15. Demand Projections WC/WDM Strategy Table 10-6 Impact of WC/WDM Year new supply augmentation will be needed LWR HWR No WC/WDM 2016 2008 Sustaining efficiency from restrictions 2020 2013 10 yr WC/WDM Strategy 2051 2026
The City of Cape Town (CCT) Long Term Water Conservation /Water Demand Management (WC/WDM) strategy was published in 2007. It is a comprehensive strategy and has a set of specific goals to be achieved through the implementation of project programmes in the following ten years (from 2006 up to 2016). The CCT has committed itself to the implementation of the WC/WDM strategy and targets saving approximately 90 million m 3 /annum by 2016/17. It has now become imperative that progress with the implementation of the strategy is assessed, three years after the inception of the strategy. The impact of the strategy on water demand and conservation must be measured and it must be established whether its original goals are being achieved and if not, why not. The WC/WDM strategy is a critical component in the future planning of the Western Cape Water Supply System The City of Cape Town (CCT) Long Term Water Conservation /Water Demand Management (WC/WDM) strategy was published in 2007. It is a comprehensive strategy and has a set of specific goals to be achieved through the implementation of project programmes in the following ten years (from 2006 up to 2016). The CCT has committed itself to the implementation of the WC/WDM strategy and targets saving approximately 90 million m 3 /annum by 2016/17. It has now become imperative that progress with the implementation of the strategy is assessed, three years after the inception of the strategy. The impact of the strategy on water demand and conservation must be measured and it must be established whether its original goals are being achieved and if not, why not. The WC/WDM strategy is a critical component in the future planning of the Western Cape Water Supply System 10/11/11
Being pro-active by doing it after 3 years 10/11/11
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The Western Cape Water Supply System Reconciliation Strategy Status Report published by Department of Water Affairs (DWA) in September 2009 (1) indicates that should CCT only achieve 50% success with the implementation of the WC/WDM strategy and the current growth in water demand continues a new augmentation intervention will be required by 2015. No supply interventions could however be available for implementation by that date, not on a normal or a fast-tracked programme. The message from DWA therefore rings loud and clear, namely that the successful implementation of the WC/WDM is crucial and if CCT anticipates problems with the achievement of the WC/WDM goals it must inform DWA without delay. Therefore CCT has now initiated a monitoring programme to measure and report on the achievement and effectiveness of the WC/WDM strategy. 10/11/11
CCT WDM has implemented a wide range of projects from highly technical interventions to community engagement campaigns to reduce water demand and losses and conserve water. Numerous projects have been commenced and successfully completed. Pressure management successfully implemented in more than 13 settlements including pressure reduction devices for 49 schools 1693 Consumer meters audited in Automated Meter Reading Pilot project (Epping, N2 Gateway and Sunset Beach). Total of 1775 consumers fitted with automated meter reading devices 4 . 20 574 consumer water meters replaced ,17 998 consumer meters re-located and fixed and 70 652 water connection leaks fixed in last 3 years (2007/8 – 2009/10) 95 treated effluent users which accounts for 80.5 Ml/day of re-use. 10/11/11
More than 50 0000 households in low income areas have been visited, inspected, leaks repaired etc. More than 15 major pressure management projects Numerous awareness campaigns, educational initiatives and events have been done 10/11/11
The CCT has actively managed the strategy budget and a number of revisions have been necessary. In the first two years of implementation the budget was increased by 45% in 2007/8 and 19 % in 2008/9. However, the budget was cut significantly in the third year of implementation (2009/10) by 51% and in the current year the budget has been reduced by 53% from the original budget. Following two graphs provide graphic comparisons of the original total strategy budget and the latest amended budget reported in August 2010. In the first year of implementation the CCT overachieved the revised budget and similar performance was achieved in the second year with 99% of the budget spent. However, in the past year (2009/10) the CCT managed to spend only 69% of the revised budget. It is noted that the reported actual expenditure for 2009/10 does not include staff costs and this still needs to be finalised. Budget revision and actual expenditure information received from CCT (D.Klopper) in the spreadsheet wcrsWCWDMBudgetAug2010.xls 10/11/11
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In estimating expected water savings the WC/WDM Strategy budget assumed a directly proportional relationship between money spent and achievable savings. It is important to note that this implies that achievable savings are independent of the type of intervention. This assumption needs to be revised. Figure depicts the anticipated savings for each measurement year predicted by the strategy document and the budget. 10/11/11
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The impact of the WC/WDM strategy on curbing water demand basically depends on two main elements: The unconstrained growth in water demand (i.e. what the demand would have been without any WC/WDM measures). The actual savings realised through the WC/WDM strategy (including abating water demand growth). 10/11/11
When the overall savings achieved with the strategy implementation is assessed two facts must be kept in mind: The expected or predicted savings are based on the assumption of uniform cost for unit water demand reduction. It is not possible to measure all the savings that have been achieved up to date for the following reasons: Not all the savings can be physically or directly measured (such as the savings resulting from customer awareness campaign) and must be estimated Where estimations have to be made, limited data is available and thus the accurate estimations cannot be made. The CCT is in the process of collecting relevant data so that more accurate estimations can be made. Where savings can be directly measured, not all the zones have been set up to measure yet, or in some cases it will be too expensive to do so, and will thus not be done. Therefore, for the purposes of this first assessment, a conservative approach was followed. The graph shows the total reported savings reported for Goal A and Goal E of the strategy for the pressure management programmes and treated effluent re-use programmes. Therefore no estimated savings are used in the assessment. It is imperative to note that the actual savings could be significantly higher as this assessment excludes all the savings from Goal B, D and D and the other programmes in Goal A and E. Furthermore, it was also assumed that for treated effluent re-use, that only 40% of the re-use replaces potable water use. 10/11/11
There are a number of demand projections that have been developed over the last few years. The DWA Western Cape Water Supply System Reconciliation Strategy used a demand growth rate of 3% to estimate unconstrained demand (i.e. a ‘Do nothing’ scenario) based on the historical trend for the period between 1991 and 2000 and basing the curve on the reported potable water demand from 2000. The DWA Reconciliation Strategy has also adopted two future water requirement curves namely the High Water Requirement Curve with a demand growth of 3.09% per annum and a Low Water Requirement Curve with a demand growth of 1.43% per annum. Both curves using the demand of 2006 as starting point 10/11/11
The WC/WDM strategy assessed the impact of the implementation of the Strategy on the need for a new dam and found that the full implementation of the WC/WDM strategy will result in a new dam only being required by: 2051 if water demand followed the Low Water Requirement curve and, 2026 if water demand followed the High Water Requirement curve. However, it is very important to note that this impact assessment was based on the assumption that there will be no growth in demand after the start of the strategy implementation in 2006 for: the first 27 years in the case of the LWR (i.e. from 2006 to 2033) and the first 13 years in the case of the HWR (i.e. from 2006 to 2019). This assumption was based on the anticipation that the full implementation of the WDM strategy will abate the natural demand growth to 0%. This assumption was based on the anticipation that the full implementation of the WDM strategy will abate the natural demand growth to 0%. It is important to understand that these assumptions were made, to the best knowledge available at that stage and that the CCT worked closely with DWA in the development of the strategy. Now, with hindsight after three years of implementation and close monitoring, these assumptions can be adjusted and the impact of the Strategy re-evaluated. Table 10-6 on page 67 of the Cape Town WC/WDM Strategy, Apr 2007. Refer to calculation in spreadsheet Strategy tables calcs V7.2.xls worksheet 6c Impact of WC received from M Engelbrecht City of Cape Town 10/11/11
The actual average annual demand growth over the period 2006 to 2010 since the inception of the Strategy is 2.98 % p.a. This graph demonstrates the impact of the implementation of the WDM Strategy, and that growth in demand has been curbed, but not to a zero percent growth level as the assumption of the original impact assessment dictates. The following two questions leap to mind: What would the demand and the demand growth have been without the full implementation of the strategy? How accurate were the assumptions of the strategy? 10/11/11
What would the demand and the demand growth have been without the full implementation of the strategy? The water demand and the demand growth would certainly be much higher than without the strategy implementation. How much? The annual growth in demand in 2006/7 was 4.75%. If this demand growth is applied to the annual demand reported for 2006/7 the following projection 10/11/11
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In understanding this steady increase in NRW rather than the reduction expected one has to understand and report on the sub-components that make up NRW, as defined by the IWA water balance 10/11/11
In understanding this steady increase in NRW rather than the reduction expected one has to understand and report on the sub-components that make up NRW, as defined by the IWA water balance 10/11/11
This slide presents the IWA water balance for the City of Cape Town and the various components for which data is available. It is important to note that the calculation of the IWA water balance was performed using the best available information at present and in some cases estimation based on input from officials within Water and Sanitation. Therefore the accuracy of the IWA water balance can still be improved but should give a good indication of the current state of affairs with regards to the sub-components of NRW. The CCT is giving a very high priority to comprehensive non-revenue water reporting (WSDP February 2010). Detail reporting will be done through the Data Integration and Monitoring System (DIMS) project and includes phased installation of more zone and bulk supply meters as well as automated remote logging thereof. The DIMS project is set to go live in the latter part of 2010. These volumes reported here may still be subject to revision. From the balance it can be seen that the major contributor to NRW is Real Losses ( 46.1% of NRW). Apparent Losses accounts for 36.4% of NRW and Unbilled Authorised Consumption makes up the remaining 17.5 %. In effect the Strategy targets the components of NRW indirectly in all the Goals, but directly in Goal A and its associated project programmes. If the Strategy budget and its revisions are analysed it is evident that Goal A is appropriately focussing most of the resources on targeting Real Losses: Received data from CCT (B Saayman) for most components except System Volume Input, Authorised Consumption. Data on Volume input and authorised consumption obtained from CCT (J de Bruyn in the monthly portfolio committee report. 10/11/11
The estimated savings for this Goal after the first three years of implementation is 40.8 Ml/day, which is right on target with the projected savings of the strategy after 3 years of implementation. However, it should be noted that 20.4 Ml/day can be confirmed with field measurements for pressure management projects that have been completed and measured. The remainder of the savings are estimated. Even, if one takes a conservative approach, and only uses the confirmed and measured savings, it is evident that the CCT is on track in achieving the anticipated savings. 10/11/11
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Currently, approximately 80.5 Ml /d of treated effluent is used. It is important to note that the volume of treated effluent use does not directly translate into water demand savings, as not the full volume of treated effluent use replaces potable water demand. A portion of the use replaces ground water use or in specific cases what otherwise would be no use at all. If a conservative assessment is done and only 40% of re-use is assumed to replace potable water demand the estimated saving is 32.2 Ml/day. This conservatively estimated saving is on par with the expected savings (34 Ml/d) at the end of year 3 (2009/10) of the strategy implementation The Western Cape Reconciliation Strategy report on Water Re-Use Potential (February 2010) page 44 states 35% of annual volume re-use replaces potable use. Need to confirm this M Engelbrecht to send latest spreadsheet on re-use – see comment in report 10/11/11
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The short answer is that most of the assumptions were fairly accurate were made to the best knowledge available at that stage of the strategy development. With hind sight and improved data collected through the strategy implementations (such as the setting up of DMAs) some of the assumptions and base data can be adjusted. The most significant assumption with potentially the prevalent impact on strategy achievement is that the population growth rate used might be too low (1.61% (CCT) vs. 3.49% (StatsSA) which has a direct impact on the water demand growth. The use of uniform cost for unit water demand reduction can also now be improved, with better information and understanding available. 10/11/11
There may be several reasons that can be offered as an explanation for the interesting finding that discharge to the sewer system is greater than billed potable water and it requires further investigation: Significant groundwater/ rainwater infiltration The unbilled authorised and unauthorised components of NRW are significant Re-use / recycling of effluent may contribute Billing data inaccuracies The steady decrease in “water billed” may be an indication of the successful implementation of the WC/WDM strategy. Since water supplied to the reticulation system does not exhibit a significant increase over the last 2 measurement years it may also serve as an indication that NRW in the reticulation system is being addressed and which in turn raises a question with regards to NRW in the bulk system. However, it is important to note that bulk treated water’s steady increase is also reflected in the steady increase in the discharge to the sewer system, although this may possibly be due to the impact of the re-use of treated effluent (80.5 Ml/d). 10/11/11
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