https://commons.ru.ac.za/vital/access/manager/Index en-us 5 https://commons.ru.ac.za/vital/access/manager/Repository/vital:26313 Wed 12 May 2021 23:08:33 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4826 Wed 12 May 2021 19:12:49 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4833 Wed 12 May 2021 16:27:19 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4824 80%) of the bed material transport. Only large floods (termed 'reset'discharges) with average return periods of around 20 years generate sufficient stream power and shear stress to mobilise the entire bed. The macro-channel is thus maintained by the large ' reset' flood events, and the active channel is maintained both by the range of effective discharges and the ' reset 'discharges. These are the geomorphologically 'effective' flows. Results from the Mhlathuze River have indicated that the Goedertrouw Dam has had a considerable impact on the downstream channel morphology and bed material transport capacity and consequently the effective and dominant discharges. It has been suggested that the Mhlathuze River is now adjusting its channel geometry in sympathy with the regulated flow environment. Under present-day conditions it has been demonstrated that the total bed material load has been reduced by up to three times, but there has also been a clear change in the way in which the load has been distributed around the duration curve. Under present-day conditions, over 90% of the total bed material load is transported by the top 5% of the flows, whereas under virgin flow conditions 90% of the total bed material load was transported by the top 20% of the flows. For the Olifants River there appears to be no relationship between the estimated bankfull discharge and any hydrological statistic. The effective discharge flow class is in the 5-0.01% range on the 1-day daily flow duration curve. It has also been pointed out that even the highest flows simulated for the Olifants River do not generate sufficient energy to mobilise the entire bed. It is useful to consider the Olifants River as being adapted to a highly variable flow regime. It is erroneous to think of one ' effective' discharge, but rather a range of effective discharges are of significance. It has been argued that strong bed rock control and a highly variable flow regime in many southern African rivers accounts for the channel architecture, and that there is a need to develop an ' indigenous knowledge' in the management of southern African fluvial systems]]> Wed 07 Aug 2024 16:37:21 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:30709 150% intensity) were old gravity schemes. Farmers on approximately 75% of Limpopo smallholder schemes are currently engaging in land exchange transactions in a highly insecure and un-formalised institutional setup. Land exchange prevalence longer than two years was moderately associated with cropping intensity and strongly associated with commercialisation. This result has three important implications. First, it suggests that more land is utilised on the schemes when there is vibrant land-leasing activity. Secondly, schemes with a higher prevalence of long-term leasing seem to have a strong tendency to be more commercialised. Thirdly, the duration of the lease is significant, as neither single-season, nor annual leases yielded any positive associations, while those exchanges that were two years or longer, were associated with increased performance. These findings highlight the potential for longer-term land-exchange interventions to address the widespread low land utilisation on smallholder schemes, and to catalyse more commercially-oriented farming. An irrigation scheme typology was derived from the cluster analysis and was aligned to a contemporary irrigation farming typology. The key descriptors included technology type, purpose of farming and scheme management type. By matching scheme type to the farmer typology (or typologies), strategic decisions regarding technology choices for infrastructure, land, and water institutional interventions can be better informed. All schemes demand attention to the multiple factors required to achieve performance, not least water-tenure security, irrigation management organisational development, and infrastructure modernisation. Complexity was demonstrated by the finding that multiple factors contribute to success, and that there are many dimensions that change independently and have a cascading effect through the system in ways that are difficult to predict. Agricultural systems support to achieve productivity and profitability are essential for success. The research findings lead to the recommendation that, in addition, strategic planners must also consider the implications of the dominant factors of water-technology choices so that these are manageable, and the dynamics of farm-size change based on land exchange processes, in order to harness new opportunities to maximise irrigation scheme performance in future.]]> Thu 13 May 2021 11:26:49 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:20006 Thu 13 May 2021 06:38:30 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4892 Thu 13 May 2021 05:12:06 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4828 Thu 13 May 2021 02:49:50 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4853 Thu 13 Jul 2023 18:06:05 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4199 Mon 13 May 2024 09:49:28 SAST ]]>