom during 2013–2018 was observed in 2013. It was caused with a rather large water runoff of the Dnipro River and with significant water colour as well. In addition, the increasing of algal bloom was negatively affected with a significant cloudiness in the second half of summer, when the of algal bloom usually is the greatest. The algal bloom was significant in 2015–2016, which was caused with small water runoff and small water colour. For 2013–2018 the dates of algal bloom beginning and maximum increasing of algae were established. This is usually observed in August when warm, and most importantly, sunny weather occurs. An abnormally late algal bloom was observed 19–22.09.2018, which was facilitated with the corresponding weather. It has been revealed that under favorable conditions, the view of water surface can change significantly during one day. Such rapid changes can not be caused by changes in water temperature, since they are not sharp in the reservoirs. The wind has a great impact on the distribution of algae by water area of the reservoirs. It is able to shift the zone with the largest bloom in any direction. The predominance of the north-eastern wind over the Kremenchuts’ke and Kam’yanske reservoirs in July-August leads to the fact that the greatest algal bloom is observed near their right south-western bank.