No description available.

No description available.

Thesis (Ph.D. (Institute for Water Research)) - Rhodes University, 2009.

Two catchments of diverse hydrologic character were chosen in which to test the hypothesis that tree-ring indices contain information about runoff that is of pertinent interest to the hydrologist. These two catchments, Bright Angel Creek basin in extreme north-central Arizona and Upper San Francisco River basin in extreme east-central Arizona and west-central New Mexico, are situated in different climatic regions. Although two semiannual maxima, summer and winter, occur in the annual precipitation regime, at Bright Angel Creek the winter maximum is dominant, resulting in large amounts of snow accumulation, and at Upper San Francisco River the summer maximum is dominant. These contrasting precipitation regimes in association with the annual temperature regimes create climatic conditions for which the growth response of the trees, specifically Douglas fir, the species used in the study, and the precipitation-runoff response are greatly different and comparably complex. The complexity of the climate-growth, climate-runoff relationships necessitated the use of multivariate methods in assessing their similarities and dissimilarities. The technique used here is that of principal components, with physical meaning attached to the components by comparison with the results of other statistical approaches such as autocorrelation, cross correlation, autospectra, and cross spectra, and such tree-ring statistics as the coefficient of -mean sensitivity. The orthogonality property of the principal components was used to develop prediction equations with a minimum of variables through use of multiple linear regression. The general approach was to relate ring-width indices to climate and develop a response function, to relate runoff to climatic variables and develop a response function, and finally to develop a prediction equation for predicting runoff from ring-width indices. Prediction equations and 214-year (1753-1966) synthetic runoff series were developed for both basins. The results for Bright Angel Creek basin are not impressive because the best prediction equation accounts for only 51% of the year-to-year variance in the annual runoff. However, this was not wholly unexpected, as it is shown that the nature of the annual runoff regime and the statistical nature of the ring-width index series from this basin are not conducive to maximum hydrologic information. Nevertheless, it is shown that an improved estimate of the mean annual runoff can be gained from the synthetic series. For Upper San Francisco River basin the results were more satisfactory: 72% to 79% of the annual variance in runoff can be accounted for using prediction equations based on ring-width indices, where one equation uses untransformed values of runoff (72%) and the other uses log-transformed values of runoff (79%). The synthetic series shows an improved estimate for the mean annual runoff but also offers the hydrologist a valuable tool in providing a series from which useful information can be obtained that could be valuable in decision-making processes concerning reservoir design and operation.

Over the last several decades, the majority of the Greenland outlet glaciers have accelerated due to the increased warming in both the atmosphere and the oceans around the polar latitudes. While there is a clear overall acceleration trend over this period, there is significant variability in the glacier responses to climate on seasonal and year-to-year timescales. This variability observed around Greenland is very likely tied to the differences in internal dynamics of individual glaciers and the complex interaction with its local environment. Here I investigate the interaction between ice and water along the ice base as an important mechanism contributing to the observed variability among glaciers in Greenland. I use a range of modeling and radar sounding approaches to study the subglacial hydrology for three types of outlet glaciers, including slow moving, marine terminating glaciers in the west, a land-terminating system in the southwest, and a fast moving, marine-terminating glacier in northern Greenland. These case studies allow me to characterize the basal water distribution, its variability throughout the year and how this drainage behavior varies across different regions of Greenland. To start, I use a hydrological routing model to characterize the subglacial hydrology for three neighboring slow moving (< 100myr−1), marine terminating glaciers in western Greenland. The hydrologic model allows me to examine the sensitivity of basal water routing to subtle changes in basal water pressures. My results reveal that Greenland subglacial drainage can be rerouted across 100’s of km in response to changes in basal water pressures as small as 10%. I conclude that water piracy and subsequent dramatic changes in ice velocity, similar to that observed around the Siple Coast in West Antarctica, can occur in Greenland. Next, I move to a more data-orientated approach and use airborne radar sounding to examine the seasonal variability of basal water distribution. To robustly characterize basal water from radar bed power, I use a novel radar analysis approach that integrates a thermomechanical ice-sheet model to predict the spatial variations of radar attenuation. I improve this approach by including a least-squares minimization to correct for power offsets due to the different radar systems deployed in multiple field seasons. This improved method is first applied to two land-terminating glaciers in the southwest, Russell Glacier, and Isunnguata Sermia. Using two seasons of radar sounding data, I find that the basal water distribution can change between the wintertime and the summertime. My results reveal that during the winter, water resides primarily in small pockets on top of bedrock ridges. In the summer, these pockets of water on the ridges connect and drain into the nearby basal troughs. This seasonal shift in the basal water distribution is actively controlled by the material properties of the bed. Therefore, in addition to the bed topography, the permeability of the bed and the presence of basal sediments could also exert a critical influence on the seasonal development of subglacial drainage. Finally, I apply the radar analysis approach to a fast-flowing marine terminating glacier for Petermann Glacier in Northern Greenland. Here I incorporate an additional step to address the spatial variation in ice chemistry and its effect on radar attenuation. I use this approach to examine the relationship between basal water, ice deformation and the onset of glacier flow. In addition to finding basal water in the fastest flowing region near the ice margin, I identify substantial basal water in the ice sheet interior where meltwater must either be related to the advection of water from upstream or be generated by internal heating due to ice deformation. My results show there are three basal water networks beneath Petermann that connect the ice sheet interior to the margin. Together, the interaction between these basal water networks and the ice deformation enhances and sustains fast flow in the interior of the Petermann catchment. Overall, the research presented in this dissertation suggests that subglacial hydrology is high variable in both space and time. This variation in the hydrologic system can influence the fundamental structure of the ice sheet through changing the transport and storage of basal water and through interacting with ice deformation and the thermal properties of the bed.

It was found that the systems analysis technique is a useful tool for hydrologic systems and is not only applicable to artificial hydrologic systems but also to natural catchments. The general equation describing the relationship between surface runoff and rainfall excess of a hydrologic system is a second order nonlinear equation. The damping coefficient for hydrologic systems is approximately unity and the other parameters in the transfer function (Eq. 5-4) such as the time constant and the nonlinear parameter depend on basin characteristics and input intensity. / Ph. D.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, in fulfilment of the requirements for the degree of Master of Science August 2017. / Streamwater chemistry is influenced by several factors that include: geology, soil-geology interactions, land use, climate change, topography, vegetation, mechanical and chemical weathering. The dominance of these factors when determining the chemistry of streamwater varies from one situation to the other. Four different catchments in the Drakensberg were monitored to identify the processes determining temporal and seasonal patterns in streamwater chemistry. The land uses of the catchment include: CP03 (previously afforested, degraded), CP04 (pristine grasslands), CP06 (pristine grasslands) and CP09 (protection from fire). All the catchments were investigated for differences in major ion concentrations, streamwater temperatures, dissolved organic carbon (DOC), dissolved oxygen, pH, conductivity. There were comparisons made between historical and recent data collected at the Cathedral Peak Research Site. Comparisons were made between CP03 and CP06 to identify effects of storm events on streamwater chemistry. CP03 and CP09 had significant statistical differences in terms of major ions. Land use and stormflow path ways were most influential in determining the streamwater chemistry across catchments. / LG2018

M. Tech. Architecture: Professional / The origins of the Apies River within Fountains Valley, established the foundation of the city of Pretoria as well as the inspiration for this design. The significance of Fountains resides not only in its natural features but also its historical and cultural layers, forming a complex matrix of time and influence. The proposal explores the potential role that architecture plays in the conservation of Pretoria's cultural waterscapes, through the process of fabric renewal and public engagement. The study identifies the need for a hydrological research and conservation facility within Fountains Valley, unifying the significance of the site which stems from natural features as well as historical and cultural layers. Fountains Valley currently forms a place with cultural value, leisure and recreation opportunities, and an escape from the busy city. The proposed intervention consists of a cultural waterscape that creates a new relationship between people and nature. The future built landscape will be a platform and catalyst which researches, informs, and preserves Pretoria's natural spaces and aims to facilitate the integration of a hydro-logical research facility within a cultural recreational park.

Thesis (MScFor)--Stellenbosch University, 1980. / No Abstract Available

Hydrological models are widely used tools in water resources estimation, but they are simple representations of reality and are frequently based on inadequate input data and uncertainties in parameter values. Data observation networks are expensive to establish and maintain and often beyond the resources of most developing countries. Consequently, measurements are difficult to obtain and observation networks in many countries are shrinking, hence obtaining representative observations in space and time remains a challenge. This study presents some guidelines on the identification, quantification and reduction of sources of uncertainty in water resources estimation in southern Africa, a data scarce region. The analyses are based on example sub-basins drawn from South Africa and the application of the Pitman hydrological model. While it has always been recognised that estimates of water resources availability for the region are subject to possible errors, the quantification of these uncertainties has never been explicitly incorporated into the methods used in the region. The motivation for this study was therefore to contribute to the future development of a revised framework for water resources estimation that does include uncertainty. The focus was on uncertainties associated with climate input data, parameter estimation (and recognizing the uncertainty due model structure deficiencies) methods and water use data. In addition to variance based measures of uncertainty, this study also used a reservoir yield based statistic to evaluate model output uncertainty, which represents an integrated measure of flow regime variations and one that can be more easily understood by water resources managers. Through a sensitivity analysis approach, the results of the individual contribution of each source of uncertainty suggest regional differences and that clear statements about which source of uncertainty is likely to dominate are not generally possible. Parameter sensitivity analysis was used in identifying parameters which are important withinspecific sub-basins and therefore those to focus on in uncertainty analysis. The study used a simple framework for evaluating the combined contribution of uncertainty sources to model outputs that is consistent with the model limitations and data available, and that allows direct quantitative comparison between model outputs obtained by using different sources of information and methods within Spatial and Time Series Information Modelling (SPATSIM) software. The results from combining the sources of uncertainties showed that parameter uncertainty dominates the contribution to model output uncertainty. However, in some parts of the country especially those with complex topography, which tend to experience high rainfall spatial variability, rainfall uncertainty is equally dominant, while the contributions of evaporation and water use data uncertainty are relatively small. While the results of this study are encouraging, the weaknesses of the methods used to quantify uncertainty (especially subjectivity involved in evaluating parameter uncertainty) should not be neglected and require further evaluations. An effort to reduce data and parameter uncertainty shows that this can only be achieved if data access at appropriate scale and quality improves. Perhaps the focus should be on maintaining existing networks and concentrating research efforts on making the most out of the emerging data products derived from remote sensing platforms. While this study presents some initial guidelines for evaluating uncertainty in South Africa, there is need to overcome several constraints which are related to data availability and accuracy, the models used and the capacity or willingness to adopt new methods that incorporate uncertainty. The study has provided a starting point for the development of new approaches to modelling water resources in the region that include uncertain estimates.