Some aspects of the ecology of the Groot Letaba River in the Northern Province,South Africa

The aim of this pilot study was to evaluate the current ecological status of the Groot Letaba River and to compare this information with historical data. The objective was to determine the effects of various impacts on the fish populations of the river. This was done by analysing the water quality and by considering the effect of weirs and dams, as well as various illegal angling activities, on the fish community.

The Groot Letaba River is not highly polluted and the decline in its flow seems to be the greatest threat to the system. During a preliminary study to develop the river's resource potential, it was stated that the annual water allocation from Tzaneen Dam was 103.9 million m³/annum for irrigation, 8.4 million m³/annum for domestic and industrial use and 14.7 million m³/annum for environmental purposes. However, the yield from Tzaneen Dam was only 98 million m³/annum, suggesting that more water had been allocated than was available. As a result only 20% of the simulated natural flow is observed at Letaba Ranch Weir at the lower end of the river.

Over the past few years many weirs and dams, none of which have fishways, have been constructed in the Groot Letaba River, impacting on the flow regime and on the migration potential of many fish species. Tiger fish (Hydrocynus vittatus) and the largescale yellowfish (Barbus marequensis) are two of the more prominent species influenced negatively by these barriers. This problem is aggravated by the illegal netting of fish stranded below these barriers during their spawning migrations.     

The impact of land use on water quality of the Lwiro River,Democratic Republic of Congo,Central Africa

The water quality of the Lwiro River, Democratic Republic of Congo (DRC), Central Africa, was investigated on a monthly basis from December 1999–October 2000, at six stations along a hydraulic gradient from source to mouth, to evaluate the impact of land use on temperature, Dissolved Oxygen (DO), Biological Oxygen Demand (BOD₅), alkalinity and suspended solids. Upstream, where forests are conserved, minimal changes of physico-chemical parameters of water were observed. Downstream, DO was reduced, due to the increased organic matter content which increased the decomposition rate. BOD₅ and suspended solids increased downstream. Greater changes were found near agricultural areas and villages. Wetlands appear to mitigate BOD₅ and DO impacts.     

The macroinvertebrates of the Cunene River from the Ruacana Falls to the river mouth and assessment of the conservation status of the river

The proposed construction of a second hydroelectric power-generating dam on the Cunene (Kunene) River on the Namibia-Angola border, more than 100km downstream of the Ruacana hydroelectric power plant, will have a major influence on the aquatic biota of this river. In order to assess the potential impact of this impoundment a more detailed inventory of the biota in the river prior to this development was needed. Unfortunately the river presently does not represent an entirely undisturbed system as the operation of the Ruacana hydroelectric power station since 1970 has had a long-term effect on its biota. In the low-flow mid-summer season in particular, large areas of the river become irregularly inundated and exposed, sometimes on a daily basis, making them unsuitable for macroinvertebrate colonisation. There are six impoundments along the Cunene River upstream of the Ruacana Falls in Angola. These, however, do not have any major disruptive effects on daily flow variation in the Cunene River in Namibia although whole system biological consequences could be considerable but are unstudied. The Cunene River has a diverse freshwater fish fauna but, prior to the surveys reported here, the aquatic macroinvertebrates had been poorly studied. Surveys conducted by staff of the Department of Water Affairs (DWA) of Namibia and the Albany Museum, Grahamstown, in 1997 and 1998 have resulted in 216 aquatic macroinvertebrate species being recorded from Ruacana to the river mouth. The lower Cunene River, flowing through a very arid region, is biogeographically isolated and therefore highly vulnerable to change. The biota recorded reflects a fauna of widespread species and several elements of tropical origin. Several undescribed species may reflect some endemics but because of limited knowledge of the tropical rivers, this cannot be ascertained with certainty. From the aspect of conservation, the river contains a diversity of species with an abundance of filter-feeding species. Further surveys conducted during different seasons will undoubtedly record more taxa.     

Raptor conservation in the Northern Cape Province,South Africa

Anderson, M.D. 2000. Raptor conservation in the Northern Cape Province, South Africa. Ostrich 71 (1 & 2): 25–32.

The semi-arid Northern Cape is the largest and most sparsely populated province in South Africa. One of the main economic activities is sheep farming, and the properties are generally very large (>5 000 ha). A heterogeneous environment results in many habitats for a wide diversity of raptors. Fifty-one different species have been recorded, of which 37 are resident, 21 are common, and eight species are listed in the South African Red Data Book—Birds. As habitat degradation is limited, besides the areas immediately adjacent to the perennial rivers, raptors are still commonly encountered in many areas. Conflict with small-stock farming, however, results in some birds being inadvertently or directly persecuted each year. Two farmer questionnaire postal surveys (1976 and 1992) indicated a decrease in range and abundance of certain scavenging species, such as the Tawny Eagle. The more recent survey also indicated that most stock mortalities occurred in the mountainous areas, with the Black Eagle being the apparent culprit. In the Northern Cape there are both positive and negative anthropogenic effects on raptors. For example, 14 species have been recorded breeding on man-made structures, while 18 species have been documented to drown in farm reservoirs. Through the activities of the Raptor Conservation Group, the Northern Cape Nature Conservation Service and the Northern Cape Raptor Conservation Forum various threats are being addressed. Raptor conservation activities include: monitoring of raptor breeding populations, road censuses, farmer extension, establishment of raptor conservancies, rehabilitation of injured raptors, issuing of certificates to land-owners who have breeding raptors on their properties, presentation of the annual Gariep Raptor Conservationist Award, production and distribution of raptor pamphlets and booklets, modification of farm reservoirs to prevent raptor drownings, modification of powerlines to prevent electrocutions, and establishment of “vulture restaurants”. Through these efforts, the status of many raptor species is improving and species such as the Bateleur and Lappet-faced Vulture are becoming increasingly common.     

Potential environmental impacts associated with the proposed abstraction of water from the Okavango River in Namibia

The Namibian Department of Water Affairs has in the past faced considerable pressure to relieve the water shortages caused by recent droughts. One of the options considered in 1996, following poor runoff during the 1994/95 and 1995/96 seasons, was a proposal to abstract some 17Mm³ of water per year from the Okavango River at Rundu, and transfer this via a 260km long pipeline to the head of the Eastern National Water Carrier at the town of Grootfontein. Part of the overall evaluation of this scheme included an assessment of the potential environmental impacts that could arise. An initial environmental evaluation was conducted from a point approximately 40 kilometres upstream of Rundu in Namibia, to the distal end of the Okavango Delta at Maun in Botswana.

Hydrological studies showed that the proposed abstraction represented a reduction of approximately 0.32% in the mean annual flow of the Okavango River at Rundu. The abstraction represents 0.17% of the mean annual flow at Mukwe, downstream of the Cuito River confluence. The adverse effects of the proposed water abstraction scheme would be extremely small along the Okavango River in Namibia, whilst outflows from the lower end of the Okavango Delta to the Thamalakane River would be reduced by some 1.44Mm³/year (11%). Additional studies showed that these effects could be reduced by some 10–13% if abstraction was confined to the falling limb of the hydrograph.

Hydrological simulations have shown that the maximum likely loss of inundated area in the Okavango Delta would total approximately 7km² out of some 8 000km². This potential loss in inundated area would be concentrated in the lower reaches of the seasonal swamps and seasonally inundated grasslands, specifically in the lower reaches of the Boro, Gomoti, Santantadibe and Thaoge channels. However, these effects would most likely be expressed as a shoreline effect, with the loss in area spread out over the shoreline and periphery of islands and would not be restricted to a single specific area. This anticipated loss in inundated area is unlikely to have measurable impacts on environmental components.

Overall, the study found no 'fatal flaws' which would prevent the water abstraction scheme from proceeding and the anticipated effects on the Okavango system are more likely to be seen in the Okavango Delta, rather than along the Okavango River. The anticipated ecological implications of the scheme were small in spatial extent and are unlikely to be perceptible against the natural year-to-year variability in inundation of the Okavango Delta or outflows to the Thamalakane River. However, the public perceptions of the proposed water transfer project were strongly negative and appeared to be at least in part due to the very low water levels in the Okavango River and Okavango Delta during the past three years and during the study period. These low water levels were amongst the lowest on record and it is likely that the public would attribute any adverse effect recorded in the future to the abstraction scheme, whether this were true or not. These negative perceptions of the desirability and acceptability of the proposed scheme were strongly linked to potential adverse affects on the tourism industry along the Okavango River and in the Okavango Delta, with possible adverse economic effects on local residents.     

Community composition and distribution of macroinvertebrates in the Umzimvubu River,South Africa: a pre-impoundment study

This paper presents baseline biological data on aquatic macroinvertebrates and water quality in the Umzimvubu River and selected tributaries, Eastern Cape Province, South Africa, prior to the construction of proposed large-scale water resource developments. Sampling was conducted seasonally at 14 sites between 1996 and 1998. The macroinvertebrate community composition was strikingly similar (±70%) across sites. Faunal diversity was low (104 taxa in total), but many taxa found were sensitive to water quality change (ASPT 5.0 to 9.6), indicating good water quality, which is attributed to the currently undeveloped nature of the catchment. Concentrations of water quality variables fell within a narrow range, except for total suspended solids, which at times was very high (up to 8 532mg l^–1). The highly variable concentration of the total suspended solids and its potential effects on biodiversity need to be investigated further. It is likely that bilharzia will spread and that pest blackflies may become a problem to livestock if the water resources become developed as is proposed. We suggest that more flow gauging weirs are needed to measure flows better for future management and also that the implications of the proposed developments on the estuary need to be investigated.     

Heavy metals in the water and sediments of Oued Es-Souk,Algeria, a river receiving acid effluents from an abandoned mine

The Sidi Kamber Mine, abandoned since 1976, is still a source of acidic drainage entering the Oued Es-Souk River. An investigation of the rate of pollution of the Oued Es-Souk and the variation of its water quality showed that the mining waters are very acidic, with high concentrations of sulphate ions and dissolved heavy metals. Only lead reaches a significant level in the suspended matter. During mixing of the acid stream waters with uncontaminated river water, an amorphous orange precipitate forms and contributes to the removal of sulphate and certain heavy metals by adsorption and co-precipitation. Downstream, zinc and lead are concentrated in the sediments, while cadmium is mainly transported in the dissolved phase.     

An ethnobotanical survey of the Agter–Hantam, Northern Cape Province, South Africa

The use of a rapid appraisal methodology, followed by a new approach that we refer to as the Matrix Method, has revealed a wealth of traditional knowledge on useful plants amongst people of Khoi–San decent in the Agter–Hantam, Calvinia district, Northern Cape Province of South Africa. The data include 14 new species records of useful plants; 20 new vernacular names and 99 new uses for 46 of the plant species, showing that Khoi–San ethnobotany is still incompletely recorded and that there is an urgent need to document this wealth of traditional knowledge before it is lost forever. This article also introduces two new terms — the Ethnobotanical Knowledge Index (EKI), a quantitative measure of a person's knowledge of local plant use (value between 0 and 1), and the Species Popularity Index (SPI), a quantitative measure of the importance or popularity of each species (value between 0 and 1). In the Agter–Hantam, the EKI varied from 0.20 to 0.93 in older people but even young children had EKI values of 0.27. The best known and most popular indigenous useful plants in the Agter–Hantam are Aloe microstigma (a new species record, with a SPI of 0.97), Hoodia gordonii (SPI = 0.94), Microloma sagittatum (0.94), Sutherlandia frutescens (0.92), Quaqua incarnata (0.92) and Galenia africana (0.85). The new quantitative method will allow for direct comparisons of the preservation of traditional plant knowledge and the importance of various plants species in different communities.     

Occurrence and abundance of waterbirds at an ephemeral pan in the Northern Cape Province,South Africa

Bi-monthly counts of waterbirds were made between March and September 2003 at an ephemeral pan in the Northern Cape Province following the first substantial inundation since 1988. Bi-annual counts between 1991 and 2003 indicated that the pan infrequently supported waterbirds, with waterfowl and small waders generally being the dominant species. During the bimonthly counts, a total of 50 waterbird species was recorded, with the most dominant species, both in terms of numbers and duration of presence, being Black-winged Stilt Himantopus himantopus (max. 378), Cape Shoveller Anas smithii (max. 260) and South African Shelduck Tadorna cana (max. 200). Most other waterfowl and wader species were regular but in lower numbers. Species groups that occurred in limited numbers or for short periods include primarily herons, grebes, flamingos, ibises and storks. Species abundance and richness reached a peak one month after the pan was inundated, followed by a gradual decline over the ensuing two months.     

Black Jews in the Northern Province: a study of ethnic identity in South Africa

The article examines ways in which the Lemba people of the Northern Province of South Africa have used their oral history and traditional customs associated with distant Semitic origins in Yemen, to claim a modern Jewish identity in racially divided South Africa. While Lemba live in Mozambique and Zimbabwe as well as in South Africa, it is only in the latter that belief in a Jewish origin is found. The article seeks to show that early white missionaries and colonial officials propagated a Semitic identity for the Lemba and in their writings emphasized the differences between the Lemba and their African neighbours through comparisons of Lemba customs with Jewish communities in Europe. Such writings contributed to an ethos of a distinct identity, through which, via the establishment of the Lemba Cultural Association, middle-class Lemba intellectuals sought to promote the Lemba. This was achieved in a situation where the apartheid regime in South Africa pursued a divide and rule policy which allowed the Bantustans to discriminate against ethnic minorities under their control.     

A new species of Pearsonia (Fabaceae) from dolomites in Northern Province, South Africa

The Wolkberg Centre of endemism (northeastern Drakensberg escarpment) has a high proportion of species endemic to dolomite- and quartzite-derived soils. The Legalameetse Nature Reserve falls largely within the Chuniespoort Formation, which constitutes the dolomite component of the Wolkberg Centre. A number of species that occur within Legalameetse do not match existing material. Among the new taxa discovered is a species of Pearsonia Dümmer, which also occurs on the Wolkberg and in the Ribbokkop area. Pearsonia callistoma is most closely related to P. uniflora. In this paper, the new species is described and its geographical distribution, habitat, flowering time and conservation status are discussed. We also present a revised key for the genus Pearsonia.     

The nutrient status of the Kromme River estuary,South Africa

The Kromme is a small estuary in rural eastern Cape, South Africa with a relatively unpopulated and undisturbed catchment. Physical and chemical variables including the major nutrients and E. coli were examined. It was found to be a well oxygenated, well mixed estuary with some stratification in its upper reaches. Nutrient levels were generally low with nitrate values higher in winter than during summer. While no overt seasonality was detected for phosphorus, levels were comparatively high. Faecal E. coli levels were low with a mean count of 26 per 100 ml for the estuary. Along the Kromme, nutrients were highest at the confluence of the Geelhoutboom tributary suggesting it was a major nutrient contributor. At the head of the Kromme, silicate and E. coli were significantly linked to riverflow, while nitrate was correlated with rainfall. In the Geelhoutboom, only nitrate was correlated with riverflow and rainfall. When nutrient gradients (total inorganic nitrogen, total phosphorus and silicate) were correlated against salinity, significant relationships were observed for nitrogen and silicate (Kromme and Geelhoutboom) and for phosphorus along the Geelhoutboom, but not the Kromme, reflecting differences in sub-catchments. An overall N:P atomic ratio of 0.89:1 was found for the system, with more nitrogen relative to phosphorus at the head of the Kromme and vice versa for the Geelhoutboom and mouth. The Kromme is low in nitrogen, conservative in silicate and low in phosphorus while the Geelhoutboom supplies nitrogen, phosphorus and silicate to the system. Although there may be nutrient absorption by sediments in the upper estuary, and by macrophytes in the lower estuary, the Kromme may be classified as a non-conservative mesotrophic marine-dominated estuary which probably exhibits some nutrient recycling.     

Heavy metal concentrations in water and sediment of the Steelpoort River,Olifants River System,South Africa

Steelpoort River has been adversely affected by human activities in the catchment. Water and sediment quality of the river was assessed in 2015. The concentrations of some of the metals in water were found to be high and exceeded the guideline values and the concentrations of metals in sediment were found exceeding the guideline values for Cr, Cu and Zn. The high concentrations of Cu and Zn at Site 1 and Site 2 (upstream) could have originated from anthropogenic sources, such as fertilisers and pesticides from discharge of agricultural wastes, whereas the high concentrations of Cr at Site 3, Site 4 (midstream) and Site 5 (downstream) could have originated from the mine waste, and from domestic/ industrial wastes respectively. The principal component analysis results showed two main components: PC-1 with high positive loading of Cu and Mn, and PC-2 with high positive loading of Zn. These findings indicate the presence of pollution. Therefore, control measures should be implemented to reduce river contamination from anthropogenic sources.     

Salinity and dissolved substances in the Vaal River at Balkfontein,South Africa

Seasonal variation and interrelationships between environmental variables and salinity in the Vaal River at Balkfontein were investigated between 1985 and 1989. The salinity levels were high (min. 108, max. 1032, average 512 mg 1^-1), and indications are that salinisation of the river water is continuing at a rate of 15 mg 1^t-1 a^-1. The concentration of major ions (mg 1^-1 or meq 1^-1) in the river water occurred in the proportions of cations, i.e. Ca²⁺ Na⁺ > Mg²⁺ > K⁺ and of anions, i.e. SO₄^2- > HCO₃^- > Cl^-. The high S0₄ concentration (average 212 mg 1^-1) indicated SO₄ pollution at Balkfontein. High Ca concentrations (average 59 mg 1^-1) evidently interfered with the solubility of phosphate (PO₄) which could play an important role in the availability of PO₄ to phytoplankton in the system. Measured electrical conductivity (EC) values can be used to estimate salinity (S, in mg 1^-1) in the Vaal River, i.e. e. S = 7.13 * EC - 27.8 (from regression analysis) or S = 6.72 * EC (from TDS:EC ratio). Salinity in the river tends to be higher during the dry season, i.e. winter months. All the dissolved ions (except Si) showed decreased concentrations with increased run-off. The main importance of the high salinity in the Vaal River is evidently its influence on turbidity and the possible clarification of the water-column, which results in a deeper euphotic zone and thus more favourable conditions for photosynthesis followed by a biomass build-up of phytoplankton.     

Levels of organochlorine pesticides in raptors from the North-West Province,South Africa

Smith, I. & Bouwman, H. 2000. Levels of organochlorine pesticides in raptors from the North-West Province, South Africa. Ostrich 71 (1 & 2): 36–39.

The levels of organochlorine pesticides in raptors from southern Africa remain poorly known. We found generally low levels of DDE, dieldrin and endosulfan in the blood of 20 raptors from the North-West Province, South Africa. Despite the low levels, these pesticides were present in all the birds, raising the issue of combined effects. The continuing use of organochlorines, despite their ban in many developed countries, remains. Trends in contamination and use elsewhere should therefore be monitored on a more regular basis, while the sampling of blood, rather than eggs seems to provide adequate information. The effects of other pesticides should also be investigated.     

Risk factors of porcine cysticercosis in the Eastern Cape Province, South Africa

There is a high prevalence of Taenia solium taeniosis/cysticercosis in humans and pigs in the Eastern Cape Province (ECP) of South Africa. The objective of this study was to identify risk factors of porcine cysticercosis in select districts of the ECP. Data were collected in 2003 by interviewing 217 pig producers from the area. Blood samples were collected from 261 of their pigs, which were tested using two enzyme-linked immunosorbent assays (ELISA) for the presence of antibodies to cysticercosis. Frequencies of both owner- and pig-level characteristics were determined. For pig-level analysis, all bivariable and multivariable associations were determined using the surveylogistic procedure of the SAS/STAT? software to accommodate for the intraclass correlation that exists for clusters of pigs within one owner and for clusters of owners within a district. All tests for significance were performed at the α?=?0.05 level, and adjusted odds ratios (aOR) and 95% confidence intervals (CI) were determined. Among the respondents, 48% of their households lacked a latrine, 98% slaughtered pigs at home, and 99% indicated that meat inspection services were not available. On bivariable analysis, there was a significant association between porcine infection and district (p?=?0.003), breed (p?=?0.041) and the absence of a latrine (p?=?0.006). On multivariable analysis, the absence of a latrine was the only variable significantly associated with porcine infection (aOR?=?1.89; 95% CI?=?1.07, 3.35) (p?=?0.028). The increased odds of porcine infection with households lacking a latrine contributes to our understanding of the transmission of this parasite in the ECP. Determining and addressing the risk factors for T. solium infection can potentially lower the very high prevalence in humans and pigs in this endemic area.     

Concentrations of zinc in Barbus marequensis from the lower Olifants River, Mpumalanga, South Africa

Zinc was detected in all the tissues examined, but in variable concentrations. The highest zinc concentrations were detected in the skin and ovaries. These zinc concentrations also differed significantly from the concentrations in the other tissues. The bioaccumulation pattern of zinc in the fish was determined as: skin >ovaries>liver>gills>vertebrae>testes>hindgut>foregut contents >kidney=foregut>hindgut contents>muscle>blood>fat>bile.Although significant differences (P<0.05) between localities were detected no clear trend as to where the highest bioaccumulation had occurred, could be established. Significant seasonal differences were detected, but it was not always the same tissue that indicates these seasonal differences. The zinc concentrations detected in the fish suggest no serious zinc pollution in the lower Olifants River. Zinc levels detected in some of the tissues might indicate chronic exposure, causing possible sub-lethal effects. However, this should be investigated before final conclusions can be made.