4.1 Water systemsIB Environmental Systems and Societies SL: Subtopic test

1. 1
   In a high Alpine valley in Switzerland, snow falls on the upper slopes each winter. In spring the snow melts and water flows downhill in streams into a lake on the valley floor. Some water soaks into the gravelly soil and moves slowly downwards through the rock, emerging later at springs lower down the valley. On bright, cold, windy days some of the snow disappears without ever becoming liquid.

   (a)

   Which pair of factors is mainly responsible for driving the movements of water described in the valley?

   [1 mark]

   • AWind and ocean currents
   • BPhotosynthesis and respiration
   • CSolar radiation and gravity
   • DTidal forces and volcanic heat

   (b)

   What name is given to the process in which snow changes directly into water vapour?

   [1 mark]

   • ASublimation
   • BCondensation
   • CAdvection
   • DTranspiration

   (c)

   Distinguish between infiltration and percolation.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student summarises the global distribution of water as percentages of the total: oceans 96.5%, glaciers and ice caps 1.7%, groundwater 1.7%, surface freshwater 0.02%, atmosphere 0.001% and organisms 0.0001%.

   (a)

   According to the student's data, which store holds the smallest percentage of the Earth's water?

   [1 mark]

   • ASurface freshwater
   • BAtmosphere
   • CGroundwater
   • DOrganisms

   (b)

   Approximately how many times larger is the oceans store than the surface freshwater store?

   [1 mark]

   • AAbout 48 times
   • BAbout 4,800 times
   • CAbout 480 times
   • DAbout 48,000 times

   (c)

   Using the data, explain why the atmosphere is a very small store yet is important in the hydrological cycle.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A small lowland lake in England has the following annual water budget, in millions of cubic metres (million m³). Inputs: streamflow in 8.0, direct precipitation 2.0, groundwater flow in 1.0. Outputs: streamflow out 7.5, evaporation 2.5, abstraction for drinking water 1.0. The water level has stayed almost constant for many years.

   (a)

   Calculate the total annual inputs and outputs for the lake, and explain what the results show about the state of the lake.

   [3 marks]

   (b)

   A housing estate is built in the catchment. Paving reduces groundwater flow into the lake to 0.5 million m³ per year, abstraction rises to 2.0 million m³ per year, and all other flows stay the same. Predict the effect on the lake and explain one effect of paving on the flows in the catchment.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Researchers in the southern Amazon basin compare three land uses: intact rainforest, rainforest cleared for soy fields and cattle pasture, and a fast-growing town built on formerly forested land with paved roads and roofs. Streams in the cleared areas and below the town respond more quickly and more strongly to rainfall than streams in the intact forest.

   (a)

   Explain how deforestation alters the flows and stores of the hydrological cycle.

   [6 marks]

   (b)

   Compare and contrast how agriculture and urbanization alter the flows and stores of the hydrological cycle.

   [6 marks]

   Total for question 4: 12 marks

End of questions