0.10 The hydrosphere  (Page 2/5)

Investigation : investigating the hydrosphere

1. Choosing a study site For this exercise, you can choose any part of the hydrosphere that you would like to explore. This may be a rock pool, a lake, river, wetland or even just a small pond. The guidelines below will apply best to a river investigation, but you can ask similar questions and gather similar data in other areas. When choosing your study site, consider how accessible it is (how easy is it to get to?) and the problems you may experience (e.g. tides, rain).
2. Collecting data Your teacher will provide you with the equipment you need to collect the following data. You should have at least one study site where you will collect data, but you might decide to have more if you want to compare your results in different areas. This works best in a river, where you can choose sites down its length.
   1. Chemical data Measure and record data such as temperature, pH, conductivity and dissolved oxygen at each of your sites. You may not know exactly what these measurements mean right now, but it will become clearer later.
   2. Hydrological data Measure the water velocity of the river and observe how the volume of water in the river changes as you move down its length. You can also collect a water sample in a clear bottle, hold it to the light and see whether the water is clear or whether it has particles in it.
   3. Biological data What types of animals and plants are found in or near this part of the hydrosphere? Are they specially adapted to their environment?
   Record your data in a table like the one shown below:

   	Site 1	Site 2	Site 3
   Temperature
   pH
   Conductivity
   Dissolved oxygen
   Animals and plants

3. Interpreting the data Once you have collected and recorded your data, think about the following questions:
   • How does the data you have collected vary at different sites?
   • Can you explain these differences?
   • What effect do you think temperature , dissolved oxygen and pH have on animals and plants that are living in the hydrosphere?
   • Water is seldom 'pure'. It usually has lots of things dissolved (e.g. ${\mathrm{Mg}}^{2+}$ , ${\mathrm{Ca}}^{2+}$ and ${\mathrm{NO}}_3^{-}$ ions) or suspended (e.g. soil particles, debris) in it. Where do these substances come from?
   • Are there any human activities near this part of the hydrosphere? What effect could these activities have on the hydrosphere?

The importance of the hydrosphere

It is so easy sometimes to take our hydrosphere for granted and we seldom take the time to really think about the role that this part of the planet plays in keeping us alive. Below are just some of the very important functions of water in the hydrosphere:

• Water is a part of living cells Each cell in a living organism is made up of almost 75% water, and this allows the cell to function normally. In fact, most of the chemical reactions that occur in life, involve substances that are dissolved in water. Without water, cells would not be able to carry out their normal functions and life could not exist.
• Water provides a habitat The hydrosphere provides an important place for many animals and plants to live. Many gases (e.g. ${\mathrm{CO}}_2$ , ${\mathrm{O}}_2$ ), nutrients e.g. nitrate ( ${\mathrm{NO}}_3^{-}$ ), nitrite ( ${\mathrm{NO}}_2^{-}$ ) and ammonium ( ${\mathrm{NH}}_4^{+}$ ) ions, as well as other ions (e.g. ${\mathrm{Mg}}^{2+}$ and ${\mathrm{Ca}}^{2+}$ ) are dissolved in water. The presence of these substances is critical for life to exist in water.
• Regulating climate One of water's unique characteristics is its high specific heat . This means that water takes a long time to heat up and also a long time to cool down. This is important in helping to regulate temperatures on earth so that they stay within a range that is acceptable for life to exist. Ocean currents also help to disperse heat.
• Human needs Humans use water in a number of ways. Drinking water is obviously very important, but water is also used domestically (e.g. washing and cleaning) and in industry. Water can also be used to generate electricity through hydropower.