Parts of a river and its functions + Hydrological Cycle Flashcards
What is a Drainage Basin?
- The drainage basin or catchment area is an area of land drained by a river and its tributaries. It is seen an open system comprising inputs, flows/ transfers, outputs and storage. The amount of water in the system in the basin varies over time, since water can be added in the form of precipitation and lost in the form of evapotranspiration.
- The drainage basin can be divided into three courses: upper, middle and lower.
What can the drainage basin be divided into?
upper, middle and lower courses
What is at the start and end of a drainage basin?
Start: Source
End: Mouth
Definition of Drainage Basin
The area of land drained by a river.
Definition of Watershed
The edge of highland surrounding a drainage basin. It marks the boundary between two drainage basins.
Definition of Source (of a river)
The beginning or start of a river.
Definition of River
Natural wide flows of freshwater across land that stores water temporarily before water flows into another water body.
Definition of River Banks
Physical confines of a river.
Definition of Confluence
The point at which two rivers or streams join.
Definition of Tributary
A stream or smaller river which joins a larger stream or river.
Definition of Distributary
Where rivers branch off to form smaller streams (somewhere at the mouth of the river).
Definition of Mouth (of a river)
The point where the river comes to an end, usually when entering a sea.
Definition of Ground Water
Groundwater is water that is stored in layers of soil and rocks following percolation of water, lying above an impermeable layer.
Definition of Water Table
The top level of saturated ground in the soil - it rises and falls depending on the amount of rain.
What is the Hydrological Cycle?
• The hydrological cycle is a sequence of processes that occur to ensure that water is naturally replenished on the Earth. This is a global circulation of water – a giant closed system. This means that there is a fixed amount of water in the system because water neither enter nor leaves the Earth and its atmosphere.
What does the Hydrological Cycle consist of?
- Inputs → when water is added to a system - Transfers → when water is moving within a system - Stores → when water is stationary within a system - Outputs → when water leaves (exits) a system
Inputs
→ when water is added to a system
Transfers
→ when water is moving within a system
Stores
→ when water is stationary within a system
Outputs
→ when water leaves (exits) a system
Precipitation
Input
- Any moisture that falls from the sky.
→ e.g. rain, snow
Sun
Input
- Produces heat which makes water evaporate/condense.
Infiltration
Transfer
- When water travels from the surface of the earth into the ground beneath.
Surface run-off (overland flow)
Transfer
- When water travels across the surface of the earth.
Channel Flow
Transfer
- Water that is travelling in rivers or streams.
Through Fall
Transfer
- water that passes directly through a canopy or is initially intercepted by aboveground vegetative surfaces and subsequently drips from the canopy.
Stem flow
Transfer
- When intercepted water drains from outlying leaves and branches and is channelled to the stems and trunks of vegetation.
Leaf Drip
Transfer
- Intercepted water dripping off vegetation onto the ground.
Percolation
Transfer
- When water travels deeper into the ground, from unsaturated ground into saturated ground.
Groundwater flow
Transfer
- The movement of water through saturated ground, known as aquifer.
- Aquifer = rocks under surface that can hold moisture
Through-flow
Transfer
- The lateral (horizontal) movement of water through unsaturated ground, close to the land surface.
Interception
Stores
- When an object (building, tree) stops precipitation from reaching the ground beneath. (prevents water from falling directly on the ground).
Vegetation Storage
Stores
- all moisture that is stored in vegetation.
Surface Storage
Stores
- Any water that is held on the surface of the earth
→ e.g. lake or pond.
→ Some surface stores like puddles may only be temporary.
Soil-Moisture Storage
Stores
- Water that is stored below the surface in unsaturated ground.
Groundwater Storage
Stores
- Water that is stored in saturated ground.
Channel Storage
Stores
- the volume of water contained within the banks of a river will operate as a water store between its initial input and ultimate output.
Saturated Ground
basically soil with moisture or water absorbed
Unsaturated Ground
basically soil with no moisture or water absorbed
Evaporation
Output
- Liquid water from surface stores and rivers turning into water vapour (gas).
Transpiration
Output
- Liquid water evaporating from vegetation.
What is Evaporation and Transpiration collectively known as?
Evapotranspiration
River runoff/discharge
Output
- Eventually most rivers enter the sea and discharge the river’s flow into the sea.
What are the products of the hydrological cycle?
Water vapour and water
Does the atmosphere store water?
Yes
it is part of stores
Condensation
Output
Water vapour condenses into water.
Why does infiltration and percolation occur?
Percolation is the movement of water through the soil itself. As the water percolates into the deeper layers of the soil, it reaches ground water, which is water below the surface. The upper surface of this underground water is called the “water table”. Ground water can intersect with surface streams to appear at the surface as springs, and it flows generally downhill toward the ocean.
The nature of the surface influence the rate of infiltration, while the nature of the subsurface terrain affects the flow of groundwater.
What is porosity?
• Porosity is a measure of the pore spaces between rock sediments and its ability to hold a fluid.
- Mathematically, it is the open space in a rock divided by the total rock volume (solid and space). The average soil has a porosity of about 50%, and the pores are filled with air or water depending on the moisture content.
What is Permeability/ Pervious(ness)?
• Permeability (or pervious(ness)) is a measure of the ease of flow of fluids through a porous material.
- A rock may be extremely porous, but if the pores are not connected, it will have no permeability.
- Likewise, a pervious rock may have a few continuous cracks or joints which allow ease of fluid flow, but when porosity is calculated, the rock doesn’t seem very porous.
ability of a rock to allow fluid to flow through an interconnected network of pores is called _____?
permeability
the ability of a rock to allow fluid to flow through an interconnected network of pores is called permeability.
Are porosity and permeability related?
Yes
• Porosity and permeability are related properties of any rock or loose sediment. Both are related to the number, size and connections of openings in the rock. They affect the flow of water and control the distribution of groundwater. An underground layer of rock or sediment that serves as a storage reservoir for large volumes of groundwater is called an aquifer. Groundwater is an important source of freshwater.
Does porosity and permeability affect the flow of water and control the distribution of groundwater?
Yes
• Porosity and permeability are related properties of any rock or loose sediment. Both are related to the number, size and connections of openings in the rock. They affect the flow of water and control the distribution of groundwater. An underground layer of rock or sediment that serves as a storage reservoir for large volumes of groundwater is called an aquifer. Groundwater is an important source of freshwater.
Definition of Aquifer
- Aquifer = rocks under surface that can hold moisture
An underground layer of rock or sediment that serves as a storage reservoir for large volumes of groundwater is called an aquifer.
Groundwater is an important source of freshwater. Is this true?
Yes
Rank the 3 types of soil by its ability to handle water.
Sand, Clay, Loam
- Sand
- The water goes down the deepest vertically/ extensively - Loam
- Clay
