The Effects of Water Transfer from Swakoppoort and Omatako Dams on the Water Quality of Von Bach Dam, Namibia

Sirunda, Johannes; Mazvimavi, Dominic

doi:10.1007/978-94-007-7097-3_5

Cited by 4 publications

(6 citation statements)

References 49 publications

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“…Sediments act as both carriers and potential sources of contaminants in marine ecosystems and can serve as a pool which holds or discharge contaminants to the river column by different remobilization processes [12][13][14]. There have been some studies recently on the sediment quality of water bodies in Namibia [5,[15][16][17] and the findings indicate that the rivers are contaminated with varying degrees of organic and inorganic compounds.…”

Section: Introductionmentioning

confidence: 99%

Assessment of heavy metals pollution in sediment at the Omaruru River basin in Erongo region, Namibia

Onjefu

Shaningwa

Lusilao

et al. 2020

Environmental Pollutants and Bioavailability

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This study determined the contamination levels of some heavy metals: Mn, Cr, Cu, Ni, Fe, As, and Al obtained from the delta basin of Omaruru River, using Inductively Coupled Plasma-Optical Emission Spectrophotometer (Optima 8000, Perkin Elmer). Chemical analysis showed that the sediments samples have metal concentrations ranging from 88 to 128mg/kg for Mn, 3973 to 4369mg/kg for Fe, 96 to 107mg/kg for Cr, 6 to 9mg/kg for Cu, 9 to 11mg/kg for Ni, 17 to 19mg/kg for As, and 11750 to 9002mg/kg for Al. The concentrations of Cr and As showed suggest that the sediment samples were heavily polluted according to United States Environmental Protection Agency's regulatory guidelines of the heavy metals. Additionally, the concentrations of Cr and As in the sediments exceeded the effect low range, effect medium range, threshold effect level, and the probable effect level proposed by the Canadian Council of Ministers of the Environment.

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Section: Introductionmentioning

confidence: 99%

Assessment of heavy metals pollution in sediment at the Omaruru River basin in Erongo region, Namibia

Onjefu

Shaningwa

Lusilao

et al. 2020

Environmental Pollutants and Bioavailability

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“…The Von Bach (21 44.97 E) are located in a dry subtropical desert region in central Namibia. These impoundments are warm monomictic man-made dams that, are stratified throughout the year and only experiences overturn or mixing during the winter season due to cold conditions (Figure 1) [35]. The dams are used to supply water to the city of Windhoek, Okahandja Town, Karibib Town, Otjimbingwe Village, and Navahacb Mine [39,40].…”

Section: Characteristics Of the Study Area And Field Sampling Sitesmentioning

confidence: 99%

“…The Swakoppoort and Von Bach dams are important water sources in central Namibia [35]. They are located in a subtropical desert climate characterized by large differences in day and night-time temperature, low rainfall, low humidity, and high evapotranspiration [36].…”

Section: Introductionmentioning

confidence: 99%

“…They are located in a subtropical desert climate characterized by large differences in day and night-time temperature, low rainfall, low humidity, and high evapotranspiration [36]. The two dams are within an ephemeral river, which only flows sporadically during the rainy season [35]. Since the Swakoppoort Dam water is transferred to Von Bach Dam before treatment [35,37], the mixing of this water could cause treatment challenges in the future if the vertical and temporal dynamics of cyanobacteria as a function of water column depths and season are not well understood.…”

Section: Introductionmentioning

confidence: 99%

“…The two dams are within an ephemeral river, which only flows sporadically during the rainy season [35]. Since the Swakoppoort Dam water is transferred to Von Bach Dam before treatment [35,37], the mixing of this water could cause treatment challenges in the future if the vertical and temporal dynamics of cyanobacteria as a function of water column depths and season are not well understood. Furthermore, the water in the two dams under study is abstracted selectively at different intake points [35], and the abstraction at these points is informed by water quality results of more than seven days on average from the time the water samples are collected to analyses in the laboratory.…”

Section: Introductionmentioning

confidence: 99%

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The Assessment of Phytoplankton Dynamics in Two Reservoirs in Southern Africa with Special Reference to Water Abstraction for Inter-Basin Transfers and Potable Water Production

Sirunda

Oberholster

Wolfaardt

et al. 2021

Water

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Toxic phytoplankton in the aquatic ecosystems are dynamic, affecting water quality. It remains unclear as to how possible toxic phytoplankton assemblages vary vertically and temporally in Swakoppoort and Von Bach dams, located in a dry subtropical desert region in central Namibia. The following variables were analyzed: pH, Secchi depths, turbidity, water temperature, total phosphorus, orthophosphate, chlorophyll-a, phytoplankton cells, and water depths. Cyanobacteria dominated the phytoplankton community in the autumn, winter and spring (dry) and summer (wet) seasons, at all the depth ranges in both dams. Microcystis dominated the vertical and temporal dynamics, followed by Dolichospermum. In the dry seasons, higher cyanobacteria cell numbers were observed in comparison to the rainy season in both dams. Spring blooms of cyanobacteria were evident in the Von Bach Dam while autumn and spring cyanobacteria blooms were observed in the Swakoppoort Dam. In the Swakoppoort Dam, the preferable depth ranges for toxic cyanobacteria species were at 5 to 10 m while in the Von Bach Dam at 0 to 5 m range. The findings of the current study indicate that the traditional selective withdrawal of water in the two dams should be performed with vertical and temporal dynamics of possible toxic cyanobacteria accounted for to aid the abstraction of water with the lowest possible toxic phytoplankton numbers, which could lower the public health risk.

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Comparison of phytoplankton control measures in reducing cyanobacteria assemblage of reservoirs found in the arid region of Southern Africa

Sirunda

Oberholster

Wolfaardt

et al. 2021

Water Environment Research

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Ecological restorations of reservoirs are implemented worldwide; however, minimal successes are reported and understood for warmer African lakes like Swakoppoort Dam, Namibia. The objectives of the study were (a) to establish the effectiveness of the two control measures in reducing cyanobacteria growths in comparison with untreated control areas and (b) to compare the results generated before and after control measures with the reference Von Bach Dam. During Phoslock ® treatment, the average cyanobacteria cells and total phosphate (TP) were 90,521 cells/ml and 0.3 mg/L in the treated area and 55,338 cells/ml and 0.1 mg/L in the control area. During Solar Powered Circulation (SPC) treatment, the average cyanobacteria cells were on average 906,420 cells/ml in the treated areas and 121,891 cells/ml in the control area. The TP on average was 0.3 mg/L during SPC treatment, while during the combined treatment, the average cyanobacteria cells, TP, and total nitrogen (TN) were 18,387,226 cells/ml, 0.27 mg/L, and 2.41 mg/L before and 22,836,511 cells/ml, 0.42 mg/L, and 1.50 mg/L after treatment. This was higher compared to the reference site. PCA triplot indicates no grouping pattern, and the repeated-measures mixed model analyses indicate that treatment had no significant effect on cyanobacteria cells. It was evident that the two control measures were ineffective in reducing cyanobacterial cells.Practitioner points:• Key findings of the article:• Two phytoplankton control measures were found ineffective to reduce the cyanobacterial cell numbers. • High cell numbers of cyanobacteria were recorded at the treatment areas compared to untreated control areas during both treatments.• The combined effect of the two control measures was ineffective as more cyanobacterial cells were recorded during the treatment.• During control measure treatment, the Swakoppoort Dam was hypertrophic, which could be due to a malfunctioned WWTP upstream.• The inefficiency of the control measures could be due to small treatment area, higher nutrients, or treatment period.

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The Effects of Water Transfer from Swakoppoort and Omatako Dams on the Water Quality of Von Bach Dam, Namibia

Cited by 4 publications

References 49 publications

Assessment of heavy metals pollution in sediment at the Omaruru River basin in Erongo region, Namibia

Assessment of heavy metals pollution in sediment at the Omaruru River basin in Erongo region, Namibia

The Assessment of Phytoplankton Dynamics in Two Reservoirs in Southern Africa with Special Reference to Water Abstraction for Inter-Basin Transfers and Potable Water Production

Comparison of phytoplankton control measures in reducing cyanobacteria assemblage of reservoirs found in the arid region of Southern Africa

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