Academic literature on the topic 'Katse dam (Lesotho)'

Water quality is of prime importance to Rand Water’s core business of ensuring a reliable supply of good quality drinking water to more than 10 million people. Rand Water has, therefore, implemented a water quality monitoring programme of the source water as well as the drinking water produced. The establishment of the Lesotho Highlands Water Transfer scheme necessitated the expansion of the monitoring programme. In 1996, Rand Water and Lesotho Highlands Development Authority (LHDA) signed an agreement to jointly develop an extensive water quality monitoring programme for the Lesotho Highlands Water Project (LHWP). Prior to this agreement, monitoring was mainly undertaken by consultants on behalf of LHDA in the main feeder rivers within the Katse Dam catchment (donor system). On the recipient system (Ash/Liebenbergsvlei), extensive physical and chemical monitoring was undertaken by Rand Water and Department of Water Affairs and Forestry (DWAF). Biological monitoring was however only carried out superficially prior to the release of water. Information gained from carrying out biological and chemical assessments clearly indicates that the water from LHWP has negatively impacted on the biological communities in the recipient system. The importance of detailed before and after biological and physio-chemical monitoring of both donor and recipient systems is emphasised.

The Vaal River has become so nutrient-enriched that algal blooms pose problems. A unique opportunity arose to determine if there were changes in the chemistry en algal composition of the Vaal River after oligomesotrophic Katse Dam (Lesotho) water was imported to augment supplies in the light of growing water demands in the Vaal River catchment area. Algal concentration and composition in the Vaal River during three periods (between 1992 and 1994, 1998 and 2000, as well as 2004 and 2006) were compared to those in the Katse Dam (1998–2006). Some algal species, initially absent from the Vaal River, appeared in the river during and after transfer. Mixed algal assemblages found in the Vaal River before transfer of Katse Dam water gradually changed after transfer to assemblages mainly composed of cyanobacteria. The total algal concentration in the Vaal River Barrage doubled from the period between 1992 and 1994 to that between 2004 and 2006, indicating that the transfer of clear, oligomesotrophic Katse Dam water did not dilute the eutrophic Vaal River water sufficiently in order to reduce algal concentrations. Results showed that continuous downstream pollution and eutrophication of the Vaal River system eliminated the diluting effect of Katse imports. This resulted in changes in algal composition and concentration in the Vaal, characteristic of those associated with increasing eutrophication.

A survey of the reptile fauna of the Katse Dam catchment area in the Lesotho Highlands was conducted to assess the possible impact of the dam, once it is full, on reptile populations in the area. With only seven lizard and five snake species recorded to date, species richness in the catchment area is much lower than expected. It is inferred that species richness in the western and central districts of the Lesotho Highlands in general, is low, emphasising the role of the Drakensberg-Maluti mountain complex as a barrier to species dispersal. The reptile fauna of the western/central highland areas is primarily composed of widespread generalist species. The eastern highland areas, on the other hand, have a substantial endemic component. indicating the greater potential of these areas as a conservatory of geographical isolates. The direct impact of the Katse Dam on the local reptile fauna is expected to be minimal. Snake numbers are low in the catchment area and this may be the result of human impact. Reproductive cycles of the lizard species in the catchment area do not differ from the cycles of the same species at lower altitudes elsewhere.

The construction of the Katse dam was completed in 1996. The dam started filling in 1995 and reached full capacity in early 1998. It forms part of Phase 1A of the Lesotho Highlands Water Project (LHWP). The main aim of the project is to provide revenue to Lesotho, by transferring water from the catchment of the Senqu (Orange) River in Lesotho to South Africa’s major industrial and population centres. During the implementation of the project, an estimated 130 people were displaced. However, the most serious impact has been the loss of the traditional way of life in the form of arable and grazing land as a consequence of inundation. One of the obligations of the project is to ensure that the standard of living of those affected by the project is not impaired. The Lesotho Highlands Development Authority identified a number of rural development projects, which included fisheries development. This study is an integral part of fisheries development in Lesotho. The aim of this study was to gain an understanding of the biology and the demographics of the fish species in the lake. This information would serve as the basis for the development of a management plan for the sustainable utilisation of the fisheries resources. To achieve this aim, the following specific objectives were addressed: 1. Investigation of the biology of the three principal species. 2. Description of the key population parameters (growth, mortality & recruitment). 3. Investigation of the distribution and relative abundance of the three species. The three principal species in the Katse dam are rainbow trout, Oncorhynchus mykiss, and the two cyprinids, Barbus aeneus and Labeo capensis. Sectioned otoliths were used to age O. mykiss while both otoliths and scales were used to age B. aeneus and L. capensis. Marginal zone analysis revealed that slow growth was experienced in winter for the three species. The maximum-recorded age for both B. aeneus and L. capensis was 12 years while O. mykiss reached 4 years. There was no significant difference in growth rates of the different sexes and growth was best described by the 3 parameter Von-Bertalanfy growth model as Lt = 603[1-e⁻°·¹⁵⁽t ⁺ °·°³⁾] for B. aeneus, Lt = 526[1-e⁻°·²¹⁽t ⁺ °·⁹⁾] for O. mykiss and Lt = 521[1-e⁻°·¹⁷⁽t ⁺ °·²¹⁾] for L.capensis. Male and female O. mykiss attained 50% sexual maturity (Lm₅₀) at 235 and 275mm FL, respectively. There was no difference in Lm₅₀ for male and female B. aeneus and L. capensis. B. aeneus reached sexual maturity at 285mm FL while L. capensis reached sexual maturity at 244mm. Both cyprinid species spawned in summer (November to January) while O. mykiss spawned in winter (May to August). The mean total mortality rate (Z) estimated from catch curves and Butterworth et al (1989) equation was 0.72 yr⁻¹ for B. aeneus, 0.62 yr⁻¹ for L. capensis and 1.32 yr⁻¹ for O. mykiss. The estimate of natural mortality was 0.41 yr⁻¹ for both B. aeneus and L. capensis and 0.81yr⁻¹ for O. mykiss.

Water quality is an essential and critical aspect in meeting basic human and environmental needs. The scarcity of rainfall and water in South Africa prompted the need to augment water supply by transferring water from other catchment areas through inter-basin transfers, such as the transfer of water through the Vaal River system from the Lesotho Highlands. The Katse Dam is the main dam in the Lesotho highlands feeding water into the Vaal Dam, through the Ash River. Five rivers, namely the Malibamatso, Bokong, Pelaneng, Liphofung and Mokhoulane, feed into the Katse Dam. Surface water resources are susceptible to chemical, physical and microbiological contamination, either through human or natural activities. It became important that the raw water flowing from the five rivers into the Katse Dam be monitored to ensure that the dam water be preserved. The aim of the study was to investigate the surface water quality of the five rivers feeding the Katse Dam in Lesotho. The approach was to determine the activities occurring in the catchment area and whether these activities have any effects on surface water resources, and consequently, on the users of the water resources. Also, to examine the historic (2000 to 2011) and current (2012 to July 2014) water quality data to establish if the water quality has changed. To determine the surface water quality, samples were taken from the five rivers respectively. Samples were taken once a month for Study Period A (2000 to 2005), every second month for Study Period B (2006 to 2011) and four times a year for Study Period C (2012 to July 2014). Physical determinants such as temperature, dissolved oxygen, pH and turbidity were measured in situ. Selected chemical, physical and microbiological determinants were analysed at the Rand Water Analytical Services Laboratory. The water quality of the five rivers was relatively good, influenced mainly by both natural processes and human activities occurring within the Katse Dam catchment area. The water quality varied between rivers and over the study periods. The historic water quality data was not compliant with most water quality guidelines whilst current water quality data showed improved water quality. The Bokong River had the highest number of non-compliant determinants with water quality guidelines, especially for the World Health Organisation (WHO) and Department of Water Affairs & Sanitation (DWS) Aquaculture guidelines indicating that the water quality might have been compromised. The Pelaneng River had the least number of non-compliant determinants, thus indicating even better water quality when compared to other rivers. Natural processes such as rock weathering and geological composition of the catchment area influenced chemical determinants such as aluminium, copper, manganese and zinc, as well as physical determinants such as turbidity, total dissolved solids, water hardness, pH and suspended solids being non-compliant with most of the guidelines. Chemical determinants could have been influenced by the mining activities occurring in the catchment area. However, this requires further investigation. Agriculture and human settlements were to a large extent the most influential activities impacting the water quality. Chemical determinants such as ammonium, nitrates, nitrites and microbiological determinants such as Escherichia coli, coliphage bacteria, faecal coliform, Giardia and Cryptosporidium were linked to the application of manure and other agricultural inputs to crop fields, the lack of proper sanitation, and extensive livestock farming. The concentrations of these microbial determinants far exceeded the WHO, South African National Standard (SANS) drinking water and DWS guidelines. The surface water in this catchment area is used for domestic, livestock and farming purposes, therefore a compromise in the quality could have health and environmental effects on the communities living within the catchment area and the aquatic ecosystem at large. On the basis of these findings and conclusions, it is recommended that a long-term continuous monitoring programme be implemented, especially in areas where increased human activities have been observed. Monitoring should be strengthened for the Bokong and Liphofung Rivers since these rivers showed the highest number of non-compliances and microbial contamination. All anthropogenic activities in the catchment areas of these rivers must be monitored and strictly managed to prevent and mitigate their possible impacts. Specific emphasis should be placed on agricultural development, which should be controlled to ensure sustainable livestock and cropping practices. Sanitation facilities, systems and community programmes should be put in place to minimise faecal contamination. It would be beneficial for the Lesotho Highlands Development Authority (LHDA) to establish a central database for all information that will be accessible to both South African and Lesotho citizens.
Dissertation (MSc)--University of Pretoria, 2015.
Geography, Geoinformatics and Meteorology
MSc
Unrestricted

The main purpose of this study is to determine the difference in water quality of the rivers between the Katse and Vaal Dams (Wilge River and Vaal Dam reservoir sub-catchments) after the construction of the Lesotho Highlands Water Project. These rivers include the Ash, Liebenbergsvlei and Wilge Rivers. The temporal changes in water constituents, namely: electrical conductivity, chemical oxygen demand, pH, turbidity, ammonia, calcium, manganese and chlorophyll a, at selected water sampling points were analysed to clarify if Katse Dam water has had any impact on the water quality of the Ash, Liebenbergsvlei and Wilge Rivers and the Vaal Dam. The water quality was studied over an eleven-year period from November 1994 until December 2005. This includes a five-year period prior to, and a six-year period following the completion of the Katse Dam. The Ash, Liebenbergsvlei and Wilge Rivers fall within the Wilge sub-catchment, and the Vaal Dam falls within the Vaal Dam reservoir sub-catchment. Both the aforementioned sub-catchments form part of the Vaal River catchment. Physical, chemical and microbiological sampling results were obtained from Rand Water. The results were compared with the in-stream water quality guidelines as set by the Vaal Barrage Catchment Executive Committee. The results of the selected constituents were depicted visually in the form of graphs. Trends in the constituents over the period were then determined. The graphs were divided into two sections namely, pre-Katse Dam (before 1999) and post-Katse Dam (1999 to 2005). Differences in water quality before and after the construction of the Katse Dam were determined from sampling and chemical analysis at six locations, and hence evaluations were made whether the release of Katse Dam water has had a significant effect on the water quality results in the Vaal River System. The water quality results with respect to the different water constituents illustrated a distinct change in water quality over the period. Northwards, towards the Vaal Dam, the difference in water quality became less apparent. Sampling points throughout the study area experienced decreases in: electrical conductivity, chemical oxygen demand, turbidity, ammonia, and manganese. Hence, the release of Katse Dam water into the Vaal River system has had a ii positive influence on the water quality and thus changed the riverine environments in the Vaal River system. The high quality water from the Katse Dam that enters the Vaal River system thus initially increases the quality of the water in the recipient system with a lesser effect downstream. The result is an improvement of water quality in the upper reaches of the Vaal River system and no significant influence on the Vaal Dam itself. However, the change in water quality may have a detrimental effect on the river environment as a result of the increased volume of water entering the system and the resultant soil erosion, which serves for further studies. Consequently, the advantageous high quality water from the Lesotho Highlands is not being optimally utilised, hence the proposed recommendation by Rand Water to alternatively transfer Katse Dam water via a gravity-fed pipeline to the Vaal Dam thereby receiving the full benefit of high quality water, leaving river environments unaltered and possibly lowering purification costs.
Prof. J. T. Harmse Prof. H. J. Annegarn