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Flashcards in this deck (37)
  • What is one physical effect of removing riparian plants next to rivers and streams?

    • More sunlight reaches the water, making it warmer
    riparian temperature
  • How does removing leaves and wood from riparian zones affect aquatic animals?

    • Reduces food and shelter available for animals
    riparian habitat
  • What happens to water when more soil and dirt wash into rivers from agricultural land?

    • Water becomes muddier and habitats for fish and insects can be clogged
    sediment waterquality
  • How do cows walking near rivers or farmers disturbing soil affect streambeds?

    • They cause dirt to wash into the water, filling spaces in the streambed and reducing habitat
    sediment agriculture
  • What metaphor is used to describe a streambed clogged by sediment?

    • A streambed is like a sponge full of holes; sediment clogs the holes making it hard for animals to live there
    sediment metaphor
  • What is a common purpose for farmers to straighten rivers?

    To move water faster for irrigation or drainage.

    channelization agriculture
  • How do straightened rivers differ from natural winding rivers in terms of water movement and habitat?

    Straightened rivers move water faster and lose natural curves that slow water and create habitats for animals.

    habitat channelization
  • Give the example comparison used to describe a straightened river's effect on wildlife.

    A straightened river is like a highway for water—fast but not good for wildlife.

    example channelization
  • What is one effect of farmers pumping groundwater from wells for crops?

    It can lower the water table and change how rivers flow.

    groundwater agriculture
  • How can groundwater pumping cause a river that gains water from underground to change?

    The river can start losing water back into the ground and may dry up if too much water is pumped.

    groundwater rivers
  • What do farmers do to floodplains and what is one consequence for river systems?

    Farmers modify floodplains to grow crops or build infrastructure, which reduces natural flooding important for river health.

    floodplain agriculture
  • What fertilizers are mentioned as sources of nitrogen and phosphorus that help crops grow?

    • Nitrogen: urea
    • Phosphorus: superphosphate
    agriculture nutrients
  • What is eutrophication in freshwater systems as described in the text?

    Excess nutrients washing into rivers and lakes cause algae to grow too much, a process called eutrophication.

    eutrophication pollution
  • How do algae blooms harm aquatic life according to the text?

    Algae blooms block sunlight and, when they die and decompose, use up oxygen, lowering dissolved oxygen for fish.

    algae oxygen
  • What effect does low oxygen from decomposition have on fish?

    Low oxygen levels kill fish and disrupt food chains.

    fish ecosystem
  • How does cow waste contribute to freshwater pollution?

    Cow waste contains nitrates that rain can wash into rivers, acting like fertilizer for algae and increasing algae growth.

    animalwaste nitrates
  • How does soil erosion contribute to nutrient pollution?

    When soil washes into rivers it carries phosphorus with it, adding to nutrient pollution and making the water muddy.

    erosion phosphorus
  • What are tile drains and why are they important for pollution transport?

    Tile drains are underground pipes that quickly drain water from fields and also transport chemicals like nitrates into rivers.

    tiledrains hydrology
  • What is 'water abstraction' for irrigation?

    • Water abstraction: taking water from rivers or underground for crops
    water irrigation
  • How does water abstraction for farming affect rivers?

    • It reduces river water amounts, affecting aquatic life
    water ecology
  • What are 'environmental flows' in rivers?

    • Environmental flows: the amount of water rivers need to stay healthy
    flows rivers
  • What happens if too much water is taken from rivers for agriculture?

    • Rivers cannot support fish, plants, or people
    impacts agriculture
  • How does removing riparian plants affect river water?

    • Increases sunlight, reduces shade, warms water and makes it muddier
    riparian temperature
  • How does soil erosion from farming and livestock harm streams?

    • Eroded soil (sediment) clogs streambeds, reducing habitats for small animals
    sediment habitat
  • What is the effect of straightening river channels for agriculture?

    • Channelization destroys natural curves that create wildlife habitats
    channelization habitat
  • Name one physical change agriculture causes in freshwater systems.

    • Sedimentation: soil erosion that clogs waterways
    physical freshwater
  • How does groundwater pumping affect rivers?

    • Lowers the water table
    • Can change rivers from 'gaining' water to 'losing' water
    hydrology groundwater
  • What physical floodplain modification by farmers affects river health?

    • Farmers modify floodplains, reducing natural flooding that helps rivers stay healthy
    floodplain agriculture
  • What is 'nutrient enrichment' in agricultural freshwater impacts?

    • Fertilizers (nitrogen, phosphorus) wash into rivers, causing algae blooms
    eutrophication nutrients
  • How do algae blooms from nutrient enrichment harm aquatic ecosystems?

    • Blooms block sunlight and use up oxygen, killing fish and disrupting ecosystems
    algae ecology
  • How does animal waste from livestock affect freshwater chemistry?

    • Adds nitrates to water, fueling algae growth and polluting rivers
    pollution livestock
  • What role do tile drains play in agricultural pollution?

    • Underground pipes quickly move water and chemicals like nitrates into rivers, increasing pollution
    tile-drains transport
  • What is meant by 'environmental flows' in relation to rivers?

    • Rivers need enough water to stay healthy; taking too much for agriculture harms ecosystems
    flows ecosystems
  • Give examples of how agriculture alters freshwater systems physically and chemically.

    • Riparian zone removal and warming
    • Sedimentation clogging habitats
    • Channelization and faster flows
    • Groundwater pumping and low flows
    • Nutrient enrichment and eutrophication
    • Tile drains as pollution pathways
    summary impacts
  • What is eutrophication in a lake?

    • Eutrophication: Excess algae growth that blocks sunlight and, when algae die, depletes oxygen causing fish to suffocate
    ecology eutrophication
  • How does sediment affect streambed habitats?

    • Sediment problems: Sediment clogs the holes in a streambed 'sponge', making it hard for small animals to live there
    sediment habitat
  • What effect can excessive groundwater pumping have on a river?

    • Groundwater pumping: Excess pumping can cause a river fed by underground springs to dry up as water flows back into the ground
    groundwater flows
Study Notes

Freshwater impacts of agriculture — concise study notes

Quick overview

  • Agriculture alters freshwater physically (habitat, flow, sediment) and chemically (nutrients, pollutants, altered water balance), degrading rivers, streams and lakes.

1) Physical changes

  • Riparian zone removal: Clearing trees and plants next to waterways increases light and temperature, reduces organic inputs (leaves, wood) and weakens bank stability, harming habitat and food sources.

  • Sedimentation: Soil disturbed by ploughing or livestock enters streams, clogging pore spaces in beds and reducing refuge and feeding areas for invertebrates and fish.

  • Channel modification: Straightening or dredging rivers speeds up flow, removes pools and meanders, and reduces habitat complexity for aquatic life.

  • Groundwater pumping: Irrigation wells can lower the water table, changing rivers from gaining to losing reaches and potentially drying springs and low flows.

  • Floodplain alteration: Converting or draining floodplains reduces natural flood storage and the periodic nutrient/organic replenishment that supports river health.

2) Chemical changes

  • Nutrient enrichment (fertilizers): Nitrogen and phosphorus runoff fuels algal growth (eutrophication). When algae die and decompose, oxygen is consumed, causing hypoxia that kills fish and disrupts food webs.

  • Livestock waste: Manure and urine add nitrates and organic matter, increasing nutrient loads and bacterial contamination.

  • Soil-attached phosphorus: Eroded soil transports phosphorus bound to particles, combining sediment and nutrient problems.

  • Tile drains and drainage systems: Subsurface drains rapidly convey nitrate-rich water to streams, acting like highways for pollutants.

  • Water abstraction for irrigation: Removing surface or groundwater reduces in-stream flows and can prevent maintenance of environmental flows needed for ecosystems.

3) Ecological consequences (summary)

  • Eutrophication and algal blooms: Reduce light penetration and oxygen; can create fish kills and loss of biodiversity.
  • Habitat loss: Warmer, muddier, simplified channels support fewer and different species than intact systems.
  • Altered flow regimes: Faster runoff, lower base flows, and loss of seasonal floods change life cycles of aquatic organisms.

4) Key examples and analogies

  • A shaded, cool stream becomes warmer and muddier when riparian trees are removed, reducing fish survival.
  • A streambed is like a sponge; sediment clogs the holes and eliminates habitat for small animals.
  • Excess fertilizer makes a lake turn green with algae; when algae die, oxygen falls and fish suffocate.
  • Pumping groundwater can reverse a spring-fed river, causing it to lose water into the ground and dry up.

5) Important terms to remember

  • Riparian zone, sedimentation, eutrophication, hypoxia, tile drains, environmental flows, water table, channelization.

6) Focus questions (study prompts)

  • How does removing riparian vegetation change temperature, habitat structure, and sediment inputs?
  • Why does phosphorus often travel attached to eroded soil, and how does that link physical and chemical impacts?
  • How do tile drains change the timing and concentration of pollutants reaching streams?
  • What is an environmental flow and why is it critical for freshwater ecosystems?

7) Short mitigation notes (conceptual)

  • Maintain or restore riparian buffers, reduce soil erosion (cover crops, reduced tillage), manage fertilizer application and timing, treat or contain livestock waste, and set environmental flow requirements to reduce damage.