3.3 Understanding the catchment concept

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UNDERSTANDING THE CATCHMENT CONCEPT


Curriculum Alignment ACT ELAs 2, 6, 17, 18, 19, 25 NSW KLAs Years K-6: Science and Technology, HSIE Years 7-10: Geography, Science Years 11-12: Agriculture, Chemistry, Earth and Environmental Science, Biology, Society and Culture QLD KLAs SOSE, Science, Geography SA ELs Futures, Interdependence, Thinking VELS Science, Thinking Processes, Geography

Objectives
>Students gain an understanding of the river catchment concept
>Students learn to identify those land use activities that may be having an impact on their own catchment
>Students develop responses to those impacts threatening the health of their local waterway

Duration
2 hours

Materials required
>Clipboards and paper, pencils
>Topographic map of the nearby creek, stream or river section showing prominent landmarks
>Investigating a river system (Homework sheet)

Background
A catchment is an area of land bounded by natural features such as hills or mountains, from which all runoff water flows to a low point – like rain on a roof flowing to a downpipe (see schematic diagram above). In the case of a catchment, low points include any body of water such as a creek, river, lake, estuary, wetland, sea or ocean.

Catchments may also be referred to as a catchment area, a drainage, river or water basin or a watershed.

Schematic diagram of the typical catchment. Source: http://www.waterprotection.ca/images/watershedb.jpg

Catchments vary in size. Large catchments may be bounded by mountain ranges and include a large network of many creeks and rivers. These networks can be broken up into smaller sub-catchments, bounded by lower hills and ridges and drained by smaller creeks or gullies. The map of the Pine Rivers catchment in Queensland (see below) shows the entire river valley and the smaller sub-catchments.

How each of these sub-catchments is managed affects the overall health of the river, as what occurs upstream affects areas downstream.
The relationship between a river and its catchment is one of the dominant themes of hydrology and thus also in studies of river geomorphology (shape and form – see Module 4.2 in Part 4) and aquatic ecology. The range of flows experienced, the timing of floods and droughts, the nutrients and sediments carried and the underlying terrain all reflect the strong interaction between a river and its catchment.

For example, times of flood are important in many aspects of river behaviour: they are the few occasions when erosion can cause rapid changes in the shape and form of the river channel. At the same time effective rainfall and runoff carry sediments from exposed areas and generally ‘flush out’ the system.
Land use practices within a catchment have a major impact on the health of the waterways. Land use information can be used to develop solutions for natural resource management issues such as water pollution. For instance, the waterways in a region that has been deforested or has extensive erosion will have different water quality than those in areas with well forested and maintained river banks.

Integrated catchment management and planning is a holistic approach where land users are central. By managing land and water use at a catchment-wide level — the long-term quality of the land for human use, the prevention or resolution of social conflicts related to land and water use, and the conservation of high value ecosystems and biodiversity are secured.
By focusing on the links between the catchment and the river, Integrated Catchment Management (ICM) is an increasingly attractive means to resolve potentially conflicting activities. Operations which taken alone, might be within the tolerance of a river system could become highly damaging in the presence of other pressures. Algal blooms provide a good example.

ICM allows a river system to be considered as a whole and for the resources of its catchment to be managed sustainably and in harmony with the various demands such as water supply, fishery management, effluent disposal and nature conservation. ICM can therefore be regarded as comprising catchment management plans to which all the major interests in the catchment subscribe. To be effective, such plans must be consistent with local authority development plans and asset management plans of water supply utilities and vice versa.
Understanding river systems and their links to wider catchment processes is a fundamental aspect of integrated management.

Vocabulary
Catchment
Integrated Catchment Management
Urban
Rural landuse
Industrial landuse
Commercial landuse
Transect
Landuse
Vegetation
Erosion
Residential
Non-point-source pollution
Point source pollution
Topographic
Native species
Exotic species
Gross pollution trap
Constructed wetland
Impervious surface
Water sensitive urban design

Lesson plan
1. Prior to going to the nearby river or stream, examine topographic maps, Google Earth imagery or aerial and satellite photos to identify key landmarks with the class (such as, the location of the school, location of the waterway relative to the school etc).
Also locate the catchment boundaries and the path of the waterway from the headwaters to the sea.

2. Identify where the catchment or sub-catchment boundaries are in relation to the landscape. The catchment may be defined by surrounding hills or in the case of larger catchments, the catchment boundaries may be hundreds of kilometres away.
Challenges students to think about which areas are most vulnerable to erosion based on steep slopes or loss of vegetation. Draw on the map the edge of the catchment by finding the highest point and following the ridges.

3. Valuable first hand information can be gathered from a catchment walk. Walk a ‘transect’ through the catchment along a line between two chosen points.

Suggestion to consider.
Start at the riverbank and
walk up through different
land-uses to a high point in the
catchment area, or walk a
transect that starts at the
school and takes the class
through a variety of land-uses.

4. Have students sit quietly next to the river for a few minutes. Quiz them about:

>what can they see, smell and hear?
>what’s the condition of the banks?
>what’s the vegetation cover like?
>what proportion are native or exotic plants?
>were there any creek lines, stormwater or other drains?
>where do they discharge into the river?
>were there any visible signs of pollution?
>were there any pollution control devices (e.g. constructed wetlands, gross pollution traps)

5. Have students gather the following information for a sketch map of the catchment:

>catchment boundaries
>flow and path of water-course
>drainage patterns of surrounding land
>native vegetation
>parks, golf courses and playing fields
>cleared land
>erosion areas
>land-uses (residential, industrial, commercial, agricultural)
>location of the school
>major roads and rail links
>potential pollution sources, including stormwater drains entering the waterway and sewage outflow points
>dams, weirs and road crossings.

6. Back in the classroom, create a catchment mural. Mark in the catchment boundaries. (A topographic map and satellite photographs will help). Use coloured pencils or crayons to illustrate major land uses and other information collected during the catchment walk.

7. Have students consider and discuss:

>How would they describe the overall state of stormwater runoff in their catchment?
>How do they feel about the current state of their catchment?
>Based upon their catchment walk, what are some problems facing their catchment today?
>Did they discover any potential sources of pollution?
>Has the flow or course of the creek/river been altered by human intervention?

Extensions
Have students assess impact of their school on the catchment. Students should walk through the school grounds and identify the different kinds of surfaces (for example; roofs, paths, garden, lawn and sporting fields etc) then devise a system of symbols to represent these surfaces.

Tip
- the RiverSmart Australia
website (www.riversmart.org.au)
has a ready made-schools
audit form to help with
this exercise

Using a school map and graph paper, have students draw a detailed map of the various surfaces.
Mark on the map any systems that the school has installed to reduce the area of impervious surfaces within the school grounds.

Develop an action plan
Challenge students with how they can reduce the school’s impact (‘footprint’)?
As a class, brainstorm strategies to reduce the schools volume of stormwater runoff and impact on the local waterway.
Encourage students to conduct research into Water Sensitive Urban Design (WSUD) to assist the development of a school action plan.
Have students prepare a report and action plan.

Assist students in organising a meeting with the school principal and school executive to report on the results of their investigations and present the ideas developed in their action plan.
With the agreement from the school executive, it may be possible to extend the action plan to become part of the school implementation plan.

Secondary pathway
Have students expand on the questions found in step 7 of the lesson plan into independent research. These questions can be targeted specifically to sites near the school or student’s home.
Their findings can be presented via Powerpoint presentation or with of GIS mapping (if available).


Downloads HOMEWORK – INVESTIGATING A RIVER SYSTEM