Unit 6 - Managing water supplies

6.1 Global water distribution

• Salt water in oceans

• Surface fresh water: glaciers, lakes, rivers, permafrost

  • Inflows: precipitation, overland runoff, groundwater seepage, & glacial/snow melt

  • Outflows: evaporation, infiltration into ground stores, & abstraction by humans

• Sub-surface fresh water: groundwater, soil moisture, permafrost

  • Aquifer = zone of rock saturated with water

    • Top of this zone = water table (rises & falls based on input + output)

  • Confined aquifers lay below + above impermeable material (aquitard)

    • Unconfined aquifers are more susceptible to drought

• Atmospheric water (e.g. rain)

• Water security: the ability to access sufficient quantities of clean water to maintain adequate standards of food and manufacturing of goods, adequate sanitation and sustainable health care

Causes of water insecurity

• Climate change → changes in rainfall because warmer air holds more moisture

  • Can cause increased drought, flooding, & decline in snow fall

• Natural disasters:

  • Flooding → erosion of topsoil, pollutes water supply (e.g fertilizer), damages sanitation infrastructure

• Pollution events:

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  • Water pollution: can occur after a point-source event or misuse of a water resource for dumping of waste

    • Run off of: domestic waste (e.g. sewage), industrial waste (e.g. heavy metals), agricultural chemical & fertilizer run off (eutrophication)

  • Groundwater can be contaminated by metals like iron & fluoride

    • From: leachate, septic tanks, storm water drains, saltwater intrusion (saltwater moves into freshwater aquifers)

    • Salt-water intrusion: over abstraction of freshwater reduce pressure & salt water can enter the aquifer

• Population growth: population increases → demand for water increases

  • Leads to more waste & over abstraction of water from aquifers (drops water table + makes them harder & more expensive to access)

    • Impacts flora & fauna: springs + streams that wildlife rely on may dry out & trees that access the water table with deep roots will dehydrate + die

  • Changes in land usage → deforestation & urbanisation

    • Forest + wetlands can act as natural water reservoirs → water can’t infiltrate & recharge groundwater supplies

• Competing demands from agricultural, industrial, and domestic sectors

  • Industrial: power plants, metal/plastic manufacturing

  • Municipal: households (toilet, shower, drinking water)

  • Agriculture: water for livestock, irrigation water for crops

    • Most human water use

• International competition over water sources: conflict b/t regions/countries over water access

  • Waterways being damned can deprive users of water source

  • Some rivers cross int’l borders (e.g. Jordan River b/t Syria/Israel)

• Inequality of water availability: people in LICs are less likely to have access to clean drinking water than HICs (can pay for infrastructure for a safe water supply)

• Differing access to safe drinking water in urban and rural areas: urban areas have better access to clean water (have financial resources) than rural ones

  • Urban areas may face significant water supply problems + impoverished urban areas may not have access to clean water + sanitation

• Mismanagement of irrigation (e.g. salinisation): water supplies can run out & create human-drought conditions

  • Overuse of water → soil salinization → salt on top layer & reduces productivity

  • Eutrophication, increased turbidity, toxic water pollution, harm to ecosystems + groundwater

• Inadequate sanitation: sewage systems + water management plants

  • Sanitation mismanagement: changes in supply/demand + aging infrastructure

    • Septic waste contamination → cholera, diarrhea, etc.

Impacts of water insecurity

• Reduced crop yield, crop failure, livestock death → food shortages, malnutrition and famine

• Illness caused by contaminated drinking water: polluted water can cause insecurity + illness

  • Exposure to bacteria in septic waste → cholera & diarrhea

• Poverty: unable to grow food & stay healthy

  • “Poverty trap” = sick person is unable to work & struggles to afford healthcare

Strategies for managing water insecurity

• Sustainable water extraction and improved supply:

  • piped supply: transports water

    • Improves access & reduces water insecurity, BUT can be expensive & leaks add to water stress

  • aquifers and artesian wells: body of rock/sediment that holds groundwater; well drilled into an aquifer where pressure pushes water out

    • Steady supply (none lost to evaporation) & cheap to extract, BUT can get depleted if over-pumped, saltwater intrusion in coastal areas, & difficult to de-contaminate

  • boreholes: narrow hole to locate water

    • Affordable, safe water that can be used for non-potable actions, BUT can lead to contamination + be over-extracted

  • gravity-fed schemes

    • Cheap & effective for a smaller sized crop area, BUT not applicable in flat terrain + needs management

  • reservoirs and dams

    • Cheap electricity, year-round water supply, BUT flooded land destroys land + displaces people, migration and spawning of fish may be disrupted

    • Increasing holding supply can protect water supply during stress

• Reduction in water usage

  • Domestic: rainwater tanks, low flow shower heads, low flush toilets, overall awareness

  • Agricultural: improved irrigation techniques (e.g. drip irrigation/soil moisture), growing crops less dependent on high water supply

  • Industrial: reusing/recycling clean water, upgrading technology to more efficient solutions, routine maintenance (checking for leaky pipes)

• Education on sustainable water use: gives people knowledge about their responsibility for their own water consumption

• Poverty reduction: population will be healthier, agricultural development/cultivation, & produce manufactured goods (job opportunities)

• International agreement and water-related aid

  • Water Convention of 1996: established 3 main pillars to promote cooperation b/t nations & ensure fair + secure water usage

  • Water aid: aims to ensure a safe water supply → reduce infant mortality + food insecurity

• Rationing

  • Existing resources last longer, BUT doesn’t find an alternative & difficult to manage

• Distillation of saltwater: heating saltwater until it evaporates

  • Improves access to clean water & cheap, BUT leaves behind waste (brine) and requires an energy sources