Water: cycle and sustainability issues

What is water?

• The only natural substance that can be found

  on Earth in all three states

  • solid, liquid, and gas

  • water most dense at 4c

Key processes: from air to water Evaporation

• Liquid → vapor, driven by solar radiation providing

  energy for state change.

  • Oceans dominate (86% of global evaporation).

  • 50 - 85 % of O2 produced in oceans and

    freshwaters

• Oceans influence and regulate world

  climate and weather – most rainfall

  comes from oceans

  • Sensitive to temperature, wind, and humidity

  gradients

Key processes: from air to water Transpiration

• Plants release water vapor via stomata.

• Transpiration involves biological processes within plants, such as water uptake, storage and stomatal control

• Sensitive to type of plant, temperature, wind, and humidity gradients.

• Evapotranspiration = evaporation +transpiration, linking the biosphere to the atmosphere

Key processes: from air to water Sublimation

• Direct solid ice → vapor transition

  • no liquid intermediate phase

• important in cryosphere

• Sensitive to atmospheric pressure and

  humidity.

  • Example: freeze-drying techniques and dry ice mist

• Deposition: Direct vapor → solid ice transition

Key processes: from air to water Condensation

• Water vapor → liquid droplets or ice crystals in the atmosphere.

  • rain

• Loss of energy: “warm” humid air meets “cold” air / surfaces →molecules slow down, and attraction becomes stronger.

  • aerosols up in the air where drops can latch onto

  • we want to have fewer aerosols

• Forms clouds, dependent on temperature, pressure, and aerosols(cloud condensation nuclei).

Key processes: from air to water Precipitation

• Rain, snow, sleet, hail.

• Transfers water from atmosphere to land and ocean.

• Most (~78%) fall over the oceans

• Precipitation rates vary geographically and over time

Key processes: water on the ground

• Infiltration & Percolation

  • Water enters soil, replenishes groundwater.

  • Controlled by soil texture, vegetation, land use.

• Runoff

  • Surface flow of water back to rivers, lakes, oceans.

  • Major driver of sediment and nutrient transport.

• Subsurface Flow

  • Groundwater flow through aquifers, much slower than surface water.

  • Residence times: days (shallow aquifers) to millennia

    (deep aquifers)

Global Water-Cycle

• The water cycle is the continuous

  movement of water within the Earth System, linking the atmosphere, hydrosphere, lithosphere, and biosphere.

• It is a closed system globally (no significant input or output of water to space),

• but it contains many open subsystems where fluxes and

  residence times differ.

  • SA can export rain water

Energy and feedbacks

• Solar radiation drives evaporation and transpiration.

• Condensation and evaporation processes regulate climate

  through latent heat fluxes by release/absorption of heat.

• What happens when we add more heat?

  • warming → more evaporation → more water vapor and

    energy → amplifies warming through positive feedback →more rain and more extreme weather events.

    • speed up and intensify the cycle

• But also, clouds can cool (by reflecting solar radiation) or

  warm (by trapping longwave radiation)

Diversity of aquatic systems

• Wide variety of morphology and connectedness in aquatic systems

• These define characteristics, functions, processes and biota

• Some characteristics:

  • Latitude: tropical to polar

  • Salinity: fresh – brackish - marine

  • Flow: velocity and stagnation

  • Size and depth

  Nutrient richness

  • Altitude

  • Connectedness

latitude

• explains ocean currents

  • Horizontal currents

  • mainly friction between water and wind

  • Earth rotation and Coriolis forc

Vertical ocean currents

• Upwellings and downwellings

• caused by density differences through

  temperature and salinity

• Thermohaline circulation driven by cold, salty

  water sinking at the poles

• continuous, slow-moving "conveyor belt" →

  circulates water and heat throughout the world's

  oceans, influencing global climate patterns and

  sea levels

Salinity

• Freshwater <1 % salinity

• Marine water ~ 3.5 % salinity 22

• Groundwater is saline in many places (also NL)

• Landlocked lakes among the most saline environments e.g. Don Juan Pond 40.2% and Lake Assal 34.5%

Water column is not homogeneous

• Sunlight travels to ~1000m deep

• Light extinction depends on water clarity – aphotic zone = < 1 % sunlight

• creates zonation for biota

  • = depth makes a big different in biota and biochem

  • Not only light changes with depth:

    • temperature

    • pressure

    • oxygen

    • macronutrients

    • micronutrients

    • associated biota

Lake zonation

Ecology:

• Limnetic / pelagic: open water

• Littoral: near the shore

• Benthic: bottom of lake

• Light: Euphotic vs aphotic

• the first layer is warm and bottom is cold

Velocity

• Lentic = slow moving water

  - e.g., ponds, pools, lakes

• Lotic = faster moving water

  - e.g., streams, rivers

• Wetlands = soil is saturated or

  inundated at least part of the time

  - e.g., marshes, swamps, intertidals, floodplains, bogs, …

Lakes and Rivers

• Standing water (more or less)

  • Freshwater storage

  • More time for chemical and ecological interactions

• Flowing water

  • Freshwater transport

  • Stronger geological influence

Rivers

• Cover ca 0.6% of land surface

  • Flow from high lands to lowlands

  • Mostly fed by run-off and melt water

  • Collect all water from the catchment

  • Transport water to lakes and oceans

  • Transport matter and organism

• Headwaters:

  - Lowest flow, erosion > deposition

• Transfer zone:

  - Flatter slope, more flow, erosionand deposition important processes

• •Deposition zone:

  - Highest flow, slope minimal,deposition > erosion

• Flow = the volume of water moving

  past a particular point during a

  given time period

Lakes

• • Account for ~ 3 % of Earth’s surface

• vary from ephemeral ponds to permanent waterbodies

• Lakes formed by:

  • geological processes,

  • movement of glaciers,

  • rivers,

  • human activities e.g.

  reservoirs.

Primary succession

• Lakes and ponds slowly turn into land

  Biomass dies off / settles -> generating

  nutrients and sediments.

• Shallower systems allow for establishment of

  submerged vegetation

• Subsequently larger plants and animal

  communities can grow

Secondary succession

• Secondary succession happen when a previously established ecosystem recovers from a (natural) “disaster”.

• The biodiversity of surrounding ecosystems plays a role in how fast this recovery happens

Wetlands

• Cover ~ 6-7 % of land surface

  • Peatlands, mangroves, seagrass

  beds…

  • Large water-sediment interaction

  areas, hence important for carbon

  and nutrient cycles

  • the water is not moving or standing its both

  • lot of potential for biochem to happen

• High productivity:

  - Support high concentrations of animals, provide nurseries

  - Support cultivation of e.g. rice

• Ecosystem services

  - water filtration, storm protection, flood control and recreation.

• Carbon sinks

  • if it takes up cos and stores it

    - Store ca 30% of all land-based carbon

    - As long as you keep them wet…

• • Carbon source

  • - When drained -> carbon sources

Large-scale peatland restoration

• Restoration effort

  • ~ 50 % wetland surface lost since the 1900s

    EU Nature Restoration Law

    aims to rewet 15% of peatland areas. “Given their

    importance, rewetting peatlands is important to

    reach a number of EU objectives, including the

    climate neutrality and biodiversity targets, as well

    as goals of the Water Framework Directive”

• LIFE PEAT RESTORE : restoring peatlands – sequester carbon

• project area = one of the global emission Hot Spots, where the

  potential to save greenhouse gas emissions is exceptionally hi

Last but not least: Groundwater

• depends on how high groundwater is for the landscape

• Groundwater ca 30 % of all freshwater

• Groundwater levels help to dictate types of freshwater

  ecosystems (e.g., marshes

Biomass pyramid

• Snapshot of the standing biomassper trophic level often given as dry- weight

• often inverted in lakes and oceans

  -> low standing primary producer biomass in the water column, but high production

• healthy waters are not green

Freshwater change planetary boundary

• water availability and quality are critical for ecosystems, agriculture, and human survival.

  Original 2009 Approach

• Focus: Global freshwater use (blue water = rivers, lakes,

  groundwater) for consumptive use.

• withdraw too much, ecosystems collapse and downstream users lose water

• PB and sustainability issues

• But this was criticized as freshwater resources and uses are highly regional and seasonal

  2023 Refinement

  • Freshwater change is now assessed by first establishing the Holocene baseline of blue water (lakes, rivers, groundwater) and green water (soil moisture from precipitation)

  • looks at original but also the indirect use like soil measure rather then rain fed water

• Boundaries set:

  - 4,000 km³/year of blue water use

  - percentage of land where root-zone soil moisture deviates from baseline

  variability

  • Both blue water (groundwater depletion, river drying) and green water (soil moisture stress) are under pressure, indicated by the widespread increase in both abnormally dry and wet soil moisture conditions globally

Green water boundary

• new boundary so why choose it?

• considers the water cycle's terrestrial components: precipitation, evaporation, and soil moisture.

• takes into account the role of water, especially soil moisture, in

  - the resilience of the biosphere,

  - securing terrestrial carbon sinks

  - regulating atmospheric circulation

• Link to deforestation

Link to deforestation

• More tree cover leads to more transpiration

• • More transpiration to more rainfall

• • More rainfall + tree protection –> higher soil moisture

• • Self-reinforcing feedback

vs:

• Loss of tree cover and replacement by short vegetation

• Less transpiration and drier soils

• More difficult for trees to recover

• Also a self-reinforcing feedback

• -> see regime shifts a little late

• = Deforestation effects

  • several regions of the Amazon will

    be transformed into savannah and hard to bring the rainforest back

Stabilizing vs amplifying feedbacks

how cna we generalize whats happenign in the amazon?

• Understanding these green water feedback

  processes allows generalizing insights to other

  systems,

  • Characterising them by

  • stabilizing (minus sign) or

  • amplifying (plus sign) feedbacks

  • green water-related changes in the Earth system are amplifying rather (more warming ) than stabilizing.

  • Can lead to runaway change

Alternative stable states

• Alternative stable states:

• Complex systems that can occur in two or more internally stabilized states given the same external conditions

• produces a:

• Regime shift:

• a sudden and fundamental shift in the structure, function, and feedback mechanisms of a system caused by passing a tipping point

  • hard to predict

Regime shift in lakes

• Regime shift: big, often sudden change in the

  structure and function of an ecosystem despite

  only incremental changes in drivers.

• Classic example: clear and turbid lakes due to

  phosphorus eutrophication and reoligotrophication

• Characteristic of regime shifts:

  Once it flips, it’s often hard to reverse because of

  internal stabilizing feedback loops

Eutrophication regime shif

• Clear state

  • Macrophytes stabilise clear state through sediment

  stabilisation, providing shelter for zooplankton.

  • Piscivore fish control population of planktivore fish

• Hysteresis: Alternative stable states in shallow lake

• Turbid state

  • Phytoplankton stabilise turbidstate through shading,changes in fish community(no visual predators).

  • Dominance of benthic feeding fish prevent sediment stabilisation

  • takes alot of work and fertilizer to get back to how the lake was before

Alternative stable states

• Complex systems have stabilizing feedback

  cycles-> initially absorb stress without showing signs

  of degradation

Hard to predict and to reverse

• Why hard to predict?

  • Due to internal feedbacks no easily visible

  changes in ecosystem functions despite changing

  nutrient concentrations.

• Why Hard to Reverse?

  • Even if nutrient input is reduced, algae dominate because plants are gone.

  • Fish communities and food webs have shifted.

  • Restoration often requires major interventions

    (dredging, fish removal, re-planting vegetation)

Apply knowledge: Alternative stable state

• As a water manager, how can you use this concept

  • you could look at coagulants that take out the plankton

  • look at the inflow and sediment nutrition, dredging, p fixation reduction

  • look at biomanipulation

Ecosystem Services

• To provide services reliably, systems need to be

  resilient and resistant

• Link to ecosystem services freshwater

  • What ecosystem services do you connect with water?

Human influences on freshwater

• Aquatic systems are under multiple and often

  interacting stresses

Rivers and lakes as sentinel

• Rivers and lakes integrate all changes in

  the catchment

  - sentinels of global change

  - sentinels of land use change

• Observed effects in lakes and rivers

  - Combination of external and internal

  processes

  - Explains the amount of research on lakes

  despite their small landcove

Freshwater systems biodiversity hotspot

• Freshwater habitats are extremely diverse per unit

  habitat volume on Earth Freshwater ecosystems cover

  less than 1% of Earth's surface yet are home to at least

  140,000 specialist freshwater species i.e. 10% of Earth's

  species.

• Disproportionate diversity

  loss

Major threats to aquatic system

Major threats to aquatic systems

• dams

Marine sustainability issue

• acidification , noise, habitat loss etc

Invasive species

• Invasive species

  Substantial variation in the spatial patterns of invasion

• Main recipients: Global North, newly industrialized countries and small tropical island

• Sources: South Americas and Eurasia

  39% were introduced only intentionally

  26% only unintentionally,

  22% both intentionally and unintentionally dominant pathway for species invasions: horticulture and the nursery trade

• example: invasive macrophytes

What is actually water quality?

• Chemical (novel entities of concern, like chemical) and ecological status (species and biomass)

Water quality Water framework directive

• looks at main rivers rather than small water bodies

  • the majority in the NL is small water bodies

• Ecological Quality Small Waterbodies

  • citizen science campaign

  • we look across all water bodies, if 1 is bad they all score bad

  • only 4% were in good condition

Overharvesting: Water abstraction Lake Ara

• unsustainable cotton cultivation and little rainfall

• Water abstraction

  • Sinking of land due to groundwater abstraction

  • inking of land due to drying and decomposing peat

    • loosing heigh off the land

Bending the curve

• 1.Let rivers flow more naturally;

  2.Improve water quality in freshwater

  ecosystems;

  3.Protect and restore critical habitats;

  4.End overfishing and unsustainable sand

  mining in rivers and lakes;

  5.Prevent and control invasions by non-

  native species; and

  6.Protect free-flowing rivers and remove

  obsolete dams

Threats to aquatic ecosystems

• Habitat loss, fragmentation or degradation: e.g. dams and

  reservoirs, urbanisation

• Invasive species or diseases

  Pollution: Eutrophication and other chemicals

• Climate change: e.g. warming, changes in precipitation patterns

  Overexploitation: Water withdrawal / overharvesting

water quality and quantity

• If water is scarce, then you don’t worry about quality

• But that has costs

• Water Sustainability Issues: too much, too little, too dirty

• Drinking water scarcity: quantity and quality

• Drinking water scarcity occurs even in areas where there is plenty of rainfall and freshwater ->

  physical and economical scarcity

• Water scarcity affects 1 in 3 people on everycontinent of the globe

• Almost 1/5th of the world’s population

  (approx. 1.2 billion) live in areas where water isphysically scarce

• More than 10% of people worldwide consume foods irrigated by wastewater that contain chemicals or disease-causing organisms

ex Kombolcha: Industrialising city, N.Ethiopia

• Textile, pH (compliant)

• steel works (Zn)

• Brewery

  (organics and

  nutrients)

The Kuznets Curve – maybe, but much debated

• species richness

• per capita income

• diversity is higher when people are poor

• but ppl are rich enough and at one point care

Water footprint

• Shows extent of water use in relation to human consumption

• Expressed as water volume consumed and / or polluted (so quality only indirectly shown)

• Calculated on various user levels (individual to global, private to corporate), processes and / or products and services

Types of Water Footprints

• Blue water footprint

• Consumption of surface water and groundwater

• Examples: Irrigation from rivers or aquifers, water

  for industrial processes, household tap water.

• Case: Growing irrigated crops like rice in dry

  regions → large blue water footprint

• Green water footprint

  Use of rainwater stored in the soil (moisture

  available to plants).

  Examples: Rainfed agriculture, forestry,

  pastureland.

  Case: Growing wheat in temperate regions with

  rainfall → mostly a green water footprint

• Grey water footprint

  The amount of freshwater required to dilute

  pollutants to meet water quality standards.

  Examples: Runoff of fertilizers and pesticides

  from fields, wastewater from factories or

  households.

  Case: Cotton farming → large grey footprint

  because of pesticide and fertilizer runof

Global Human Water Footprint

• Freshwater use

  Nearly 8-fold increase from 1900-2010

• World population

  Nearly 8-fold increase from 1820-2019

• most water is used for irrigation and livestock

• industry uses it for dilution, steam, washing and cooling

• top food products water use

  • beef, nuts, sheep/goats

• freshwater exports

  • “virtual water”

• domestic freshwater use

  • 134 liters

Some critiques to take along

• Oversimplification by providing one volumetric

  number -> local overconsumption can not be

  traded to another region.

• Renewal rates differ regionally and by type

• Grey water footprint lacks solid scientific

  underpinnin

Solutions to freshwater sustainability

• Solutions to the Freshwater Crisis:

  • - Bending the curve

  • - Efficiency in irrigation and industry

    • Sugarcane Upper Egypt

      • Traditionally irrigation is to flood it

      • water evaporates instead of sugarcane absorbing it

      • drip system helped reduce water evaporation and plants soaked it up

    • Precision farming sounds promising

      - Lower input waste

      - Increase yield

      - Increase efficiency (time, expenditure,

      resources)

      But also has common challenges

      - Upfront investment

      - Adaptability and willingness to learn

      - Compatibility and connectivity

  • - Sustainable diets (less water-intensive foods)

  • - Pollution control and grey water recycling

  • - Governance & transboundary cooperation

Today’s concepts

• Water cycle components and key processes

  • stages

• Some of the huge diversity in waterbodies and a few of their functions

• HIPCO, but then in water

• Regime shifts: concept and how it helps understand unexpected outcomes in complex systems

• Some consequences of human alterations to water

• And water foot printing across different sectors

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