Water Lesson 3: Drainage Basins Flashcards
Define drainage basin
The area of land drained by a river and its tributaries. This area can also be referred to as the rivers catchment area.
What type of system is a drainage basin?
Open system
External inputs and outputs that cause the amount of water in the basin to vary over time
Define watershed
The boundary of a drainage basin. This is usually a ridge of high land which divides and separates the water flowing into different rivers
Effect of climate on drainage basins
Influencing the type and amount of precipitation overall and the amount of evaporation. This also has an impact on the vegetation type
Effect of soils on drainage basins
Determines the amount of infiltration and throughflow and, indirectly, the type of vegetation
Effect of geology on drainage basins
Impact on subsurface processes such as percolation and groundwater flow (and therefore aquifers). It also indirectly alters soil formation
Effect of relief on drainage basins
Altitude can impact on precipitation totals. Slopes can affect the amount of runoff
Effect of vegetation on drainage basins
Presence or absence of vegetation has a major impact on the amount of interception, infiltration and occurrence of overland flows, as well as on transpiration rates
Name 3 human factors affecting drainage basins
-Deforestation
-Changing land use
-Over abstraction
Describe the effect of deforestation
Areas of dense vegetation mean that rates of interception and evapotranspiration is high. This causes high humidity and heavy local convectional rainfall
Removing this vegetation disrupts this cycle, reducing evapotranspiration and therefore precipitation in the area. This results in an increase in runoff and river discharge
Which river in the Amazon increased in discharge by how much between 1960-97 coinciding with increased rates of deforestation?
Tocantins River
25% increase in discharge
Describe the effect of changing land use
Increase of urbanisation creates impermeable surfaces that reduce infiltration and increase surface runoff and throughflow through artificial drains, resulting in the rapid increase of stream and river discharge as water takes less time to flow to the channel
Where flooded in the UK in 2014?
Winchester and Maidenhead
Where flooded in the UK in 2015?
Carlisle, York and Manchester
Describe the effect of over abstraction
World population increases there is a higher demand for water supplies.
In some locations, groundwater is abstracted from aquifers faster that it is replaced, causing a reduction in ground water flow and a lower water table
