Exercises: The hydrosphere

Classify these bodies of water as saltwater or freshwater: the Atlantic Ocean, a glacier, a lake, a river, the Mediterranean Sea, and water from an aquifer.

The diagram shows the water cycle with five numbered processes. Name the processes labelled 1 to 5 and briefly describe what happens in each.

What is the hydrological cycle? Name its main processes and explain why we say that the Earth's water is always the same.

Explain the role played by the Sun as the "engine" of the water cycle.

Distinguish between surface runoff and infiltration, and state how ground slope and vegetation cover influence each of them.

Where does the water from a spring come from? Relate it to rainfall, infiltration, and aquifers.

In a debate on sustainability, a municipal representative states: "Given that 71 % of the Earth's surface is covered by water, the fear of water scarcity is unfounded: water is a virtually inexhaustible resource."\na) Using data from the hydrosphere (97.5 % of the planet's water is salt water and only 2.5 % is fresh water; and of that fresh water, 69 % is frozen in glaciers and barely 0.3 % is found in accessible surface rivers and lakes), calculate what exact percentage of the planet's total water is represented by liquid surface fresh water.\nb) Based on your numerical calculation, reasonably refute the representative's statement and predict the hydrological and ecological consequences of managing a region's water resources under the assumption that available water is limitless.

After the construction of a housing development with paved streets and impermeable roofs on a forested hillside, technicians find that during heavy rainfall, it takes only 30 minutes for water to reach the river instead of the usual 4 hours, and that the peak flow rate has tripled, flooding the town located downstream.\na) Justify this hydrological change by analyzing how paving the ground alters infiltration, evapotranspiration, and surface runoff.\nb) To prevent further flooding, a company proposes channeling the river with concrete in a straight line to the river mouth. Critically evaluate this proposal by predicting what will happen in areas located even further downstream, and design two alternative measures based on sustainable drainage or environmental restoration to promote aquifer recharge.

At the top of a permeable mountain, an accidental spill of a biodegradable, water-soluble dye occurs. Weeks later, dyed water is detected in an agricultural well in the valley and, months later, at the mouth of a river in the ocean, without the dye having been observed in the surface torrents on the hillside.\na) Reasonably reconstruct the path followed by the dyed water from the summit to the sea, naming and explaining the processes of the water cycle involved (infiltration, groundwater flow, spring emergence or discharge, and surface runoff).\nb) Explain through which physical processes of the water cycle that same seawater will be able to return to the mountain peak, and justify whether the dye would travel with it in water vapor and precipitation.