River regimes Learning objectives: Recap on flood hydrographs Understand infiltration rates and the factors affecting them Understand what a river regime is

Recap: Storm (or Flood) Hydrographs A storm hydrograph shows the changes in river discharge after precipitation has fallen. Peak Rainfall Lag Time Falling Limb Peak Discharge Peak rainfall - discharge - what is lag? - rising - falling Rising Limb

How and why will the hydrographs vary in these two locations?

F D F F D F D F D D F Flashy or delayed? Thin Soils No Dam fields Many tributaries Thick soils Steep Slopes Water extracted from river Gentle slopes Tarmac/ impermeable surfaces F F D F D F D D F

Infiltration rates When water reaches the ground some of the water may seep into the ground  this is INFILTRATION Infiltration rates will affect rivers and people because...

Why will it make a difference to infiltration rates? Factor Why will it make a difference to infiltration rates? Rock Type  whether the rock is permeable (lets water through) or impermeable (does not let water through) If the rocks in the drainage basin are permeable, infiltration will happen _____________ because the water will seep through the rocks. However, if the rocks are impermeable, infiltration might not happen because the water will simply flow over the surface (surface run-off) back to the river. Soil  whether the soil is very thin or very deep. Natural Vegetation  does the area have lots of forests or is it built up? Remember in cities there is lots of tarmac/concrete. Drainage Density  this means how many streams/rivers there are in a drainage basin. High density = lots. Low density = not very many. Relief  how steep/hilly the land is. If the land is very steep, water might not have as much time to infiltrate into the soil; instead it is more likely to run down the side of the mountain back towards the river. However, if the land is flat _____ ____________________________________________________________________________________________________________

Why will it make a difference to infiltration rates? Factor Why will it make a difference to infiltration rates? Rock Type  whether the rock is permeable (lets water through) or impermeable (des not let water through) If the rocks in the drainage basin are permeable, infiltration will happen _____________ because the water will seep through the rocks. However, if the rocks are impermeable, infiltration might not happen because the water will simply flow over the surface (surface run-off) back to the river. Soil  whether the soil is very thin or very deep. Deep soil allows for more infiltration than thin soil because there is more space for the water to seep in. Natural Vegetation  does the area have lots of forests or is it built up? Remember in cities there is lots of tarmac/concrete. Drainage Density  this means how many streams/rivers there are in a drainage basin. High density = lots. Low density = not very many. Relief  how steep/hilly the land is. If the land is very steep, water might not have as much time to infiltrate into the soil; instead it is more likely to run down the side of the mountain back towards the river. However, if the land is flat _____ ____________________________________________________________________________________________________________

Why will it make a difference to infiltration rates? Factor Why will it make a difference to infiltration rates? Rock Type  whether the rock is permeable (lets water through) or impermeable (des not let water through) If the rocks in the drainage basin are permeable, infiltration will happen _____________ because the water will seep through the rocks. However, if the rocks are impermeable, infiltration might not happen because the water will simply flow over the surface (surface run-off) back to the river. Soil  whether the soil is very thin or very deep. Deep soil allows for more infiltration than thin soil because there is more space for the water to seep in. Natural Vegetation  does the area have lots of forests or is it built up? Remember in cities there is lots of tarmac/concrete. Forested areas allow for more infiltration. Water does not seep into the ground when there is concrete and tarmac – it just flows over the surface Drainage Density  this means how many streams/rivers there are in a drainage basin. High density = lots. Low density = not very many. Relief  how steep/hilly the land is. If the land is very steep, water might not have as much time to infiltrate into the soil; instead it is more likely to run down the side of the mountain back towards the river. However, if the land is flat _____ ____________________________________________________________________________________________________________

Why will it make a difference to infiltration rates? Factor Why will it make a difference to infiltration rates? Rock Type  whether the rock is permeable (lets water through) or impermeable (des not let water through) If the rocks in the drainage basin are permeable, infiltration will happen _____________ because the water will seep through the rocks. However, if the rocks are impermeable, infiltration might not happen because the water will simply flow over the surface (surface run-off) back to the river. Soil  whether the soil is very thin or very deep. Deep soil allows for more infiltration than thin soil because there is more space for the water to seep in. Natural Vegetation  does the area have lots of forests or is it built up? Remember in cities there is lots of tarmac/concrete. Forested areas allow for more infiltration. Water does not seep into the ground when there is concrete and tarmac – it just flows over the surface Drainage Density  this means how many streams/rivers there are in a drainage basin. High density = lots. Low density = not very many. If there are lots of rivers/streams, the water is more likely to fall directly into it, or get back to the river quicker. If there are fewer streams, the water is more likely to travel as groundwater, throughflow or surface run off. Relief  how steep/hilly the land is. If the land is very steep, water might not have as much time to infiltrate into the soil; instead it is more likely to run down the side of the mountain back towards the river. However, if the land is flat _____ ____________________________________________________________________________________________________________

Why will it make a difference to infiltration rates? Factor Why will it make a difference to infiltration rates? Rock Type  whether the rock is permeable (lets water through) or impermeable (des not let water through) If the rocks in the drainage basin are permeable, infiltration will happen _____________ because the water will seep through the rocks. However, if the rocks are impermeable, infiltration might not happen because the water will simply flow over the surface (surface run-off) back to the river. Soil  whether the soil is very thin or very deep. Deep soil allows for more infiltration than thin soil because there is more space for the water to seep in. Natural Vegetation  does the area have lots of forests or is it built up? Remember in cities there is lots of tarmac/concrete. Forested areas allow for more infiltration. Water does not seep into the ground when there is concrete and tarmac – it just flows over the surface Drainage Density  this means how many streams/rivers there are in a drainage basin. High density = lots. Low density = not very many. If there are lots of rivers/streams, the water is more likely to fall directly into it, or get back to the river quicker. If there are fewer streams, the water is more likely to travel as groundwater, throughflow or surface run off. Relief  how steep/hilly the land is. If the land is very steep, water might not have as much time to infiltrate into the soil; instead it is more likely to run down the side of the mountain back towards the river. However, if the land is flat water will infiltrate into the ground more easily.

River Regimes Definition: the pattern of a river’s flow over a period of time (usually one year) is the river’s regime.

RIVERS 6: River regimes The pattern of a rivers flow over a period of time (usually a year) is the river’s regime. Several factors affect this regime: Precipitation – amount, type and seasonality. Temperature – affects evaporation and plant growth (and hence transpiration). Water abstraction – domestic and industrial use of water. 4. Dams – control river flow and store water ‘flattening’ the regime.

B A C E D

Answers A – Antelope Creek, USA Climate (4) Mediterranean Description – (V) B - River Thames, UK. Climate (3) Temperate Description – (Z) C- Missouri, USA Climate (1) Mountain, snowmelt Description – (Y) E - River Sonjo, Tanzania Climate (2) Humid Tropical Description – (W) D - River Congo, Congo Climate (5) Equatorial Description – (X)

2. Identify which graph shows the regime of rivers A to D.[3] 1. Define the term river regime [2] 2. Identify which graph shows the regime of rivers A to D.[3] 3. For TWO of the regimes explain your answers to question 2.[6]

3 marks allocated for each regime explained: Answers Define the term river regime [2] Answer: the pattern of a river’s flow over a period of time (usually one year) is the river’s regime. B C A D 2. Identify which graph shows the regime of rivers A to D.[3] 3. For TWO of the regimes explain your answers to question 2.[6] 3 marks allocated for each regime explained: 1-2 marks allocated to an appropriate explanation 1 mark allocated to appropriate reference to the graphs