water cycle and insecurity EQ1

what’s solar energy

a main driver for the hydrological cycle. Energy from the sun heating water and causing evaporation/ transpiration

whats gravitational potential energy

a main driving factor in the hydrological cycle. Ways in which water accelerates under gravity, thus transporting it to rivers and eventually the sea

whats a closed system

doesn’t have any external inputs or outputs, so the total volume of water is constant and finite. However, the water can exist in different states (liquid, vapour and solid) and the proportion held in each state can vary for both physical and human reasons

what’s blue water

water stores in liquid form (visible parts of the water cycle).

e.g. oceans, ground water, rivers and lakes, and atmospheric moisture

whats green water

water stored in the soil and vegetation (invisible part of the hydrological cycle).

e.g. soil moisture

whats residence time

average time a water molecule will spend in a reservoir or store

whats fluxes

the rate of flow between the stores

whats processes

the physical mechanisms that drive the fluxes of water between the sources

describe the global water budget

oceans lose more water through evaporation (an output) than they gain through precipitation (an input), whereas the opposite is true for landmasses.

surface runoff makes up the difference- known a the balance (i.e. removes excess water from ppt and returns to oceans to replace water lost through evaporation.

if the balance is disrupted, the oceans would receive more water and the continents would dry

the balance is known as the global water budget and it ensures this does not happen.

how is climate change altering the main stores in the hydrological cycle

reduces the main store of the cryosphere (ice caps) with major losses of ice in Greenland and Antarctica, and significant rises in sea level

which are the most important fluxes (rate of flow between stores) and transfers in the cycle

evaporation gets water into the system, vapor transport distributes it, and so does precipitation

what is fossil water

ancient deep groundwater from former pluvial (water) periods

why is fossil water regarded as non renewable

there is little to no significant recharge, effectively making this type of groundwater a non- renewable source. Recharge= process by which water is added to groundwater aquifers

what is the link between residency times and levels of water pollution

Residence times impact on turnover within the water cycle. the longer water spens in the distribution system, the more likely it is to encounter contamination

how much of the earths water is accessible to humans

1%

what’s polar hydrology like

there’s limited vegetation and <200mm ppt a year. winter snow insulates the ground and 85% of solar radiation is reflected.

spring causes rapid runoff from formally frozen rivers and lakes. summer thaw increases evaporation by 10x.

freeze thaw cycle causes the seasonal release of biological gases (caused by plant decomposition) as well as C2 and nutrients into rivers and seas.

in the cryosphere, seasonal thaws bring increased surface saturation and thinning permafrost. if this thaw becomes continuous, water flows away and is lost (known as cryosphere loss)

what’s tropical rainforest hydrology like

>2,000mm rain, generates its own rain mostly recycled within tropics. <25% of it reaches the Forrest floor as dense veg consumes 75% of it.

Evapotranspiration cools the air as energy is uses during this process. Deforestation reduces evaporation, in turn reducing vapour and local rainfall.

There’s constant high temps, conventional rainfall and high humidity.

Permanently dense Forrest produces high rates of evaporation, with water returning to the surface as precipitation that feeds large rivers such as the Amazon

Why are the tropics important for the hydrological cycle

Steep angle of the sun over tropical ocean allows intense solar radiation, causing high evaporation.

Trade winds transfer water vapour towards Inner Tropical Convergence Zone (ITCZ). There, convection currents lift the air so it can cool and condense into clouds causing heavy rainfall.

Most of the world’s rain is created in the ITCZ so it’s the biggest flux transferring water from oceans to land. These huge atmospheric flows of moisture are called tropospheric rivers

Why are the polar regions important for the hydrological cycle

2/3 of earths freshwater is locked in the cryosphere. But as the climate warms, some frozen cryosphere water is released by melting to flow into the sea, adding to the closed hydrological cycle.

The polar regions contribute to the circulation of water and the transfer of heat around the world which drives the global hydrological cycle. A circulation occurs known as the thermohaline circulation (sometimes called the global conveyor belt)

What’s a drainage basin

A system within the global hydrological cycle. It’s an open system with external inputs and outputs that cause the amount of water in the basin to vary over time.

5 ways precipitation patterns vary in a drainage basin

1) the amount of precipitation (the more ppt, the more predictable its pattern).

2) the type of precipitation (snow can act as a temporary store and larger fluxes of water can be released into the system after a thaw).

3) seasonality (strong seasons, patterns of rain or snow will have major impacts on the physical processes operating in the drainage basin system).

4) intensity of precipitation (difficult for rain to infiltrate if it’s very intense as soil capacity is exceeded).

5) distribution of precipitation within a basin (e.g. Nile where tributaries start in different climatic zones, or the location of a storm in a small basin as temporary inputs would vary)

Interception definition (type of flow)

Prowess by which water is stored in the vegetation

Overland flow definition (type of flow)

Surface runoff. The movement of water that is unconfined by a channel across the surface of the ground.

Infiltration definition (a type of flow)

The movement of water from the ground surface into the soil

Saturated overland flow definition (type of flow)

The upward movement of the water table into the evaporation zone.

Percolation definition (type of flow)

The transfer of water firm the surface or from the soil into the bedrock beneath.

Groundwater flow definition (type of flow)

Slow transfer if percolated water through pervious or porous rocks

Throughflow definition (type of flow)

The lateral transfer of water down a slope through the would via natural pipes and percolines

Evaporation definition (output)

Physical process where moisture is lost directly into the atmosphere from water surfaces and soil. It’s the result of the suns heating and air movement.

Rates are high when it’s warm, windy and dry. Climatic factors that influence it are temp, hour of sunshine, humidity and wind speed. Also size, depth and quality of water body. Also veg type, cover, and colour of surface.

Transpiration definition (output)

Biological prowess where water is lost from plants through miniature pores, and transferred into the atmosphere.

Rates determined times of year, amount of veg cover, availability of moisture, and length of growing season.

What is evapotranspiration and potential evapotranspirstion

Evapotranspiration= combined effect of evaporation and transpiration.

Potential Evapotranspiration= ester loss that would occur if there was an unlimited supply in the soil for use by vegetation.

What’s orographic precipitation (also known as relief precipitation). Where’s it most common

Wind from the sea contains lots of moisture, and when it reaches a mountain it’s can’t continue and is forced upwards. As the air mass goes up, it cools and condensed into orographic clouds. The clouds soon can’t hold mor water so it begins to rain.

Most of the ppt ends up on the side of the mountain facing the ocean (windward side). The leeward side gets little ppt (rain shadow effect). So windward= full of veg, leeward= dry.

Most common at coastal areas with a mountain range

What’s frontal precipitation (also known as cyclonic precipitation) and where’s it most common

When a warm, moist air mass meets a cold, dry one, the warm air rises and the water vapour in the warm air condenses forming clouds.

If it’s a warm front, the warm air will gradually rise causing mild, prolonged rainfall. If it’s a cold front, the warm air will ride quickly, causing unstable weather including thunderstorms.

Most common in the British Eyles

Discharge definition

The volume of water passed through a given cross section per unit time. Measured in cumecs

What’s convectional precipitation, where is it most common

On hot days the sun heats the ground. The ground releases some of that heat, warming the air. That warm air rises, cools and condenses into rain almost instantly.

Most common in tropical areas as where the sun hits at a more direct and intense angle

5 physical factors that influence drainage basins

1) climate (influences the type and amount of ppt overall, and the amount of evaporation also has an impact on the types of veg. High temps increase evapotranspirstion, reducing discharge low temps do the opposite as well as reduce plant growth).

2) soil, 3) geology (permeable sound snd rocks allow more infiltration and percolation, which provide greater recharge of groundwater. Impermeable prevents infiltration and causes surface saturation).

4) relief (steep slopes promote faster movement and shorter storage times. Large drainage basins collect more ppt and are affected by more basin wide factors eg.g land use, veg).

5) vegetation (Forested slopes intercept more ppt, increase enapotranspirstion and reduce surface runoff. Increases lag time.)

4 human factors thst influence the drainage basin system

1) overabstraction (taking more water out of a river system/ ground water that can be replaced. Reduced groundwater flow and a lower water table).

2) changing land use, urbanisation (urban surfaces are impermeable, low drainage density means slow movement of water across basin, increased surface runoff from artificial drains so river discharged rapid,t increase).

3) defforeststion (increased rush of groundwater flooding if the water table reaches the land surface).

4) reservoirs (creates new surface stores, increases evaporation and reduces downstream river discharge)

What’s a water budget and the calculation

The difference between inputs and outputs in any given area.

Drainage basin water budget calculated by P= Q+ E (+-) S.

P= ppt, Q= discharge , E= evapotranspirstion, S= changes in storage

What are the global variations of water budget

Africa has least + water balance. Ppt and evapotranspirstion are very similar leaving little water to enter rivers as surface runoff.

South America has the most + water balance. Have large ppt and evapotranspirstion difference so large surface runoff.

In monsoonal areas (Asia mainly) there are seasonal differences in surface flow.

What’s a river regime

The annual variation in discharge or flow of a river at a particular point or gauging station, usually measured cumecs (cubic metre per seccond). (How a river responds and changes over a period of time).

6 factors that influence the character of river regimes

1) size of the river and where the measurements are taken in the basin. Large rivers have complex regimes resulting from varied catchments.

2) MOST IMPORTANT ONE the amount p, pattern and intensity of ppt. Regimes reflect rainfall seasonal maxima or when the snow fields or glaciers melt.

3) temperatures experienced.

4) the geology of overlaying soils (especially their permeability and porosity). Water gradually released into river as base flow from groundwater tends to regulate the flow during dry periods.

5)amount and type of veg cover. Wetlands hold the water and release slowly into the system.

6) human activities such as dams which can regulate the flow.

What are the 2 types of regime

1) simple regime. (Where the river experiences a period of seasonally high discharge, followed by low discharge. They are typical of rivers where the inputs depend on glacial meltwater, snowmelt, or seasonal storms.

2) complex regime (where larger rivers cross several different relief and climatic zones and so experiance the effects of different seasonal climatic events. E.g. rivers like the Mississippi. Human factors can contribute to their complexity like damming rivers for energy or irrigation.

What is a storm hydrograph

Shows changes in discharge of a river over s short time

What are all the components of a storm hydrograph

Peak rainfall,

rising limb (discharge increases),

lag time (time interval between peak rainfall and peak discharge),

peak discharge (when the river reaches its highest flow),

falling limb (water in river starts to decrease once the storm input has ceased),

Base flow (the normal day to day discharge of a river)