Observed river discharge data is an important
component to the evaluation of any model
dealing with regional water balance.  As a
result, the project has been actively
assembling a comprehensive river discharge
database for the study region.  Comparisons to
other discharge databases are shown in Table 1. 
Of particular importance to the regional water
balance estimates are the number of large
gauges for drainage basins greater than 15,000
km.  It is these which will be used for model
comparison.  Figure 1a shows the spatial
distribution of the UNESCO gauges and Figure 1b
shows the distribution of the large gauges from
the new data set.  The density of gauges has
increased by an order of magnitude over our
previous holdings. 


In order to compare water balance simulations
over the pan-Arctic region it is necessary
to generate a surface topology of the entire
land mass draining into the Arctic Ocean.  This
allows the modelled runoff calculations to be
'cascaded' downstream from each grid cell to
the Arctic Ocean. Figure 1 (a,b) shows such a
digital river network (STN-30) which connects
all 1/2 degree (latitude x longitude) grid
cells.  The creation of the river network is a
two-step approach which uses automated methods
to generate the initial network followed by
extensive human intervention to make
corrections.  Figure 2 shows a graph of
drainage areas given by the database (observed)
and reported by STN-30 before manual editing
(a) and after editing (b).  The information
content of the digital elevation models is
insufficient to automatically generate a river
network for this part of the globe.  Figure 1
also shows the boundaries of the different
Arctic seas as well as the land surface
elevation.