Pub Date : 2023-07-31DOI: 10.17159/wsa/2023.v49.i3.3995
Monica M Correia, T. Kanyerere, N. Jovanovic, J. Goldin
Climate and land use change (CLUC) impact studies on water and groundwater resources have evolved in recent years. To determine whether all research gaps have been or are being addressed through the current intellectual structure, a bibliometric analysis, as well as a record review, was enacted to determine the intellectual structure of CLUC impacts on water resources, with a particular focus on the implications for groundwater resources research in the Breede Gouritz Water Management Area (BGWMA) in South Africa. Methods applied included publication-related trends and science mapping. This study found that CLUC impact research being published has increased by 600% between 2014 and 2021, localised research is being done in 95 countries, and land use change (LUC), specifically urbanisation, is being considered more often as a variable. However, a few gaps in the research remain, including smaller spatiotemporal scales in more locations, a stronger focus on LUC in all its forms, LUC versus climate change (CC) impact studies, and multi-modal approaches to related research. CLUC impacts on water and groundwater resources research have made significant progress over the years, but more research is necessary to make this a robust area of research.
{"title":"Investigating the knowledge gap in research on climate and land use change impacts on water resources, with a focus on groundwater resources in South Africa: a bibliometric analysis","authors":"Monica M Correia, T. Kanyerere, N. Jovanovic, J. Goldin","doi":"10.17159/wsa/2023.v49.i3.3995","DOIUrl":"https://doi.org/10.17159/wsa/2023.v49.i3.3995","url":null,"abstract":"Climate and land use change (CLUC) impact studies on water and groundwater resources have evolved in recent years. To determine whether all research gaps have been or are being addressed through the current intellectual structure, a bibliometric analysis, as well as a record review, was enacted to determine the intellectual structure of CLUC impacts on water resources, with a particular focus on the implications for groundwater resources research in the Breede Gouritz Water Management Area (BGWMA) in South Africa. Methods applied included publication-related trends and science mapping. This study found that CLUC impact research being published has increased by 600% between 2014 and 2021, localised research is being done in 95 countries, and land use change (LUC), specifically urbanisation, is being considered more often as a variable. However, a few gaps in the research remain, including smaller spatiotemporal scales in more locations, a stronger focus on LUC in all its forms, LUC versus climate change (CC) impact studies, and multi-modal approaches to related research. CLUC impacts on water and groundwater resources research have made significant progress over the years, but more research is necessary to make this a robust area of research.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"15 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78257753","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-31DOI: 10.17159/wsa/2023.v49.i3.3907
J. Okedi, Malesela Michael Mogano
In the period 2015–2017, the City of Cape Town, South Africa, faced the possibility of taps running dry due to a prolonged drought. To mitigate the impacts of water scarcity, many households installed rainwater tanks to harvest water to use for non-potable purposes such as toilet flushing and washing. The installation of the rainwater tanks was mainly arbitrary, in response to perceived impact of water scarcity rather than a systematic needs assessment. This study was thus undertaken to determine the available opportunity to optimise the use of these rainwater tanks using real-time control (RTC) techniques. Many studies have demonstrated the potential of rainwater harvesting (RWH) systems to supplement potable water supply and minimize stormwater flows to downstream drainage networks. RTC technology can be used to enhance the performance of RWH systems in achieving these two objectives, by receiving a rainfall forecast and initiating pre-storm release in real time. In this study, RTC was applied on the RWH system at the New Engineering Building, University of Cape Town (UCT) to enhance water supply and increase rainwater retention period. The performance with RTC was compared with the conventional management of the RWH system. It was determined that RWH with RTC technology was generally superior in simultaneously achieving water supply and rainwater retention benefits compared to the conventional management approach. RTC provides an active operation which optimizes the performance of the system across varying conditions but requires an assiduous management process designed to meet set objectives. It was concluded that the active release mechanism employing RTC exhibited great potential; the system opens up the possibility of delivering a more robust and reliable system due to its ability to provide failure detection and centralised control. The system can readily be adapted to variation of local climatic conditions in the short and long term.
{"title":"Assessing the benefits of real-time control to enhance rainwater harvesting at a building in Cape Town, South Africa","authors":"J. Okedi, Malesela Michael Mogano","doi":"10.17159/wsa/2023.v49.i3.3907","DOIUrl":"https://doi.org/10.17159/wsa/2023.v49.i3.3907","url":null,"abstract":"In the period 2015–2017, the City of Cape Town, South Africa, faced the possibility of taps running dry due to a prolonged drought. To mitigate the impacts of water scarcity, many households installed rainwater tanks to harvest water to use for non-potable purposes such as toilet flushing and washing. The installation of the rainwater tanks was mainly arbitrary, in response to perceived impact of water scarcity rather than a systematic needs assessment. This study was thus undertaken to determine the available opportunity to optimise the use of these rainwater tanks using real-time control (RTC) techniques. Many studies have demonstrated the potential of rainwater harvesting (RWH) systems to supplement potable water supply and minimize stormwater flows to downstream drainage networks. RTC technology can be used to enhance the performance of RWH systems in achieving these two objectives, by receiving a rainfall forecast and initiating pre-storm release in real time. In this study, RTC was applied on the RWH system at the New Engineering Building, University of Cape Town (UCT) to enhance water supply and increase rainwater retention period. The performance with RTC was compared with the conventional management of the RWH system. It was determined that RWH with RTC technology was generally superior in simultaneously achieving water supply and rainwater retention benefits compared to the conventional management approach. RTC provides an active operation which optimizes the performance of the system across varying conditions but requires an assiduous management process designed to meet set objectives. It was concluded that the active release mechanism employing RTC exhibited great potential; the system opens up the possibility of delivering a more robust and reliable system due to its ability to provide failure detection and centralised control. The system can readily be adapted to variation of local climatic conditions in the short and long term.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"43 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74094861","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-31DOI: 10.17159/wsa/2023.v49.i3.3980
R. Schroeder, I. Loots, M. Dijk, GL Coetzee
South Africa is in a critical power situation and is in dire need of additional generation capacity. Thus, renewable energy sources such as wind, solar and hydropower should be evaluated to identify high-potential and cost-effective sites. Rivers in South Africa, as a water-scarce country, are already heavily impounded, meaning that there are limited sites available for conventional hydropower generation. Instead, novel solutions such as retrofitting hydropower installations to existing infrastructure, like existing dams, are required. To estimate the retrofit hydropower potential at dams, a set of five tools was developed using Python 3, known as the University of Pretoria Retrofit Hydropower Evaluation Software (UP-RHES). The UP-RHES screens potential sites where historic flow records are available, then downloads the required flow records from the national database and performs a first-order hydraulic assessment of the site, as well as a first-order life cycle cost analysis. By applying the UP-RHES to 118 dams operated by the Department of Water and Sanitation (DWS), it was found that a total estimated hydropower potential of 128 MW with an annual energy output of between 385 and 469 GWh exists at South African dams. The Vaal, Pongolapoort, Goedertrouw and Blyderivierpoort Dams were found to be feasible sites with a combined capacity of 77 GWh/annum.
{"title":"Development of a procedure and tool for retrofit hydropower evaluation at South African dams","authors":"R. Schroeder, I. Loots, M. Dijk, GL Coetzee","doi":"10.17159/wsa/2023.v49.i3.3980","DOIUrl":"https://doi.org/10.17159/wsa/2023.v49.i3.3980","url":null,"abstract":"South Africa is in a critical power situation and is in dire need of additional generation capacity. Thus, renewable energy sources such as wind, solar and hydropower should be evaluated to identify high-potential and cost-effective sites. Rivers in South Africa, as a water-scarce country, are already heavily impounded, meaning that there are limited sites available for conventional hydropower generation. Instead, novel solutions such as retrofitting hydropower installations to existing infrastructure, like existing dams, are required. To estimate the retrofit hydropower potential at dams, a set of five tools was developed using Python 3, known as the University of Pretoria Retrofit Hydropower Evaluation Software (UP-RHES). The UP-RHES screens potential sites where historic flow records are available, then downloads the required flow records from the national database and performs a first-order hydraulic assessment of the site, as well as a first-order life cycle cost analysis. By applying the UP-RHES to 118 dams operated by the Department of Water and Sanitation (DWS), it was found that a total estimated hydropower potential of 128 MW with an annual energy output of between 385 and 469 GWh exists at South African dams. The Vaal, Pongolapoort, Goedertrouw and Blyderivierpoort Dams were found to be feasible sites with a combined capacity of 77 GWh/annum.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"18 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74596604","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-28DOI: 10.17159/wsa/2023.v49.i2.3965
KA Seetseng, JH Barnard, LD van Rensburg, CC du Preez
In South Africa canola (Brassica napus L.) is cultivated in rotation with wheat under winter rainfall in the Western Cape Province, primarily for seed to make oil. Expansion of the crop to the other 8 provinces is proposed to reduce shortages of locally produced plant oils. At the same time, canola can serve as a rotational crop for wheat in these summer rainfall provinces. In central Free State, information on evapotranspiration and various water use indicators for canola as influenced by sustained deficit irrigation and plant density is lacking. An experiment with a line source sprinkler irrigation system was therefore conducted, comprising of full irrigation as a control with 4 sustained deficit irrigation levels (mean reduction in irrigation depth per event of 67%, 52%, 34% and 19%) and 5 plant densities (25, 50, 75, 100 and 125 plants‧m−2). Mean seasonal maximum evapotranspiration amounted to 429 mm across plant densities. Plant density did not significantly influence seasonal evapotranspiration. Reducing the irrigation depth per event by more than 20% decreased seasonal evapotranspiration by a mean 3.5 mm per percentage increase in irrigation depth. A maximum biomass water productivity of 22 kg‧ha−1‧mm−1 was measured with full irrigation and a plant density of 75 plants‧m−2. Seed water productivity amounted to a high of 11 kg‧ha−1‧mm−1 with full irrigation and a plant density of 25 plants‧m−2. A percentage reduction in irrigation depth and increase in plant density above 25 plants‧m−2 will reduce seed water productivity by 0.071 and 0.033 kg‧ha−1‧mm−1, respectively. Sustained deficit irrigation increased water use efficiency by a mean 0.5% per percentage reduction in irrigation depth per event.
{"title":"Canola (Brassica napus L.) water use indicators as affected by sustained deficit irrigation and plant density in central Free State, South Africa","authors":"KA Seetseng, JH Barnard, LD van Rensburg, CC du Preez","doi":"10.17159/wsa/2023.v49.i2.3965","DOIUrl":"https://doi.org/10.17159/wsa/2023.v49.i2.3965","url":null,"abstract":"In South Africa canola (Brassica napus L.) is cultivated in rotation with wheat under winter rainfall in the Western Cape Province, primarily for seed to make oil. Expansion of the crop to the other 8 provinces is proposed to reduce shortages of locally produced plant oils. At the same time, canola can serve as a rotational crop for wheat in these summer rainfall provinces. In central Free State, information on evapotranspiration and various water use indicators for canola as influenced by sustained deficit irrigation and plant density is lacking. An experiment with a line source sprinkler irrigation system was therefore conducted, comprising of full irrigation as a control with 4 sustained deficit irrigation levels (mean reduction in irrigation depth per event of 67%, 52%, 34% and 19%) and 5 plant densities (25, 50, 75, 100 and 125 plants‧m−2). Mean seasonal maximum evapotranspiration amounted to 429 mm across plant densities. Plant density did not significantly influence seasonal evapotranspiration. Reducing the irrigation depth per event by more than 20% decreased seasonal evapotranspiration by a mean 3.5 mm per percentage increase in irrigation depth. A maximum biomass water productivity of 22 kg‧ha−1‧mm−1 was measured with full irrigation and a plant density of 75 plants‧m−2. Seed water productivity amounted to a high of 11 kg‧ha−1‧mm−1 with full irrigation and a plant density of 25 plants‧m−2. A percentage reduction in irrigation depth and increase in plant density above 25 plants‧m−2 will reduce seed water productivity by 0.071 and 0.033 kg‧ha−1‧mm−1, respectively. Sustained deficit irrigation increased water use efficiency by a mean 0.5% per percentage reduction in irrigation depth per event.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"30 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79092833","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-28DOI: 10.17159/wsa/2023.v49.i2.3992
RM Petersen, JM Nel, T Strydom, E Riddell, C Coetsee, E February
The role of groundwater, in general, is often overlooked in freshwater ecosystem management policies and in the management of South Africa’s flagship conservation area, the Kruger National Park (KNP). To address this gap, a generalised conceptual model of surface water–ground water (sw–gw) interactions in the southern and central regions of the KNP was developed. To do this, stable isotope ratios (d18O and d2H) of groundwater, rainfall and surface water were used to determine the extent to which the base flow of perennial, seasonal and ephemeral streams on different geologies (granite vs. basalt) is driven by rainfall or groundwater. These results show that the δ18O and δ2H ratios of perennial rivers are similar to that of groundwater, while seasonal and ephemeral rivers on basalts have values closer to rainfall. On granite substrates, however, the isotope ratios of the seasonal and ephemeral rivers have values closer to groundwater than rainfall. The larger seasonal Mbyamiti River had similar isotope ratios to that of groundwater, and the highly ephemeral Nwaswitsontso had episodic interaction with groundwater (i.e. isotopic ratios overlap occasionally). These results show that decisions necessary for the sustainable management of groundwater resources are better informed when the natural interaction, movement, and exchange between groundwater and rivers are understood. This has particular relevance for large conservation areas in southern Africa that are expected to experience more variable climates in the future with both increases in drought and rainfall intensities.
{"title":"The use of stable isotopes to identify surface water–groundwater interaction in the Kruger National Park, South Africa","authors":"RM Petersen, JM Nel, T Strydom, E Riddell, C Coetsee, E February","doi":"10.17159/wsa/2023.v49.i2.3992","DOIUrl":"https://doi.org/10.17159/wsa/2023.v49.i2.3992","url":null,"abstract":"The role of groundwater, in general, is often overlooked in freshwater ecosystem management policies and in the management of South Africa’s flagship conservation area, the Kruger National Park (KNP). To address this gap, a generalised conceptual model of surface water–ground water (sw–gw) interactions in the southern and central regions of the KNP was developed. To do this, stable isotope ratios (d18O and d2H) of groundwater, rainfall and surface water were used to determine the extent to which the base flow of perennial, seasonal and ephemeral streams on different geologies (granite vs. basalt) is driven by rainfall or groundwater. These results show that the δ18O and δ2H ratios of perennial rivers are similar to that of groundwater, while seasonal and ephemeral rivers on basalts have values closer to rainfall. On granite substrates, however, the isotope ratios of the seasonal and ephemeral rivers have values closer to groundwater than rainfall. The larger seasonal Mbyamiti River had similar isotope ratios to that of groundwater, and the highly ephemeral Nwaswitsontso had episodic interaction with groundwater (i.e. isotopic ratios overlap occasionally). These results show that decisions necessary for the sustainable management of groundwater resources are better informed when the natural interaction, movement, and exchange between groundwater and rivers are understood. This has particular relevance for large conservation areas in southern Africa that are expected to experience more variable climates in the future with both increases in drought and rainfall intensities.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"9 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81302207","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-28DOI: 10.17159/wsa/2023.v49.i2.4026
SN Theron, E Archer, CJ Engelbrecht, S Midgley, S Walker
Drought is one of the most hazardous natural disasters in terms of the number of people directly affected. An important characteristic of drought is the prolonged absence of rainfall relative to the long-term average. The intrinsic persistence of drought conditions continuing from one month to the next can be utilized for drought monitoring and early warning systems. This study sought to better understand drought probabilities and baselines for two agriculturally important rainfall regions in the Western Cape, South Africa – one with a distinct rainfall season and one which receives year-round rainfall. The drought indices, Standardised Precipitation and Evapotranspiration Index (SPEI) and Standardised Precipitation Index (SPI), were assessed to obtain predictive information and establish a set of baseline probabilities for drought. Two sets of synthetic time-series data were used (one where seasonality was retained and one where seasonality was removed), along with observed data of monthly rainfall and minimum and maximum temperature. Based on the inherent persistence characteristics, autocorrelation was used to obtain a probability density function of the future state of the various SPI start and lead times. Optimal persistence was also established. The validity of the methodology was then examined by application to the recent Cape Town drought (2015–2018). Results showed potential for this methodology to be applied in drought early warning systems and decision support tools for the province.
{"title":"Using SPI and SPEI for baseline probabilities and seasonal drought prediction in two agricultural regions of the Western Cape, South Africa","authors":"SN Theron, E Archer, CJ Engelbrecht, S Midgley, S Walker","doi":"10.17159/wsa/2023.v49.i2.4026","DOIUrl":"https://doi.org/10.17159/wsa/2023.v49.i2.4026","url":null,"abstract":"Drought is one of the most hazardous natural disasters in terms of the number of people directly affected. An important characteristic of drought is the prolonged absence of rainfall relative to the long-term average. The intrinsic persistence of drought conditions continuing from one month to the next can be utilized for drought monitoring and early warning systems. This study sought to better understand drought probabilities and baselines for two agriculturally important rainfall regions in the Western Cape, South Africa – one with a distinct rainfall season and one which receives year-round rainfall. The drought indices, Standardised Precipitation and Evapotranspiration Index (SPEI) and Standardised Precipitation Index (SPI), were assessed to obtain predictive information and establish a set of baseline probabilities for drought. Two sets of synthetic time-series data were used (one where seasonality was retained and one where seasonality was removed), along with observed data of monthly rainfall and minimum and maximum temperature. Based on the inherent persistence characteristics, autocorrelation was used to obtain a probability density function of the future state of the various SPI start and lead times. Optimal persistence was also established. The validity of the methodology was then examined by application to the recent Cape Town drought (2015–2018). Results showed potential for this methodology to be applied in drought early warning systems and decision support tools for the province.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"39 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88352155","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-28DOI: 10.17159/wsa/2023.v49.i2.3957
Brenda Mehlo, Alison Lewis, Jemitias Chivavava
South Africa produces significant quantities of brines but there is insufficient information on their biological and physicochemical characteristics and nature, which limits the ability to propose sustainable brine handling procedures. This study aimed to comprehensively characterize selected brines from major brine-producing industries in South Africa. This was achieved through an analysis of the majority of the brine constituents, thereby allowing for the proposal of suitable brine handling procedures, the identification and harnessing of potential economic value, as well as the identification of the environmental impact of the brines. The brines were analysed for physical, metallic, organic, and inorganic constituents using a variety of methods including inductively coupled plasma-mass spectrometry (ICP-MS) and gas chromatography-mass spectrometry (GC-MS). The total dissolved solids (TDS) of most of the brines was below 35 000 mg/L and it was concluded that most South African brines may be brackish. All the brines contained toxic constituents in concentrations that exceeded set discharge and re-use limits. It was concluded that comprehensive characterization is crucial in understanding the quality of brines and is a crucial step in proposing suitable brine handling strategies.
{"title":"Comprehensive characterization of selected South African brines","authors":"Brenda Mehlo, Alison Lewis, Jemitias Chivavava","doi":"10.17159/wsa/2023.v49.i2.3957","DOIUrl":"https://doi.org/10.17159/wsa/2023.v49.i2.3957","url":null,"abstract":"South Africa produces significant quantities of brines but there is insufficient information on their biological and physicochemical characteristics and nature, which limits the ability to propose sustainable brine handling procedures. This study aimed to comprehensively characterize selected brines from major brine-producing industries in South Africa. This was achieved through an analysis of the majority of the brine constituents, thereby allowing for the proposal of suitable brine handling procedures, the identification and harnessing of potential economic value, as well as the identification of the environmental impact of the brines. The brines were analysed for physical, metallic, organic, and inorganic constituents using a variety of methods including inductively coupled plasma-mass spectrometry (ICP-MS) and gas chromatography-mass spectrometry (GC-MS). The total dissolved solids (TDS) of most of the brines was below 35 000 mg/L and it was concluded that most South African brines may be brackish. All the brines contained toxic constituents in concentrations that exceeded set discharge and re-use limits. It was concluded that comprehensive characterization is crucial in understanding the quality of brines and is a crucial step in proposing suitable brine handling strategies.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"3 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87935191","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-28DOI: 10.17159/wsa/2023.v49.i2.3919
KG Seanego, GC Pitcher, TA Probyn, A Du Randt, LM Mansfield
Vanderkloof Dam was periodically sampled between November 2014 and April 2016 for a range of water quality parameters to assess the potential for cage culture of rainbow trout, Oncorhyncus mykiss. The dam is strongly stratified in summer and autumn, although upper water column temperatures remain relatively cool, largely <25°C. The dam is considered oligotrophic, characterised by phosphorus limitation of primary production, particularly during summer. Light is strongly attenuated in the epilimnion and heterotrophic community metabolism is observed through much of the water column. Surface nutrients are depleted through the summer with phytoplankton assemblages dominated by the green algae, Oocystis lacustris, Desmodesmus bicaudatus and Coelastrum microporum. The water column turns over during the winter and the nearly isothermal impoundment approaches 11°C. Nutrients are re-introduced into surface waters following winter mixing coincident with an increase in diatoms. The preferred environmental window for rainbow trout becomes severely contracted during the summer in that epilimnion temperatures exceed 21°C and thermocline/hypolimnion oxygen concentrations fall below 3 mg‧L−1. The coincidence of relatively high pH >9.5 could exacerbate these physiological challenges. Hydrological conditions for fish farming are most suitable in the proximity of the dam wall as opposed to further upstream. Here the hypoxic conditions that develop in the thermocline/hypolimnion during summer and autumn are less pronounced, particularly towards the southern bank, where concentrations of total suspended solids are generally <10 mg‧L−1 and water clarity is more favourable for visual feeders such as fish. Although rainbow trout may survive the adverse conditions prevalent during the summer, growth is likely to be compromised and susceptibility to disease may increase.
{"title":"Water quality characteristics of Vanderkloof Dam and its potential for rainbow trout farming","authors":"KG Seanego, GC Pitcher, TA Probyn, A Du Randt, LM Mansfield","doi":"10.17159/wsa/2023.v49.i2.3919","DOIUrl":"https://doi.org/10.17159/wsa/2023.v49.i2.3919","url":null,"abstract":"Vanderkloof Dam was periodically sampled between November 2014 and April 2016 for a range of water quality parameters to assess the potential for cage culture of rainbow trout, Oncorhyncus mykiss. The dam is strongly stratified in summer and autumn, although upper water column temperatures remain relatively cool, largely <25°C. The dam is considered oligotrophic, characterised by phosphorus limitation of primary production, particularly during summer. Light is strongly attenuated in the epilimnion and heterotrophic community metabolism is observed through much of the water column. Surface nutrients are depleted through the summer with phytoplankton assemblages dominated by the green algae, Oocystis lacustris, Desmodesmus bicaudatus and Coelastrum microporum. The water column turns over during the winter and the nearly isothermal impoundment approaches 11°C. Nutrients are re-introduced into surface waters following winter mixing coincident with an increase in diatoms. The preferred environmental window for rainbow trout becomes severely contracted during the summer in that epilimnion temperatures exceed 21°C and thermocline/hypolimnion oxygen concentrations fall below 3 mg‧L−1. The coincidence of relatively high pH >9.5 could exacerbate these physiological challenges. Hydrological conditions for fish farming are most suitable in the proximity of the dam wall as opposed to further upstream. Here the hypoxic conditions that develop in the thermocline/hypolimnion during summer and autumn are less pronounced, particularly towards the southern bank, where concentrations of total suspended solids are generally <10 mg‧L−1 and water clarity is more favourable for visual feeders such as fish. Although rainbow trout may survive the adverse conditions prevalent during the summer, growth is likely to be compromised and susceptibility to disease may increase.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"41 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90494076","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this study, an experiment was conducted to investigate the optimum lateral spacing and irrigation frequency for subsurface drip irrigated okra in the semi-arid region of Haryana (India). Two lateral spacings (45 cm and 60 cm) and four irrigation frequencies (daily, after 1, 2 and 3 days) were selected to grow okra in the Kharif season of 2019 and 2020. The effect on soil water dynamics, growth parameters, efficiency and yield were assessed using equal amounts of water under all the treatments on the basis of pan evaporation. The results from the study depict that the overall soil moisture decreased laterally, but increased vertically downward with the increase in the irrigation interval. On the basis of soil water dynamics, plant growth parameters, efficiency and yield of okra, it was concluded that subsurface drip irrigation with daily irrigation at 45 cm lateral spacing gives better performance than all other treatments in sandy loam soil. The present study highlights the significance of proper irrigation frequency and lateral spacing for maximum production of okra. Using these guidelines, the income of okra growers/farmers in the semi-arid region may be increased by choosing the best frequency and lateral spacing of subsurface drip irrigation.
{"title":"Production of subsurface drip-irrigated okra under different lateral spacings and irrigation frequencies","authors":"Narender Kumar, Sanjay Kumar, Darshana Duhan, Amandeep Singh, MS Sidhpuria, Sundeep Kumar Antil, Ashish Kumar, Vikas","doi":"10.17159/wsa/2023.v49.i2.3990","DOIUrl":"https://doi.org/10.17159/wsa/2023.v49.i2.3990","url":null,"abstract":"In this study, an experiment was conducted to investigate the optimum lateral spacing and irrigation frequency for subsurface drip irrigated okra in the semi-arid region of Haryana (India). Two lateral spacings (45 cm and 60 cm) and four irrigation frequencies (daily, after 1, 2 and 3 days) were selected to grow okra in the Kharif season of 2019 and 2020. The effect on soil water dynamics, growth parameters, efficiency and yield were assessed using equal amounts of water under all the treatments on the basis of pan evaporation. The results from the study depict that the overall soil moisture decreased laterally, but increased vertically downward with the increase in the irrigation interval. On the basis of soil water dynamics, plant growth parameters, efficiency and yield of okra, it was concluded that subsurface drip irrigation with daily irrigation at 45 cm lateral spacing gives better performance than all other treatments in sandy loam soil. The present study highlights the significance of proper irrigation frequency and lateral spacing for maximum production of okra. Using these guidelines, the income of okra growers/farmers in the semi-arid region may be increased by choosing the best frequency and lateral spacing of subsurface drip irrigation.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"31 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74826220","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-24DOI: 10.17159/wsa/2023.v49.i2.3942
Murat Kilic
The wetting pattern which occurs under surface drip irrigation is an important component for the optimum design of the system and for irrigation programming. The aim of this investigation was to devise a model which enables estimation of the 2D cross-sectional area of the wetting pattern which occurs under a surface dripper by an analytical method. The main parameters of the wetting pattern are the wetting diameter on the soil surface, the maximum wetted depth and maximum wetted width in the soil profile, and the depth of this maximum wetted width from the soil surface. In the laboratory experiments, water applications were carried out on two soil textures (clay loam and clay) with homogeneous soil profiles at two discharge rates over 125 min and 170 min periods. The sizes of the parameters of the wetting pattern were measured as consecutive series over 5-min intervals during the water application period. The general/main shape which represents the wetting patterns which occur under different irrigation conditions was defined and mathematically modelled. When the results were evaluated statistically, a correlation of 0.9128 was found between the momentary rates of change of the maximum depth of the wetting pattern predicted by the model and those measured in the experiment. The correlation between the momentary variations of accelerations of the same parameter was 0.9205. In addition, the size of the wetting pattern showed an increment in reducing velocities during the water application period. The results indicate that the model devised in this investigation can be used in the prediction of the cross-sectional area of the wetting pattern which occurs under a surface dripper.
{"title":"Estimation of the 2D cross-sectional area of the wetting pattern under drip irrigation and spatio-temporal variation of the components of the wetting pattern","authors":"Murat Kilic","doi":"10.17159/wsa/2023.v49.i2.3942","DOIUrl":"https://doi.org/10.17159/wsa/2023.v49.i2.3942","url":null,"abstract":"The wetting pattern which occurs under surface drip irrigation is an important component for the optimum design of the system and for irrigation programming. The aim of this investigation was to devise a model which enables estimation of the 2D cross-sectional area of the wetting pattern which occurs under a surface dripper by an analytical method. The main parameters of the wetting pattern are the wetting diameter on the soil surface, the maximum wetted depth and maximum wetted width in the soil profile, and the depth of this maximum wetted width from the soil surface. In the laboratory experiments, water applications were carried out on two soil textures (clay loam and clay) with homogeneous soil profiles at two discharge rates over 125 min and 170 min periods. The sizes of the parameters of the wetting pattern were measured as consecutive series over 5-min intervals during the water application period. The general/main shape which represents the wetting patterns which occur under different irrigation conditions was defined and mathematically modelled. When the results were evaluated statistically, a correlation of 0.9128 was found between the momentary rates of change of the maximum depth of the wetting pattern predicted by the model and those measured in the experiment. The correlation between the momentary variations of accelerations of the same parameter was 0.9205. In addition, the size of the wetting pattern showed an increment in reducing velocities during the water application period. The results indicate that the model devised in this investigation can be used in the prediction of the cross-sectional area of the wetting pattern which occurs under a surface dripper.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"13 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91031133","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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