The spatial and temporal variations in water quality of selected rivers in the Durban Metropolitan Area were investigated using a Geographical Information System. Dissolved oxygen (DO), turbidity, pH, phosphorus and Escherichia coli (Ecolt) were selected as water quality parameters for the study. The study reflects a pattern of water quality deterioration due to the numerous land use practices that have had an adverse impact on the receiving waters.
Spatially, the impoverishment of water quality conditions is noticeable with increases in phosphorus, turbidity, DO and E coli. The parameter E coli represented the worst state of water quality in all catchments of the studied area. A variety of land use practices that greatly affect water quality must be considered.
List of Definitions
Declaration
Introduction
- Introduction
- Role of the Department of Wastewater Management
One of the most common objectives of a water quality study is to characterize the water quality of a water body or river basin. In addition to the above, invertebrates and fish are also used as indicators of water quality. In addition, many have failed to provide an overview of water quality and related problems within the DMA.
The determination of water quality will facilitate the identification of points along the different rivers (within catchments), which reflect poor water quality. To determine different levels of water quality ranging from acceptable to poor for different points in the study area. To determine spatial variation of water quality by land use patterns (such as industry, farming, formal and informal settlements) using GIS.
Literature Review
- Geographical Information Systems
- Water Quality Parameters
Poor water quality is a direct effect of the presence of contaminants and pollutants found in the water body. The choice of parameters for any water quality assessment program depends on the objectives of the program (Meybeck et al, 1992). The aim of this study is mainly focused on the water quality of recreational water bodies.
Spatial and temporal assessment of water quality in major river and dam systems in the Umgeni watershed from 1990 to 1997 (Pillay and Howard, 1998). Analysis of Water Quality Status in the Buffalo River Basin (Ashton et al, 1996). The objective of the conducted study was to assess the water quality of the Nile River in the Helwan area.
Spatial and temporal water quality variability in the Piracicaba River Basin, Brazil (Krusche et aI, 1997). A water quality monitoring program was established as early as 1978 in the state of San Paulo, Brazil.
Materials and Methods
On the plus side, more than a quarter of the land area in the DMA is still vegetated, though not undisturbed, open space. Many of the DMA's natural systems have been transformed by urban, commercial and industrial development. Coverages of both the large and small river systems for the DMA were obtained from the DWWM.
The clip command in Arclnfo was used to clip the catchment coverage to the boundaries of the DMA. Sample points for the DMA were recorded by Durban Metro Waterdiens at a scale of 1:10 000. A digital file of all the sample points for the DMA was obtained from the DWWM.
A database was obtained from the DWWM with the water quality measurements for the DMA sampling points. The choice of 1998 as the year for this study was largely determined by the lack of consistent data for previous years for the DMA from the DWWM. Precipitation data were obtained from the South African Weather Bureau for stations in the DMA.
A water quality index (WQI) makes it possible to quantify 'good' and 'poor' water quality by reducing the large amount of data on a number of determinants to a single number in a simple, objective and reproducible way (House & Newsome, 1989). Precipitation data for the DMA were obtained from the South African Weather Services for the stations of Blackburn, Virginia (Mhlanga catchment), Kloof, Mt. Since the study deals with water quality for the DMA for the year 1998, it is assumed that data for this year for all the above stations were obtained.
The data set of sample points for DMA was too large to be presented and compared individually with precipitation.
Results
- Spatial Investigation
- Mhlanga I
- D.Bay I
This indicates a catchment showing the lowest water quality average for the DO. This indicates that the catchment exhibits the highest average water quality in terms of turbidity. This indicates that the catchment has the highest average water quality for phosphorus.
Mlazi Mlaas 14 Urban formal Mlaas 10 Urban mixed Mlaas 18 Urban mixed Mlaas 15 Urban mixed Mlaas 20 Urban mixed conversation 04 Urban formal conversation 07 Urban formal conversation 08 Urban formal conversation Urban formal conversation 09 Urban formal conversation 101 formal Urban 101 formal Urban 03 Industry. Mbokodweni Mboko 01 Mixed Urban/Industrial Mboko 02 Mixed Urban/Industrial Mboko 03 Mixed Urban/Industrial Mboko 07 Mixed Urban/Industrial Little Toti Ltoti 04 Formal Urban. This provides an indicator of the watershed exhibiting the highest average water quality for E.
Discussion
- Spatial Investigation
- Temporal Investigation
Results from the analysis of points in the extreme category of water quality showed that the predominant land use classes are those of sugarcane plantations, urban formal and to a lesser extent those of urban informal, urban mixed and industrial. DO does not appear as a variable in the summary of water quality guidelines for domestic use and will therefore have very little impact on this use. In addition, low levels of sanitation in certain areas of the DMA need to be rapidly improved to help alleviate poor water quality.
Results from the analysis of points in the extreme category of water quality (Table 4.3.) showed that the predominant land use classes were those for urban formal and industrial and to a lesser extent those for sugarcane plantations and mixed cities. As a management mechanism, an ICM approach should be adopted to facilitate the improvement of water quality in terms of improvements in turbidity levels. Water Quality for Domestic Use (Department of Water Affairs and Forestry, 1993a), suggests the range of 6-9 units as acceptable.
Results from the analysis of points in the extreme category of water quality (hypertrophic) showed that the dominant land use classes were a mixture of urban formula, industry and, to a lesser extent, that of mixed urban plantations and sugarcane plantations. Phosphorus is not included as a parameter in the summary of domestic water quality guidelines (DWAF, 1993a) and, as a result, will have very little impact on this use. Results from the analysis of points in the extreme category of water quality showed that the predominant land use classes were the classes of formal cities and urban mixtures and to a lesser extent that of cities, industry and sugar cane.
As shown in Appendix 2, 65 of the 98 points reflected water quality in the extreme class for more than one water quality variable (phosphorus, E.eo/i, DO, turbidity). A combination of poor water quality for a multitude of variables results in an increase in the intensity of the problem. However, due to the extreme magnitude of the water quality problem within the DMA, it is also very difficult to determine whether rainfall patterns influence some variables.
ICM suggests that all elements of the physical catchment must be treated to produce an improved water quality.
Conclusions and Recommendations
There are numerous other water quality parameters that need to be addressed as they will help provide further insights into the water quality issues within the DMA. In addition, the introduction of new sampling points inland will be able to provide information on water quality for those areas not investigated in this study. Although there appears to be regular monitoring of the rivers of the DMA by the authorities, there has been little effort to form a structure to deal with the land use issues, which have a direct impact on water quality.
Water quality is affected by human activity and land use and as such should be the focus towards improving water quality. Responsibility for implementing the catchment management plan would normally rest with a legally established catchment authority representing the interests of all stakeholders (DWAF, 1996a). In the context of water resources management, the management dimension requires a particularly broad assessment of the need to strike a balance between protecting water resources and meeting the various needs of stakeholders (DWAF, 1996a).
As such, a River Basin Management Plan should be prepared for each river basin and a committee formed by interested and concerned parties should ensure that water quality is maintained to meet the requirements of all users within the DMA. There should be strict enforcement of water quality guidelines, especially for industries and others involved in wastewater discharge. An ICM attempts to manage all components of the watershed and as such involves management of both land and water.
This seeks to alleviate the water quality issues faced by the DMA. This data can then be used to statistically relate it to the average water quality measurements at the sampling points. The findings of this study have highlighted the intensity of the water quality problem in the DMA.
Although it has attempted to provide an overview of water quality and somewhat failed to provide details about the sources of pollution, it points to the development of a series of catchment management plans as the mechanism towards an overall water improvement. quality in DMA.
Chapman (ed.), Water quality assessments - A guide to the use of biota, sediments and water in environmental monitoring. Integrated catchment management philosophy and practice: Implications for water resources management in South Africa. Watershed - A message to decision makers in the Mlazi River catchment from the Ntshongweni Watershed Management Programme, Arrow Press, Pietermaritzburg.
Water quality and fauna studies in the Umzimvubu catchment, Eastern Cape, with special emphasis on species as indicators of environmental change. Chapman (ed.), Water quality assessments - A guide to the use of biota, sediments and water in environmental monitoring. A spatial and temporal assessment of water quality in the main river and dam systems in the Umgeni watershed from 1990 to 1997.
Appendices