Catchment integration
In order to estimate base water yields for different areas we considered
that base flows were generated either by the full watershed as defined
by its surface topography (i.e. topographically defined catchment) or,
alternatively, by a more restricted zone that was defined considering
the uniform spacing among the relatively parallel stream lines observed
in the region and recognized as the typical fishbone structures of
sapping erosion regimes (Grau Galofre & Jellinek, 2017). We observed
distinctive regular spacings of 2.6 and 12.5 km in the
higher-intermediate and intermediate-lower belts of the catchment
(respectively upstream and downstream of the rock basement level drop
line, Figure 2A), and used those widths combined with the length of
streams crossing each zone to calculate their contributing area (i.e.
geometrically defined catchment)