Potential changes in the water quality of the rivers in the uMngeni catchment under a future climate

The 3rd highest risk facing the water utility - Umgeni Water - responsible for supplying potable water to consumers within the uMngeni catchment, including those in the greater Durban-Pietermaritzburg area in South Africa, is the potential impact of a changing climate on both the quantity and quality of the water resource. This case study will focus on improving the understanding of the potential changes in water quality in the uMngeni catchment under a future climate.


Issue to be addressed

T​he uMngeni catchment in South Africa is ​highly diverse in climate and land use. The catchment has two large urban areas, Durban and Pietermaritzburg, as well as several smaller urban areas which are diverse in nature from wealthy, upper class residential suburbs to informal settlement areas which lack access to basic services. The uMngeni catchment supports a range of intensive commercial agricultural practices including sugarcane, dairy and commercial forestry. Scattered between these commercial agricultural areas are subsistence farming areas and poor rural communities who lack access to services. The water-related infrastructure which exists in the catchment is under severe strain. Coupled with this is the need to expand the infrastructure to those areas currently under-serviced (e.g. stand pipes; pit latrines) or lacking accessing to basic services. The agricultural activities in the catchment, lack of access to sanitation in some areas and aging sanitation infrastructure in others as well as the pressures on the solid waste management have degraded the water quality of the catchment. The water utility - Umgeni Water - is responsible for supplying drinking water to those areas with access to piped potable water. This water is sourced from four large reservoirs in the catchment which are at risk of becoming eutrophic.  Further to this, those communities without access to piped water are dependent on the river system. The risk of eutrophication of the large reservoirs is due to agricultural activities, aging infrastructure and a large component of society who have no access to basic sanitation. These activities are also resulting in a significant decline in the river health and quality on which many depend. 
Public health and safety are affected when bacteria counts exceed 400 per 100 ml according to South African guidelines; the actual concentrations in the uMngeni river systems have reached up to 1 000 000. A changing climate into the future could exacerbate this problem.

Decision support to client

The climate impact indicators (CII’s) produced through this project will assist Umgeni Water to better understand how the water availability, nutrient and pathogen loadings will change temporally and spatially through the uMngeni catchment under future climate scenarios.
​With this understanding, critical areas which have good water quality or improve the water quality of the river systems can be identified by Umgeni Water. Actions can then be taken to preserve and protect these area. Further to this, the understanding can identify hotspot areas of poor water quality where interventions are needed. These interventions could include rehabilitation of degraded landscapes to restore ecosystem services.
At a more local scale, the irrigation boards and conservancies in the catchment, particularly in the upper areas of the uMngeni catchment can use the CII's to better understand how the water quantity and quality in their areas may change under a future climate. This could facilitate the identification of changes in agricultural water use related practices that are needed to preserve or improve water quality, such as improved slurry water management and irrigation scheduling.

Temporal and spatial scale

The hydrological modelling will be undertaken for the greater uMngeni catchment (4 349.4 km2) with results summarized to the thirteen water management units that have been delineated in the catchment.
The period 1960 – 1999 will be used to produce the historical (benchmark) CII’s as high quality data is available for this period. Future climate scenarios to 2050 will be considered.

Knowledge brokering

The Centre for Water Resources Research (CWRR) has a close and ongoing relationship with the client, Umgeni Water. Umgeni Water support an endowed research Chair i.e. the Umgeni Water Chair of Water Resources Management, who is housed in the CWRR at the University of KwaZulu-Natal. The project team meets monthly with the Umgeni Water Chair to discuss the data to be produced and how this will be communicated through the interactive Atlas. The Umgeni Water Chair reports these activities at the Umgeni Water Internal Research Direction meetings and in quarterly reports. Using the Chair as a facilitator for communication ensures that the CII's are in alignment with the needs of the client and feedback reaches the correct decision makers in Umgeni Water. Training on the ACRU agrohydrological model will be held in September 2018 for Umgeni Water staff and consultants who work directly with them. The CDS will be promoted as a source of climate data, and the interactive atlas demonstrated to highlight the areas that are a) already under stress with regards to water quality and quantity b) will likely become stressed c) will be stressed but can be contained perhaps with intervention now.
Further to this, the irrigation boards and conservancies in the catchment are considered clients. Once the interactive Atlas is completed these clients will be emailed and where possible, visited in person, trained provided, and the Atlas promoted. 


Centre for Water Resources Research, University of KwaZulu-Natal

Poster displayed at the Kick–Off meeting, 7/8 September 2017, Norrköping, Sweden