Chapter 12: Freshwater Systems and Water Resources

Freshwater Systems and Water Resources

  • Water is important part of the environment
  • Earth is a blue planet, because on Earth there is proof that water exists
  • Water shapes the surface of the earth
  • It allows for life
  • It makes Earth different from all other planets
  • Water exists in all 3 states: solid, liquid, gas
  • It exits in the atmosphere, on the surface, and under the ground
  • It makes up the atmosphere and is a important component of the major cycles

Water in Atmosphere

  • Water is an important component as it moves heat from equator to poles through processes such as evaporation, where water enters the atmosphere as vapour, through which it is regulates heat around the Earth
  • It rises as vapour, and falls as rain/snow through precipitation

Water on Surface

  • Ocean currents
  • Sculpts terrestrial landscape
  • Water acts as a carrier for many substances

Water is Locked Up in Minerals in the Earth’s Mantle

  • Water makes the mantle elastic and flexible, which affects the dynamics of plate tectonics
  • Water therefore is a dynamic component of Earth

Hydrology is “Water Science”

  • Hydrology refers to the study of water in hydrosphere, both on the surface of the earth and under ground
  • This includes studying movement, distribution, quantity and quality of water
  • Also includes studying reservoirs, processes, and ecosystems of the hydrosphere

Water is Abundant (Plentiful), But Drinkable Water is Rare

  • Drinkable water is usually rare
  • Most water on Earth is in oceans, but most fresh water is tied up in ice
  • Fresh water has few dissolved salts and not a whole lot
  • Surface fresh water tends to be in lakes mostly
  • Managing and maintain freshwater systems involves
  • Integrity of freshwater ecosystems
  • Knowing and managing the quantity and quality of water for drinking and other uses
  • Earth is not 100% a closed system, which means our water can be affects from the outside

Hydrologic Cycle from a Systems Perspective

  • Reservoirs of hydrologic cycle include ocean; ice capes and glaciers; and then groundwater
  • Processes include precipitation, surface runoff, infiltration, percolation, evaporation, transpiration
  • Fluxes
  • The global hydrologic cycle maintains mass balance, which means the total amount of water is fixed

Solar Energy and Gravity Drive the Hydrologic Cycle

  • Solar energy drives and engines processes such as evaporation, transpiration, condensation
  • Gravity drives precipitation, runoff, groundwater percolation

Surface Freshwater

  • Surface freshwater includes rivers and streams, springs, lakes and ponds, wetlands
  • Surface fresh water tends to be in lakes mostly

Rivers Shape the Landscape

  • Due to rivers, water from rain, snowmelt, and springs tends to run off over the surface
  • Surface runoff (sheet flow) organizes into rills and gullies, then streams and rivers
  • Tributary: refers to a smaller river flowing into a larger one
  • Due to the work of erosion, rivers carry remains of water to the ocean

Drainage Basin

  • A drainage basin is a local hydrologic unit
  • Drainage basin or catchment or watershed is the area drained by one river
  • Catchments are separated from one another by divides

Catchments have Inputs and Outputs

  • Example of an input of a system: Precipitation
  • Example of an output: Runoff
  • Example of an output: Evaporation + transpiration
  • Example of Catchment: Storage in lakes, aquifers etc


  • Groundwater is located beneath the Earth’s surface in soil pore spaces and in fractures of rock formations
  • Groundwater is the largest unfrozen freshwater reservoir
  • Aquifer: underground reservoir of rock and sediment. It is the second largest reservoir of water after glaciers
  • Residence time in aquifer may be thousands of years
  • Canada has much more water underground than on the surface
  • Aquifers store and transmit water
  • Porosity is the % pore space
  • Permeability refers to the interconnectedness of pores
  • Aerated zone: includes some air and some water. Located at the the top (soil moisture)
  • Saturated zone: zone which is completely filled with water (ex. Groundwater)
  • Water table: located on top of the saturated zone
  • Groundwater moves down from the surface to the saturated zone

Groundwater Flow is Controlled by Gravity

  • Water table mimics topography because where water table intersects, it equals surface water
  • Recharge: water flows into an aquifer (underground reservoir) through preceiptation/infiltration
  • Discharge: water flows out of an aquifer and into streams, ocean, and springs

  • Canada tends to use water mainly for industrial purposes, India; agriculture, Lithuania; Domestic
  • Many areas with high population density are water poor and face serious water shortages
  • Water use exceeds supply in many areas of the world, including Canada
  • Canada is criticized today for wasteful water consumption

Global Water Management Challenges Include

  • Urban and rural drinking water sanitation
  • Water for industry and agriculture purposes
  • The protection of aquatic ecosystems
  • “Holistic” watershed management
  • Impacts of environmental change on water resources

Human Use of Surface Water has Environmental Impacts

  • Surface water being lakes, rivers, and ponds used by humans has significant environmental impacts
  • When humans use rivers, the environmental impacts may be downstream and transboundary
  • Decreased flow of water in such rivers, lakes may be another environmental impact as we take out water from such places
  • Human use of surface water can change how fast erosion might occur and siltation rates as we alter the shape and so forth when we extract water from such places
  • There may be changes in water salinity because as humans extract water, it may change how much soil is getting into the water if you change the level of the water. Therefore changing salt levels may have an effect on some organisms
  • Creating reservoirs and increasing irrigation increases evaporation as you are spreading water over a larger area, which therefore leads to loss of water
  • Environmental impacts of human use of surface water also include impacts on habitat, wildlife, ecosystems
  • Pollution, eutrophication
  • In conclusion, whenever we affect flowing water, we are effecting the hydrological cycle and all kinds of things related to it in the whole catchments

We have Erected Thousands of Dams

  • Dam refers to obstruction (barrier) which blocks the flow of water in a river so the water can be stored in a reservoir
  • Dams are not always constructed for water to be stored in a reservoir, sometimes they are done to create a higher fall of water for hydro electrical purposes, to extract water easily, for agricultural purposes etc.
  • Diversion Dam: When water is diverted but is not stored in a reservoir
  • Dams are done to prevent floods, provide drinking water, allow irrigation, generate electricity
  • Problems with dams are that they affects on large rivers such as changing the flow of water in these rivers, and hydrologic cycle
  • Rivers are ecologically complex: Different organisms adapted to different areas of rivers, different type of vegetation surrounding the river etc. If you are making changes to such rivers by creating dams, you are changing the speed of the flow of water in the river, the temperature of the river, the ph of the river etc.

Benefits and Drawbacks of Dams


  • Power generation: less reliant on fossil fuels
  • Emission reduction
  • Crop irrigation
  • Drinking water flood control
  • Shipping
  • New recreational opportunities: artificial lakes created through impoundments etc.


  • Dams need to be better planned when made.
  • Habitat alteration: Affects habitats by changing and creating habitats which originally existed which changes and affects the structure of the community
  • Fisheries decline
  • Population displacement
  • Sediment capture: may cause sediment clogging in rivers
  • Waterlogged land
  • Risk of dam failure
  • Lost recreational opportunities

Dam Removal (Decommissioning)

  • Removing dams restores riparian ecosystems, fisheries, river recreation
  • In Canada only a few dams have been removed, whereas in the U.S. there have been over 500 dams removed

Inefficient Irrigation Wastes Water

  • Today more water tends to be withdrawn for irrigation purposes
  • Today the amount of irrigated land has doubled

The Aral Sea is a Case Study of Diversion

  • It was once the 4th largest lake on Earth
  • It lost 80% of volume due to the diversion of two input rivers
  • Because of this 60,000 fishing jobs were lost
  • Pesticide-laden dust blows from the lake bed
  • Cotton cannot bring back the region’s economy

Environmental Impacts of Groundwater Use

  • Depletion of aquifers: aquifers are underground which are confined (limited) and unconfined (unlimited), and are charged by runoffs. However aquifers commonly recharge from infiltration (penetration) through soils. Aquifers take a while to fill up, which is why when you take more water out; it will reduce the system, which in this case is the aquifer
  • When you deplete the aquifer you are going to drop the water table, and if there is no water to fill up the aquifer, it leads to a big empty space which has overburden on top of it such as soils and trees; it will collapse dramatically, leading to ground subsidence
  • Declining water tables
  • Urban flooding
  • Contamination of the aquifer
  • Cone of Depression: As you are withdrawing water from well, it leads to cone of depression as the water table starts to drop because you are extracting water from underground (aquifers)
  • If discharge (or withdrawals i.e. if you are pulling out more water) is greater than recharge, water table can become depressed. Your water table therefore will drop

Climate Change will Cause Additional Water Problems and Shortages

  • Changes in precipitation patterns will occur due to climate change
  • Shift northward in mid-latitude rain belt
  • Earlier snowmelt and spring runoff
  • More evapotranspiration
  • Drier summers in the interior continental region
  • Biologists get worried about the concept of phonology when talking about climate change. PHONOLOGY is the idea that organisms are adapted to things that happen at a certain time of the year. When you mess with the timing of things such as earlier snow melt and spring runoff, it causes disturbance to the environment which the organisms have adapted to.  This can lead to major disasters for organisms.
  • Warmer rivers (impacting fish)
  • Lower water levels in the Great Lakes
  • Higher ocean water levels (salinization)

Quality is as Important as Quantity

  • Water quality is as important as its quantity
  • Major pollution has caused reduction in the quality of our water today
  • Superfundacites: areas which have been rehabilitated. Example: Cuyahoga River which was rehabilitated after the fire in 1952
  • Point Sources: separate locations where pollutants are generated or located
  • Emissions from factories, slaughterhouses, mines, industrial effluent, or sewage outfall pipes
  • You can indicate point sources on a map from where the pollution is coming from
  • Nonpoint Sources: multiple cumulative inputs over a large area. Located in multiple areas
  • Nonpoint sources are tiny areas which are hard to locate on a map
  • Many small point sources together, such atmospheric fallout from car emissions. Many cars which cause pollution due to emission would be considered a nonpoint source. However on a large scale map, you could indicate where pollution is coming from clearly and is visible, through point sources
  • Point source vs. nonpoint sources depends on the scale

Types of Surface Water Pollution

  • Nutrient pollution: from fertilizers, etc: causes eutrophication
  • Pathogens and waterborne diseases which occur from improperly treated waste: cause disease and death
  • Toxic chemicals from industrial sources, which cause genetic somatic damage
  • Sediment pollution from agriculture, mining, Clearcut logging, construction; can lead to degrades aquatic habitat, affects light levels
  • Thermal pollution from heat and hot water; kills fish, affects oxygen levels

Sources of Groundwater Pollution

  • Natural Sources: mercury from wet lands, fluoride, sulphate, etc.
  • Anthropogenic Sources: landfills and other disposal sites, underground storage infected tanks may leak, agricultural pollution- nitrates from fertilizers, hazardous wastes etc.

Groundwater Pollution is Particularly Difficult to Manage

  • Because contaminated groundwater tends to be hidden, which is difficult to monitor
  • Groundwater can retain contaminants for decades and longer

Slow breakdown due to dissolved oxygen levels

Note Created by
Is this note helpful?
Give kudos to your peers!
Wanna make this note your own?
Fork this Note