At the height of summer in early 2018, when Day Zero looked like it was just three months away, the City set its tightest water restrictions yet. Hoping to stretch what water was left in its fast-drying dams, the aim was for the entire city to keep water use down to below 500 million litres per day. But while it was trying to drive these urgent demand-side water savings, it also needed to kick into gear a series of projects that would boost water supplies, even though many of these would only deliver water well after the drought was expected to have ended.

These built on the City’s longer-term water strategy, which planners were able to revisit once the winter rains of 2018 started to refill the dams, giving everyone a chance to pause and plan outside of crisis-mode. The new Water Strategy lays out various options for boosting the amount of water coming into the growing city water system. It includes utility-scale boreholes to tap groundwater reserves; a longer-term permanent desalination plant; and improved waste-water recovery. The strategy calculates the volumes of water each option is expected to deliver, the likely timeframes for getting them up and running, and the expected cost.

A number of external experts, including development and environmental consultants, helped to shape the thinking that went into these plans. One of those was international civil society organisation, The Nature Conservancy (TNC).

‘The City calculated that demand for water will outstrip supply by 2028. To avoid this, it would need to get an additional 350 million litres of water into the system per day by then,’ explains TNC’s South African director Louise Stafford. ‘This target would need a capital expenditure of up to R8 billion, based on current estimates, a cost that is likely to climb in future.’

Many of the big engineering solutions being offered in the water augmentation plans grabbed the newspaper headlines during the drought. Although details were sometimes hard to find, this planning signalled that the City was making plans to avoid a Day Zero scenario during the drought or at some point in future. But while this planning was going on, TNC briefed a team of resource economists to do its own bit of number-crunching around another critical threat to the city’s water: the invasive alien trees growing in the main water catchments for the province.

Clearing these wouldn’t cost much in the longer-term, they found, and doing so would release as much as two months’ supply of water back into the system.

The City was under enormous pressure to ‘pull the trigger’ on many of the engineering solutions being recommended by the tech advisers, but the resource economists urged caution. Don’t rush into any costly projects in future without a sober and rational review of the numbers and where the best return on investment would be, they said.

The resulting analysis from these economists will prove important in shaping how the state and its various partner institutions manage the Western Cape’s water system over the next three decades. This kind of external support by knowledge brokers proved to be critical throughout the drought.

Where’s the best bang for buck?

TNC’s brief for this analysis was to look at the impact of invasive alien trees growing either ‘wild’ in the Western Cape’s main water catchments, having escaped from forestry operations over many decades, or farmed in commercial plantations.

These trees, mostly pine, eucalyptus, and wattle, drink as much as 20 percent more water than the indigenous fynbos vegetation, according to TNC. At the height of the water restrictions, when the target was for a city-wide daily limit of under 500 million litres per day, these trees were using the equivalent of almost two months’ worth of Cape Town’s water. According to Stafford, this figure will double by 2045 if they aren’t cleared.

Resource economist Dr Jane Turpie, from Anchor Environmental Consultants, headed the team that took on the analysis. They looked at what it would cost to clear alien trees from around the main dams, restore the ‘ecological infrastructure’ in those water catchments, and keep them alien-free for the next three decades. What would the return on investment be, compared with the engineering solutions the City was suggesting for future water augmentation?

Alien invasive trees in the catchments drink as much as 20 percent more water than the indigenous fynbos. Clearing these trees from the main water catchments wouldn’t cost much in the longer-term, and it would release as much as two months’ supply of water back into the system.

In a nutshell, the conclusion of this study was that a relatively small investment of R370 million in today’s value over the next 30 years would restore the priority water catchments around the city’s three main dams. This, they concluded, would produce a significantly better return on investment than the engineered solutions. Though the total yield of water would amount to a third of the total combined yield from the engineering projects, it would be at significantly lower cost, according to Stafford, and should be prioritised alongside the other recommended engineering solutions⁴.

Zooming in on the farmed pine plantations that surround the Steenbras and Wemmershoek Dams, which cover 420ha and are owned by the City of Cape Town (meaning it is the City’s legal responsibility to manage the plantations), Turpie and team showed that the cost of clearing these, and making sure the area then stayed alien-free, would be almost half the cost per litre of sinking boreholes into the Steenbras aquifers⁵.

The call to arms from Turpie, who also works with the Environmental Policy Research Unit (EPRU) at the University of Cape Town’s School of Economics, was that the City needs to prioritise invasive alien clearing in its longer-term water management strategy. While the City does have an alien-clearing plan, for many reasons the work isn’t being done at a scale close to meeting the ongoing spread of these trees.

The conclusion of this study was that a relatively small investment of R370 million in today’s value over the next 30 years would restore the priority water catchments around the city’s three main dams.

TNC added another layer of analysis to the discussion, where it showed how extremely complex it can be to manage these kinds of long-term projects, in terms of institutional cooperation, funding, and year-on-year implementation. This job will involve pulling together funding and operational decision-making from national and provincial departments, state bodies such as SANParks and CapeNature, private contractors, and various municipalities responsible for the catchment areas in question⁶.

By the end of 2018, once the drought broke, TNC had set up a ‘water fund’. This is an interna-tionally-used model aimed at helping cities pull together the many partners that might need to be involved in coordinating and managing funds associated with projects that are geared towards restoring or improving ecological infrastructure relating to water⁷.

Bringing in the external experts

This piece of the story shows how necessary it is for a city to draw on the knowledge and analysis of skilled experts – academics, researchers, development practitioners, civil society organisations, and even retired technical experts who previously had worked for local government – in order to make informed, evidence-based decisions in the short- and long-term, even within the urgency of day-to-day decision-making.

Many technical personnel in the City admit that they didn’t have strong networks that they could draw on to find the type of information they needed, often urgently. Some said they turned to the Internet to find examples of other cities’ best practices relating to crisis water management. One water manager said he had two tourists come to his office one day, who turned out to be urban water management experts. They had taken it upon themselves to give up some of their holiday to offer some advice, which the manager was grateful to receive.

But as the analysis of the alien-clearing programme showed, managing projects like this calls for coordination across multiple government and non-government interests, funding from many varied sources, and planning that spans decades. A City management team will be just a small cog in a much bigger project, but one whose success ultimately determines how vulnerable the wider province’s water system is. This kind of complexity is true for so many of the other water system interventions that the City, province, and national governments need to spearhead in future.

Once the winter rains finally started topping up dam levels again in 2018, TNC’s Louise Stafford, writing in the Daily Maverick⁸, urged the City not to become complacent or lift water restrictions too soon. This was a chance, she wrote, ‘to pause and use the best scientific evidence to support the decisions we make as a region and community to manage the shared water resources upon which our lives, health, and economy depend’.