EQ1 Flashcards
Closed system
When there is a transfer of energy but not matter between the system and its surrounding. There are no external inputs/outputs, any inputs come from within the system.
Flows (fluxes)
Measurements of the rate of flow between stores.
Processes
Are the physical mechanisms such as evaporation that drive the flows of water between the stores.
Stores (stocks)
Reservoirs where water is held, e.g. oceans.
Blue water
Water that is stored in rivers, streams, lakes and groundwater in liquid forms (visible).
Green water
Water stored in the soil and vegetation (invisible).
Precipitation
The input into a drainage basin system. It includes all forms of moisture entering: hail, snow, dew, frost, sleet and rain.
Interception storage
The storage of water when it lands on vegetation (or structures like buildings) before it reaches the soil. It is a temporary store before evaporation or stemflow.
Surface storage
The storage of water on the surface including puddles, ponds and lakes.
Soil water (sub-surface) store
The storage of water in soil. Water is held in the small gaps between soil particles.
Groundwater store
The storage of water in the ground rocks of permeable rock. The water is held in cracks (limestone) bedding planes (sedimentary rock) or pores (chalk). Rocks with lots of water storage are called aquifers.
Channel store
The storage of water in the river channel. As water is being transported to the sea it is a store of water.
Vegetation store
The storage of water in the vegetation. Plants and trees take up water through their roots and water is stored here.
Surface run-off
The horizontal flow of water over the surface of the land either in little channels or over the whole surface – this is usually a quick flow.
Stemflow
The downwards flow of water moving downwards from interception storage to the surface.
Soil (sub-surface) throughflow
The horizontal flow of water moving through soil (between the particles) towards the river.
Infiltration
The downwards movement of water from the surface into the soil.
Percolation
The downwards movement of water from the soil to the permeable ground rock.
Groundwater (base) flow
The horizontal movement of moving through the rocks (cracks/bedding planes/pores) slowly towards the river. This is the movement of water below the water table sideways to the river.
River channel flow out to the basin’s exit (lake, reservoir, ocean)
The movement of water in the river channel moving towards the sea.
Evaporation
The output of water when water is heated and turned from a liquid into a gas.
Transpiration
The output of water where moisture is taken into plants through their roots, moved to the leaves by capillary action and then evaporates from the leaves into a gas.
Evapotranspiration
The combined output of water from evaporation and transpiration.
River discharge
The output of water from a river channel out to sea.
Orographic (relief) rainfall
As the moist air is forced to rise on the windward side of the mountain, rainfall occurs as a result of adiabatic cooling (when the volume of air increases but there is no addition of heat), and condensation to dew point. The air, without much water left in it, is then drawn over the mountains where it descends and is adiabatically warmed by compression. This leads to a very dry ‘shadow’ area.
Frontal (cyclonic) rainfall
This happens when warm air, which is lighter and less dense, is forced to rise over cold, sense air. As it rises, the air cools and its ability to hold water vapour decreases. Condensation occurs and clouds and rain form.
Conventional rainfall
When the land becomes hot, the air above it becomes warmer, expands and rises. As it rises, the air cools and its ability to hold water vapour decreases. Condensation occurs and clouds develop. If the air continues to rise, rain will fall.
Water budget
Water budget reflects the natural annual balance between inputs and outputs in a given river area. The formula used is: P=Q+E+/-S where:
Precipitation (P) = Channel discharge (Q) + Evapotranspiration (E) +/- Change in Store (S).
Whatever falls as precipitation should be balanced by the other components, otherwise it means there might be flood or drought.
Field capacity
The normal amount of water that can be held in the soil.
Potential evapotranspiration
The amount of water that could be lost by evapotranspiration if there was sufficient moisture available.
Actual evapotranspiration
The amount of water that is lost through transpiration (release from leaves) and evaporation (heating of water on surfaces) to the atmosphere.
Soil moisture surplus
Occurs when the soil moisture store is full and there is excess water available for plants, runoff and recharge. (Prec>E/T).
Soil moisture utilisation
Occurs when moisture from the soil stores is being used by vegetation/humans as the precipitation rate is less than E/T. (E/T > Prec).
Soil moisture recharge
Occurs when moisture from precipitation infiltrates and percolates in the stores to repay the soil moisture utilisation/deficit. (Prec>E/T).
Soil moisture deficit
There is not enough water left in the soil to match potential e/t. Rivers run dry and drought ensues. (P E/T > Prec for a prolonged period).
Water budget/balance graphs
- Water Budget/Balance graphs provide a direct comparison of natural water supply and demand and the impact this has on soil water permeability.
- They help us identify where P>ET = Possible balance (flood) and where P
River regime
River regimes indicate the annual variation of discharge of a river at a particular point and is measured in cumecs.
Glacier melt (river regime)
Glacier melt - European mountain rivers have a high-water period (July-August) when glaciers feeding them melt most rapidly.
Snow melt (river regime)
Snowmelt - melting of snow cover either in mountainous areas during early summer or over the Great Plains of North America in spring.
Tropical seasonal rainfall (monsoonal) (river regime)
Tropical seasonal rainfall (monsoonal) - in tropical areas, evapotranspiration tends to be stable (high) but summer rains cause a peak.
Oceanic rainfall/evapotranspiration (river regime)
Oceanic rainfall/evapotranspiration - in many oceanic areas of Europe, rainfall is evenly distributed but high evapotranspiration in summer leads to low run-off.
Hydrograph
A hydrograph is a graph showing variation in discharge (volume) of water at a given point over a short period of time, normally an individual storm (few days).
