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Economic evaluation of chemical and biological control methods on four aquatic weeds in South Africa

  • Authors: Maluleke, Mary
  • Date: 2020
  • Subjects: Invasive plants -- Biological control -- Economic aspects -- South Africa , Introduced organisms -- Biological control -- Economic aspects -- South Africa , Aquatic weeds -- Biological control -- Economic aspects -- South Africa , Aquatic weeds -- Control -- Economic aspects -- South Africa , Aquatic resources -- Management , Cost effectiveness , Net present value , Herbicides -- Cost effectiveness , Working for Water Programme , Water conservation -- South Africa
  • Language: English
  • Type: Thesis , Masters , MCom
  • Identifier: http://hdl.handle.net/10962/145953 , vital:38481
  • Description: Invasive alien plants (IAPs) of various kinds pose a threat to ecosystems, biodiversity, conservation and overall economy. In a world experiencing exponential increase in IAPs – this issue has become endemic, especially for developing countries such as South Africa. South Africa is a water scarce country and IAPs increase water stress. Thus, South Africa must invest in a more realistic, environmentally and economically inclusive policy outlook on the management of IAPs including aquatic weeds. This is especially urgent when considering the changing global climate, which is predicted to further reduce the quantity and quality of potable water. The Working for Water Programme (WfW) in South Africa aimed at addressing the issue of IAPs in a way that protects the environment as well as produces maximum return to society through poverty alleviation. As such, the aquatic weeds management strategy put in place for four of South Africa’s aquatic weeds Pista stratiotes, Salvinia molesta, Azolla filiculoides and Myriophyllum aquaticum - should be one that is cost-effective, efficient and sustainable; yielding the best possible return on investment. Since these four weeds are already under complete biological control, in the absence of biological agents, the WfW programme would have used herbicides to control these weeds. As such, this thesis conducted a retrospective analysis of the relative herbicide cost-saving associated with the use of biological control. To do this, due to existing limitations, E. crassipes was used as a surrogate weed and its herbicide control costs were used as proxy for the herbicide control cost estimates of the four selected weeds; with reasonable conversion factors applied to cater for the biological difference of the five weeds. Using the cost benefit analysis (CBA) framework, the net present cost (NPC) of each control method was calculated to which the relative cost-saving was considered to represent the avoided cost of using biological control instead of chemical control on these weeds. The avoided cost was used as the main benefit component when deriving the relative benefit cost ratios (BCR). Two scenarios were used, one assuming no follow-up requirement and the other assuming one follow-up requirement for chemical control. Using an 8% discount rate, the study found that the estimated cost of the biological control method on all four aquatic weeds was about R7,843,205 while for chemical control the estimated costs would have costed R149,580,142, R268,264,838 and R881,711,738 for application by means of a boat, bakkie and knapsack. Chemical control cost estimates would have increased to about R164,538,052, R295,216,120 and R1,008,761,000 for boat, bakkie and knapsack approach respectively when including a possible follow-up programme. These would have led to positive BCRs of 90.24:1, 164.97:1 and 557.99:1 across the three chemical control approaches without a follow-up (with BCR of about 99.67:1, 182.00:1 and 631.56:1 for the boat, bakkie and knapsack approach respectively with the accepted follow-up programme). When running a sensitivity test with varying discount rates of 5% and 10%, these results remained robust. As such, failing to reject the dominant hypothesis in literature, the main conclusion of the study is that biological control is indeed the more cost-effective management option compared to chemical control with respect to herbicide cost-saving. Further, biological control is most-likely to produce more environmental cost-saving and water-saving over chemical control. The study recommends the continued use of the biological control investment on the four aquatic weeds under study as well as on emerging aquatic weeds such as Iris pseudacorus, Nymphaea mexicana and Sagittaria platyphylla in South Africa.
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  • Date Issued: 2020

The political ecological economics of coal mining and water resources: a participatory economic valuation approach in Carolina, Mpumalanga

Determinants of household water consumption: a study on sociodemographical and psychological factors associated with intention to conserve water

  • Authors: Kana, Gcobani
  • Date: 2018
  • Subjects: Water conservation -- South Africa , Water-supply -- South Africa South Africa -- Economic conditions -- 21st century
  • Language: English
  • Type: Thesis , Masters , MBA
  • Identifier: http://hdl.handle.net/10948/30683 , vital:31013
  • Description: South Africa is a water scarce country characterised by a rainfall below the global average and has for a long time ignored the importance of treating water as a scarce commodity. Therefore, the water scarcity challenge necessitates implementation of effective water demand management strategies to stimulate behaviour changes by South African water consumers (Coetzee, Nell, & Bezuidenhout, 2016). Due to the current (2017) severe drought experienced by the City of Cape Town Municipality of the Western Cape Province in South Africa, policy makers are forced to consider water demand management strategies that are centred on behaviour change in the efforts to curtail present urban water demand while also securing future water supplies. Studies have shown that residential users are the biggest consumers of water, particularly in the larger metropolitan areas. As a result, it is crucial for policy makers to conduct research and deepen their understanding of the social and behavioural aspects of household water use (Khalid, Ahmed, & Ashraf, 2016). The aim of the current study is to identify key determinants of household water use and the objective is to assist water authorities and policy makers to improve water demand management strategies through identification of those behavioural and psycho-social factors that could be targeted by water demand management campaigns. This study is framed by the Theory of the Planned Behaviour (TPB) model and is specifically looking at investigating the role of socio-demographic, psycho-social and attitudinal factors associated with household water demand. Self-reported data from an online survey was collected from 113 respondents residing within the boundaries of the City of Cape Town (CCT) municipality. Results revealed that household culture and past behaviour (habits) were significant predictors of every day intentions to save water around the house and garden while subjective norms were associated with intentions to install water efficient appliances. The emergence of household water culture as a significant determinant of household water use suggest that policy makers should focus on water demand management campaigns that consider household water use as a collective behaviour that is influenced by behaviour of others.
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  • Date Issued: 2018

The feasibility of artificial recharge of the Bushmans River Mouth Aquifer

  • Authors: Nickall, Enéz Sarah-Leigh
  • Date: 2008
  • Subjects: Artificial groundwater recharge -- South Africa -- Bushmans River Estuary , Water conservation -- South Africa , Aquifer storage recovery -- South Africa -- Bushmans River Estuary
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10657 , http://hdl.handle.net/10948/704 , http://hdl.handle.net/10948/d1012886 , Artificial groundwater recharge -- South Africa -- Bushmans River Estuary , Water conservation -- South Africa , Aquifer storage recovery -- South Africa -- Bushmans River Estuary
  • Description: The main aim of the project is to investigate the feasibility of artificial recharge of the Bushmans River Mouth Aquifer in the Eastern Cape. The suggested method of recharge is through natural infiltration through a series of wetlands in the back dune area. The proposed site was the Klipfontein Vlei which is located just north of the Bushmans River Mouth. Artificial recharge is defined as augmenting the natural movement of surface water into underground formations by some method of construction, the spreading of water, or by artificially changing natural conditions. A variety of methods have been developed, including water spreading, recharging through pits and wells, and pumping to induce recharge from surface water bodies. The choice of a specific method is controlled by local topography, geology and soil conditions, and the quantity of water to be recharged and ultimate water usage. In special circumstances, land value, water quality, and climate play an important role. Artificial recharge is not a foreign concept to South Africa and this project is to test its feasibility in a back dune wetland area. Augering done in the study area revealed the dominance of sandy loam in the upper layers of the pans, loamy sand in the middle levels and the presence of some sand lenses in the lower reaches. Particle size analysis done by sieving and hydrometer test, showed a dominant 3f fraction. There was variation in modes in pan 1 from unimodal to bimodal to trimodal. Pan 2 showed no variation as all samples were unimodal and moderately well sorted. Infiltration tests were done by a double ring infiltrometer. These results showed that the infiltration rates of the pans became stable after 15 to 20 minutes, thus indicating that the soil had reached its saturation point. The resistivity surveys revealed a stepped water table. The inclination of the water is controlled by the predominately argillaceous horizons of the Bokkeveld Group. Based on the above results, it is recommended that the Klipfontein Vlei be used as an artificial recharge site.
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  • Date Issued: 2008
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