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Freshwater - Drainage Basin - Coggle Diagram
Freshwater - Drainage Basin
Drainage Basin hydrology and geomorphology
A drainage basin is an area of land on which precipitation falls and that water is drained into oceans. A drainage basin is an open system
Inputs
Precipitation
Outputs
Evaporation
Evapotranspiration
Potential Evapotranspiration - dependent on moisture availability and water content of soil
Stores
Vegetation
Interception - water stopped by plants from entering rivers
Throughfall - water that falls through gaps in plants
Stemflow - water that trickles along stems and roots until it enters ground
Soil
Aquifers
Cryosphere - the snow and ice environment
Flows
Infiltration - water soaking/being absorbed by soil
Overland flow
Throughflow - water flowing through the ground and soil
Base flow - throughflow flowing into the bed of a river increasing the discharge
Stream flow
Strength of flow subject to gravity, frictional resistance, shape of channel, depth of channel.
Velocity - velocity is the fastest middle of the river at a third of depth as it is away from the sides as has no surface friction
Channel shape - ideal shape is semicircular and can be measured by calculating the wetted perimeter
Channel roughness - can be increased by irregularities of rock, vegetation, trees etc.
River processes
Erosion
Factors determining rate of erosion
Load
Velocity
pH - increased acidity aids with erosion
Gradient - increased gradient increases rate
Human impact - interference with the flow of water can lead to increased rate
Geology - softer rock is eroded faster
Abrasion
Attrition
Hydraulic Action
Solution
Methods of transport
Saltation
Solution
Traction
Suspension
River regime - annual variation of flow within a river - influenced by amount of precipitation, permeability of rocks, amount and type of vegetation cover
Land formations
Waterfalls 1. Hard rock overlays soft rock 2. The soft rock is undercut by hydraulic action and abrasion 3. The lack of support causes the overlaying hard rock to collapse and fall. 4. This and the constant slamming of water vertically create a plunge pool. 5. This process repeats and creates a gorge over time
Floodplains 1. When river slows down and alluvium and silt is deposited
Levees 2. Over hundreds of years, silt and finer material is deposited further away, while coarser material is deposited closer. This eventually builds up a barrier where the river can no longer flood.
Meanders
Oxbow Lake
Delta - river sediments being deposited as a river reaches it's mouth
the amount of size and load - greater the load and size larger the delta
salinity of water - salt and clay stick together increasing load size and increasing deposition
vegetation will slow water and increase depositon
delta normally forms more on gentle coastlines
Flooding and Flood Mitigation
Hydrographs
Hydrograph Size
Larger the rainfall, larger the hydrograph
Larger the basin, larger the hydrograph
Factors which impact flashiness of hydrograph
More flashy
Higher drainage density
Used for industry, dam built
Thin grass, moorland
Urbanisation
Impermeable rock
Very thin soil
Steep slopes
Less Flashy
Lower density
Limited use of river
Forest
Rural area
Permeable rock
Deep soil
Gentle slopes
Urbanisation and it's effects
Urbanisation tends to affect flood risk more in the lower course than upper course as urban areas are generally found on flatter terrain
Removal of trees - decreased evaporation, transpiration, evapotranspiration, transpiration
Construction of houses - decreased infiltration and lowering of water tables meaning water must travel deeper
Development of commercial areas - this leads to decreased soil permeability
Storm drains - water enters river faster
Channel modification tends to increase flood risk as water will enter the channel a lot faster
Flood prediction and mitigation
Improving flood warnings
improved rainfall and snowfall estimates, better and further in advance forecasts of rainfall
better mapping of rivers and channels
improved demographic information collection to better assess flood risk
better distribution of information to news agencies, more timely information distribution
improved technology of forecasting news agencies
Amelioration of floods
Disaster aid
Insurance
Event modification
Flood abatement
reforestation
protection of vegetation
revegetation
clearance of sediment/debris from streams
construction of floodable areas/water storage zones
Flood diversion
into rivers
into lakes
into reservoirs
See Study Guide for Channel Modification
River modification
Straightening the river which lessens friction and speeds up velocity
Heightening the banks to decrease flood risk
creating flood relief channels
Water scarcity and Water quality
Environmental impacts of agricultural activities
Irrigation - Addition of water where there is insufficient for crop growth. This can result in changes in precipitation, inefficient use of water, and the water table will lower significantly.
Salinization - increase in amount of salt in soil, when groundwater reaches the surface and capillary forces bring water to the surface where it evaporates leaving behind the salts
Eutrophication - fertilizers leak into water, this leads to increase in plant and algal growth, algal bloom results in lack of sunlight reaching plants because it covers surface, results in plants dying, bacteria decompose the plants and use up all the oxygen, without oxygen the water is dead-zoned
many people suffer the consequences of this such as the farmers who are damaging the water, governments who want to keep water clean but also need to increase food production by use of fertilizers, and consumers who are trading food for lack of clean water.
Human impacts
Increased urbanization
more population dense so increase demand for water
more water required for agricultural use so more water on tap is required
Population growth - more people need more food which means more water and more agriculture which is inefficient water use
Acidification of lakes by sulfur, nitrogen and other chemicals
Water management and futures
