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There are four key physical characteristics that have an impact on the Colorado River basin.

Climate

• north/south divide in terms of temperature and rainfall
• much of the lower basin experiences very high temperatures of 40˚ C or more
• months of extremely high summer temperatures in much of the basin leads to excessively high rates of evaporation
• total rainfall is low and unreliable
• river flows in a largely desert region, much receiving less than 250 mm rainfall per annum
• rainfall is seasonal, with thunderstorms and flash flooding a possibility

Rock types

• mainly sedimentary rock, such as sandstone
• high temperatures lead to expansion and contraction of the rock, which opens up rock fissures
• the resulting landscape is stunning

Soils and vegetation

• the soil is a thin, red desert soil
• the soil is unable to support much vegetation

River flow

• flow is seasonal - the river is fed by spring melt water
• rainfall in the system is unpredictable