Water Cycle and Water Insecurity Flashcards
(70 cards)
1
Q
Global Hydrological Cycle
A
- Closed system
- Inputs = Outputs
2
Q
2 Processes driving the hydrological cycle
A
-
Solar Energy:
- Sun heats water
- Evaporation Increases
-Moisture level Increases
- Condensation and precipitation Increase as air cools -
GPE:
-Water moves by gravity
- Runoff and groundwater flow transport water to the sea
3
Q
Flux
A
Transfer of water by flows
4
Q
Annual Flux
A
Variations in flow due to seasonal and temperature change
5
Q
Global Stores and Fluxes
A
- Most freshwater is locked in the cryosphere
Oceans: 97%
Freshwater: 2.5%
6
Q
Global Water Budget
A
- Balance between inputs and outputs
- Oceans lose more water than gain
- Land masses gain more than lose
- Residence time in atmosphere is much shorter than oceans
7
Q
ITCZ- Inter Tropical Convergence Zone
A
- Air rises and cools due to convectional currents, forming clouds
- Biggest flux, transferring water from oceans to land
8
Q
Importance of Polar Regions
A
- Cryosphere locks 66% of freshwater, warm climates release it into the sea
- Polar region contributes to the circulation of heat + water, driving thermohaline circulation
- Polar ocean water sinks (dense and cold)
- Drawing in warm water from above and the tropics
- Water movement from the tropics draw cold water from ocean depths to be warmed again
9
Q
Fossil Water
A
- Exploited due to technology
- Aquifiers beneath Kenya hold 70 years worth of freshwater (non-renewable)
10
Q
Drainage Basin
A
Area drained by rivers and tributaries (catchment areas) within the watershed- open system. (inputs and outputs can be independent of each other)
11
Q
3 paths Precipitation follows
A
Infiltration
Surface Runoff
Evaporation
12
Q
Precipitation is delayed by :
A
-Interception by plants/buildings before evaporation or infiltration occurs
- Percolation through rocks as groundwater and subsequent storage in aquifers
13
Q
Throughflow
A
Water flow within the soil
14
Q
Infiltration
A
Soil Composition:
- Sandy soils have higher infiltration than clay
Previous Precipitation:
- Saturation decreases infiltration (increases surface runoff after heavy rainfall)
Vegetation:
-Root growth can intercept and prevent infiltration
Relief of Land:
-Sloped land encourages runoff, less infiltration
15
Q
Surface Runoff
A
Faster flow where gradient is greater, primary transfer is to river
16
Q
Throughflow
A
- Clay soil has a high field capacity, smaller pores and a smaller flow rate
- Sandy soils have low field capacity, larger pores, faster flow rates
17
Q
Percolation
A
- Flow of water ground/soil to rocks
- Rate dependent on rock fractures and permeability
18
Q
Groundwater Flow
A
Flow of water from/through porous due to gravity (slow)
19
Q
Outputs of Drainage Basins
A
Evaporation:
- Increases when air is warm, dry and windy
- Larger SA, more evaporation
- Reduced sunlight, less evaporation
- Black absorbs heat, more evaporation
Transpiration:
- Water moves from the plants to the atmosphere, affected by seasons
20
Q
Stores
A
Soil Water:
- Water utilised by plants (mid-term)
Groundwater:
- Stored in porous rocks (long-term)
River Channel:
- Stored in river (short-term)
Surface:
- Stored in puddles, ponds and rivers (variable)
21
Q
Factors affecting Drainage Basin
A
Climate:
- Influences rainfall and vegetation growth
Soil Composition:
- Influences infiltration rate and throughflow
Vegetation:
- Affects interception, overland flow
Geology:
- Affects percolation and groundwater flow
Relief:
- Steeper gradient encourages faster surface runoff
22
Q
Deforestation
A
- Less vegetation, less interception, less infiltration, more flooding, cycle fastens
23
Q
Land-use change
A
-Infiltration 5x faster in forests than in grasslands
- Converting to farmlands decreases interception and increases surface runoff
24
Q
Ground-water abstraction
A
- Water taken out faster than recharged decreases groundwater flow
e.g. China, groundwater irrigates 40% of farmland, 70% drinking comes from ground water
25
Irrigation
- High water usage = drop in water table
e.g. **Arai Sea Khazikastan, shrink due to farmers using water to grow cotton**
26
Reservoirs
- Delays flows, removes water from the basin
- More water is evaporated from reservoirs globally than used
27
Convectional Rainfall
- Occurs daily
- Morning heat warms ground, moisture evaporates and rises, as more accumulates it rains
e.g. **in tropical climates convectional rainfall is most common**
28
Frontal / Cyclonic Rainfall
- 2 air masses meet
- Wedge can occur of hot air within cold air- **depression**
At **front** moist air rises above cold , causing **cyclonic precipitation, approx. 100 depressions a year in UK**
29
Relief (Orographic) Rainfall
- Moist air meets land of high relief, forced to rise above and cools, condenses to form orographic rainfall- dependant on relief and location **(many are low-lying, cold or too far)**
30
Water Budget
- Balance between inputs and outputs
**Inputs**:
- Precipitation
- Water diversion IN
- Groundwater flow IN
**Outputs**:
- Evapotranspiration
-Water diversion OUT
31
Water Budget
- Balance between inputs and outputs
**Inputs**:
- Precipitation
- Water diversion IN
- Groundwater flow IN
**Outputs**:
- Evapotranspiration
-Water diversion OUT
- Groundwater flow OUT
32
Water Balance
**Precipitation = Discharge +Evaporation ± Changes in stores**
33
Precipiation > Evaporation
- Soil moisture **surplus**, risk of flood
34
High Temperature High Evaporation
- Soil moisture utilisation
35
Point of maximum evaporation
- Highest risk of drought
36
Evaporation > Precipitation
Soil moisture **deficit** e.g. Summer
37
Field infiltration capacity
- Maximum soil can hold, reduced during deficit
38
Flash floods
- Occur after heavy rainfall after drought, soil cannot absorb quick enough
39
River Regime
- Annual variation in discharge of a river
40
Seasonal Variations
- High discharge followed by low discharge due to: **snowmelt, monsoons, glacial melt water** - sudden fluctuations in river input e.g. Rhone
41
Complex Regimes
- Occur for larger rivers which cross several reliefs and climate zones **e.g. Ganges**
42
Factors affecting River Flow (discharge)
- Climate
- Geology
- Soils (affects input of groundwater)
- Human intervention **e.g. building dams, terracing land**
43
Storm Hydrograph
- Variation in discharge over short periods of time (days)
- As storm develops, infiltration and surface runoff increase, increasing throughflow
44
Features of a Storm Hydrograph
1. **Rising Limb**- Increase of River Discharge
2. **Peak Flow**- Maximum discharge, delayed after maximum precipitation
3.** Lag time**- Time delay between peek rainfall and peak discharge
4. **Falling limb**- Decreased precipitation, discharge decreases over time
5. **Base flow**- Discharge level returns to normal
45
Physical factors affecting Flashy Storm Hydrograph
1. **Basin Size**: Small
2. **Hydrograph**: Short lag time, short rising limb, high peak
3. **Rock type**: Impermeable encourages surface run off e.g.**granite**
4. **Soil**: Low infiltration rate
5. **Relief**: High, steep slopes, increases runoff
6. **Vegetation**: low-density vegetation, decreased interception, increases movement of water
7. **Human activity**: urbanisation, deforestation, channelisation, dams
46
Phyical factors affecting Subdued Storm Hydrograph
1. **Basin Size**: Large
2. **Hydrograph**: Long lag time, sloping rising limb, low peak
3. **Rock type**: Permeable encourages infiltration e.g.**limestone**
4. **Soil**: High infiltration rate
5. **Relief**: Low, gentle slopes, less runoff
6. **Vegetation**: high-density vegetation, increased interception, increased evapotranspiration
7. **Human activity**: Afforestation
47
Management of Drainage Basins
- Vegetation on roofs, increases interception + temporary store within plants
- Permeable pavements, increases infiltration, decreases runoff
- Rainwater harvesting, use as domestic grey water
- Wetlands, **march and vegetation**, act as natural sponges and increase temporary water storage
e.g. **UK planners decide if development affects flood risk, accounting environmental factors vs Economic development
48
Meteorological Drought
- Rainfall deficit
- Low precipitaion
- High temperatures
- Reduced snow cover
**Impacts**:
- Loss of soil moisture
- Decreased irrigation supply
- Decreased water for consumption
49
Hydrological Drought
- Streamflow deficit
-Reduced infiltration
- Reduced percolation
- Reduced groundwater recharge
**Impacts**:
- Decreased water for urban supply
- Threats to wetlands and habitats
50
El Nino Southern Oscillation- ENSO
- Change in water body patterns in Southern Hemisphere, resulting in unusual weather conditions
- Cool water found **Peruvian Coasts**, warm water around **Australia**
- Switches every **3-7 years for 18 months**
- Can trigger dry conditions in South Asia, weakening annual monsoon
51
Wetlands
- Temporary water stores, mitigate river floods due to sudden storm discharge
- Traps, recycles nutrients and pollutants
- Biological productivity
52
Impacts of Droughts on wetlands
- **Meteorological droughts** caused due to reduced interception, less precipitation
- Vegetation wilts and dies, impacting soil nutrients level and complex food web
53
Physical Causes of Desertification
- Reduced precipitation, vegetation dies, removing protective layer on soil, exposure to wind and rain- accelerating **soil erosion** - **positive feedback loop**
- **Global warming**, increasing rate of evaporation in tropical areas, less water for convectional rainfall, stunting plant growth, killing vegetation
54
Human Causes of Desertification
- **Population growth**, increasing demand for food, water and resources, pressure on agricultural methods to change to meet demand
- Increasing cattle farming, deforestation for grazing
- **Crop farming**, over-cultivation, trampling of vegetation and loss of soil nutrients
55
Vulnerable to Surplus in Hydrological Cycle
**Low-lying land, base of river valley, estuaries**:
- Close to water table so vulnerable to flooding as it saturates
**Urbanised, built environments**:
- Impermeable surfaces, increasing surface runoff and decrease lag time, resulting in **flash floods**
**Small basins in semi-arid/arid areas** :
- Very short lag-time, resulting in flash floods
56
Mitigation and Adaptation of Flood Risk
**Afforestation of upland areas**:
- Increasing vegetation cover - reducing surface runoff
**Restricting construction on flood plains**:
- Decreased economic loss
- Decreased social loss
- Less urbanisation = more interception
**Temporary extra flood plains** :
e.g. **UK football pitches used to channel storm discharge in extreme conditions to reduce flood risk**
57
Climate change on the Hydrological Cycle
- Anthropogenic global warming due to increased GHGs in atmosphere
- Increase in land and sea temperatures leads to decrease in periods between ENSO cycles- more unusual climates in SA and Australia
- Increased temperature leads to increased evaporation, causing potential droughts and water scarcity
- Rise in temperature in some locations leads to convectional rainfall + **enhanced tropical cyclone or depression intensity**,and more periodic flooding
- Climate change may reduce inputs and stores but may increase **outputs**:
-Less precipitation
-Less water available in stores
- High rates of evaporation
- Reduced size of snow and glacier mass
- Managing future change is challenging as climate change and ENSO cycles are unpredictable
58
Inequality and Insecurity over water
- Water is distributed unevenly across the glove **66% live in areas with access to only 25% of the annual global rainfall**
59
Water demand increases due to
- Population growth
- Growing middle-class, development increases domestic and lifestyle demand
- Economic growth = industrial demand increase
60
Water supply cannot meet demand due to
- Aquifiers and deep-water wwells being dug for water intensive agriculture
- Water tables dropping
- Water extracted at faster rate than soil recharge
61
Causes of Water Insecurity
- **Precipitation** varies across different climates- **mid-latitude areas receive most rainfall**
- **Topography**- **high relief gets the most precipitation, surface runoff is greater for inclined planes, larger channel flow and water is easily stored by dams and reservoirs**
- **Geology**- permeable rocks can be infiltrated, water is stored underground
62
Human Causes of Water Insecurity
- **Industrial activity** causes pollution and population pressure reduces access to clean water.
- Saltwater encroachment due to over-extraction and rising sea levels, reducing freshwater stores
63
Consequences of Water Insecurity
- Increased price of clean water
- Agriculture consumers **67% of all water extractions and industrial water consumption**, Fields and grazing lands are dependant on rainwater and aquaculture
64
Solutions to Water Insecurity
- Farmers store water for irrigation
-Increase in HEP
65
Hard Engineering
**Mega Dams**:
Advantages:
- Provide large volume of water
-Generates HEP
- Reduced demand for groundwater
Disadvantages:
- Floods land, expensive
- Areas downstream have lack of water
- Quick evaporation
**Desalination Plants**
Advantages:
- Provides large volume of clean water
-Reduced demand for groundwater
Disadvantages:
- Energy-intensive
- Releases lots of CO2
- Expensive
**Water transfer schemes**:
Advantages:
- Provides water for arid areas
- Valuable resource for undeveloped countries
Disadvantages:
- Dry up sources
-Expensive
66
Water Scarcity
Less than 1000m3 available per person per year
67
Water Stress
Less than 1700m3 available per person per year
68
Water insecurity
Present and future supplies cannot be guaranteed
69
Water Poverty Index WPI
Accounts for:
**Water Resources**: Availability and quality of water
**Access to water**: Distance from safe water domestic use
**Handling Capacity**: Management, infrastructure, income
**Use of water**: Domestic, agricultural and industrial processes
**Environmental Indicators**: Ability to sustain nature and ecosystems
70
Sustainable Water Management
- Automatic spray technology, advanced irrigation system
- Reducing city waste water- conserves freshwater in areas of high demand
- GM crops- tolerant of dry conditions
