Drainage Basin: Inputs and Outputs

• The balance of inputs and outputs in a water body can be represented using flow diagrams.
• Inputs into a drainage basin mainly come from precipitation.
• Inputs can also come from transfer from other drainage basins and groundwater flow.
• Outputs from a Drainage Basin: evaporation and transpiration (the process of a plant taking water from the soil and losing it from the leaves.
• Other outputs from a Drainage Basin: discharge out of the basin, groundwater flow into other drainage basins

Intro

• Six transfers of ocean water: gravity-groundwater outflow, infiltration-water, precipitation-gas to liquid.
• Six transformations of ocean water: evaporation causes temperature increase.

Inflows and Outflows of a Lake

Inflows

• Rainfall/precipitation
• Overland flow from surrounding areas
• Sewage inputs from domestic, industrial, and agricultural sources

Outflows

• Evaporation
• Water infiltration into groundwater
• Water abstraction for domestic, industrial, or agricultural use

Additional information

• Input -> Process storage -> Output
• The water hydrological cycle is balanced
• Slow hydrological cycles lead to damp bedrock for community growth and mud.
• Fast hydrological cycles cause rapid evaporation and desertification due to air exposure.
• Compact soil is not permeable; rainwater accumulates on the surface, shifting to bodies of water, causing murkiness from runoff.
• Porous soil can lead to landslides after contact with large amounts of rainwater.

Human Impacts on the Hydrological Cycle

• Deforestation lowers soil infiltration as microorganisms and roots no longer create pores, resulting in desertification.
• Urbanization alters water flow by creating impermeable barriers (roads, houses) which block water infiltration, increasing runoff.
• Heavily grazed permanent pasture has lower infiltration rates than old permanent pastures due to compact soil, which causes runoff.
• Increased surface runoff from agricultural practices can create unstable ground, leading to landslides.
• Impermeable surfaces in urban areas stop water infiltration and evaporation, allowing water trapped under them to remain while surface water runs off.

Agriculture

• Permanent pasture is farmland utilized for more than 5 years.
• Monoculture is farming only one plant or overuse of animals, leading to soil exposure, mud creation, runoff, and desertification.
• Moderate grazing involves switching animal locations to prevent overgrazing and allow land recuperation.
• Different agriculture types impact drainage basin stores and flows differently.
• Arable farming removes all grass on pasture, focusing on specific vegetation, leading to significant erosion.
• Pastoral farming maintains year-round grass cover but may replace diverse forests with monoculture grass, reducing interception, storage, and infiltration.

Deforestation

Effects

• Increases flood risk due to reduced interception and increased runoff
• Increases river sediment transport
• Increased overland flow leads to more frequent erosion
• Reduces infiltration and evapotranspiration.

Causes

• Agricultural expansion
• Industrial and tourist developments
• Urbanization

Urbanization

Effects

• Creates impermeable surfaces, reducing infiltration and increasing runoff
• Increases drainage density with drains, gutters, and underground sewers
• Lower drainage basins have a more significant impact in urban areas
• Conflicting impacts on hydrological processes: increased erosion from higher river water volumes, faster material flow due to enlarged channels, and reduced erosion in areas with riverbank protection योजनाओं.

Steady State of Water Bodies

Polarity in H-bonding

• Molecules can have polar bonds where electrons shift from one atom to another.
• If there's a general direction among molecules, they're considered polar, like in water.
• Oxygen attracts electrons from hydrogen, creating partial negative charge on oxygen and partial positive charge on hydrogen, making water a polar molecule.
• The attraction between partially charged hydrogen and oxygen atoms of different water molecules forms hydrogen bonds.
• These bonds keep water molecules close together- cohesion
• Water has a high specific heat capacity, meaning it takes longer to heat up and cool down.
• High heat capacity moderates maritime climates near water bodies and creates extreme continental climates inland.
• Strong hydrogen bonds give water high surface tension, allowing insects to walk on its surface.
• Water molecules stick to other surfaces due to their polarity, called adhesion.
• On clean glass, adhesion is greater than cohesion, forming a thin film.

Ocean as a Carbon Sink

• Oceans are Earth's most significant CO2 sink.
• Over 90% of the world's carbon has settled in the ocean over geological time.
• Photosynthesis converts CO2 into organic material, eventually settling in the deep ocean.
• The deep ocean has a higher concentration of carbon than the upper ocean.
• Oceans reduce atmospheric CO2 by storing large amounts in seawater and deep-sea sediments.
• Released carbon stored on the ocean floor could turn oceans into a CO2 source.
• Sequestration of carbon occurs short-term when it is dissolved in oceans. This leads to ocean acidification

Ocean Acidification Causes

• Anthropogenic sources, such as carbon emissions from industries, power plants, cars, and planes.

Chemical processes

• CO₂ + H₂O = H₂CO₃

• H₂CO₃ = H⁺ + HCO₃⁻

• HCO₃⁻ = H⁺ + CO₃²⁻

• Oceans have absorbed over half of the CO2 released from fossil fuel burning in the last 200 years.

• Absorbed CO2 in seawater forms carbonic acid (H2CO2), lowering the pH, and acidifying the ocean.

• Increased H+ concentration in water acidifies the ocean and reduces marine organisms' access to carbonate ions, essential for forming shells and hard parts.

Water Stratification

• Stratification is the separation of densities and water temperatures, forming three layers:

• Epilimnium: Warm Region (low density)

• Metalimnium: Intermediate Region (thermocline separating layer)

• Hypolimnion: Cold Region (high density)

• Stratification intensifies in summer due to the top layer heating up.

• In winter, the top layer cools, increasing its density and causing it to sink, which lowers stratification.

Factors Affecting Stratification Stability

• Lake depth, size, and shape influence stratification.
• Wind speed and water movements can disrupt or maintain stratification.
• Lakes with high water flow do not develop persistent stratification due to shorter water residence time.

Permanent Stratification (Meromictic Lakes)

• Some lakes experience permanent stratification.
• Layers include:
• Mixolimnion
• Chemocline
• Monimolimnion-hypoxic (low O2), saltier, and dense.

Thermoclines in Oceans

• Sunlight energy is mainly absorbed in the top few centimeters of the ocean.
• Waves mix surface water
• Distributing heat to about 100m depth.
• Below the mixed layer, the temperature remains relatively stable.
• Ocean temperature declines with depth.
• Thermoclines vary by latitude: steepest in the tropics, variable in temperate regions, and lowest in polar areas (where sea ice insulates the water below).

Autumn & Winter Mixing

• Surface temperature drops, making water more dense.
• Dense surface water sinks, mixing the layers and bringing nutrients to the surface, which may trigger an algal/phytoplankton bloom.

Water Security

• Involves having access to sufficient safe drinking water as a key component of sustainable societies.
• Relies on the reliable availability of an acceptable quantity and quality of water for health, livelihood, and production, along with water-related risk management.
• Water security depends on water availability, clean water, sufficient funding for water resource development, and political stability
• Includes access to water, sanitation, and hygiene (WASH) and integrated water resource management (WRM).
• Water insecurity is caused by a lack of sufficient good-quality water, resulting from water scarcity, pollution, climate change impacts, natural disasters, poverty, and political conflicts.
• Water insecurity can hinder food production and economic growth.

Other Factors Affecting Water Supply

• Population growth
• Rising living standards
• Increased demand from farming and industry
• Pollution from agriculture, industry, and transport
• Irrigation, defined as watering plants
• General uses of water include hydroelectricity, agriculture, drinking in households, and factories.
• Key factors driving increased demand: population growth, rising middle-income population, dietary changes, urbanization, climate change, and growth in tourism and recreation

Water Stress

• Involves conflicts over water due to pollution, scarcity, or overuse.
• Criteria: water supply of less than 1700m³ per year per capita of clean, accessible water.
• Considers water quality, environmental flows, and accessibility

Natural Causes of Water Stress

• Climate Change. Rising temperatures increase evaporation rates, reduce rainfall, and alter precipitation patterns.
• Droughts: Extended dry periods reduce surface water availability.
• Seasonal Variability: Some regions experience seasonal water shortages due to fluctuating rainfall.
• Geographical Factors: Arid and semi-arid regions naturally have limited freshwater resources.

Human-Induced Causes of Water Stress

• Population Growth
• Urbanization
• Agricultural Overuse
• Industrial Water Use
• Pollution
• Deforestation
• Poor Water Management. Water collected is filtered ineffectively after use from households, firms, and agriculture.
• Conflicts Over Water Resources: Shared water bodies cause conflict between countries or regions.

Water Scarcity

• Limited availability of water in human societies.

Types of Water Scarcity

• Physical water scarcity: It occurs when water consumption exceeds 60% of the usable supply. Countries invest in desalination and food imports.
• Economic water scarcity: Country has enough water but lacks infrastructure to store and transport it.
• Grey water is non-toilet wastewater, like from washing vegetables.

Domestic Conservation

Monitoring and Rationing Water Use

• Using a water meter to track consumption, taking shorter showers, and boiling only the necessary amount of water.

Recycling and Collecting Water

• Recycling grey water for lawns and gardens.
• Using a water butt to collect rainwater.

Efficient Water Usage

• Installing a low-flush toilet.
• Detecting and fixing leaks in pipes and fittings.
• Using pressure-reducing valves and shut-off nozzles on hose pipes.

Water-Conscious Gardening

• Growing drought-resistant plants and mulching to retain moisture.

Energy-Efficient Appliances and Habits

• Using energy-efficient washing machines.
• Running the washing machine only when full.

Water-Saving Habits

• Taking short showers, turning off the tap while brushing teeth or soaping hands, using a brush instead of a hose to clean, watering gardens at optimal times to reduce evaporation and washing cars on the lawn.

Industrial Conservation

Methods to save water

• Greenhouses: recycle water by trapping evaporation.
• Aquaponics: plant roots are in the water while fish below consume them as they release plant nutrients.
• Drip irrigation: very efficient, uses dripping to prevent water evaporation.
• Drought resistant crops: These are created through genetic modification.
• Vegetarianism: Plant growth is less water intensive than developing whole organ systems in livestock

Water Footprint

Types of Water

• Grey Water: water used by households that can be used to water plants.
• Green Water: natural water available for plants and microorganisms.
• Blue Water: Natural water reservoirs containing fresh water.

Challenges and Misinterpretations of Water Footprint

• Footprints can be misleading, as high footprints may suggest overconsumption and environmental risks; low footprints in dry areas can also be problematic.
• An ample water supply along with good water quality sustains consumption and production
• Water quality including levels of pollution has long-term sustainability.
• Citizen scientists accurately measured orthophosphates and nitrates.
• Killarney Study in Ireland showed citizen scientists had less agreement with lab results in biochemical oxygen demand (BOD) and pH levels.
• Citizen scientists achieved more reliable results in cleaner water bodies but not in polluted ones
• Digital measurement tools provided data that were more objective