3.4 Environmental effects of reservoir construction

Reservoirs may totally alter the water resources of a country. Before the Aswan Dam was completed in Egypt, more than half of the 8 × 1010 m3 of water that flowed down the River Nile through Egypt each year ran into the sea. Most of the water can now be used in Egypt, mainly for irrigation, and instead of a single annual crop grown after seasonal flooding, more than one crop can be grown each year. However, advantages such as these must be considered in conjunction with
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

2 River flow

The total land area drained by a river system, including all its tributaries, is called a river catchment. The water in a river comes not only from direct precipitation, springs and overland flow (i.e. water flowing across the ground surface, excluding that in streams and rivers; this is rare in temperate vegetated areas) but also from the underground flow of water, directly to the river. Part of this underground flow is interflow, that part of infiltration which moves th
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

1 Springs

We have seen that where precipitation reaches the ground, some runs off the surface into streams and rivers and some of it infiltrates, passing through the soil. Water that reaches the water table to become groundwater may eventually re-emerge at the surface as springs where the water table intersects the surface. Almost all streams and rivers have springs or seepages as their ultimate source, or are fed by them at various points along their courses.

Artesian springs that are associated
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

Learning outcomes

By the end of this unit you should be able to:

  • list the types of springs, and how each type relates to a different geological setting;

  • use hydrographs to distinguish overland flow and interflow from baseflow, and make inferences about the climate of an area;

  • expain how various changes in land use in a river catchment will change the hydrograph of a river;

  • distinguish the different types of reservoir construction, and decide whether a
    Author(s): The Open University

    License information
    Related content

    Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

Acknowledgements

Grateful acknowledgement is made to the following sources for permission to reproduce material in this unit:

The content acknowledged below is Proprietary and used under licence (not subject to Creative Commons licence). See Terms and Conditions.

Figures

Figure 1 Copyr
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

8 Summary

  1. The rate at which water infiltrates into the ground depends on the permeability of the rocks and the state of the ground surface. Below the ground surface there is an unsaturated zone which has air in the pore spaces, and a saturated zone which has all the pores filled with water. The water table is the boundary between the unsaturated zone and the saturated zone, and is the level at which water stands in wells. Water below the water table is called groundwa
    Author(s): The Open University

    License information
    Related content

    Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

7 Aquifers

A layer of rock that is sufficiently porous to store water, and permeable enough to allow water to flow through it, is called an aquifer. Consolidated porous and permeable rocks, for example, sandstone and limestone, can form important and extensive aquifers (e.g. Figure 15). Unconsolidated sands and gravels may also be good
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

6 Permeability

It is important to distinguish clearly between porosity and permeability. Porosity is a measure of how much water can be stored in a rock, whereas permeability is a measure of the properties of a rock which determine how easily water and other fluids can flow through it (see Section 4). Permeability depends on the exte
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

8.6 Line spectra: Activity 8 Quasar redshifts

Activity 8: Quasar redshifts

Read Peterson section 1.3.5 (pages 16 and 17) by clicking the link below.

1.4 The invisible Sun

Figure 7 shows an image of the Sun, taken when a huge prominence was visible (bottom left). The image was recorded using instruments that are sensitive to ultraviolet radiation rather than visible light, so the colours that you see are ‘false’. They simply indicate different levels of intensity of ultraviolet radiation. The u
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

9 Wildebeest migration

The skill of thinking in a scientific way is as much a part of being a scientist as is knowing facts – perhaps more so. In this series of units, you'll not only come across facts about particular techniques, such as radio transmitters and bat detectors, but also the tactics that scientists use to inves
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

8.3 Shortage of minerals

You may be familiar with salt licks that are provided for domesticated cattle. In the wild, grass is also often low in minerals (e.g. it has almost no sodium and very little calcium), so grazers may have to go to extraordinary lengths to supplement their diet with additional minerals obtained from the most unlikely places. LoM gives some examples, but the most impressive activity takes place in the caves of Mount Elgon in Kenya [pp. 113–114]. You'll probably recall this spectacular footage
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

7 Plant defences

Activity 5

Watch the ‘Plant Predators’ programme from 05.03–12.07 and make notes in answer to the following questions.

(a) In what ways do plants shown in this sequence protect themselves against their predators?

(b) H
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

5.2 Pseudo-ruminants

Animals in the third suborder of the Artiodactlya, the pigs, peccaries and (according to most authorities) the hippopotamuses (suborder Suina), use a slight variant on the ruminant method, and are often referred to as pseudo-ruminants. You might like to add this information to your version of Table 2. These animals do have st
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

4.2 Digesting cellulose

Figure 3 in this section contains a lot of information and many terms that are probably new to you. Set aside the detail for the moment, read
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

2 The herbivore lifestyle – living on leaves

Leaves are a much less nutritious food than most kinds of animal material, so large herbivores have to eat large quantities of plants and they have special ways to digest their food. As author David Attenborough (DA) says, ‘Leaves are extremely poor food’ [p. 89]. To find out why living on a diet of leaves is particularly difficult, we need to know something about how leaves work.


Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

5.2 Differences between the sexes

In biology, ‘sex’ refers to a particular form of reproduction, sexual reproduction, that is distinct from asexual reproduction. As you know, sexual reproduction involves the production of eggs by females and sperm by males; eggs (or ova) and sperm are known as gametes. It is a universal feature of mammalian biology that in sexual reproduction there are two types of gametes and that progeny are produced by the fusion of two unlike gametes to form a single cell called the zygote. The zygote
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

3.1 Water distribution and usage issues

People in many parts of the world currently face a chronic shortage of water. This is a developing crisis that is expected to get worse. As you read in Section 1, several factors underlie this dire prediction. In addition, climate change is expected to cause major changes in the distribution of freshwater. The uneven distribution of freshwate
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

3.8.1 Standard deviation: finding how reproducible a series of measurements are

Even if we know the maximum and minimum and middle values in a group of numbers, we still don't have a clear idea about the distribution of values within that range: are most of the values all bunched up at one end or spread evenly across the results?

For instance, if I count my pulse rate on the hour every hour, nine times over the course of a day, I might get the following values for the number of beats per minute (bpm): 61, 59, 60, 62, 60, 100, 59, 63, 61. The average result is 65 bp
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

3.6.3 Exponential decrease: radioactive decay

The most familiar example of exponential decrease is provided by radioactive decay. Radioactivity is a natural phenomenon that is used routinely in many medical applications, from imaging (radioactive tracers in PET scanning) to therapy (radiotherapy to destroy tumours). During radioactive decay, the number of radioactive atoms halves at a constant rate, called the half-life. For instance, the radioactive isotope 11C, pronounced ‘carbon 11’, has a half-life of 1224 seconds (a l
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share