Term	Definition
Source	Highest point from sea level (Upper course)
Mouth	Lowest point from sea level (Lower course), connection to largest body of water
Tributary	Small rivers connecting to main channel (Many tributary)
Confluence	Where different rivers meet

Flows:
Throughfall	Water that falls through gaps in vegetation or drops from leaves and twigs
Throughflow	Water flowing through the soil - Flows in percolines ](lines of concentrated water flow between soil horizons) - Occurs most quickly in porous soils such as sand
Stemflow	Water that trickles along twigs and branches and finally down the trunk of the tree
Overland flow	Water that flows over the land’s surface. Occurs when precipitation exceeds infiltration or when the land is impermeable or saturated
Channel flow	The movement of water in channels such as streams and rivers
Infiltration	When water soaks into the soil The infiltration capacity is the maximum rate at which rain can be absorbed by a soil. Infiltration is most effective on porous soils like sand. Infiltration is also more effective under vegetation, because interception slows water reaching the ground. Antecedent moisture is the pre-existing levels of moisture. If this is high then infiltration rates are low.
Percolation	When water moves slowly down from the soil into the bedrock - occurs more quickly in permeable rock such as limestone and chalk
Groundwater	Subsurface water flow through aquifers - BELOW THROUGHFLOW
Baseflow	Part of a river’s discharge that is provided by groundwater seeing into the bed of the river
Stores:
Interception	The water that is caught and stored by vegetation
Interception loss	Water retained by plant surfaces and later evaporated away or absorbed by the plant - most effective on dense vegetation, especially deciduous woodland in summer as the trees have broad leaves
Soil water	The subsurface water held in soil above the water table. Water may be held in pores, and lots can be held in porous soils such as sands
Field capacity	Amount of water held in the soil after excess water is drained away
Wilting point	Range of moisture content in which permanent wilting of plants occurs
Soil moisture deficit	How far below field capacity soil moisture falls - after long periods without precipitation the deficit is large
Soil moisture recharge	When dried up pores are refilled with water
Soil moisture surplus	Period when soil is saturated and so additional water flows over the surface
Soil water utilisation	Process by which soil moisture is drawn to the surface by capillary action
Surface water	Temporary stores such as puddles, and permanent stores such as lakes
Groundwater	Water stored in the phreatic zone (permanently saturated zone within solid rocks) Upper layer of this is called the “water table”
Channel storage	All water stored in rivers and streams - Not all rivers are permanent; some may be seasonal or disappear underground

Outputs:
Evaporation	Process by which a liquid is changed into a gas (water vapour) - occurs most under warm, dry, and windy conditions
Sublimation	Misses out the liquid phase and a solid changes into a gas - eg. when intense sun shines on a snow field the frozen water changes directly into water vapour
Transpiration	Process by which water vapour escapes from a living plants into the atmosphere
Evapotranspiration	The combined effects of evaporation and transpiration - accounts for the majority of water loss in areas with vegetation
Potential evapotranspiration	Water loss that would occur if there was an unlimited supply of water in the soil for the vegetation
River discharge	Movement of water in a channel, and water may leave the drainage basin by flowing out into the sea

Groundwater:
Aquifers	Rocks containing significant quantities of water, and are permeable rocks such as sandstone and limestone - water moves very slowly and acts as a natural regulator of water, water may reach the surface as a spring
Groundwater recharge	Occurs due to: - Infiltration and percolation from above - Seepage from surface water such as lakes - Artificial recharge from reservoirs, irrigation, etc.
Groundwater losses	Occurs due to: - Evapotranspiration where water table is close to surface - Seepage into rivers - Leakage into other aquifers - Artificial abstraction for irrigation and human use
River flows:
Laminar flow	Water flows in sheets (laminae) parallel to the channel bed. ◦ It requires a smooth, straight river channel with a low velocity. ◦ Rarely occurs.
Turbulent flow	- Water flows in irregular patterns. ◦ This occurs when a river has a complex channel morphology and a high velocity. ◦ Bed roughness also creates turbulence.
Helicoidal flow	◦ Water flows in a corkscrew motion (not down the centre). ◦ This is due to alternating pools (deeper parts) and riffles (shallow parts). ◦ This flow forms meanders.
Erosions:
Erosion	The wearing away of rock and soil found along the river bed and banks - involves the breaking down of the rock particles being carried downstream by the river
Abrasion (or corrosion)	The wearing away of bed and banks by sediment carried in the flow of the river
Attrition	Erosion caused when rocks and boulders transported by the river bump into each other and break up into smaller pieces
Hydraulic power	The process by which the water itself compresses pockets of air in cracks in the bed or banks. The pressure may cause the crack to widen, breaking off rock Solution Soluble particles are dissolved into the river
Transportations:
Traction	Heavy rocks and boulders are rolled along the river bed - happens in times of flood when current is strongest
Solution	Take place when material is dissolved in the water, it is invisible and does not colour the water - occurs in limestone landscapes where the water is very acidic
Saltation	small stones and pebbles are ‘bounced’ along the river bed - saltation can take place when the river flow is less than that needed for ‘traction’ to take place
Suspension	Very small particles of sand or clay that are ‘suspended’ in the water - these particles will ‘settle’ if kept in a jar of water overnight
Channels:
Meandering channel	Reasons for this channel: 1. friction 3. sinuosity 4. helicoidal flow
Braided channel	Islands within rivers
Straight channel	Straight (very rare) The thalweg still moves side to side Large amount of sediment down middle of channel

Sinuosity	length of stream channel/length of valley
alluvium	sand and gravel that has been deposited by running water on the flood plains, really fertile
Bluff	edge of floodplain, steep shoreline slope formed in sediment
Thalweg	Line of maximum velocity

Discharge	the amount of water flowing in a river channel, measured in cubic metres per second.
Baseflow	antecedent groundwater flow.
Peak rainfall	the height of the storm.
Peak discharge	the maximum discharge of the river as a result of the storm.
Lag time	the time between the height of the storm (peak rainfall) and the maximum flow in the river (peak hydrodischarge).
Rising limb	the rising river discharge. It shows how quickly the floodwaters rise.
Recessional/falling limb	the falling river discharge. It shows how quickly the water level declines.

OPTIONS - freshwater