TD

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:

    • 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