Ins and outs of water web activity answers
Activity one - Freshwater in New Zealand
Using table on p8 Water Physical Stock Account Report
- Most of the world's water is seawater.
Only about 2.5 percent of water is freshwater.
Ice-caps and glaciers account for about 70 percent of freshwater.
Ground water makes up about 30 percent of freshwater.
Using the 2001 table from Water Physical Stock Account Annual Tables
- The West Coast. Because New Zealand is so mountains (one third of land area is over 1,000 metres). The mountains largely control the distribution of rainfall due to their orientation to the predominant west-southeast flows. Warm moist air passes over mountains, from west to east. This air rises, cools, condenses and rain forms in the west. As the air mass travels east, it warms as it descends, bringing little or no rainfall. This is called orographic rainfall.
- Students work this out using precipitation and number of people. The West Coast has the highest precipitation per person.
- Storage can be viewed as a balancing set of components. If outflows of water in the hydrological system exceed inflows, then the deficit must be coming out of storage.
- The aim here is to get students analysing and responding to data. Some discussion and debate may occur, with answers generally including references to precipitation, evapotranspiration, vegetation, soil type, land use, temperatures, day-length, supply and demand, use by people. Some may even talk about El Nino weather patterns? Soil moisture refers to water stored in land and soil, in the rooting zone (typically the top one metre, depending on soil and vegetation type) Lakes and reservoirs provide storage for irrigation, town supply and hydro-electricity generation. Groundwater is water contained in aquifers (underground rock layers that yield water in usable quantities to wells or springs) Changes in snow (at an altitude of 900m to 2,000m) will impact upon rivers and lakes in the region. Snow above 2,000 metres is regarded as permanent snow while snow below 900 metres is only temporary and soon melts (so is not estimated for the water accounts but could still affect rivers and lakes).
Using the outline map
- Students could use arrows to show the inflow and outflows.
- West Coast, Northland, Auckland, Bay of Plenty, Gisborne, Hawke’s Bay, Taranaki, Manawatu-Wanganui, Wellington, Nelson, Marlborough, Canterbury, Otago, Southland should be shaded.
- The West Coast. Because New Zealand is so mountainous (one third of land area is over 1,000 metres). The mountains largely control the distribution of rainfall, due to their orientation to the predominant west-southeast flows. Warm moist air passes over mountains, from west to east. This air rises, cools, condenses and rain forms in the west. As the air mass travels east, it warms as it descends, bringing little or no rainfall. This is called orographic rainfall. Source: Water Physical Stock Account Report
Activity two
Using the hydrological cycle
- Students should sketch the Water Cycle model and include figures (from your region) on the appropriate place on the diagram.
Homework activity answers
We use water for irrigation, livestock use, private industrial use, private domestic use, geothermal electricity generation, recreation. If we had to pay for it, the cost would depend on the type of use, quality, scarcity and the cost of abstraction and reticulation. Point out that an average family of four uses 720 litres of water every day. That’s 72 big buckets!
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