TSHWANE | INDUSTRY INSIGHT
Ageing infrastructure, non-revenue water, non-payment for services and rising water demand present myriad challenges for the City of Tshwane. Dr Erik Loubser, senior executive, GLS Consulting, discusses the development of a multipronged intervention that provides a viable return to profitability model and a bankable document for potential funders.
Taking Tshwane’s water-loss programme
S
outh Africa’s largest municipality in terms of landmass, the City of Tshwane (CoT) has 240 water distribution management zones (DMZs) either supplied by a reservoir, water tower or direct connection to a bulk pipeline. The supporting infrastructure network is extensive, comprising 658 km of bulk pipeline, 9 943 km of reticulation pipes, 183 pumping stations, 151 reservoirs and 31 water towers. The construction value of the system is estimated at more than R20 billion. From the onset, the scope of our water-loss reduction feasibility study was to analyse each DMZ as the starting point for system improvements. To achieve this, a DMZ database was compiled and populated with all the requisite water-use/billing, water-loss, water pressure, customer debt and water system condition information. Once completed, this was then used to develop a set of rulesbased decision-trees to determine first-order, optimal water-loss interventions and costs for each DMZ.
to the bank
The capex, opex and water-loss reduction benefits associated with each indicated intervention (Table 1) were formulated in a 20-year cash flow model. These incremental cash flows were then discounted to net present value (NPV) terms. Each DMZ model considered their unique characteristics, including average tariff earned, collection rate and water balance. City-wide modelling was also performed to evaluate the impact of four alternative DMZbased intervention implementation strategies.
The evaluation was based on the projected cash flows of the city’s water services as a whole. This evaluation considered its ability to service the resultant debt, and to generate future excess cash for future interventions without the need for external funding.
Water resource
Most of CoT’s bulk water is purchased from Rand Water via the Vaal River system, but there are also minor supplies from Magalies Water, plus 13 water treatment plants (WTPs), various boreholes and fountains. TABLE 1 Possible water-loss interventions Developing or extending CoT’s own POSSIBLE WATER-LOSS INTERVENTION WHEN APPROPRIATE water resources would reduce the load Install bulk meter(s) for SIV/water-loss calculation No bulk meter/for loss calculation on the Vaal River system. On the other Log bulk meter No logging/determine MNF/calibrate AADD hand, though, increased sewer return Pressure management High static and/or dynamic pressures flows into the Crocodile River basin are Leak detection and fixing Indication of high real losses/high MNF important for current and future Pipe replacement Indication of deteriorating pipe condition downstream users, which include proposed Eskom coal-fired power plants Meter audit/replacement Indication of old and/or improperly sized meters in Lephalale via the Mokolo Crocodile Connection replacement Indication of old and/or deteriorating connections Water Augmentation Project. Retrofitting Indication of high MNF/UWDs and cost recovery risk Water management devices
Indication of excessive UWDs
Billing data clean-up
Indication of many unbilled stands/areas
Check DMZ boundary discreteness
Indication of cross-boundary flows
Rezoning/sectorisation
Large zone or potential PRV sub-zone
Punitive tariffs
Indication of excessive UWDs (overconsumption)
(AADD = Annual Ave. Daily Demand; SIV = System Input Volume; MNF= Minimum Night Flow; UWD = Unit Water Demand)
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IMIESA November/December 2020
Current (actual) water demand and water balance Data from the 2017/18 financial year was available as the basis for this study. The actual water balance for CoT as shown in Table 2 was determined using invoices from Rand Water and Magalies