Water and Carbon Cycles

(5) Types of systems in physical geography and their concepts?

Open systems - when systems receive inputs and transfer outputs of energy/matter with other systems.
Closed systems - when energy inputs equal outputs.

Dynamic equilibrium - when inputs equal outputs despite changing conditions.

Positive feedback - when a chain of events amplified the impacts of the original event.

Negative feedback - a chain of events that nullify the impact of the original event.

What types of systems are carbon/water cycles? (2 answers)

Both open systems on a local scale, but globally are closed systems.

What are inputs of the water cycle?

PRECIPITATION

• convectional rainfall condenses at higher altitudes after being heated by sun

• relief rainfall is when warm air is forced up by a barrier, causing it to condense and fall

• frontal rainfall is when warm air rises over cool air and meet. This means warmer air condenses and fall as rain.

What are outputs of the water cycle??

EVAPOTRANSPIRATION

• evaporation and transpiration. Evaporation when sun heats water, making it a gas and rising into atmosphere.

• transpiration occurs in plants when they respire, releasing water that was absorbed from roots, which evaporates from the sun.

STREAMFLOW

all water that enters a drainage basin leaves through the atmosphere or through streams (as tributaries or into other rivers)

What are flows of the water cycle?

INFILTRATION

• process of water moving from above surface to soil. Infiltration capacity is how quick this occurs.

• vegetation creates passages for water to flow through, increasing this capacity.

OVERLAND FLOW (surface runoff)

• occurs when precipitation falls at a greater rate than the infiltration capacity

PERCOLATION

• water moves from soil to rock

• rate is dependent on permeability of rocks or fractures in it.

THROUGHFLOW

• water moves through soil into streams/rivers

• speed of flow dependent on type of soil

GROUNDWATER FLOW

• water moves through rocks.

• ensures water is in rivers, even after dry periods of weather

STREAMFLOW

• water moves through established channels

STEMFLOW

• flow of water intercepted by plants/trees

GOTPISSS

What are the stores of water?

SOIL WATER - water stored in soil, used by plants (midterm)

GROUNDWATER - stored in pore spaces of rock (long term)

RIVER CHANNEL - water stored in rivers (short term)

INTERCEPTION - intercepted by plants on branches/leaves before reaching ground (short term)

SURFACE STORAGE - water in puddles, ponds etc. (variable)

What is a water table?

The upper level at which the pore spaces/fractures in ground become saturated. Used by researchers to assess drought conditions, health of wetland, success of forest restoration programs etc.

What is the water balance?

Used to express the process of water storage/transfer in a drainage basin system.

Precipitation= total runoff + evapotranspiration + change in storage

This is dependent on physical factors, esp during seasonal variations.

Local scale changes to water cycle reasons (5)

DEFORESTATION

• less interception, increased surface runoff. soil water storage and transpiration decrease

STORM EVENTS

• large volumes of rainfall quickly saturate ground to field capacity. increases surface runoff.

• less effective at recharging water stores than prolonged rainfall

SEASONAL CHANGES

• spring, more vegetation growth so more interception

• summer, less rain, hard ground so more impermeable, more surface runoff

• autumn, less vegetation growth/interception, more rainfall

• winter, frozen ground impermeable and more runoff. snow discourages runoff as takes time to melt, slowing processes

AGRICULTURE

• pastoral farming. livestock trample ground, reducing infiltration

• arable farming (crops). ploughing increases infiltration from looser soil, decreases runoff. however, drainage ditches increase surface runoff and streamflow

• hillside terracing increases surface water storage, decreasing runoff

• irrigation leads to groundwater depletion.

URBANISATION

• impermeable surfaces reduce infiltration and increase runoff, reduce lag time and increase flood risk.

• green roofs and SUDS use grass/soil to reduce no. of impermeable surfaces

What is the soil water budget and what is dependent on? how does it vary by seasons? (7, seasons are 4 of those marks)

the annual balance between inputs/outputs in the water cycle and their impact on soil water storage/availability.

Depends on soil type, depth and permeability and bedrock.

maximum possible level of water storage is field capacity (no more rain infiltrates after this).

spring - plants grow again, evapotranspiration increase w higher temps/more sun. water surplus

summer - use of soil water from peak in evapotranspiration, minimum rainfall. output of evapotranspiration greater than input of rain, soil water depletes. water deficit if long hot temps, lack of winter rainfall or drought from year before.

autumn - great precipitation input as trees lose leaves, cooler temps so less photosynthesis. soil moisture increases, water surplus.

winter - evapotranspiration at minimum from cold temps. precipitation continues, infiltration and percolation refill water table.

distribution and size of water stores globally

largest store is oceans, 97% globally.

2.5% are freshwater, of that 69% is cryosphere and 30% is groundwater.

surface and other freshwater is around 1% of global stores, usually made up of permafrost, lakes, swamps, marshes, rivers etc.

aquifers (underground water), uneven distribution globally. shallow aquifers last 200 years, deeper fossil aquifers 10,000 years. glaciers store water for 20-100 years. seasonal snow covers/rivers store water for 2-6 months, whilst soil water is 2 months.

how do cloud formations affect magnitude of each water store?

water droplets form around particles in the air, like dust. attract to eachother to form larger droplets and eventually grow to a point where gravity causes them to fall from their weight. Causes more precipitation, atmosphere to other stores like biosphere.

intertropical convergence zone, tracks with the seasonal movement of the sun, north and south of the equator resulting in intense low pressure rain with the movement. (global time/space change)

how do seasonal changes affect magnitude of each water store?

Summer - less precipitation, more evapotranspiration from higher temps

• reduced flows in winter as water becomes ice. less interception, deciduous trees lose leaves.

• increased evapotranspiration in summer as leaves grow back

how do storm events affect magnitude of each water store?

sudden increase in rainfall, flooding and replenishes some water stores. no long-term change.

how do droughts affect magnitude of each water store?

major stores depleted, activity of flows decreases. may cause long term change if more common from climate change.

how do cryospheric processes affect magnitude of each water store?

in past, glaciers and icecaps stored significant proportions of fresh water from accumulation.

all glaciers are now shrinking, rising sea levels.

more hydrosphere storage. this further destabilises the ice caps (positive feedback loop)

How does water abstraction affect water stores?

reduces volume of water in surface stores/hydrosphere.

increases in dry seasons for irrigation etc.

abstraction from aquifers is often greater than inputs into the aquifer, decline in global long term water stores.

flood hydrograph terminology YEAAA (8)

DISCHARGE - volume of water passing through cross-sectional point of river at any one point in time (m^3/s). made up of baseflow and stormflow

RISING LIMB - represents discharge increasing

FALLING LIMB - represents decreasing discharge

LAG TIME - time between peak rainfall and peak discharge (the peaks on the two different lines)

BASEFLOW - level of groundwater flow

STORMFLOW - overland flow and groundwater flow combined

FLASHY HYDROGRAPH - short lag time, high peak discharge

SUBDUED HYDROGRAPH - low lag time, low peak discharge

differences between flashy and subdued hydrographs

LAG TIME

• short in flashy, long in subdued

RISING/FALLING LIMB

• steep in flashy, gradual in subdued

FLOOD RISK

• high in flashy, lower in subdued

PEAK DISCHARGE

• high in flashy, lower in subdued

factors affecting hydrographs (hit reference to starter activity)

NATURAL

high rainfall intensity - soil reaches capacity quicker, more surface runoff, decrease lag time

antecedent rainfall (occurs before) - more surface runoff as ground is saturated. decrease lag time.

impermeable geology - decreased percolation, more groundwater flow. decrease lag time

land relief - valley shape, moves water to river slower/quicker from gravity. small basin, rainfall reaches river quicker and less capacity.

low temperatures - less evapotranspiration, greater peak discharge.

precipitation type - snow takes time to melt

vegetation cover - intercepts rainfall, decreases flood risk. more stem flow.