Catchment and River Management

What is a riparian zone?

The area alongside a river. Birds, wildlife and vegetation depend on rivers and the vegetation in this zone.

What are wetlands?

Marshes and swamps found in some drainage basins and catchment areas. They trap and store water, regulate stream flow, and filter/purify water.

5 functions of wetlands

1) Remove harmful bacteria and reduce water acidity.

2) Filter sand and prevent silt reaching rivers.

3) Slow water flow, acting as a sponge.

4) Reduce flood damage.

5) Provide breeding areas and habitats for organisms.

Why are water sources important?

1. Clean water prevents water-borne diseases like cholera.

2. Agriculture, industry and development depend on water.

3. Rivers and dams provide hydroelectricity.

4. Fresh water sources supply food.

5. Used for recreation, tourism, cultural activities.

What is Integrated Water Resource Management?

The policy that groundwater, rivers and wetlands must be managed together, as they are all linked within the water cycle. Management must include land and human activities that impact water sources.

Why must drainage basins be managed?

So that: everyone can access water, river ecosystems remain healthy, flooding can be controlled, sustainable development can be maintained, water sources are safeguarded for present and future generations.

What is lag time?

The period between maximum precipitation and peak discharge in a river.

What is a drainage basin system?

A system of inputs, stores, flows and outputs. It collects precipitation, allows infiltration, stores/purifies rainwater in wetlands, and channels runoff into streams and rivers.

What is DWAF?

Department of Water Affairs and Forestry. Responsible for sustainable use and health of SA’s rivers. The National Water Act provides for Catchment Management agencies.

What is DEAT?

Department of Environmental Affairs and Tourism. Runs a wetlands conservation programme. Wetlands are protected if they are Ramsar sites (internationally important).

What is the River Health Programme (RHP)?

Introduced in 1994 by DWAF, DEAT and the Water Research Commission. Collects information about rivers and their drainage basins, writes reports on present health of rivers.

What is the IHI indicator?

Index of Habitat Integrity. Assesses diversity of habitats and the impact of disturbances, removal of water and channel modification.

What is the GI indicator?

Geomorphological Index. Assesses channel condition due to impacts of weirs and dams, channel stability in relation to erosion of banks and bed.

What is the RVI indicator?

Riparian Vegetation Index. Indicates the status of vegetation around the river and indicates influence such as removal of vegetation.

What is Hydrology?

The study of the distribution, movement and quality of waters on Earth, and the relationship between Earth’s water supply and the environment.

Impact 1: Boreholes

Boreholes remove water from the saturated groundwater zone, so less groundwater flows into the river (reduced baseflow).

Impact 2: Mining on groundwater

Groundwater can be polluted by human activities such as mining, contaminating the water quality underground.

Impact 3: Overgrazing & vegetation clearing

Decreases infiltration, reduces groundwater supply to rivers. Surface water increases, carrying more silt into the river.

Impact 4: Agricultural runoff

Contains high amounts of salt, nutrients and pesticides. Harmful to aquatic life and the food chain. Leads to increase in algae.

Impact 5: Urban surfaces

Concrete and tar are impermeable. Infiltration decreases, surface runoff increases. Together with vegetation removal, causes shorter lag time and higher flood peaks.

Impact 6: Wetland conversion

Many wetlands converted to crops, timber plantations, waste disposal sites, pastures and dams. Often badly polluted by industry, sewage, mines and agriculture.

Impact 7: Water removal for irrigation

Removing water for irrigation, domestic use, industry and mines changes river flow, reduces river habitats and affects ecological processes.

Impact 8: Dams

Water transfer schemes and dams result in unnatural flow patterns and disturb ecology. River deposits load in the dam, then erodes downstream. Disrupts life cycles of species.

Impact 9: Recreation in riparian zone

Disrupts ecology and results in litter and other forms of pollution.