Undergraduate Thesis - Feasibility of Rainwater Harvesting in Paarden Island

This section looks at the economic feasibility of implementing rainwater harvesting systems in Paarden Island by comparing the cost savings that will be achieved through rainwater collection and use versus the cost of implementing a rainwater harvesting system.

 

Assumptions

The following assumptions were made concerning the economic feasibility of implementing rainwater harvesting systems:

• It was assumed that other additional benefits that could not be directly or easily be measured using monetary values were not considered. These include but are not limited to environmental and social impacts;

• It was assumed that the estimated cost of the rainwater supply and rainwater harvesting equipment that was calculated was reasonable for the comparison. The main aim of this thesis was to provide an estimate of the number of feasible erven that would be able to implement rainwater harvesting systems and not an accurate estimate of the cost of implementing rainwater harvesting systems in Paarden Island; and

• It was assumed that the outcome of the feasibility analysis would be valid provided all the previous assumptions still remained valid. An example would be that the estimate of the yearly increases in water tariffs. If this assumption were to fail and the cost of tariffs don’t increase as expected then the resulting feasibility analysis would be an over estimate.

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Calculation of economic feasibility of implementing a rainwater harvesting system in Paarden Island

Table 6-6 and 6-7 show the results of the number of erven that will be feasible for non-potable rainwater harvesting systems and scenarios given for varying municipal rate increases. Table 6-6 and 6-7 show the cost saving that will be possible with the implementation of rainwater harvesting systems. Figure 6-4 to 6-9 show how the number of erf’s that are feasible, increase with an increasing annual tariff rate for all the different models.

 

Table 6‑6: Summary of economic feasibility of non-potable rainwater harvesting system calculations using 5.0% annual municipal water charge increase

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 6‑7: Summary of economic feasibility of non-potable rainwater harvesting system calculations using 9.5% annual municipal water charge increase

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 6‑4: Number of feasible erven for Scenario 1 non-potable rainwater harvesting systems based on different cost saving models for varying annual tariff rate increases

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 6‑5: Number of feasible erven for Scenario 2 non-potable rainwater harvesting systems based on different cost saving models for varying annual tariff rate increases

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 6‑6: Number of feasible erven for Scenario 3 non-potable rainwater harvesting systems based on different cost saving models for varying annual tariff rate increases

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 6‑7: Number of feasible erven for Scenario 1 potable rainwater harvesting systems based on different cost saving models for varying annual tariff rate increases

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 6‑8: Number of feasible erven for Scenario 2 potable rainwater harvesting systems based on different cost saving models for varying annual tariff rate increases

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 6‑9: Number of feasible erven for Scenario 3 potable rainwater harvesting systems based on different cost saving models for varying annual tariff rate increases

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Assessment of economic feasibility of implementing a rainwater harvesting system in Paarden Island

The number of erven that are able to make the implementation of rainwater harvesting in Paarden Island feasible increase as the tariff rate increases or the amount of rainwater that can be harvested and used is increased. Based on the various tariff models that are available the most likely real world models are model 1 and model 4. Scenario 3 allows for the best outcome for the number of erven that can implement rainwater harvesting systems feasibly. Scenario 3 Model 1 estimates that about 76 erven are able to implement non-potable rainwater harvesting systems at average inflation which can be increased to about 161 erven at the current municipal tariff rate increases. Scenario 3 Model 1 has actual real world possibilities due to the current cost structure of the sewage billing system and the current municipal water tariffs that are in place. Paarden Island would thus be able to implement non-potable rainwater harvesting systems in 34% to 72% of the current water account paying erven depending on the future municipal tariff rate increases.

 

The implementation of potable rainwater harvesting systems is not as high as non-potable rainwater harvesting systems. In Scenario 3 Model 1 it is estimated that 11 erven are able to implement potable rainwater harvesting systems at average inflation which can be increased to about 40 erven at the current municipal tariff rate increases. Paarden Island would thus be able to implement potable rainwater harvesting systems in 5% to 18% of the current water account paying erven depending on the future municipal tariff rate increases.