River Basin Management Higher Geography

Structure of unit: Characteristics of the Colorado River Basin Need for water management Dam site selection Consequences of water control projects

Introduction to River Basin Management Learning intentions: We are learning about River basin management. Success Criteria: I can describe the characteristics of the Colorado River Basin. https://www.youtube.com/watch?v=xt5uJrWW1gE

Starter Each table has an A4 piece of paper on it. You will visit each table for 1 minute You should write down everything you know! (it doesn’t matter if it is already written) What is it? Why do we need it?

Characteristics of the Colorado river basin A river is a physical feature of the landscape where water is naturally channelled towards a large body of water like the sea or a lake. A river basin is the land area that is drained by a river and its tributaries. However, humans can alter and control this natural channel to use for their own purposes. When this happens we say that the river is ‘managed’. One of the most ‘managed’ rivers in the world is the Colorado River in the USA.

Characteristics of the Colorado river basin The Colorado River basin lies in the south-west of the USA. It is 1450 miles long. Its source is found in the Rocky Mountains, Colorado. The river then flows through Utah, Nevada, Arizona, New Mexico, California & Mexico before entering the Gulf of California.

Physical Characteristics - Climate: There is a north/south divide in terms of climate (temperature & rainfall). In the upper basin rainfall and snowmelt are extremely variable & unpredictable. In the lower basin many areas such as Nevada, New Mexico, California experience high temperatures of 40°C or more. There are months of high summer temperatures which leads to excessively high evaporation rates. The total rainfall is low and unreliable. Most of the river flows through desert areas (e.g. Mojave desert) which receive less than 250mm of rainfall per annum. The rainfall the area does experience is seasonal with thunderstorms and flash floods a possibility.

Physical Characteristics – Rock type: The rock in the Colorado River Basin is mostly sedimentary rock e.g. Sandstone. This rock is made from layers of dead sea creatures compacted under pressure over millions of years. The high temperatures cause the rock to expand and contract resulting in rock fissures. This made the landscape stunning and unusual which is why the Grand Canyon (part of the basin) is one of the Natural Wonders of the World.

Physical Characteristics – Soils and vegetation: The soil is thin, red desert soil. It is unable to support much vegetation resulting in a barren landscape.

Physical Characteristics – River flow: Flow is seasonal as the river is fed by spring melt water. Therefore if there is adequate snowfall in winter, there will high discharge levels. Low snowfall means less water entering the system.

Task Describe the physical characteristics of the Colorado river basin 6 marks

Physical Characteristics – Perfect Answer: In the upper basin rainfall and snowmelt are extremely variable & unpredictable. In the lower basin many areas such as Nevada, New Mexico, California experience high temperatures of 40°C or more. There are months of high summer temperatures which leads to excessively high evaporation rates. The total rainfall is low and unreliable. Most of the river flows through desert areas (e.g. Mojave desert). The rainfall the area does experience is seasonal with thunderstorms and flash floods a possibility. The rock in the Colorado River Basin is mostly sedimentary rock e.g. Sandstone, made from layers of dead sea creatures compacted under pressure over millions of years. The high temperatures cause the rock to expand and contract resulting in rock fissures. This made the landscape stunning and unusual which is why the Grand Canyon (part of the basin) is one of the Natural Wonders of the World. The soil is thin, red desert soil and is unable to support much vegetation resulting in a barren landscape. Flow is seasonal as the river is fed by spring melt water, therefore if there is adequate snowfall in winter, there will be high discharge levels. Low snowfall means less water entering the system.

Plenary Without using your notes Write down 4 Physical characteristics of the Colorado river basin