Focus unit 2: Managing catchments
This unit introduces students to the geographical study of catchments. Catchment studies demonstrate the interrelatedness of people and the environment. A catchment is a dynamic system which includes land, water, vegetation, crops, wildlife, people, animals, farms, industries and cities.
The geographical study of catchments is a multidisciplinary one, drawing on ideas from geomorphology, climatology, hydrology, economics and sociology. Geography’s special contribution to the study of catchments lies in its focus on synthesising ideas from the physical and social sciences to produce a comprehensive explanation of the health of a catchment. These explanations can help in the development of catchment management plans and biodiversity conservation.
This unit provides a focus for the study of a range of concepts, patterns and processes in physical and human geography.
This unit introduces students to the geographical study of catchments. Catchment studies demonstrate the interrelatedness of people and the environment. A catchment is a dynamic system which includes land, water, vegetation, crops, wildlife, people, animals, farms, industries and cities.
The geographical study of catchments is a multidisciplinary one, drawing on ideas from geomorphology, climatology, hydrology, economics and sociology. Geography’s special contribution to the study of catchments lies in its focus on synthesising ideas from the physical and social sciences to produce a comprehensive explanation of the health of a catchment. These explanations can help in the development of catchment management plans and biodiversity conservation.
This unit provides a focus for the study of a range of concepts, patterns and processes in physical and human geography.
The water cycle
Around the world, access to water has always been a key factor of how and where human population have flourished. Water is essential to our economy and our way of life and its use has continued to increase due to population growth and expansion of agriculture and other industries. Australia is no different; it faces challenges of a growing and urbanising population, of growing demand for water for food and fibre production, and of environmental sustainability, especially in the face of climate change, which are only some of the issues we will be looking at in the course of this unit. |
But before we have a closer look at the correlation between our growing population and water usage, we have to understand what influences our water availability and how water circulates through the four different spheres: hydrosphere, atmosphere, biosphere and lithosphere.
River catchments
Rivers are dynamic, open systems, meaning they have inputs and outputs. The most obvious input is rain but e.g. snow, hail and dew all act as inputs too. These inputs are grouped under the term precipitation, as we have already learned. Furthermore, river systems also have outputs. Evaporation is a significant one as water turns into a gas and becomes part of the atmosphere. Transpiration is similar to evaporation but is the loss of water as a vapour from plant and tree leaves. The combined effect of evaporation and transpiration is called evapotranspiration. The final output, the one that a lot of people forget, is water flowing out of the river, which is called river discharge. The inputs and outputs determine the water quantity in any river.
Of upmost importance for our survival are river catchments. River catchments are geographical units that vary in size and complexity of characteristics. There are many elements of catchments; these elements can be mapped and its quantity can be measured. These elements include topography, drainage patterns, geology, vegetation cover, rainfall, soil types, land use and settlement patterns. This means, these elements will have to be taken into consideration when studying specific catchment areas. We will do this on three different scales during the course of this unit: On a national scale, e.g. the Nile River in Egypt, on a regional scale, e.g. the Murray-Darling River, and on a local scale, looking at the Barron River.
Rivers are dynamic, open systems, meaning they have inputs and outputs. The most obvious input is rain but e.g. snow, hail and dew all act as inputs too. These inputs are grouped under the term precipitation, as we have already learned. Furthermore, river systems also have outputs. Evaporation is a significant one as water turns into a gas and becomes part of the atmosphere. Transpiration is similar to evaporation but is the loss of water as a vapour from plant and tree leaves. The combined effect of evaporation and transpiration is called evapotranspiration. The final output, the one that a lot of people forget, is water flowing out of the river, which is called river discharge. The inputs and outputs determine the water quantity in any river.
Of upmost importance for our survival are river catchments. River catchments are geographical units that vary in size and complexity of characteristics. There are many elements of catchments; these elements can be mapped and its quantity can be measured. These elements include topography, drainage patterns, geology, vegetation cover, rainfall, soil types, land use and settlement patterns. This means, these elements will have to be taken into consideration when studying specific catchment areas. We will do this on three different scales during the course of this unit: On a national scale, e.g. the Nile River in Egypt, on a regional scale, e.g. the Murray-Darling River, and on a local scale, looking at the Barron River.
River systems
A river system is a way of describing the larger networks of streams, lakes and rivers that are part of a larger river's network. These networks are interconnected and the health of one can have an impact on the other part in the same river system. Additionally, land can be part of a river system, such as the floodplains and wetlands that are impacted by a main river and its tributaries.
A river system is a way of describing the larger networks of streams, lakes and rivers that are part of a larger river's network. These networks are interconnected and the health of one can have an impact on the other part in the same river system. Additionally, land can be part of a river system, such as the floodplains and wetlands that are impacted by a main river and its tributaries.
Stages of rivers
A river is often divided into three stages (or parts) and has features that are specific and evident to each stage. Different stages of our rivers are affected in distinct ways by erosion and deposition, which are some of the factors influencing the course and extend of a river. Erosion is the wearing away of materials whereas deposition is the dumping of rocks, sand and silt wherever the river slows down. Therefore, our river catchments are changing continuously in response to these natural processes but also due to human activity. These changes within a catchment are affecting the natural systems and the social and economic systems of people living within the catchments; which is important as it affects the processes in and the management of our rivers.
A river is often divided into three stages (or parts) and has features that are specific and evident to each stage. Different stages of our rivers are affected in distinct ways by erosion and deposition, which are some of the factors influencing the course and extend of a river. Erosion is the wearing away of materials whereas deposition is the dumping of rocks, sand and silt wherever the river slows down. Therefore, our river catchments are changing continuously in response to these natural processes but also due to human activity. These changes within a catchment are affecting the natural systems and the social and economic systems of people living within the catchments; which is important as it affects the processes in and the management of our rivers.
Drainage patterns
As we have already learned, rivers are shaped due to different influences, such as erosion, transportation and deposition, and can have diverse patterns, which are called drainage patterns; they are formed by the streams, rivers, and lakes in a particular drainage basin. Therefore, over time, a river achieves a particular drainage pattern to its network of stream channels and tributaries as determined by local geologic factors. Drainage patterns are classified on the basis of their form and texture. Their shape or pattern develops in response to the local topography and subsurface geology. |
Drainage channels develop where surface runoff is enhanced and earth materials provide the least resistance to erosion. The texture is governed by soil infiltration, and the volume of water available in a given period of time to enter the surface. If the soil has only a moderate infiltration capacity and a small amount of precipitation strikes the surface over a given period of time, the water will likely soak in rather than evaporate away. If a large amount of water strikes the surface then more water will evaporate, soaks into the surface, or ponds on level ground. On sloping surfaces this excess water will runoff. Fewer drainage channels will develop where the surface is flat and the soil infiltration is high because the water will soak into the surface. The fewer number of channels, the coarser will be the drainage pattern.
There are four main drainage patterns, as you can also see in the image above:
- A dendritic drainage pattern occurs when the tributary systems subdivides headway like the limbs of a tree. These patterns usually form in horizontal sedimentary or in intrusive igneous rocks where the rock mass is reasonably homogeneous. The tributaries in steep terrains tend to be somewhat subparallel and join at acute angles. Any marked structure (like e.g. joints, faulting) will tend to interfere with the development of the dendritic drainage pattern.
- A radial drainage pattern occurs when the tributaries flow radially outward and downward from a central topographic high. This type of pattern is typical of volcanic cones, isolated hills, and elevated domes.
- A rectangular drainage pattern is identified by its main streams and their tributaries displaying many right-angle bends and exhibiting sections of approx. the same length; it is indicative of streams following prominent fault or joint systems that break the rocks into rectangular blocks.
- A trellis drainage pattern occurs where subparallel streams erode a valley along the strike of less resistant formations. These beds are usually steeply dipping and may be part of a fold system. The tributaries often intersect at right angles where a notch, called a water gap, cuts through a harder formation. If the notch and the surrounding formation are later uplifted, the water gap becomes a wind gap.
Water availability and use in Australia
In this part of our unit, we will be drawing on a selection of different scales of study; on a regional scale (Marry-Darling Basin) and on a local scale (Barron River). Firstly, we will be looking at current water availability and use in Australia. Secondly, we will be looking at water quality issues. Thirdly, we will be looking at the future of our urban water supply with the main focus of this part of our unit being water distribution and management issues. As we will learn, long-term responses to water availability in catchment areas require planning and coordinated action through the informed action of individual users and managers of resources (such as governments) in order to achieve sustainability and balance between economic development and conservation of land and water resources; it also requires individuals to contribute to the resolution of catchment management problems in order to have a long-lasting positive effect.
In this part of our unit, we will be drawing on a selection of different scales of study; on a regional scale (Marry-Darling Basin) and on a local scale (Barron River). Firstly, we will be looking at current water availability and use in Australia. Secondly, we will be looking at water quality issues. Thirdly, we will be looking at the future of our urban water supply with the main focus of this part of our unit being water distribution and management issues. As we will learn, long-term responses to water availability in catchment areas require planning and coordinated action through the informed action of individual users and managers of resources (such as governments) in order to achieve sustainability and balance between economic development and conservation of land and water resources; it also requires individuals to contribute to the resolution of catchment management problems in order to have a long-lasting positive effect.
Case study: Murray-Darling Basin
The Murray-Darling River Basin (MDB) is one of the world’s largest river systems, spans four states and is known as Australia’s ‘food bowl’. Centuries of agricultural irrigation and development have seen the river’s water levels depleted to such an extent that it no longer consistently flows into the Southern Ocean in South Australia. The health of the Murray-Darling River Basin and its biomes is vital to Australian food security as it alone supplies one third of all food produced in Australia. Continued population growth in Australia and the region makes this river system vital to food security both in Australia and globally.
Water is a vital resource for agricultural production in Australia and maintains food security. In the context of continued population growth, the Federal Government is seeking advice on a sustainable strategy to improve water quality and river flows while also maintaining food security in the Murray-Darling River Basin.
The Murray-Darling River Basin (MDB) is one of the world’s largest river systems, spans four states and is known as Australia’s ‘food bowl’. Centuries of agricultural irrigation and development have seen the river’s water levels depleted to such an extent that it no longer consistently flows into the Southern Ocean in South Australia. The health of the Murray-Darling River Basin and its biomes is vital to Australian food security as it alone supplies one third of all food produced in Australia. Continued population growth in Australia and the region makes this river system vital to food security both in Australia and globally.
Water is a vital resource for agricultural production in Australia and maintains food security. In the context of continued population growth, the Federal Government is seeking advice on a sustainable strategy to improve water quality and river flows while also maintaining food security in the Murray-Darling River Basin.
Case study: Water supply in Cairns
Water availability in other parts of our planet
The distribution of water on the Earth's surface is extremely uneven. Only 3% of water on the surface is fresh; the remaining 97% resides in the ocean. Of freshwater, 69% is locked in glaciers, 30% underground, and less than 1% is located in lakes, rivers and swamps, which are not always easily accessible water sources. These facts make it difficult for a lot of people to get clean, safe drinking water, which is crucial for our survival.
The distribution of water on the Earth's surface is extremely uneven. Only 3% of water on the surface is fresh; the remaining 97% resides in the ocean. Of freshwater, 69% is locked in glaciers, 30% underground, and less than 1% is located in lakes, rivers and swamps, which are not always easily accessible water sources. These facts make it difficult for a lot of people to get clean, safe drinking water, which is crucial for our survival.
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Case study: Nile River
The Nile River can be seen as the father of African rivers and is the longest river in the world. It rises south of the Equator and flows northward through northeastern Africa to drain into the Mediterranean Sea. It has a length of about 6,650km and drains an area estimated at 3,349,000km². Its basin includes parts of Tanzania, Burundi, Rwanda, the Democratic Republic of the Congo, Kenya, Uganda, South Sudan, Ethiopia, Sudan, and the cultivated part of Egypt. Its most distant source is the Kagera River in Burundi. The Nile is formed by three principal streams: the Blue Nile and the Atbara, which flow from the highlands of Ethiopia, and the White Nile, the headstreams of which flow into Lakes Victoria and Albert. |
Practical exercise
Practical exercises are divided into two parts:
Practical exercises are divided into two parts:
- Part A is about data manipulation.
- Part B is where evidence of student performance of analytical processes and decision-making processes is gathered. The analysis and decision making is based on the outcomes of Part A but might be supported by additional data.