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Institute for Water Research

Background

South Africa is a water scarce country. It ranks as one of the 30 driest countries in the world, with an average rainfall that is around 40% less than the annual world average. Supplemental supply options must be designed with this in mind, and water conservation initiatives are critical to long term success.

Locally, Makhanda is drought prone with regular droughts experienced over the 124-year rainfall record. There are also a range of factors that have contributed to water insecurity in Makhanda, including municipal mismanagement and infrastructural problems which have resulted in frustrating water cuts.

Makhanda rainfall statistics from 1900 to 2023 highlighting average rainfall (green) and the 10 driest years in the 123 year record.

The University wants to improve water supply security for campus, aiming to move away from reliance on a consistent Makana Municipal water supply. Chief Financial Officer Mr Kamlesh Riga and Director of Facilities and Infrastructure Mr Dawie van Dyk have been working with researcher’s Dr Jane Tanner and Dr Rebecca Powell from the Institute for Water Research (IWR) to assess the potential for harnessing a supplemental water supply for the University. This undertaking has a number of different components namely the scientific, engineering, social and political components.

So far, the scientific component has been completed (summarised below), while the political and engineering components have just begun. The scientific analysis examined the potential for water supply supplementation from rainwater harvesting, greywater reuse, and finally groundwater supplementation. The project aims to provide a guide to investment in water infrastructure development for the University, that takes existing water saving initiatives into account and considers current and future growth parameters to ensure reliable supply. This will also contribute to fulfilling Rhodes’ Environmental Sustainability Goals (which are outlined in the Institutional Development Plan).

Estimated monthly water demand for Rhodes University for resident and day staff and students only (this figure excludes laboratory water use, and the various research stations water use).

Rainwater harvesting

The first potential supplemental system includes rainwater harvesting. This was examined through the use of a simple water balance tool whichsimulates reliability of supply from rainwater harvesting via rooftops (using Makhanda rainfall records from 1900 to 2024). Academic buildings and residence buildings were separated due to very different demand needs. Our findings suggest that rainwater harvesting is an ineffective measure to meet sustainable water supply goals. It is most effective as a supplementary supply for toilet flushing water demand for selected academic buildings that have a relatively large roof area and low building occupancy. This outcome is linked to the highly intermittent nature of Makhanda’s rainfall and the relatively high demand (for toilet flushing) for all residences and many academic buildings, meaning tank storage (however large) is depleted quickly.

Rain tank model main screen showing parameters (top left), output figures (bottom left), graphs showing frequency of tank storage volume, and frequency of supply volume.

Greywater reuse

The second potential supplemental system includes greywater reuse. Treated greywater can only be used for toilet flushing or irrigation. However, our findings suggest that commercial greywater systems are potentially a cost-effective water reuse option for campus. Several infrastructure and management related factors need to be considered, however. Firstly, multiple semi-centralised treatment systems would need to be distributed across campus in between or close to residential buildings suited to supply/receive greywater (the larger the system, the more cost effective). Issues of placing the semi-centralised treatment systems in and around campus would need to be carefully considered in line with the Spatial Development Plan for the University. Secondly, residences using and/or supplying greywater would need to have dual plumbing (separating out the distribution pipelines in the buildings). Thirdly, although each system is automated it still requires that a team manages the system and runs monthly maintenance checks and cleaning. We thus suggest that this work is outsourced to a private company, which may be more costly but is most feasible from a management need perspective.

PhD student Mr Siphumze Bani, operating the pilot greywater system at Robert Sobukwe House (Photo credit: Roman Tandlich)

Groundwater supplementation

For the groundwater supplementation consideration, specialist consultants GCS (Pty) Ltd assisted. The work included setting up a detailed specialised 3D groundwater model. Given the potential for uncertainty related to the fact that groundwater is a hidden resource and is difficult to measure, GCS provided state of the art expertise to reduce that uncertainty as far as possible. There are three main aquifers beneath Makhanda, each with their own characteristics in terms of yield and quality (these aquifers are quartzite, shale and tillite aquifers). Rhodes University is located on the quartzite (upper campus) and shale (lower campus) aquifers, while Makhanda Central and East are situated on the tillite aquifer. The Witteberg Quartzite aquifer was selected as the primary target due to its location being in the upper part of the catchment and underlying the majority of the university.

The Witteberg Quartzite is a secondary fractured rock aquifer that contains groundwater with a slightly acidic pH (<7) and is low in total dissolved solids (200- 400mg/l). The calculated recharge (aquifer replenishment) varies over the area with a range of 2.0% to 6.7% of Mean Annual Precipitation (MAP). Although Makhanda has intermittent rainfall, the recharge area for RU aquifer extends upstream of campus, resulting in a significant recharge area contributing to the aquifer beneath campus.

The conceptual model grid showing the three aquifers located beneath Makhanda

The model results show that the aquifer can meet the upper campus demand of approximately 87 000 KL/annum with existing boreholes (although additional boreholes are recommended to ensure system resilience in case of breakdown), with most of the impact (groundwater level drawdown) located on campus. For total campus demand of approximately 263 000 KL/annum, new boreholes will be required.

Drawdown for Upper Campus abstraction (Phase 1) (GCS Groundwater Feasibility report)

Artificial recharge via rooftop rain harvesting being fed into infiltration galleries on upper campus will assist to reduce this impact. The groundwater would have to be treated to meet domestic water quality requirement to remove the dissolved metals and precautionary disinfection for bacteria. The groundwater complies with SANS 241 in terms of other dissolved solids.

Electrical conductivity values for groundwater located in the quartzite aquifer (maroon), the shale and sandstone aquifers (green), and the tillite aquifer (grey) (Smetherham, 2019 – RU MSc thesis)

Manganese values for groundwater located in the quartzite aquifer (maroon), the shale and sandstone aquifers (green), and the tillite aquifer (grey) (Smetherham, 2019 – RU MSc thesis)

Based on the collation of the above information, it was determined that groundwater supply holds the greatest potential to reduce the reliance on a consistent Makana Municipal supply. Greywater harvesting is also being considered in terms of contributing to the fulfilment of the environmental sustainability goals of the institution.

In terms of existing infrastructure, RU campus can be divided into the upper and lower campus. The upper campus contains the majority of the student residences and is fed by single ring main from the “Green” reservoir via the municipal supply. The lower campus has several connections and is integrated into the town water supply making the connection to an off-grid water supply difficult due to the multiple connections. The pipeline distribution network for lower campus is owned by Makana Municipality, while the pipeline distribution network for upper campus is owned by RU.

Based on the current infrastructure in place at RU, it has been determined that the water management plan will take place in a phased approach. Phase one will target upper campus (around 33% of total RU water usage) as there is already an isolated water distribution pipeline network in place owned by RU. Phase two will target lower campus as well as identify areas where greywater reuse will be effective. Phase two would also likely be broken down into a series of phases due to the complexity of installing an RU owned and managed pipeline distribution network. Information gathered during Phase one will be critical in determining how Phase two develops (particularly given the aquifer response to abstraction).

Water Use Licence

The University applied for a Water Use Licence from the Department of Water and Sanitation. This process includes the setting up of a detailed groundwater model; stakeholder engagement to discuss the impact on other users and notification to relevant water management bodies such as the Catchment Management Agency. This process is normally scheduled to take 90 days.

Concurrently with the water use licence the University will carry out a feasibility study. A select number of experienced and trusted companies have been approached to submit quotes for the feasibility study. The bet36体育投注_bet36体育在线—激情赢盈中√ of Reference are currently being completed by RU.

The feasibility study will include:

1. geophysics to determine the precise location of new boreholes;
2. engineering upgrade for the upper campus distribution pipeline to get the groundwater to the treatment plant, and to expand the distribution of the treated water;
3. the specifications for two new reservoirs (one for holding raw untreated groundwater, and one for storing treated groundwater);
4. a modular water treatment plant that can be expanded as Phase two comes online; and
5. specifications for a comprehensive monitoring system that includes water abstraction, groundwater levels, and water quality parameters.

Currently the focus of the team is on both the Water Use Licence application, and preparations for a feasibility study with detailed costing to more precisely determine the way forward.

Last Modified: Fri, 14 Mar 2025 16:10:09 SAST