Hydrology and the Water Cycle

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Questions and Answers

Which process describes water changing from a gaseous state to a liquid state in the hydrological cycle?

Infiltration

Evaporation

Precipitation

Condensation (correct)

What is the primary input into a drainage basin system?

Surface Runoff

Transpiration

Evaporation

Precipitation (correct)

Which term describes the movement of water through the upper soil layers towards a river?

Throughflow (correct)

Channel Flow

Surface Runoff

Infiltration

What is a potential effect of deforestation on the hydrological cycle?

Increased surface run-off Signup and view all the answers

How might mining activities impact the hydrological cycle?

Silted up rivers and lakes Signup and view all the answers

What is the role of vegetation in the hydrological cycle?

To intercept and store water Signup and view all the answers

What is the effect of urbanization on surface runoff, in the hydrological cycle?

Increase of surface runoff due to impermeable surfaces Signup and view all the answers

What process involves water moving downwards into the soil?

Infiltration Signup and view all the answers

Which of the following best describes the rising limb of a hydrograph in an urban area compared to a rural area after a heavy rainfall?

Steeper in urban areas due to less interception and more impermeable surfaces. Signup and view all the answers

What is the primary reason for the higher peak discharge in an urban hydrograph compared to a rural hydrograph?

Reduced infiltration due to paved surfaces in urban areas. Signup and view all the answers

Which of the following best describes the lag time in an urban hydrograph compared to that of a rural hydrograph?

Urban areas have a shorter lag time due to drains and sewers quickly channeling the water. Signup and view all the answers

What contributes to the faster return to base flow in an urban hydrograph after a storm?

Less water being stored as groundwater due to more surface run-off. Signup and view all the answers

The recessional limb of an urban hydrograph is characteristically:

Steeper due to increased surface runoff. Signup and view all the answers

What is the influence of vegetation on a rural hydrograph?

Reduces peak discharge due to interception and transpiration. Signup and view all the answers

What is the baseflow discharge of the River Valency before the storm?

Around 2 cumecs. Signup and view all the answers

What is the typical lag time mentioned in the text concerning the River Valency?

Five hours. Signup and view all the answers

What is the main contributing factor to the steep rising limb of the River Valency’s hydrograph?

Impermeable surfaces causing rapid runoff, exceeding soil storage. Signup and view all the answers

What is the primary erosion process that forms a plunge pool at the base of a waterfall?

Hydraulic action and abrasion Signup and view all the answers

What causes the overhang of hard rock above the plunge pool in a waterfall?

Undercutting of soft rock beneath the hard rock. Signup and view all the answers

Which river feature is formed by erosion on the outer bend and deposition on the inner bend?

Meander Signup and view all the answers

What is the main force behind the cutting off of a meander to form an oxbow lake?

The river creating a new, straighter channel during a flood. Signup and view all the answers

What type of weathering contributes to the widening of a V-shaped valley?

Freeze-thaw weathering Signup and view all the answers

What is the direct result of the rocks that have fallen into the river in the formation of a V-shaped valley?

An increased rate of abrasion and further erosion Signup and view all the answers

Study Notes

Hydrological Cycle

Water continuously cycles, a closed system.
Evaporation (liquid to gas) from bodies of water (e.g., seas, lakes) adds moisture to the atmosphere.
Rising water vapor cools, condenses (gas to liquid), and forms clouds.
Precipitation (e.g., rain, snow) returns water to the surface,
Water may flow across land as surface runoff or channel flow in streams/rivers.
Some water is intercepted by vegetation before reaching the ground.
Water eventually returns to the sea/lakes, completing the cycle.

Drainage Basin

A drainage basin is an open system with inputs, storage, transfers, and outputs.
Inputs: Precipitation (rain, snow).
Storage: Lakes, rivers, vegetation interception.
Transfers: Surface runoff, channel flow, infiltration, throughflow.
Outputs: Evaporation, surface runoff into seas/oceans.

Human Impact on the Hydrological Cycle

Mining reduces storage capacity of lakes/rivers by causing silting.
Reduced vegetation increases surface runoff.
Irrigation reduces river flow and lowers water tables, increasing evaporation.
Deforestation increases surface runoff and extreme river flows.
Urbanization increases impermeable surfaces, accelerating surface runoff and leading to higher river levels.

Urban vs. Rural Hydrographs

Urban Area:
- Steeper rising limb due to less interception and faster runoff.
- Higher peak discharge due to impermeable surfaces.
- Short lag time due to accelerated runoff.
- Steeper recessional limb due to quicker runoff.
Rural Area:
- Gentler rising limb due to vegetation interception and slower runoff.
- Lower peak discharge due to absorption and slower movement.

River Valency Storm Hydrograph (16th August)

Discharge Changes:
- Baseflow around 2 cumecs.
- Slow rise in discharge initially (07:00-09:00).
- 5-hour lag time.
- Steep rising limb, peak discharge 100 cumecs at 18:00.
- Rapid falling limb to baseflow between 18:00-22:00.
Reasons for Changes:
- Initial slow rise due to early rainfall and vegetation interception
- Soil storage exceeded leads to steeper rise; impermeable surfaces cause rapid runoff.
- Steep catchment leads to rapid overland flow.
- Falling limb results from lack of further rainfall.

Waterfall Formation

Hard rock overlies soft rock.
Hydraulic action & abrasion erode soft rock.
Plunge pool forms.
Continued erosion undercuts overhang of hard rock which collapses.
Waterfall retreats upstream over time.

Meander Formation

Winding curves/bends in middle/lower course rivers.
Hydraulic action/abrasion erode outer bends.
Faster flow on outer bend, slower on inner bend.
Deposition on inner bend & erosion on outer bend.
Meanders migrate downstream.

Oxbow Lake Formation

Erosion (hydraulic action/abrasion) continues on outer meander bends and deposition on inner bends
Flood event creates a new, straighter channel.
Original meander is cut off forming an oxbow lake.

V-Shaped Valley Formation

Rivers in mountainous areas erode vertically quickly due to high flow velocity.
Hydraulic action and abrasion erode river channel.
Freeze-thaw weathering impacts valley sides.
Eroded material transported by river deepens channel, widening valley in V-shape.

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Description

Explore the dynamics of the hydrological cycle and drainage basins. This quiz covers processes like evaporation, precipitation, and the impact of human activities on water systems. Test your understanding of how water moves through the environment and the significance of drainage basins.