scholarly journals Influence of basin connectivity on sediment source, transport, and storage within the Mkabela Basin, South Africa

2012 ◽  
Vol 9 (9) ◽  
pp. 10151-10204 ◽  
Author(s):  
J. R. Miller ◽  
G. Mackin ◽  
P. Lechler ◽  
M. Lord ◽  
S. Lorentz
Keyword(s):  
South Africa ◽  
Best Management Practices ◽  
Management Practices ◽  
Drainage System ◽  
Sediment Source ◽  
Riparian Wetlands ◽  
Valley Bottom ◽  
Sediment Size ◽  
Catchment Areas ◽  
And Storage

Abstract. The management of sediment and other non-point source (NPS) pollution has proven difficult, and requires a sound understanding of particle movement through the drainage system. The primary objective of this investigation was to obtain an understanding of NPS sediment source(s), transport, and storage within the Mkabela basin, a representative agricultural catchment within the KwaZulu-Natal Midlands of southeastern South Africa, by combining geomorphic, hydrologic and geochemical fingerprinting analyses. The Mkabela Basin can be subdivided into three distinct subcatchments that differ in their ability to transport and store sediment along the axial valley. Headwater (upper catchment) areas are characterized by extensive wetlands that act as significant sediment sinks. Mid-catchment areas, characterized by higher relief and valley gradients, exhibit few wetlands, but rather are dominated by a combination of alluvial and bedrock channels that are conducive to sediment transport. The lower catchment exhibits a low-gradient alluvial channel that is boarded by extensive riparian wetlands that accumulate large quantities of sediment (and NPS pollutants). Fingerprinting studies suggest that silt- and clay-rich layers found within wetland and reservoir deposits are derived from the erosion of fine-grained, valley bottom soils frequently utilized as vegetable fields. Coarser-grained deposits within both wetlands and reservoirs result from the erosion of sandier hillslope soils extensively utilized for sugar cane, during relatively high magnitude runoff events that are capable of transporting sand-sized sediment off the slopes. Thus, the source of sediment to the axial valley varies as a function of sediment size and runoff magnitude. Sediment export from the basin was limited until the early 1990s, in part because the upper catchment wetlands were hydrologically disconnected from lower parts of the watershed during low- to moderate flood events. The construction of a drainage ditch through a previously unchanneled wetland altered the hydrologic connectivity of the catchment, allowing sediment to be transported from the headwaters to the lower basin where much of it was deposited within the riparian wetlands. The axial drainage system is now geomorphically and hydrologically connected during most events throughout the study basin. The study indicates that increased valley connectivity partly negated the positive benefits of controlling sediment/nutrient exports from the catchment by means of upland based, best management practices.

scholarly journals Influence of basin connectivity on sediment source, transport, and storage within the Mkabela Basin, South Africa

2013 ◽  
Vol 17 (2) ◽  
pp. 761-781 ◽  
Author(s):  
J. R. Miller ◽  
G. Mackin ◽  
P. Lechler ◽  
M. Lord ◽  
S. Lorentz
Keyword(s):  
South Africa ◽  
Best Management Practices ◽  
Management Practices ◽  
Drainage System ◽  
Sediment Source ◽  
Riparian Wetlands ◽  
Valley Bottom ◽  
Sediment Size ◽  
Catchment Areas ◽  
And Storage

Abstract. The management of sediment and other non-point source (NPS) pollution has proven difficult, and requires a sound understanding of particle movement through the drainage system. The primary objective of this investigation was to obtain an understanding of NPS sediment source(s), transport, and storage within the Mkabela Basin, a representative agricultural catchment within the KwaZulu–Natal Midlands of eastern South Africa, by combining geomorphic, hydrologic and geochemical fingerprinting analyses. The Mkabela Basin can be subdivided into three distinct subcatchments that differ in their ability to transport and store sediment along the axial valley. Headwater (upper catchment) areas are characterized by extensive wetlands that act as significant sediment sinks. Mid-catchment areas, characterized by higher relief and valley gradients, exhibit few wetlands, but rather are dominated by a combination of alluvial and bedrock channels that are conducive to sediment transport. The lower catchment exhibits a low-gradient alluvial channel that is boarded by extensive riparian wetlands that accumulate large quantities of sediment (and NPS pollutants). Fingerprinting studies suggest that silt- and clay-rich layers found within wetland and reservoir deposits of the upper and upper-mid subcatchments are derived from the erosion of fine-grained, valley bottom soils frequently utilized as vegetable fields. Coarser-grained deposits within these wetlands and reservoirs result from the erosion of sandier hillslope soils extensively utilized for sugar cane, during relatively high magnitude runoff events that are capable of transporting sand-sized sediment off the slopes. Thus, the source of sediment to the axial valley varies as a function of sediment size and runoff magnitude. Sediment export from upper to lower catchment areas was limited until the early 1990s, in part because the upper catchment wetlands were hydrologically disconnected from lower parts of the watershed during low to moderate flood events. The construction of a drainage ditch through a previously unchanneled wetland altered the hydrologic connectivity of the catchment, allowing sediment to be transported from the headwaters to the lower basin where much of it was deposited within riparian wetlands. The axial drainage system is now geomorphically and hydrologically connected during events capable of overflowing dams located throughout the study basin. The study indicates that increased valley connectivity partly negated the positive benefits of controlling sediment/nutrient exports from the catchment by means of upland based, best management practices.

scholarly journals Ecological Risk of Water Resource Use to the Wellbeing of Macroinvertebrate Communities in the Rivers of KwaZulu-Natal, South Africa

2020 ◽  
Vol 2 ◽  
Author(s):  
Olalekan A. Agboola ◽  
Colleen T. Downs ◽  
Gordon O'Brien
Keyword(s):  
South Africa ◽  
Bayesian Networks ◽  
Bayesian Network ◽  
Best Management Practices ◽  
Management Practices ◽  
Multiple Stressors ◽  
Anthropogenic Activities ◽  
Management Tool ◽  
Macroinvertebrate Communities ◽  
Kwazulu Natal

The rivers of KwaZulu-Natal, South Africa, are being impacted by various anthropogenic activities that threaten their sustainability. Our study demonstrated how Bayesian networks could be used to conduct an environmental risk assessment of macroinvertebrate biodiversity and their associated ecosystem to assess the overall effects of these anthropogenic stressors in the rivers. We examined the exposure pathways through various habitats in the study area using a conceptual model that linked the sources of stressors through cause-effect pathways. A Bayesian network was constructed to represent the observed complex interactions and overall risk from water quality, flow and habitat stressors. The model outputs and sensitivity analysis showed ecosystem threat and river health (represented by macroinvertebrate assessment index – MIRAI) could have high ecological risks on macroinvertebrate biodiversity and the ecosystem, respectively. The results of our study demonstrated that Bayesian networks can be used to calculate risk for multiple stressors and that they are a powerful tool for informing future strategies for achieving best management practices and policymaking. Apart from the current scenario, which was developed from field data, we also simulated three other scenarios to predict potential risks to our selected endpoints. We further simulated the low and high risks to the endpoints to demonstrate that the Bayesian network can be an effective adaptive management tool for decision making.

Best management practices applied to urban runoff quantity and quality control

1999 ◽  
Vol 39 (12) ◽  
pp. 117-121 ◽  
Author(s):  
M. J. Braune ◽  
A. Wood
Keyword(s):  
South Africa ◽  
Best Management Practices ◽  
Management Practices ◽  
Negative Impact ◽  
Water Runoff ◽  
Best Management ◽  
The Usa ◽  
Urban Stormwater Runoff ◽  
Accumulation Of Pollutants ◽  
Surface Water Runoff

South Africa currently has one of the highest rates of urbanisation in the world causing a significant increase in surface water runoff. This, in turn, causes increased flooding and a significant decrease in water quality due primarily to the accumulation of pollutants. The need exists to manage urban stormwater runoff on an integrated catchment basis, thereby reducing the negative impact of urbanisation on the environment and quality of life. In this paper, details on how existing problem areas can be identified and ranked, the use of Best Management Practices (BMPs) to reduce the impacts of urbanisation on the environment and the effectiveness of BMP's are discussed and illustrated, based on expertise gained from studies in South Africa as well as visits to the USA and Australia.

scholarly journals Assessing the Performance of Different Time of Concentration Equations in Urban Ungauged Watersheds: Case Study of Cartagena de Indias, Colombia

Hydrology ◽  
2020 ◽  
Vol 7 (3) ◽  
pp. 47
Author(s):  
Álvaro González-Álvarez ◽  
José Molina-Pérez ◽  
Brandon Meza-Zúñiga ◽  
Orlando M. Viloria-Marimón ◽  
Kibrewossen Tesfagiorgis ◽  
...  
Keyword(s):  
Best Management Practices ◽  
Management Practices ◽  
Overland Flow ◽  
Drainage System ◽  
Flow Time ◽  
Design Flood ◽  
Time Of Concentration ◽  
True Value ◽  
Cartagena De Indias ◽  
Ungauged Watersheds

In ungauged watersheds, the estimation of the time of concentration (Tc) is always a challenging task due to the intrinsic uncertainty involved when making assumptions. Given that Tc is one of the main inputs in a hydrological analysis for the design of hydraulic structures for stormwater management, ten equations (including one proposed in several local studies) and two Tc methodologies (overland flow time plus channel flow time) were used to compute the Tc in fifteen urban ungauged watersheds, located in Cartagena de Indias (Colombia), with different area sizes and slopes to statistically assess their performance against the value obtained via the Natural Resources Conservation Service (NRCS) velocity method (assumed to be the true value). According to the Nash–Sutcliffe efficiency index, none of the equations proved to be reliable in all watersheds as only four equations predicted the Tc value in 53% of the cases. In addition, based on the percent bias, all equations tended to significantly over- or underestimate the Tc, which affects the quantification of the runoff volume necessary for, among others, the implementation of best management practices for watershed management (e.g., conventional and/or sustainable drainage system design), flood-prone area delineation and flood risk analyses, urban planning, and stream restoration.

scholarly journals Development of stormwater exfiltration systems

2021 ◽  
Author(s):  
Zulfiqar Ali Khowaja
Keyword(s):  
Best Management Practices ◽  
Management Practices ◽  
Storage System ◽  
Urban Runoff ◽  
Best Management ◽  
Parking Lot ◽  
And Performance ◽  
The City ◽  
And Storage ◽  
Receiving Water

Pollutant loading from urban runoff has been established as a major cause of receiving water degradation. In an effort to control this problem at the source many Best Management Practices (BMP) have been developed. In this report, the Atlantis Exfiltration Tanks System, was developed as a potential BMP for the City of Sarnia. In order to analyze the efficiency and performance characteristics of the Atlantis Exfiltration Tanks, it is necessary to conduct pilot study before implementation. For this purpose, the highly impervious parking lot of the Newton's Park in Sarnia was selected to develop the Atlantis Exfiltration System (AES). The construction of AES was completed in summer of 2004. AES is an "at source" base water purification and storage system. This report includes the construction and performance of AES followed by conclusions and recommendations for further study.

Factors affecting the nutritional quality of crops

1992 ◽  
Vol 7 (1-2) ◽  
pp. 63-68 ◽  
Author(s):  
Sharon B. Hornick
Keyword(s):  
Best Management Practices ◽  
Nutritional Quality ◽  
Management Practices ◽  
Animal Health ◽  
Organic Matter Content ◽  
Organic Fertilizers ◽  
Chemical Fertilizers ◽  
Postharvest Handling ◽  
And Storage

AbstractSeveral factors can directly or indirectly affect the nutritional quality of crops. Among these are soil factors, such as pH, available nutrients, texture, organic matter content and soil-water relationships; weather and climatic factors, including temperature, rainfall and light intensity; the crop and cultivar; postharvest handling and storage; and fertilizer applications and cultural practices. This paper deals primarily with fertilizer and cultural management practices, and on certain environmental factors that affect the nutritional quality of field crops and of fruits and vegetables. Earlier research that has investigated the nutritional status of crops grown with either chemical fertilizers or organic fertilizers is discussed. These studies often have given contradictory results on crop yields and on crops' mineral and vitamin contents. Other factors, such as maturity at harvest, postharvest handling and storage, anti-nutritive components, and residues of chemical fertilizers and pesticides are reviewed with respect to food safety and quality, and their implications for human and animal health. Future research needs are identified so that comparable results and valid comparisons can be obtained to identify the best management practices to ensure that food is safe and nutritious for the consumer.

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