Water & Wastewater

Planning for KZN’s bulk water needs

The approximate 30-year projection for potable water supply in KwaZulu-Natal (KZN) is 3 000 Mℓ/day. In order to meet this, Umgeni Water compiles an annual Bulk Water Infrastructure Master Plan (IMP) to highlight the infrastructure needed and ensure adequate planning. By Kevin Meier*

The total bulk water supply capacity for KZN at present is only about 1 500 Mℓ/day. The shortfall between demand and supply can be attributed to the following: • increasing water demand as service levels in communities improve • ageing infrastructure and lack of maintenance causing high levels of water loss • insufficient resource or infrastructure supply capacity constraints • unserved (backlog) areas that still require a reliable source and supply of water. In June 2020, an update of the Umgeni Water IMP was published to include not only planning within Umgeni Water’s supply area, but also the remaining areas within KZN. This IMP is available on Umgeni Water’s website: www.umgeni. co.za/infrastructure-master-plans.

The pragmatic approach to developing this IMP follows below.

Identification of supply systems

Water resource supply considerations are as important as the infrastructure supplying the demand. The raw water source must be planned to supply the present and future demand of an area for the full length of the planned forecast period.

In compiling the Bulk Water IMP for KZN, Umgeni Water divided the province into supply systems (as shown in Figure 1). These systems include water resource areas (catchments) and the water supply ‘footprints’

FIGURE 1 Systems as defined in the Umgeni Water IMP

(homogeneous areas supplied with water from a node/reservoir).

Unfortunately, municipal boundaries do not follow water resource/supply system boundaries and the plans for supply to a municipality may have to be drawn from more than one of the 10 volumes of the Umgeni Water IMP.

Demand assessment and forecast

Umgeni Water has determined supply footprints (as shown in Figure 2) throughout the province. A supply footprint is a

FIGURE 2 Situational analysis: demographics and growth rates homogeneous supply area that has the same source of water and same level of service. In areas where water supply is metered, the actual volume of supply is used as a baseline and a 30-year forecast is determined from that baseline.

In backlogged or unreported rural areas, demographics were used to determine an expected demand based on a minimum supply of 100 ℓ per capita per day. The 30year forecast is determined for each of the supply footprint areas using natural growth estimates, migration to or from the area, and potential development of the supply footprint.

Water resources yield determination

It is important to determine the amount of water that can be supplied within a supply system or subsystem during drought years. Whether the source of water is run of river or from a dam or a borehole, the amount of water that can be abstracted during a drought is affected by the size of the catchment, dam, river or aquifer, as well as the capacity of the catchment to return water to these sources.

The amount of water that can be abstracted in a drought year is termed ‘yield’ and should be determined for all water resource supply areas at a minimum of a 1:50 return period drought (worst drought in 50 years).

These yield values were identified from studies or were estimated for supply notes when compiling the IMP. As an example, the yield of the Mgeni System at a 1:100-year return period is presented in Figure 3, together with the projected demand of the system. It is clear that the current resource has to be augmented to increase the yield so that the future demands can be supplied (increased yield in 2015 as a result of the construction of Spring Grove Dam). The project identified to increase this yield is the uMkhomazi Water Project.

Development of water supply schematics

Water supply schematics are developed for each supply system or subsystem. These schematics include a base case, which depicts the infrastructure that currently exists to supply the area and additional schematics to show the infrastructure that should be developed over the 30-year forecast period.

Specific infrastructure capacity constraints

Within each supply system, the capacity constraints of each individual infrastructure component are assessed and recommendations are made as to whether these components should be upgraded over the demand period.

In the example shown in Figure 4, the historical supply from the Midmar Water Treatment Plant is analysed to determine how often the plant has operated above the optimum operating capacity and how often it has operated above the design capacity (0% of the time in this scenario), so that potential augmentation can be planned well in advance.

It must be noted that details of much of the infrastructure positioned outside of Umgeni Water’s operating area are not well documented and hence this type of analysis could not be undertaken for many of the plants managed by water services authorities (WSAs). However, this in itself has highlighted a need to confirm infrastructure attributes or operating parameters and discussions have and will continue to be held with WSAs to ensure adequate metering of supply points such as water treatment plants.

FIGURE 3 Yield of the Mgeni System showing the projected growth in forecast demand

Recommended projects

Using the information and analysis described above, recommendations are made as to infrastructure that should be developed to meet the 30-year supply need for all areas.

Some of these projects take the form of infrastructure to augment existing systems. In other cases, entire bulk water supply schemes are recommended for supply to areas that do not have a reliable supply.

Universal access to water supply throughout KZN

As a parallel process to the development of the IMP, Umgeni Water has commissioned three phases of a Universal Access Plan (UAP) for water in the province, which can be found here: www.umgeni.co.za/ infrastructure-planning.

The UAP is a strategy that has been developed by Umgeni Water, the Department of Cooperative Governance and Traditional Affairs (CoGTA) and the Department of Water and Sanitation (DWS). The first phase of this UAP was completed in 2014 and included recommended short-term interventions that could be developed to ensure universal supply throughout the province.

The second phase highlighted potential bulk supply schemes that could be developed to ensure universal access to water throughout the province. This version only included the source of water, the water treatment plants and the supply to a command reservoir. The third phase of the UAP, to be completed in

FIGURE 4 Twelve-month operating statistics for the Midmar Water Treatment Plant

October 2020, further extends the bulk water supply components to include the secondary bulk infrastructure required to deliver water to specific water supply footprints/nodes.

Many of the plans developed in the UAP phases have formed or will ultimately form recommended projects in the future updates of the IMP. The total estimated cost of developing bulk water supply infrastructure to achieve universal access in the province is approximately R100 billion. This includes the capital needed to construct bulk and secondary bulk infrastructure but does not include estimates for reticulation.

The above plans are a good starting point to developing the infrastructure needed to supply all consumers in the province. These plans will be further developed in the future updates of the Umgeni Water IMP and, where possible, detailed feasibility studies will be undertaken to start these projects along a path that will ultimately lead to full construction. The real challenge now is to determine not only how this infrastructure can be funded, but also how it can be maintained once it is developed, as many of the WSAs in the province do not recover sufficient funds from water sales to support even the operating costs of this infrastructure.

Acknowledgements: Umgeni Water’s Planning Services Department and other staff for developing the format and content of this valuable plan. The team of Umgeni Water, DWS and CoGTA for facilitating development of the UAP phases.

*Kevin Meier is a manager: Planning Services at Umgeni Water.