What Is: GRAR?

Russia is big, really big, and to go with that, it has some very big rivers. The majority of the Russian river outflow is into the Arctic Ocean, especially in the central and eastern parts of the country, and this is generally concentrated into a series of very large rivers. The largest of these are known as the Great Russian Arctic Rivers (GRARs). From west to east, these are the Ob, Yenisety, Lena, Indigirka and Kolyma, of which the Ob and Lena are largest, and Indigirka the smallest (small enough to not count in some people’s list of GRARs).

Catchment areas of the Great Russian Arctic Rivers
Catchment areas of the Great Russian Arctic Rivers

The Ob river is the world’s fifth-longest and has the sixth-largest drainage basin, yet has only the 19th highest annual discharge, being overtaken by the smaller Yenisey and Lena rivers to the east of it. All of these river basins contain some permafrosted land, which can reduce discharge during the winter months and have a very large flood-period in late spring / early summer when the meltwater arrives (the “freshet”).

Permafrost within catchments of the GRARs
Permafrost within catchments of the GRARs

As the amount and continuity of permafrost increases from west to east, so the proportion of each permafrost type increases within the river basin. The Ob and Yenisey are largely free of continuous permafrost, allowing water to flow through the ground to the bedrock and into the river, whilst the Indigirka and Kolyma are practically 100% continuous permafrost, and thus any water discharging will have run along the top of the ground before entering the river itself. This can have consequences for the type of material, especially carbon, carried by the rivers.

Proportion of each type of permafrost within river basins
Proportion of each type of permafrost within river basins

This east-west contrast is worth exploring in more detail in a later post, since it shows how Siberia may behave very differently if the permafrost were to thaw. As a final reminder of just how large the rivers are, even the smallest, Indigirka, manages to cover more area than the British Isles! As usual the full-resolution PDFs of the figures from this article can be downloaded here: River catchments no permafrost, Catchments and permafrost, Permafrost chart, Catchments and UK.

Comparing the catchment areas to the British Isles
Comparing the catchment areas to the British Isles

 

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