What are the consequences of poor river health?
River health is an integrated measure of various conditions that are necessary for proper ecosystem functioning and the ability to supply good quality water and other services (such as shade, food, grazing, medicinal plants, and denitrification). Poor river health reflects a drop in one or more of these conditions, which may in turn, lead to a disturbance in trophic level interactions due to increased levels of toxicity or loss of predator or prey species, reduced ability to regulate water quality and flow, and reduced water availability to support domestic water requirements, agricultural irrigation and industrial processes. When water quality is compromised, it can become unfit for human consumption (drinking, cooking, and sanitation). Severe reduction in water quality may render it unfit for irrigation of crops or for industrial processes. Lack of water to meet these needs constrains our human subsistence and development.
These impacts have other knock-on effects such as increased expenditure and effort on water treatment, loss of biodiversity and increased dependence by humans on a few species of plants and animals to meet food, fibre and construction needs. It also renders ecosystems more vulnerable to change. Extreme events such as flooding and drought can be more frequent and more severe, when river ecosystems are compromised. For example, when in-stream sedimentation rates are enhanced (due to erosion in the riparian zone), the water level in a river is raised. Such a river is more likely to flood during heavy rainfall, because the buffering capacity has been reduced, and the area inundated is likely to be larger, than a river with a lower initial water level. Outbreaks of pests and diseases often have a bigger impact in communities of fewer species, and communities may take longer to recover to their natural state.
Furthermore, reduction in river health in one part of the river may have knock-on effects downstream, such as increased siltation and blocking of river mouths. The cumulative effects of poor river health upstream will have a far greater impact on downstream stretches, and if downstream stretches are themselves compromised, the river may not be able to tolerate and recover from the effects. For this reason it is important to monitor the pressures and the management responses as well as actual river conditions, in order to establish if conditions are likely to improve or worsen, and if the responses are being effective.
The importance of sustainable water use cannot be over-emphasised for long term economic, social and environmental security.
Priority action for these catchments include:
Wetland protection and rehabilitation in the areas of the headwaters of these rivers
Control of alien plants especially in riparian zones, in all catchments
Control of effluent and mining related seepage in the upper reaches of the Olifants Catchment
Release from storage dams should be based on ecological flow requirements, especially in the Olifants Catchment
Strategic assessment and management of the trout industry in the Crocodile catchment
Control of agricultural activities that involve clearing of ground cover (especially near to the riparian zone) in the Sabie Catchment
Where to from here with State of the Rivers reporting?
This is the first in a series of products that have been specifically designed to communicate the results and recommendations of the River Health Programme.
In time, all the major catchments in South Africa will be covered, and the assessment will be repeated to show whether conditions are improving or declining, and whether our responses and management activities are effective.
To find out more about the River Health Programme visit
www.csir.co.za/rhp/
RQIS
or contact:
The Director
Institute for Water Quality Studies Resource Quality Information Services
Department of Water and Sanitation Department of Water and Sanitation
Private Bag x313
Pretoria
0001
Tel: 012 808 0374 082 908 2895
Fax: 012 808 2702
e-mail : general@dwaf-hri.pwv.gov.za
River Health Programme email queries
Page modified 2015-07-14 12:19
This report was made possible through sponsorship by:
