Ongoing concerns about the efficient and sustainable utilisation of South Africa’s water resources have resulted in much interest regarding the water use of different land uses within a catchment. Research has been focussed on water use by different dryland vegetation, in particular commercial forestry which has been declared a Stream Flow Reduction Activity for which a water use license is required for production. Consequently, concerns about the water use of other dryland crops have lead to a need to quantify water use by other land uses, particularly sugarcane. In this document, previous research focussed on water use by sugarcane is reviewed and summarised, together with an experiment where an energy balance approach has been used to quantify water consumption in the form of total evaporation for an area of sugarcane production in the KwaZulu-Natal Midlands with an assessment of the seasonal variability of this water consumption for a period of 1 year. The study was performed using a Large Aperture Scintillometer to measure sensible heat flux, whilst all other energy balance components, as well as rainfall, soil moisture and other climatic data were obtained using standard methods. Total evaporation was estimated from latent heat flux which was derived as a residual of the energy balance. Total evaporation varies over the year with substantially higher values occurring in summer in response to high energy and water availability. Over the year, the crop used approximately 630mm of water which equates to 53% of rainfall at the site. The two main factors affecting the seasonal variability of water use by sugarcane are net radiation and soil moisture content. In the wetter months when soil moisture is readily available, net radiation limits total evaporation. In the drier months, soil moisture is not as readily available, and limits total evaporation. Air temperature and relative humidity proved to also be important considerations in their effect on total evaporation. The total evaporation estimates obtained could be compared to a baseline (grassland) and used in simulations for a better understanding of the stream flow reduction potential of sugarcane and the seasonal variability thereof. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.

Thesis (MScAgric)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Due to the extraordinary drought resistance of the grapevine, viticulture without irrigation in the winter rainfall coastal areas of South Africa is a feasible and commonly used practice. Wine quality is largely determined by the quality of the grapes from which it is made. Grapevine physiology is affected both directly and indirectly by water stress, which may vary according to soil type and prevailing atmospheric conditions. The water status of the grapevine can affect grape composition profoundly, either directly or indirectly, in either a positive or negative way, depending on the degree as well as the duration of water stress. There are three important factors involved in the development of water stress, namely the transpiration rate, the rate of water movement from the soil to the roots, and the relationship of soil water potential to leaf water potential. All three these factors are affected by atmospheric and/or soil conditions. In warm winelands such as South Africa (Western Cape), with a mediterranean climate which is characterised by a hot, dry summer period, the most important characteristic of soil is its ability to supply sufficient water to the grapevine during the entire growing season. Leaf water potential (Ψl) has gained wide acceptance as a fundamental measure of grapevine water status, and has been widely applied in viticultural research. Shortly before dawn, Ψl approaches equilibrium with soil water potential and reaches a maximum daily value. The study formed an integral part of a comprehensive, multi-disciplinary research project (ARC Infruitec-Nietvoorbij Project No. WW13/01) on the effect of soil and climate on wine quality, which commenced in 1993 and will be completed in 2004. This study was conducted during the 2002/03 growing season in two Sauvignon blanc vineyards situated at Helshoogte and Papegaaiberg, both in the Stellenbosch district, approximately nine kilometres apart. Two experiment plots, representing contrasting soil types in terms of soil water regime, were selected in each vineyard. At Helshoogte the two soils represented the Tukulu and Hutton forms, and the soils at Papegaaiberg were of the Avalon and Tukulu forms. The aim of this study was to determine the effect of atmospheric conditions and soil water status on the level of water stress in the grapevines for each soil at each locality, as well as the effect of grapevine water stress on yield and wine quality. This was done by determining and comparing the soil water status, soil water holding capacity of the soils and the evapotranspiration of the grapevines on the two different soils, at each of the two localities differing in mesoclimate and topography. The atmospheric conditions at the two localities during the 2002/03 season were also determined and compared to the long-term average atmospheric conditions, and the level of water stress of grapevines on each soil at each locality was measured. During the 2002/03 growing season, atmospheric conditions were relatively warm and dry in comparison to the long-term averages of previous seasons. These conditions accentuated the effects of certain soil properties that may not come forward during wetter, normal seasons. The usually wet Tukulu soil at Helshoogte was drier than expected during the 2002/03 season compared to the Hutton soil. Due to more vigorous growth on the Tukulu soil, grapevines extracted more soil water early in the season, leading to a low soil water matric potential and more water stress in the grapevines. Due to the higher vigour, resulting in more canopy shading, and more water stress, the dominant aroma in wines from the Tukulu soil was fresh vegetative. The Hutton soil maintained consistency with regards to both yield and wine quality compared to previous seasons. On the other hand the Tukulu soil supported a higher yield, but with lower than normal wine quality. The Avalon soil at Papegaaiberg maintained the highest soil water potential towards the end of the season, probably due to capillary supplementation from the sub-soil. Grapevines on the Tukulu soil at Papegaaiberg experienced much higher water stress than ones on the other three soils, especially during the later part of the season. This could be ascribed to a combination of factors, the most important being the severe soil compaction at a shallow depth, seriously limiting rooting depth and root distribution, which is detrimental to grapevine performance. Both the soil water status and atmospheric conditions played important roles in determining the amount of water stress that the grapevines experienced at different stages. The air temperature and vapour pressure deficit throughout the season were consistently lower at Helshoogte, the cooler terroir, compared to Papegaaiberg, the warmer terroir. At flowering, Ψl was lower for grapevines at Helshoogte than at Papegaaiberg, showing that diurnal grapevine water status was primarily controlled by soil water content. The difference in grapevine water status between the two terroirs gradually diminished until it was reversed during the post harvest period when Ψl in grapevines at Papegaaiberg tended to be lower compared to those at Helshoogte. The relatively low pre-dawn Ψl at Helshoogte indicated that the grapevines were subjected to excessive water stress resulting from the low soil water content. However, grapevines at Helshoogte did not suffer material water stress (i.e. Ψl < -1.20 MPa) during the warmest part of the day, suggesting that partial stomatal closure prevented the development of excessive water stress in the grapevines. This suggests that low pre-dawn Ψl values do not necessarily imply that grapevines will experience more water stress over the warmer part of the day, or visa versa. This does not rule out the possibility that side-effects of partial stomatal closure, such as reduced photosynthesis, can have negative effects on grapevine functioning in general. These results also suggest that measurement of diurnal Ψl cycles at various phenological stages is required to understand and quantify terroir effects on grapevine water status. / AFRIKAANSE OPSOMMING: Danksy die droogteweerstand van die wingerdstok is die verbouing van wingerde sonder besproeiing ‘n praktiese en algemene verskynsel in die winterreënval-areas van Suid-Afrika. Wynkwaliteit word grootliks bepaal deur die kwaliteit van die druiwe waarvan dit gemaak word. Wingerdfisiologie word direk en indirek beïnvloed deur waterstres, wat kan varieer volgens die grondtipe en die heersende atmosferiese toestande. Die waterstatus van die wingerdstok beïnvloed druifsamestelling, direk of indirek, en positief of negatief, afhangend van die graad en tydsduur van die waterstres. Daar is drie belangrike faktore betrokke by die ontwikkeling van waterstres, naamlik die transpirasietempo, die tempo van waterbeweging vanaf die grond na die wortels, en die verhouding tussen die grondwatermatrikspotensiaal tot blaarwaterpotensiaal. Al drie die faktore word beïnvloed deur die atmosferiese en/of grondtoestande. In warm wynboulande soos Suid-Afrika (Weskaap), met ‘n meditereense klimaat wat gekarakteriseer word deur ‘n warm, droë somerperiode, is die belangrikste eienskap van grond die vermoë om voldoende water aan die wingerdstok te verskaf gedurende die hele seisoen. Blaarwaterpotensiaal (Ψl) het wye aanvaarding bekom as die fundamentele meting van wingerstokwaterstatus, en word wyd toegepas in wingerdkundige navorsing. Kort voor sonsopkoms, nader Ψl ‘n ewewig met die grondwatermatrikspotensiaal en bereik ‘n maksimum daaglikse waarde. Die studie vorm ‘n integrale deel van ‘n omvattende, multi-dissiplinêre navorsingsprojek (ARC Infruitec-Nietvoorbij Projek No. WW13/01) op die effek van grond en klimaat op wynkwaliteit, wat in 1993 in aanvang geneem het en in 2004 afgehandel sal word. Hierdie studie is uitgevoer gedurende die 2002/03 seisoen in twee Sauvignon blanc wingerde geleë by Helshoogte en Papegaaiberg, beide in die Stellenbosch distrik, ongeveer nege kilometer van mekaar. Twee eksperimentele persele, elkeen verteenwoordigend van kontrasterende grondtipes in terme van grondwaterregime, is geselekteer in elke wingerd. By Helshoogte word die twee gronde verteenwoordig deur die Tukulu en Hutton grondvorms, en die gronde by Papegaaiberg is van die Avalon en Tukulu vorms. Die doel van die studie was om die effek van atmosferiese toestande en grondwaterstatus op die wingerdstok se waterstatus vir elke grond by die twee lokaliteite te bepaal, sowel as die effek van die wingerdstok se waterstatus op die opbrengs en wynkwaliteit. Dit is gedoen deur die grondwaterstatus, die grondwaterhouvermoë, sowel as die evapotranspirasie van die wingerdstokke op die twee verskillende gronde by elk van die twee lokaliteite, wat verskil in mesoklimaat en topografie, te bepaal en vergelyk. Die atmosferiese toestande by die twee lokaliteite gedurende die 2002/03 seisoen is ook bepaal en vergelyk met die langtermyn gemiddelde atmosferiese toestande. Die vlakke van waterstres in wingerdstokke op elke grond by elke lokaliteit is ook gemeet. Gedurende die 2002/03 groeiseisoen, was die atmosferiese toestande relatief warm en droog in vergelyking met die langtermyn gemiddeldes van vorige seisoene. Hierdie kondisies aksentueer die effek van sekere grondeienskappe wat nie noodwendig na vore kom gedurende normale, natter seisoene nie. Die gewoonlike nat Tukulu grond by Helshoogte was droër as verwag gedurende 2002/03 in vergelyking met die Hutton grond. As gevolg van sterker groekrag op die Tukulu grond, het wingerdstokke meer grondwater onttrek vroeg in die seisoen, wat gelei het tot ‘n lae grondwatermatrikspotensiaal en meer waterstres in die wingerdstokke. Die sterker groeikrag het meer beskaduwing van die lower asook meer waterstres veroorsaak, wat gelei het daartoe dat die dominante aroma in wyne vanaf druiwe op die Tukulu grond vars vegetatief was. Die Hutton grond het bestendig gebly in terme van opbrengs en wynkwaliteit in vergelyking met vorige seisoene. Daarteenoor het die Tukulu grond ‘n hoër opbrengs gelewer, maar met laer as gewoonlike wynkwaliteit. Die Avalon grond by Papegaaiberg het die hoogste grondwatermatrikspotensiaal behou tot die einde van die seisoen, heelwaarskynlik a.g.v. kapillêre aanvulling vanuit die ondergrond. Wingerdstokke op die Tukulu grond by Papegaaiberg het heelwat meer waterstres ondervind as op die ander drie gronde, veral later in die seisoen. Dit kan toegeskryf word aan ‘n kombinasie van faktore, die belangrikse daarvan die erge grondkompaksie vlak in die grond, wat worteldiepte en -verspreiding ernstig beperk het, wat op sy beurt nadelig is vir wingerdprestasie. Beide die grondwaterstatus en atmosferiese toestande het ‘n belangrike rol gespeel in die bepaling van die hoeveelheid waterstres wat die wingerdstok op verskillende stadiums ondervind het. Die lugtemperatuur en waterdampdruktekort was regdeur die seisoen laer by Helshoogte, die koeler terroir, as by Papegaaiberg, die warmer terroir. Gedurende blom was die Ψl laer vir wingerdstokke by Helshoogte as by Papegaaiberg, wat daarop wys dat daaglikse wingerdstok waterstatus hoofsaaklik deur die grondwaterinhoud bepaal was. Die verskil in wingerdstok waterstatus tussen die twee terroirs het geleidelik verminder totdat dit omgekeer was gedurende die na-oes periode toe Ψl in wingerdstokke by Papegaaiberg geneig het om laer te wees in vergelyking met die by Helshoogte. Die relatiewe lae voorsonop Ψl by Helshoogte het daarop gedui dat die wingerdstokke aan oormatige waterstres onderwerp was. Die wingerdstokke by Helshoogte het egter nie materiële waterstres (i.e. Ψl < -1.20 MPa) gedurende die warmste gedeelte van die dag ondervind nie, wat aandui dat gedeeltelike huidmondjiesluiting plaasgevind het om die ontwikkeling van oormatige waterstres te verhoed.Dit dui aan dat lae voorsonop Ψl waardes nie noodwendig impliseer dat wingerdstokke meer waterstres gedurende die warmste gedeelte van die dag sal ondervind nie, of visa versa. Dit sluit nie die moontlikheid uit dat negatiewe neweeffekte van gedeeltelike huidmondjiesluiting, soos ‘n vermindering in fotosintese, ‘n negatiewe effek kan hê op die wingerdstok se funksionering in die algemeen nie. Hierdie resultate stel voor dat die meting van daaglikse Ψl siklusse gedurende verskeie fenologiese stadia benodig word om die effek van terroir op die wingerdstok se waterstatus te verstaan en te kwantifiseer.

<p>An understanding of the impacts on freshwater systems from water management and development practices and the recognition that freshwater ecosystems are dependent on various aspects of the natural hydrological variability has given rise to a relatively new field of science commonly referred to as environmental flows. The assessment and application of environmental flows has advanced considerably in the last ten years. To coincide with the emergence and expansion of the environmental flows concept around the world, this survey study was undertaken aiming to identify people’s perceptions and interpretations of the environmental flows concept and its role in water management. It also aims to add to existing knowledge of the extent to which the concept is being applied, how it is being translated into policy and practice and the major challenges and opportunities that exist for continued understanding and implementation. The survey was distributed to a range of people representing different water-related sectors and regions around the world. A total of 272 responses representing 64 countries in the six major regions of the world was received. The responses were compiled and analysis of aspects of the respondents backgrounds as well as the questions were conducted using the computer statistical program SPSS. Representation of specific groups, particularly water user groups, and specific regions in the survey however was low, demonstrating possible limitations of the survey distribution method as well as the lack of concept awareness and application in many parts of the world. The ways in which people define and interpret the concept varied widely. The degree to which the concept was applied shows the growing recognition around the world of the need to consider the environmental water requirements when making decisions on water allocations. Despite the growing recognition many areas do not yet apply the concept. The survey allowed the opportunity for respondents to highlight what they perceived asthe major obstacles and difficulties for the concept within their respective areas. Lack of understanding among stakeholders of the socio-economic costs and benefits associated with concept implementation and a lack of political will were the two most common obstacles for the continued adoption and application of environmental flows around the world. Overall, the survey delivered promising signs for the continued evolution of environmental flows within water management. There was widespread opinion that the concept of environmental flows was an essential element in the efforts to achieve sustainable management of water resources.</p>

An understanding of the impacts on freshwater systems from water management and development practices and the recognition that freshwater ecosystems are dependent on various aspects of the natural hydrological variability has given rise to a relatively new field of science commonly referred to as environmental flows. The assessment and application of environmental flows has advanced considerably in the last ten years. To coincide with the emergence and expansion of the environmental flows concept around the world, this survey study was undertaken aiming to identify people’s perceptions and interpretations of the environmental flows concept and its role in water management. It also aims to add to existing knowledge of the extent to which the concept is being applied, how it is being translated into policy and practice and the major challenges and opportunities that exist for continued understanding and implementation. The survey was distributed to a range of people representing different water-related sectors and regions around the world. A total of 272 responses representing 64 countries in the six major regions of the world was received. The responses were compiled and analysis of aspects of the respondents backgrounds as well as the questions were conducted using the computer statistical program SPSS. Representation of specific groups, particularly water user groups, and specific regions in the survey however was low, demonstrating possible limitations of the survey distribution method as well as the lack of concept awareness and application in many parts of the world. The ways in which people define and interpret the concept varied widely. The degree to which the concept was applied shows the growing recognition around the world of the need to consider the environmental water requirements when making decisions on water allocations. Despite the growing recognition many areas do not yet apply the concept. The survey allowed the opportunity for respondents to highlight what they perceived asthe major obstacles and difficulties for the concept within their respective areas. Lack of understanding among stakeholders of the socio-economic costs and benefits associated with concept implementation and a lack of political will were the two most common obstacles for the continued adoption and application of environmental flows around the world. Overall, the survey delivered promising signs for the continued evolution of environmental flows within water management. There was widespread opinion that the concept of environmental flows was an essential element in the efforts to achieve sustainable management of water resources.

The change in total evaporation through alteration of vegetative cover is a major influence on catchment hydrology. The transformation of grassland and scrub habitats to commercial tree plantations, as well as the uncontrolled spread of invasive alien plants (lAPs) to ecologically sensitive systems, riparian zones in particular, are a threat to biodiversity and integrity of natural systems. Furthermore, critical low flow periods are of particular concern to water managers and local communities, as well as the associated impacts of potentially compromised water resources for rural livelihoods. The Working for Water (WfW) programme was implemented in 1995 by the Department of Water Affairs and Forestry and its main goals are to remove lAPs in order to improve water supply while at the same time providing employment to marginalised communities. In this study, the hydrological response to lAPs in the Upper Blyde River catchment is assessed. This is done by developing a classification structure for lAPs as a land use using detailed mapping available from WfW for use in a hydrological model, and then configuring and running the ACRU hydrological model for the Upper Blyde River catchment in Mpumalanga. In the classification, lAPs are represented as spatially explicit land use units in the ACRU model according to the type of habitat they invade, viz. riparian or non-riparian; as well as by type of plant, i.e. tree or shrub; and their area and density. The results obtained from simulating catchment hydrological responses using the ACRU model indicate that riparian lAPs have a great er impact on streamflow than do landscape invasions alone, specifically during periods of low flow. An increase in streamflow after removing lAPs from riparian and non-riparian habitats is a consistent outcome at both subcatchment and catchment scales. Using a spatially explicit method in order to model the hydrological response of different types of lAPs for different density classes in both riparian and non-riparian habitats is found to be a useful technique in determining the degree to which lAPs influence catchment streamflow. Recommendations for future research include focussing hydrological assessments of lAPs on critical flow periods and their impacts on water quality; investigation into the water use of invasive and indigenous vegetation for more accurate estimates from modelling exercises; and finally, applying the classification system for lAPs with other land use sensitive hydrological models for validation, and their wider application by incorporating methodologies into guidelines for use by WfW at national and provincial level. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2003.

The use of remotely sensed data to estimate forest attributes involves the acquisition of ground forest data. Recently the acquisition of ground data (field based) to estimate leaf area index (LAI) and biomass are becoming expensive and time consuming. Thus there is a need for an easy but yet effective means of predicting the LAI, which serves as an input to the forest growth prediction models and the quantification of water use by forests. The ability to predict LAI, biomass and eventually water use over a large area remotely using remotely sensed data is sought after by the forestry companies. Remotely sensed LAI values provide the opportunity to gain spatial information on plant biophysical attributes that can be used in spatial growth indices and process based growth models. In this study remotely sensed images were transformed into LAI value estimates, through the use of four vegetation indices (Normalized Difference Vegetation Index (NDVI), Corrected Normalized Difference Vegetation Index (NDVlc), Ratio Vegetation Index (RVI) and Normalized Ratio Vegetation Index (NRVI). Ground based measurements (Destructive Sampling and Leaf Canopy Analyzer) relating to LAI were obtained in order to evaluate the vegetation indices value estimates. All four vegetation indices values correlated significantly with the ground-based measurements, with the NDVI correlating the highest. These results suggested that NDVI is the best in estimating the LAI in Eucalyptus grandis x camaldulensis in the Zululand region with correlation coefficients of 0.78 for destructive sampling and 0.75 for leaf canopy analyzer. Visual inspection of scatter plots suggested that the relations between NDVI and ground based measurements were variable, with R2 values of 0.61 for destructive sampling and 0.55 for Leaf Canopy analyzer. These LAI estimates obtained through remotely sense data showed a great promise in South African estimation of LAI values of Eucalyptus grandis x camaldulensis. Thus water use and biomass can be quantified at a less expensive and time-consuming rate but yet efficiently and effectively. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2001.

Incldes bibliographical references / 1 v. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Agronomy, Waite Agricultural Research Institute, 1989

Bibliography: leaves 245-271 / xiv, 271 leaves, [47] leaves of plates : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Physiology, 1985

Diss. (sammanfattning) Alnarp : Sveriges lantbruksuniv. / Härtill 4 uppsatser.

Orientador: Antonio Evaldo Klar / Banca: João Carlos Cury Saad / Banca: Magali Ribeiro da Silva / Banca: Marcio da Silva Araújo / Banca: Geraldo Gonçalves dos Reis / Abstract: The aim of this work was to compare the final development of Pinus oocarpa Schiede seedlings using tree different underwater depth and with or without coverage fertilization. The research was done inside on a glass green house at the UNESP - College of Agronomical Science, Rural Engineering Department (Botucatu - SP - Brazil). Two trials were done to evaluate biomass, seedling height and diameter development. The first trial, using underground water on 17 cm, 31 cm and 45 cm depth, with or without coverage fertilization with N-P-K. The second trial was done with 28 flowerpots (12 liters each) and 3 seedlings per unit. The experimental design, used to evaluate the height and diameter growth and hydric potential and relative plant water content, was: 1- without water deficit and without coverage fertilization; 2- with water deficit and without coverage fertilization; 3- without water deficit and with coverage fertilization; 4- with water deficit and coverage fertilization. The underground water result showed that 31 cm and fertilization was better for seedling growing rather that 17 cm and without fertilization. The fertilized treatments showed higher plant high and diameter comparing to non fertilized samples, using Tukey test at 5%. For dry plant matter, the best results were obtained with 31 and 45 cm underground water level. The seedling root system dry mass was decrement along the soil profile. The treatment with underground water of 31 cm and fertilization was superior according to Tukey test at 5% of probability and the treatment with underground water of 17 cm and without fertilization was inferior for root dry mass (g). All the others treatment didn’t have statistical differences. It didn’t happen the irrigation effect on the plant high development; however the fertilized treatment had superior development compared to unfertilized samples. The relative water content didn’t change... (Complete abstract click electronic access below) / Doutor