A global map of mean annual runoff based on discharge observations from large catchments

<p>This report describes the development of a global map of mean annual runoff&nbsp;(MAR) based on discharge observations from 1651 large catchments (10,003 to&nbsp;4,691,000 km²) around the globe. The map was produced based on the assumption&nbsp;that the mean annual volumetric discharge difference between a station and its&nbsp;upstream neighbor(s) represents the MAR generated in the interstation region. The&nbsp;produced map represents a unique spatial estimate of MAR at a global scale useful&nbsp;for, among other things, the spatial evaluation of macro-scale hydrological models.&nbsp;Compared to an equivalent map developed at the University of New Hampshire,&nbsp;the new map (i) is based on substantially more catchments (1651 versus 663),&nbsp;(ii) has a higher resolution (&sim;0.04&deg; versus 0.5&deg;), (iii) covers a larger portion of the&nbsp;hydrologically-active, ice-free land surface (58.9 % versus 56.5 %), and (iv) agrees&nbsp;considerably better with a completely independent MAR map based on small&nbsp;catchments.</p>