IGCSE Geography Edexcel - Rivers 1 PDF

Head to savemyexams.com for more awesome resources IGCSE Geography Edexcel 1.1 The Water Cycle & Drainage Basin System CONTENTS 1.1.1 The Hydrological Cycle 1.1.2 The Drainage Basin 1.1.3 River Regime & Hydrographs Page 1 of 8 © 2015-2023 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past...

Head to savemyexams.com for more awesome resources IGCSE Geography Edexcel 1.1 The Water Cycle & Drainage Basin System CONTENTS 1.1.1 The Hydrological Cycle 1.1.2 The Drainage Basin 1.1.3 River Regime & Hydrographs Page 1 of 8 © 2015-2023 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers YOUR NOTES  Head to savemyexams.com for more awesome resources YOUR NOTES 1.1.1 The Hydrological Cycle Characteristics of the Water Cycle The hydrological cycle is a closed system Water is constantly recycled through the system Within the hydrological cycle, there are stores and transfers  Exam Tip Remember there are no inputs and outputs in the hydrological system, only transfers and stores, because it is a closed system. Page 2 of 8 © 2015-2023 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.com for more awesome resources Stores of the Water Cycle Stores are those places where water is held for a period of time. These include: Water in the atmosphere in the form of water vapour or water droplets in clouds Surface stores such as puddles, lakes, rivers and reservoirs Interception is how precipitation is prevented from reaching the ground, usually by being caught on leaves or branches Aquifers are permeable rocks such as limestone and sandstone which can hold water Ice and snow Seas and oceans Transfers of Water Within the Cycle Transfers are the ways in which water is moved around the hydrological cycle. They include: Evaporation Condensation Transpiration Evapotranspiration Precipitation Overland flow Infiltration Percolation Through flow Groundwater flow  Worked Example Identify the statement that best defines through flow (1) A Water moving through the soil Water taken up by plants from the soil and released into the B atmosphere as water vapour C Movement of water over the ground D Movement of water through rocks Answer: A (1) -Through flow is the water moving through the soil below the surface and above the water table  Exam Tip Try sketching the hydrological cycle from memory. Remember to add a key to show stores and transfers. Page 3 of 8 © 2015-2023 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers YOUR NOTES  Head to savemyexams.com for more awesome resources YOUR NOTES 1.1.2 The Drainage Basin The Drainage Basin A drainage basin is an open system Every drainage basin is unique and is different in shape and size, with different rock types, relief and land use Drainage basin features All drainage basins have some features in common: Watershed Source Confluence Tributary Mouth Channel network Every drainage basin is covered by a network of tributaries which connect to the main river channel. The numbers of tributaries in a drainage basin is referred to as the drainage density: Drainage basins with lots of tributaries have a high drainage density Drainage basins with few tributaries have a low drainage density  Exam Tip You need to ensure that you are clear about the difference between a closed system such as the hydrological cycle and an open system such as a drainage basin. Remember a closed system has no inputs or outputs whereas an open system has both inputs and outputs. Page 4 of 8 © 2015-2023 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.com for more awesome resources YOUR NOTES 1.1.3 River Regime & Hydrographs River regimes River Regimes & Storm Hydrographs The discharge of a river changes over time The river regime is a record of these changes over a year Many factors can influence the river regime including temperature, vegetation, land use and human activity Storm hydrographs A storm hydrograph shows the changes in river discharge after a storm event The graph shows a short period of time, usually 24 hours The storm hydrograph has a number of features: Base flow Peak rainfall Rising limb Peak discharge Lag time Recessional limb Storm hydrograph in an urban area Page 5 of 8 © 2015-2023 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.com for more awesome resources  YOUR NOTES Worked Example Study Figure 1 which shows storm hydrographs for rivers A and B River A River B Figure 1 Storm Hydrographs What is the lag time for river A? (1) To work out the answer you need to calculate the difference between the peak rainfall and peak discharge: The peak rainfall is between 2 and 3 hours from the start of the storm, taken at the mid point this would be 2 hours and 30 minutes. The peak discharge is at 8 hours from the start of the storm 8 hours - 2 hours and 30 mins = 5 hours and 30 mins Answer Lag time = 5 hours and 30 mins (1)  Exam Tip Remember a hydrograph shows the changes in discharge over a short period after a storm event, whereas the river regime shows changes in discharge over a long period, usually a year. Page 6 of 8 © 2015-2023 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.com for more awesome resources Factors Affecting Regimes There are many factors which affect the discharge or regime of a river The shape of storm hydrographs is also affected by these factors Factors which increase overland flow lead to: shorter lag times increased discharge steeper rising limb Factors which Influence River Regimes Factor Climate Effect Snow and ice melt leads to higher discharge - usually in the spring months High temperatures increase evaporation and reduce river discharge Higher rainfall in autumn and winter increases river discharge Convectional rainfall in summer or hot, moist climates increases river discharge Vegetation Vegetation increases interception and infiltration leading to reduced overland flow and so lower river discharge Deciduous trees lose their leaves in winter decreasing interception, increasing overland flow and river discharge Land Use Concrete and tarmac in urban areas and built environments are impermeable leading to high overland flow - this is rapidly taken by drainage systems to the rivers/streams, increasing river discharge Geology Permeable rocks increase infiltration and percolation which reduces overland flow and decreases river discharge Soils Soils which are compacted or frozen reduce infiltration, increasing overland flow and river discharge Abstraction Water taken for irrigation and domestic use decreases the river discharge Dams Relief Dams control the flow of water, so can both increase and decrease river discharge Reservoirs experience higher levels of evaporation which can decrease river discharge Steep slopes increase overland flow which leads to increased river discharge Page 7 of 8 © 2015-2023 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers YOUR NOTES  Head to savemyexams.com for more awesome resources Drainage Density  High drainage density leads to increased discharge, particularly after a rainfall event Exam Tip Remember all the factors which affect river regimes also affect the risk of flooding. Any factor which increases overland flow and discharges also increase the risk of flooding. Page 8 of 8 © 2015-2023 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers YOUR NOTES 