Untitled Page
DWA Home Page  
 
Untitled Page

Study Approach

Purpose of the Strategy

The purpose of the Reconciliation Strategy is to determine the current water balance situation and to develop various possible future water balance scenarios up to 2035 and beyond. This entails an analysis of current and future water requirements, an understanding of all of the issues which could impact on the reconciliation of supply and requirement and knowledge of possible future interventions which can be used to reconcile supply and requirement, both WC/WDM interventions and supply side interventions. One of the biggest issues affecting the reconciliation of supply and requirement in this supply system is the impacts of on-going sedimentation at Welbedacht Dam, Tienfontein Pump Station and Welbedacht Water Treatment Plant.


Water requirements and availability

The accompanying graph shows the current system yield and the expected growth in ‘high water requirement’ until 2035. Two future water requirement scenarios are show on the graph. The high growth water requirement scenario (3% p.a.) assumes a high population growth rate and high economic growth rates. The low growth water requirement scenario (1% p.a.) assumes a low population growth and low economic growth. The graph shows that the 2009 water requirement was in balance with available supply (historical firm yield) and any increase in use (as predicted by the high and low water requirement scenarios) would put the system at risk. The higher the growth in water requirements, the higher the risk would be. It is clear that measures to increase the surety of supply need to be implemented as soon as possible. The actual water requirement has decreased over the last 2 years. As the reason for the decrease is not certain (could be weather related or a heightened awareness of Water Conservation/Water Demand Management), the planning projections were based on the 2009 actual water requirements.

 


Successful implementation of WC/WDM

In 2010/2011 the MMM developed a Master Plan for the Implementation of a Water Loss Management Strategy. Specific attention was to be directed towards the particular problems experienced in the Mangaung, Botshabelo and Thaba Nchu areas of supply. The master plan included strategies for both consumption (billing database) as well as physical losses from the water distribution system up to the point of sale to consumers.

In terms of the President’s State of the Nation address, the MMM is obligated to reduce its water losses by 50% by 2014. This directive was prepared by the DWS which has prepared the National WC/WDM Strategy. The strategy as developed by MMM focuses on the need to reduce non-revenue water (NRW), which currently accounts for 50% of all potable water supplied to the Municipal area of jurisdiction. The implementation of any WC/WDM programme is a multi-phased strategy, with the ultimate objective being the need to reduce unnecessary distribution losses to an economical minimum while maximising revenues from customers. The total bulk water supplied to the Bloemfontein/Mangaung area was 79 million m3/a. The water losses amounted to 29 million m3/a (or 37% of total bulk water supplied to this area).

The MMM have developed three alternatives potential water demand projection scenarios based on alternative saving projections. These water demand projection scenarios are:

  • Do nothing approach - Water requirement and sales projections should nothing be done by MMM to stop or slow the current trends of bulk water purchases, consumer sales and system attrition. The anticipated saving for this approach is 0m3/a.

  • Best Case Scenario - This scenario represents what would happen should all the identified Non-Revenue Water Reduction Activities that have been identified be implemented by MMM. This scenario represents the current full potential for WC/WDM and would result in an anticipated saving of 25.2 million m3/a.

  • Most Probably Scenario - This scenario is closely aligned to the best-case scenario, but taking into consideration probable delays in implementation, alignment and processes within the MMM. The anticipated saving for this approach is 11.2 million m3/a.


Whilst future planning is based on the Most Probable Scenario, the recommendation from the Reconciliation Strategy is for MMM to strive to achieve the maximum possible water savings through the implementation of their WC/WDM Strategy, namely the “Best Case Scenario” savings.

Interventions Required to meet enure ongoing reocnciliaiton of supply and requirement

The following interventions should be prioritised in order to ensure the on-going reconciliation of supply and requirement:

  1. The MMM should implement their WC/WDM strategy which was developed in 2011.

  2. Two additional pump sets (1m3 each) should be installed at Tienfontein Pump Station. The first pumpset should be utilised to increase the design capacity of the pump station to 4m3/s and the second pumpset to provide additional standby capacity. With the implementation of the two additional pumpsets the total standby capacity of the pump station would be increased to 50% (based on the proposed new design capacity).

  3. The Welbedacht Dam should be scoured to increase the capacity of the dam and to ensure that the siltation at Tienfontein Pump Station does not further hamper operations and maintenance.

  4. Bloem Water should further investigate the inability of the Welbedacht WTP to deal with high turbidity levels which currently limit the production capacity of the WTP.

  5. Initiate a feasibility Study to consider the most appropriate means to scour Welbedacht Dam and to augment Knellpoort Dam. The outcome of the feasibility study will guide the selection of future water resource development interventions.

  6. Bloem Water should take steps to ensure the integrity of the Welbedacht Pipeline. Bloem Water has proposed to relay sections of the Welbedacht pipeline which are considered as high risk.

  7. Mangaung Metropolitan Municipality should construct additional storage reservoir capacity in order to ensure that the network peaks are not transmitted through to the bulk supply infrastructure.

  8. It is expected that maintenance problems and associated expenditure will continue to persist into the future, unless Tienfontein pump station is modified/redesigned to cope with the sedimentation problems. With the near equilibrium sediment regime in the Caledon River now being reached, the redesign of Tienfontein pump station should be considered.

  9. A Feasibility Study on Water Re-use should be undertaken. The timing of the feasibility study should be recommended by the Strategy Steering Committee.


Scenario Planning Example : High Water Requirement Curve, Most Probable WC/WDM Saving Scenario

This scenario takes into consideration probable delays in implementation by MMM of successful Non Revenue Water (NRW) reduction activities. It is assumed that a total water savings of 11.2 million m3/a is achieved (commencing only in 2011/2012). The Metolong Dam is assumed to be completed by July 2012 when it would start to impound water. It is imperative under this scenario that the design capacity of Tienfontein Pump Station is increased to 4 m3/s in 2012/2013. In addition the scouring of Welbedacht Dam and ensuring that the Welbedacht WTP can operate at maximum capacity are interventions which should be implemented as a matter of priority. Additional augmentation of Knellpoort Dam would then be required be required by 2018. It has been assumed for this scenario that a pump station and pipeline would be constructed between Welbedacht Dam and Knellpoort Dam. The Figure below shows the possible reconciliation of supply and requirement under this scenario.

The capacity of the Novo Transfer Scheme will also ultimately have to be increased in order to realise an increase in system yield beyond the implementation of a possible additional pump station at Welbedacht Dam (i.e. before the further increase in capacity of Tienfontein Pump Station).

The next most cost effective supply side intervention would be the direct or indirect re-use of treated effluent. Public resistance to this intervention may be encountered, possibly stemming from concerns of poor design or control of processes which may allow sub-standard water to be introduced into the potable water supply system, or for religious reasons. An alternative option would be to transfer water from Gariep Dam, either directly to Bloemfontien or to Knellpoort Dam. It is estimated that this augmentation option would be in excess of 3 times the cost of developing additional water resources from the Caledon River. This option together with water reuse should be further investigated should further studies show that abstraction of additional water from the Caledon river is not feasible (or only partly feasible) due to on-going sediment related issues and concerns.

 

Ensuring that the Strategy is Up to Date

The Reconciliation Strategy for the Greater Bloemfontein Water Supply System recommended that a Strategy Steering Committee (SSC) be established, with the monitoring and implementation functions, as shown in the figure below, which summarises the relationships and functions required for implementing the Reconciliation Strategy. For the SSC to achieve its mandate, support is required from the Administration and Technical Support Group which includes the Professional Services Provider (PSP).The Strategy Steering Committee will ensure that the Reconciliation Strategy is updated on an annual basis. Although the Reconciliation Strategy Study was only completed in June 2012, the outcome of the strategy was already clear and a Strategy Steering Committee was formed in November 2011.

 

 

 

Untitled Document
This site is best viewed with Internet Explorer 7.0 (or newer) and Mozilla Firefox 32.0 (or newer) at 1024x768 screen resolution.Click here to download Internet Explorer 7 or click here to download Firefox 32.
DWS Sitemap
If you experience any challenges regarding this site, please contact the Webmaster.