Unit 1 - Page 5 - 8

What does a storm hydrograph show?

• The annual variation in river discharge

• The daily variation in river discharge

• The response of a river’s discharge to a rainfall event

• The long-term impact of human activity on rivers

Answer explanation

Answer: c) The response of a river’s discharge to a rainfall event

• Explanation: A storm hydrograph tracks how much water flows in a river after it rains. For example, if it rains heavily in a city, the hydrograph will show how quickly the water reaches the river and how much the flow increases.

What is the main contributor to river discharge before a storm?

• Quickflow

• Groundwater flow/baseflow

• Overland flow

• Channel precipitation

Answer explanation

Answer: b) Groundwater flow/baseflow

• Explanation: Before it rains, rivers get their water mainly from groundwater slowly seeping into the riverbed. Imagine a river in a dry season—it's still flowing because of underground water sources.

During a storm, what type of flow occurs when water runs over the surface directly into a river?

• Quickflow

• Throughflow

• Baseflow

• Rising limb

Answer explanation

Answer: a) Quickflow

• Explanation: When it rains heavily, some water can’t soak into the ground, so it flows over the surface straight into rivers. Think of rain on a paved road; water quickly moves into storm drains and nearby rivers.

What does the rising limb of a storm hydrograph represent?

• The decline in river discharge after the storm

• The speed at which water infiltrates the soil

• The increase in river discharge during a storm

• The time taken for rainfall to reach the river

Answer explanation

Answer: c) The increase in river discharge during a storm

• Explanation: This part of the graph shows how fast the river's water level rises after it starts raining. For instance, during a flash flood, the rising limb is very steep because water flows into the river quickly.

What is the recessional limb of a storm hydrograph?

• The peak discharge of the river

• The decrease in river discharge after the storm

• The total volume of water in the river

• The time between the storm start and peak flow

Answer explanation

Answer: b) The decrease in river discharge after the storm

• Explanation: After the rain stops, the river's water level slowly drops. This part of the graph shows the time it takes for the river to return to normal levels. Imagine a river slowly calming down after a flood.

What does the peak flow on a storm hydrograph indicate?

• The maximum rainfall during a storm

• The maximum discharge of the river during a storm

• The time it takes for the river to return to baseflow

• The average discharge of the river over time

Answer explanation

Answer: b) The maximum discharge of the river during a storm

• Explanation: This is the highest point on the graph and shows the maximum amount of water flowing in the river. During a flood, the peak flow is when the river is at its fullest.

What is the time lag on a storm hydrograph?

• The time between the start of the storm and peak rainfall

• The time between peak rainfall and peak discharge

• The time between the end of the storm and baseflow

• The time between the rising limb and recessional limb

Answer explanation

Answer: b) The time between peak rainfall and peak discharge

• Explanation: Time lag shows how long it takes for rain to reach the river. In cities with lots of concrete, the time lag is short because water moves fast. In forests, the time lag is longer because trees and soil absorb water first.

Which of the following describes a river regime?

• The response of a river to a rainfall event

• The annual variation in river discharge due to seasonal changes

• The impact of urbanization on river discharge

• The relationship between rising and recessional limbs

Answer explanation

Answer: b) The annual variation in river discharge due to seasonal changes

• Explanation: A river regime shows how river levels change throughout the year. For example, rivers in snowy areas (like Norway) rise in summer due to melting snow, while tropical rivers rise during rainy seasons.

In a river with a glacier-fed regime, when would peak discharge typically occur?

• Winter

• Spring

• Summer

• Autumn

Answer explanation

Answer: c) Summer

• Explanation: Glaciers melt in summer, adding more water to rivers. For example, rivers in Norway or Switzerland that get water from glaciers are at their fullest in summer.

What is the main factor influencing the river regime of the Shannon in Ireland?

• Glacial meltwater

• Seasonal rainfall variation

• Urbanization

• Human-made reservoirs

Answer explanation

Answer: b) Seasonal rainfall variation

• Explanation: The Shannon's water levels change because Ireland gets more rain in winter. Unlike glacier-fed rivers, the Shannon doesn’t rely on snowmelt.