Water Cycle

• Hydrological cycle is a closed system made up of inputs, outputs, stores and flows
• solar energy drives the hydrological cycle by heat moving the water from the surface towards the atmosphere
• gravitational potential energy drives the hydrological cycle by forcing water to flow downhill on the surface and soil and precipitation to fall from the sky
• what are the 6 water stores?

  oceans

  cryosphere

  groundwater

  surface water

  atmosphere

  biosphere
• ocean is the largest store at 96.5% and biosphere is the smallest store at 0.0001%
• ocean is the most important water store as its contributes to 86% of precipitation annually
• 2 ways the global water budget limits available water for human use?

  some stores are non renewable

  some stores are economically and physically hard to get like groundwater
• non renewable water is water that has not been replenished for a long time due to its residence time, for example water held in the cryosphere and groundwater held in fossil fuels
• 4 types of water annual fluxes?

  evaporation, condensation, precipitation and cryospheric processes
• evaporation increases the atmosphere store by liquid turning into gas increasing water vapour. varies by season and location. lots of solar radiation = high evaporation, little solar radiation = low evaporation
• condensation decreases the atmosphere store as water vapour turns into liquid as it cools to its dew point. lots of water vapour + big drop in temperature = high condensation
• precipitation is main flow of water from atmosphere to ground, clouds form when warm air cools down causing water vapour to turn into water droplets. precipitation varies seasonally
• 2 cryospheric processes are accumulation and ablation
• accumulation occurs during periods of global cold as there is more inputs than outputs in the cryosphere, warmer global temperatures decreases the cryosphere store as there is more ablation than accumulation
• drainage basin is a open system within a local hydrological system
• the inputs to a drainage basin system is precipitation, there are 3 types of precipitation, frontal, orographic and convenctional
• frontal rainfall occurs when warm air is less dense than cool air, when they meet warm air is forced up above the cool air and cools down as it rises
• orographic is when warm air meets a mountain and is forced upward causing it to cool
• an example of convectional rainfall is the monsoon season in Asia and coasts facing more rainfall due to evaporation of the oceans
• flows are how water moves from one place to another in drainage basins, there are 7 flows
• what are the 7 flows in a drainage basin?

  interception

  infiltration

  direct runoff

  saturated overland flow

  throughflow

  percolation

  groundwater flow
• saturated overland flow is water flowing overland because of the soil losing capacity to infiltrate
• groundwater flow is water slowly flowing through permeable rock below water table
• the 4 outputs of the drainage basin are evaporation, transpiration, evapotranspiration and channel flow
• channel flow is water leaving drainage basin through a river or stream
• 5 physical variables determining inputs, outputs and flows of hydrological cycle?

  Climate

  Soils

  Vegetation

  Geology

  Relief
• climate determines inputs by higher temperatures = more convection rainfall. determines flows as in the summer water dries reducing flows, for example Craig Gooch reservoir 2018 heatwave
• soil determines flows by different soils having different infiltration rates, for example sandy soil allows more infiltration than clay soil
• high amounts of vegetation means that there is a high rate of interception slowing flows, but it also means more water lost to evapotranspiration
• geology affects flows as the more impermeable the rock the greater the direct runoff
• 4 ways human can disrupt drainage basin cycle?

  deforestation

  land use changes

  water storage reservoirs

  water abstraction
• deforestation disrupts hydrological cycle by reducing amount of water intercepted, increasing direct runoff = higher chance of floods
• land use changes like urbanisation disrupts the hydrological cycle as roads prevent infiltration, increasing direct runoff. on the other hand ploughing does the opposite
• water storage reservoirs like dam construction increases the amount of standing water which increases evaporation
• what is the case study for human actions disrupting the hydrological cycle?

  Amazonia
• 2 impacts of the deforestation by humans in the Amazon is more water is reaching the ground and if there's too much it wont infiltrate through soil increasing saturated overland flow increasing flood risk

  another impact is high risk of drought as deforestation means there is less evapotranspiration meaning less water vapour
• water budgets indicate how much water is stored in a drainage basin and show the balance between inputs and outputs
• uk seasonal patterns is in wet season more precipitation than evapotranspiration meaning water surplus and dry season more evapotranspiration than precipitation meaning water deficit
• what type of zone is the case study for water budgets?

  temperate
• river regime refers to the variations of river discharge annually