Response of Siberian rivers discharge to disturbance of the forests caused by wildfires

The objective of this work was to perform a quantitative analysis of the correlation between the forest burning index and abnormal decrease in river discharge under conditions of cryolithozone of Siberia. We analyzed the long-term and seasonal variation of rivers discharge in Central Siberia (Nizhnyaya Tunguska and Podkamennaya Tunguska rivers) and in Eastern Siberia (Aldan, Vilyui rivers) together with the forest burning dynamics within the river basins. The data on rivers discharge was obtained from the archive of The Global Runoff Data Centre for 1939–2015. Relative burned area (RBA) index was calculated from wildfires database collected using satellite technique for 1996–2017. RBA was evaluated as ratio of annual burned area within the river basins to the total area of the river basin. RBA values of 2.5–6.1% per year were considered as extremely high. The analysis of available chronologies of extreme fire events in Central and Eastern Siberia showed high correlation (r > –0.55) with long-term data on the runoff minima. Abnormally low level of discharge was 68–78% of the averaged annual rate. The most significant response of river discharge to the wildfire effect was shown for summer-autumn period of season after extreme burning in mid-summer.