Geography Reference
In-Depth Information
E
P
E/P = 1, arid, water limited
E = E p
humid,
energy
limited
1
Budyko curve all
world catchments
E p
P
0
< 1
1
> 1
Af
Am
Aw
Bwh
BWk
BSh
BSk
Csa
Csb
Cwa
Cwb
Cfa
Cfb
Figure 3.3. Placing a catchment in its climatic regime enables a first-order assessment of its energy and water balance at coarse time scales.
(Left) Revised Koeppen classification with location of Olifants basin in Southern Africa marked as a dot on map. From Peel et al.( 2007 ). (Right)
Budyko curve showing the relationship between evaporation index (E/P) and aridity index (E P /P).
Figure 3.4. National stream gauge networks
in Ethiopia and Austria.
be the main activity for many large-scale studies (espe-
cially at national scale).
Typically, there will also be information on the physical
characteristics of the catchment that can be used for system
characterisation. Topographic maps can be used to ascertain
catchment size, shape, morphology and drainage density.
Soil information including depth and texture, as well as
surface characteristics, can be gained from maps and trans-
lated into hydrologically relevant information, e.g., through
using pedo-transfer functions. Many countries will also
possess maps on eco-regions (or land use or vegetation
cover) and on geology, which can be used for a first-order
assessment of catchment characteristics. It is important to
remember that these maps will not be able to fully describe
the extent of natural variability that is likely in specific
locations. Local observations will be necessary to utilise
vegetation patterns as indicators of moisture stability and
landscape heterogeneity (including erosional patterns) that
can inform the nature of water redistribution processes.
3.2.3 Assessment based on local field visits including
reading the landscape
Despite the high value of remotely sensed observations and
analyses, the relative strength of different hydrological
processes and dominant runoff generation mechanisms
 
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