Introduction to Water Systems – Practice Flashcards

Twenty-five question-and-answer flashcards covering key ideas from the lecture on water systems, including the hydrological cycle, storages, flows, human impacts, and water-management strategies.

What percentage of all the water on Earth is freshwater?

Roughly 2.5 % of Earth’s water is freshwater.

Approximately what share of Earth’s total water is found in accessible rivers, lakes and shallow aquifers?

About 0.76 % of the planet’s water is readily accessible in rivers, lakes and aquifers.

Why is the global hydrological cycle regarded as a closed system?

Because the total amount of water on Earth remains essentially constant with no significant inputs or outputs to space.

What makes a lake an open system within the hydrological cycle?

It exchanges matter (water, nutrients) and energy (e.g., heat from sunlight) with its surroundings.

Give any three major water storages identified in the hydrological cycle.

Examples include oceans, surface waters (rivers/lakes), ice caps & glaciers, soil moisture, atmospheric water vapour, groundwater, and water in organisms.

What collective term is used for the combined processes of evaporation and transpiration?

Evapotranspiration.

Name two climatic factors that most strongly influence the rate of evapotranspiration.

Air temperature and wind speed (humidity is also important).

Which atmospheric process moves clouds horizontally from one place to another?

Advection.

What flow process describes water moving downward through soil to reach aquifers under the force of gravity?

Percolation.

Define infiltration in the context of the hydrological cycle.

The movement of water from the ground surface into the soil.

What is surface run-off?

Water that flows over land when rainfall or snowmelt exceeds the soil’s infiltration capacity.

How can reduced groundwater flow during drought affect river ecosystems?

It lowers river levels and can severely stress or damage aquatic life and habitats.

Roughly what proportion of global precipitation falls directly into the oceans?

About 80 %.

Which two properties of seawater control the density differences that drive thermohaline circulation (the global conveyor belt)?

Temperature and salinity.

Why could extensive melting of polar ice threaten the global conveyor belt?

An influx of warmer, fresher water lowers seawater density at the poles, hindering the sinking of cold, salty water that powers the circulation.

Why do oceans warm and cool much more slowly than the atmosphere?

Water has a high specific heat capacity, meaning it requires large amounts of energy to change temperature.

Which economic sector withdraws the largest share of the world’s freshwater?

Agriculture.

How can excessive irrigation combined with poor drainage damage soils?

It raises soil salinity, potentially making the soil sterile and unsuitable for crops.

Which nutrient pollutant can cause ‘blue baby syndrome’ (methaemoglobinaemia) when present at high levels in drinking water?

Nitrates from fertilizers.

How does deforestation increase the likelihood of downstream flooding?

Removing trees reduces interception, infiltration and root uptake, so rainwater runs off more quickly and in greater volume.

Describe the positive feedback loop that may lead from forest loss to desertification.

Loss of trees lowers transpiration and atmospheric moisture, reducing rainfall, creating a drier climate that further inhibits vegetation growth.

In what main way do impervious urban surfaces alter the hydrological cycle?

They block infiltration, increase contaminated run-off and raise flood risk in nearby waterways.

What is the primary aim of Sustainable Urban Drainage Systems (SuDS)?

To slow and treat run-off, promote infiltration, improve water quality and reduce flood peaks.

Give one SuDS technique that encourages water to soak into the ground.

Use of permeable or porous surfaces such as gravel, permeable pavers or porous asphalt.

What term describes sudden flooding that occurs when rainfall intensity exceeds the ground’s absorption capacity?

Flash flood.