RBM

What do I need to know?

Describe & Explain The Distribution Of River Basins & Rivers In The USA

Explain Water Supply Issues For A River BasinIn North America & Why A Management

Scheme Was Needed

Explain The Physical & Human Factors InvolvedIn Choosing A Site For Dams/Reservoirs

Explain Impact Of Management Schemes On The Hydrological Cycle Of Your Chosen River Basin

Explain The Political Problems Resulting From The Management Schemes On Your Chosen River Basin And Discuss How Political Issues May Hinder Such

Projects

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Describe & explain the social, economic & environmental effects of the water control project

and assess its impact in these terms

Describe & Explain The Distribution Of River Basins & Rivers In The USA

1

• There are no major rivers in the North Due to the Desert Conditions.

• The Nile Flows Northward from it’s source in the wetter Ethiopian mountains and Lake Victoria.

• Main Rivers flow east or west apart from Nile that flows North

• Nile flows into the Mediterranean. Other rivers flow into Atlantic apart from Zambezi and Limpopo which flow East to the Indian Ocean.

• The Niger, Volta and Benue are influenced by the seasonal rainfall of the ITCZ.

• Mackenzie River flows North to the Arctic Ocean and is fed by spring snow melt.

• Rocky Mountains form major watershed.

• Columbia and Colorado drain West to Pacific. Mississippi flows South to Gulf of Mexico

• The St Lawrence flows East from the Great Lakes into the Atlantic. There are a greater number of rivers flowing to the Eastern part of the USA as it receives more precipitation. This is because wet air is driven into the Gulf of Mexico by North East Trade Winds

Remember that these winds also drive the canaries current to the Equator and

the Northern equatorial current to the Caribbean (Gulf Of Mexico).

For North American river basins: • description should include reference to general

patterns/numbers of rivers, and should refer to the directions of flow

• explanation should refer to the fact that drainage basins are determined by the location of the main continental watersheds and that major rivers rise in the main mountain ranges that have greater precipitation, eg the Rockies and Appalachians in North America.

Patterns within North America could distinguish between:

• west flowing rivers are fed from the western side of the continental divide. Rivers like the Columbia-Snake and the Colorado flow west in to the Pacific Ocean

• north-flowing rivers drain to the Arctic Ocean or to Hudson Bay and are fed from the Canadian Shield

• the St Lawrence system is fed from the Great Lakes areas and flows east to the Atlantic Ocean

• most of south-eastern USA is dominated by the Mississippi and its tributaries which are fed from the Rockies in the west and the Appalachians in the east and flow to the Gulf of Mexico.

• Source of most major rivers is in the Himalayas.

• Rivers mainly flow North to Arctic Ocean or South to Pacific / Indian Ocean

2Explain Water Supply Issues For A River Basin

In North America & Why A ManagementScheme Was Needed

A need for RBM

Flooding

Droughte.g Colorado

River

Precipitation in Upper Basin

Distribute to other drier areasMonsoon

Seasons

Store water run offIn wet season

High temperatures resulting in evaporation in dry season

Navigation

Ships and trade

Tourism

Industry

Lake Mead is a majorTourist attraction:

Fishing,Water sports,

relaxing

H.E.P

Irrigation for farming

Increased food supply required for expanding cities

Population

Domestic use in cities Drinking, swimming pools, bathing

Rivers prone to floodingIn south USA due to

trop storms

Provide electricity tonearby cities

Pollution

Sustainable managementOf all river users

• When answering this question use the mind map as a structure. You also need to consider all the information they give you in maps/diagrams and charts. This will give you clues about what you should focus on and the points you should expand to gain more marks

3 Explain The Physical & Human Factors InvolvedIn Choosing A Site For Dams/Reservoirs

• solid foundations for dams • consideration of earthquake and underground movements • cost of compensating farmers and home owners • impact on communications. • narrow cross-section to reduce dam length • large, deep valley to flood behind dam• impact on hydrological cycle. • cost of construction • proximity of urban areas for water and electricity • proximity of agricultural areas for irrigation • cost of displacing people • impermeable rock beneath reservoir • sufficient water supply from catchment area • low evaporation rates, due to small surface area of reservoir

Use these factors to complete the dam diagram

4 Explain Impact Of Management Schemes On The Hydrological Cycle Of Your Chosen River Basin

Impact Of Management Schemes On The Hydrological Cycle Of Your Chosen River Basin

Considerations

Discharge Reduced Groundwater

EvaporationEvapo-transpiration

Discharge Controlled

Hydrological Cycle

• Storing large amounts of water will effect the hydrological cycle as infiltration will increase, evaporation will increase and surface run off will be decreased.

Hydrological Cycle

Hydrological CycleInfiltration

• Large areas of water such as Lake Mead over porous sandstone increase infiltration rates.

• Red Desert and Grey-Brown Podzol soil allow infiltration so have decreased water available for surface run off.

Evaporation• Lake Mead has a

surface area of 157,900 sq miles.

• Summer temperatures over 30 degrees.

• Huge surface area in hot climate increases evaporation rates.

• High evaporation results in 2 million cubic metres being lost from Lakes Powell and Mead.

Water table• The Colorado can no longer meet the growing

demand and water is drawn from underground sources.

• In some areas the water table is being lowered by over use of ground water.

Evapotranspiration

• Increased irrigation has led to more vegetation.

• Evapotranspiration has increased and therefore decreased the surface run off.

5Describe & explain the social, economic &

environmental effects of the water control project and assess its impact in these terms

• Use the sample answer given to you to complete the social/economic/environmental circles exercise

6

Explain The Political Problems Resulting From The Management Schemes On Your Chosen River Basin And Discuss How Political Issues May Hinder Such

Projects

• Mark the sample answer given to you. There should be more than 10 marks to be awarded.