| Summary: | In the search for the proper spatial
and temporal resolution at which
to manage natural resources, we
are generally guided by the flows and
stocks of water that we can ‘see’ – rainfall,
flowing water, reservoirs, dams,
etc. We use what we observe to identify
the socially optimal flows/stocks
of water, and then suggest the public
policy action required to achieve
these results. However, there are also
some ‘invisible’ factors that need to be
included in policy discussions related
to water management; one important
invisible factor is groundwater (the
focus of this brief).
The bad news is that groundwater
is ‘invisible,’ hence stocks and flows of
it are more difficult to measure. The
good news is that we are discovering
ways to more cheaply measure
groundwater stocks/flows and to predict
the spatial and temporal effects
of groundwater extraction. The SFRB
research team has developed a demonstration
model capable of examining
these effects, and what follows is
derived from simulation experiments
using that model in the Buriti Vermelho
sub-catchment area located
near Brasilia.
The Buriti Vermelho
Sub-Catchment Area
The Buriti Vermelho (BV) sub-catchment
area is a small watershed
comprised of several
types and spatial extents
of farming activities.
Figure 1 depicts the BV
site; the precise boundaries
of the sub-catchment
area are given
by the thin black line.
Water emerges from
about the south-central
part of the site, just
outside the green patch
of cerrado típico (savanna
forest) and flows from
south to north. Blue
circles identify the
location and size of
capital-intensive centerpivot
irrigation schemes,
while yellow rectangles
identify small farms. Large patches of
rainfed agriculture remain in the
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