Geography Reference
In-Depth Information
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Figure 4.1
The changes in river discharge over a year for two nearby rivers
with similar rainfall but with different catchment characteristics.
Arid zones, especially in subtropical drylands, tend to experience
very occasional but intense rainfall events. Intense rainfall along
with little vegetation cover produces iniltration-excess overland
flow, rapid runoff and high flood peaks. However, many dryland
soils are coarse and sandy with high infiltration capacities resulting
in little chance of overland flow. Therefore, there is a wide vari-
ation of response even if rainfall intensities are very high. In most
drylands river flow will stop within a few days of the rainstorm and
water often seeps into the river beds or is evaporated.
In temperate, oceanic areas precipitation occurs all year perhaps
with seasonal maximums (see Chapter 1). The river flow regime in
these areas can change in response to either seasonal changes in
groundwater storage and release, or higher evaporation and tran-
spiration rates during the summer months.
Rivers in equatorial areas tend to have a fairly regular regime
while tropical river systems outside of the equatorial areas receive
