An analysis of the cause-effect relationship of a free water table aquifer that changes laterally to an artesian aquifer was made for regions bounded internally by a circular cylinder. For a hydrologic system with a large pressure-head energy, development of the water resource by a single well is not the most practical approach and thus the study was extended to solve the problem of a line array of wells. The flow characteristic of the hydrologic system was divided into a regime of flow near the line array of wells which is titled the conduit regime, and a regime of flow distant from the line array, which is called the reservoir regime. This classification of flow type is based on the fact that the storage coefficient is not constant and accordingly the hydraulic diffusivity of the aquifer in the conduit region is much smaller than that in the reservoir region. Therefore, the mathematical continuity, which was assumed in previous analyses by other authors becomes discontinuous because linearity does not prevail throughout the flow system. The superposition principle, which is based on linearity and homogeneity, can not be applied to this non-linear system. By subdividing the flow system into the two regimes of conduit and reservoir, Carslaw's solution for the circular cylinder may be amplified by two integrations to achieve mathematical continuity of the whole system. The range that Goldenberg solved analytically for a similar problem was extended to meet practical requirements in the field of ground-water hydrology. A new approach was developed for the solution of the mutual interference problem of an infinite line array of wells. The interference is expressed in terms of what is called the discharge efficiency factor. The findings were applied to a hydrologic analysis of the ground-water resources of the Western Desert, U. A. R. (Egypt) in or der to describe its significance and importance in the design of systems for water resources development in extensive aquifers. The results aid also in defining the applicability limits of the theory of images, which has been used by several authors to solve for the interference problem of an infinite line array of wells.

Design of engineering projects involve a certain amount of uncertainty. How should design decisions be taken in face of the uncertainty? What is the most efficient way of handling the data? Decision theory can provide useful answers to these questions. The literature review shows that decision theory is a fairly well developed decision method, with almost no application in hydrology. The steps of decision theoretic analysis are given. They are augmented by the concept of expected expected opportunity loss, which is developed as a means of measuring the expected value of additional data before they are received. The method is applied to the design of bridge piers and flood levees for Rillito Creek, Pima County, Arizona. Uncertainty in both the mean and the variance of the logarithms of the peak flows of Rillito Creek is taken into account. Also shown are decision theoretic methods for: 1) handling secondary data, such as obtained from a regression relation, 2) evaluating the effect of the use of nonsufficient statistics, 3) considering alternate models and 4) regionalizing data. It is concluded that decision theory provides a rational structure for making design decisions and for the associated data collection and handling problems.

The existing theories for predicting longitudinal dispersion in straight open channels have long been recognized as inadequate when applied to natural rivers. These theories tend to grossly underestimate dispersion in real streams since an important mixing mechanism due to nonuniform river cross-section variations is not explicitly taken into account. Recognizing the important role of stream irregularities on solute transport and the analytical difficulties of classical deterministic analysis, we develop a stochastic approach for analyzing solute transport in natural streams. Variations in river width and bed elevation are conveniently represented as one-dimensional random fields, characterized by their autocorrelation functions. Advection and dispersion due to the combined effect of turbulent diffusion and nonuniform flow are described by the stochastic solute transport equation. When boundary variations are small and statistically homogeneous, a stochastic spectral technique is used to obtain closed-form stochastic solutions. In particular, closed-form expressions are obtained for effective mean solute transport velocity and effective dispersion coefficient reflecting mixing due to flow variations both within the river cross-section and in the streamwise direction. The results show that the mean behavior of solute transport in a statistically irregular stream can be described as a gradient dispersion process. The effective mean transport velocity in natural rivers is smaller than that in a corresponding uniform channel, and the effective longitudinal dispersion coefficient in natural rivers can be considerably greater than that of uniform open channels. The discrepancy between uniform channels and natural rivers increases rapidly as the variances of river width and bed elevation increase, especially when the mean flow Froude number is high.

Based on the determination of the zero-flux plane, a water balance procedure for large-scale experimental databases was automated to estimate the soil water balance based on soil water content distribution with depth through time. The automated procedure was verified using data from the BOREAS project obtained in three Intensive Field Campaigns during the spring and summer of 1994. The data used correspond to four tower sites measuring atmospheric fluxes above the forest canopy from the Northern and Southern Study Areas and are designated according to the predominant vegetation in the area as Old Jack Pine and Young Jack Pine. The total hydraulic head through time at these sites is determined to identify the position of the zero-flux plane, which separates that part of the soil profile in which water flow is upward from the region in which the water flow is downward. In conjunction with precipitation and soil water content data, the procedure allows estimation of the actual soil water balance, the water used from the region above the zero-flux plane being evapotranspiration, and the change in soil water content below the mean zero-flux plane being drainage. Prior to this study, no published attempt had been made to automate a water balance procedure for large-scale experimental databases based on the position of the zero-flux plane and soil water content distribution through time. / Graduation date: 1997

Changes in climate due to anthropogenic influences are expected to affect both hydrological and agricultural systems in southern Africa. Studies on the potential impacts of climate change on agrohydrological systems had been performed previously in the School of Bioresources Engineering and Environmental Hydrology (School of BEEH). However, refinement of these modelling tools and restructuring of the databases used was needed to enable more realistic and dynamic simulations of the impacts of changes in climate. Furthermore, it was realised that modifications and linkages of various routines would result in a faster processing time to perform climate impact assessments at the catchment scale. Baseline ("present") climatic information for this study was obtained from the School of BEEH's database. Scenarios of future climate were obtained from six General Circulation Models (GCMs). Output from the five GCMs which provided monthly climate output was used in the climate impact assessments carried out. Potential changes in variability of rainfall resulting from climate change was assessed using the daily climate output from the sixth GCM. As the spatial resolution of the climatic output from these GCMs was too coarse for use in climate impact studies the GCM output was interpolated to a finer spatial resolution. To assess the potential impact of climate change on water resources in southern Africa the ACRU hydrological modelling system was selected. The ACRU model was, however, initially modified and updated to enable more dynamic simulation of climate change. In previous hydrological studies of climate change in southern Africa Quaternary Catchments were modelled as individual, isolated catchments. To determine the potential impact of changes in climate on accumulated flows in large catchments the configuration of the Quaternary Catchments needed to be determined and this configuration used in ACRU. The changes in hydrological responses were calculated both as absolute differences between future and present values and the ratio offuture hydrological response to the present response. The large degree of uncertainty between the GCMs was reflected in the wide range of results obtained for the water resources component of this study. In addition to the climate impact studies, sensitivity and threshold studies were performed using ACRU to assess the vulnerability of regions to changes in climate. Potential change in the yields and distributions of parameters important to agriculture, such as heat units, crops, pastures and commercial tree species were assessed using simple crop models at a quarter ofdegree latitude / longitude scale. Most species were simulated to show decreases in yields and climatically suitable areas. There are many sources of uncertainties when performing climate impact assessments and the origins of these uncertainties were investigated. Lastly, potential adaptation strategies for southern Africa considering the results obtained are presented. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2001.

The demand for timber products in South Africa, and consequently afforestation, is increasing. There exists, however, abundant experimental evidence that trees utilise more soil water than other dryland crops. Because water is limited in South Africa, decision makers therefore currently face the challenge of determining a socially, and economically acceptable afforestation management plan to enable the reconciliation of increased timber demand with scarce water supply. This challenge, and the subsequent decisions that need to be made, may be accomplished by making use of suitable simulation models to predict the impacts of the forest hydrological system on water resources. Currently, these impacts are assessed through an Afforestation Permit System (APS) which is based on a model now acknowledged to have become outdated. In this dissertation an enhanced ACRU Forest Decision Support System (FDSS), now called the ACRU Forest model, is developed and proposed as a tool for modelling forest hydrological impacts on water resources. Research for this study included a literature survey, fieldwork at two locations, viz. at forest irrigation trials at Mkuze in northern KwaZulu-Natal, and at forest site preparation trials near Ugie in the Eastern Cape, as well as the evaluation, for purposes of model development, of a series of workshops. Results from the fieldwork experiments show that large tree water use potentials are possible if water is not limiting, although a water supply threshold exists at about 1400mm.annum-1, above which diminishing growth returns occur. Furthermore, trees display improved growth on more intensive forest site preparations, but at the expense of higher water usage rates. A series of workshops which had as the main objective the extraction of expert knowledge by stimulating responses to prepared questions and by constructive discussion on relative issues pertaining to forest hydrological modelling, yielded valuable information. This information, together with that gleaned from the literature, the fieldwork and a new Quaternary catchment database for South Africa, was used to develop the ACRU Forest model. The PC-based ACRU Forest model has the potential to aid decision makers by providing an initial indication of the impacts of afforestation on water resources, within a matter of minutes. An example of the model's application is used to demonstrate its operation, relative accuracy and its potential benefits in simulating hydrological responses to afforestation. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1995.

South African water management areas could find themselves without enough water for its users due to new methods of performing water allocation as stipulated in the National Water Act of 1998. A water accounting system would address the need for accurate metering, monitoring and auditing of South Africa’s water resources to ensure that users are complying with their allocations. Such a system should be able to provide information such as comparisons between the simulated and observed flow of water at a point, comparisons between the amount of water allocated to a user and the actual water used by that user, and the source and destination of water at a point. This document contains a literature review, an explanation of the methods used to develop a prototype water accounting system and a discussion of the results from testing the system. A literature review was undertaken which covered topics in water resources planning, water resources operations, local legislation for water allocation and new technologies which could be applied to aid the management of water resources in South Africa. The results from the literature review indicated real time water accounting systems can give effect to water allocation rules. The water accounting system is comprised of two simulation models and a database. The models used for the study were the ACRU2000 model and the MIKE BASIN model. These models require data as well as a means to automate the transfer of data between the models and thus a database was developed. The database was developed in Microsoft Access and, in addition to the construction of a number of tables required to house the data, a database dashboard was made to control the functions of the database. An assessment of the ACRU2000 and MIKE BASIN models was performed in order to determine if they are suitable for use as water accounting tools. ACRU2000 was used for its process based, daily rainfall-runoff modelling capabilities. Due to the process based modelling capabilities of ACRU2000, forecasts of rainfall can be used as input to the simulations. Hot starting is the storing of internal model state variables at a particular time and the use of these variables in a different simulation to start the model up again. It was expected that, due to long simulation run times for ACRU2000, it would be beneficial to enable ACRU2000 to be hot started and an attempt to hot start ACRU2000 is presented. This would have allowed for significantly decreased simulation run times as the model can be warmed up for two years and thereafter hot started to run only for one day at a time. An assessment of the MIKE BASIN network allocation model to be used as a water accounting system was performed by attempting to meet the project objectives through building a fictional water supply network. The network is composed of a small catchment containing six runoff generating regions, a reservoir and ten water users. Three network allocation scenarios were constructed in order to fully test the rule sets and allocation capabilities currently available in the MIKE BASIN model. The study has shown that the tools and models used are capable of forming a rudimentary water accounting system. This is encouraging as it shows that there is the potential to improve the water resources management in South Africa using tools that already exist. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / No presente trabalho as projeÃÃes de vazÃes para a bacia do Ãros (CearÃ) foram obtidas usando as precipitaÃÃes dos modelos globais do quarto relatÃrio do Intergovernmental Panel on Climate Change (IPCC-AR4) para o perÃodo de 2010 a 2099 do cenÃrio A1B. As vazÃes foram geradas pelo modelo hidrolÃgico Soil Moisture Account Procedure (SMAP). Para a obtenÃÃo destas, as precipitaÃÃes foram corrigidas estatisticamente a partir dos dados observados, considerando as sÃries distribuiÃÃes do tipo gama. Quanto à evaporaÃÃo de entrada do modelo chuva-vazÃo foram feitas duas consideraÃÃes, a primeira consideraÃÃo utiliza vazÃes obtidas pelo modelo hidrolÃgico SMAP inicializado com evaporaÃÃo fornecidas pelo INMET e a segunda considera que a inicializaÃÃo foi feita por evaporaÃÃes estimadas pelo mÃtodo de Penann Mothieth. Para a anÃlise das variaÃÃes interanuais foram observadas as caracterÃsticas de tendÃncias das sÃries (usando mÃtodo clÃssico de Mann-Kendall-Sen) nos padrÃes de variaÃÃo (anÃlise da mÃdia e do coeficiente de variaÃÃo da sÃrie) e a anÃlise de extremos (comparaÃÃo das curvas de distribuiÃÃo acumulada do sÃculo XX e XXI). Para anÃlise sazonal considerou-se a anomalia na climatologia mÃdia dos modelos do sÃculo XXI em relaÃÃo ao sÃculo XX. Para a anÃlise interanual foi observado que a inicializaÃÃo do modelo hidrolÃgico SMAP com evaporaÃÃes estimadas pelo mÃtodo de Penann Motheith modificado pode surgir como implementaÃÃo para o teste de hipÃtese de Mann Kendall Sen. O calculo do coeficiente de variaÃÃo demonstrou que apesar da pouca divergÃncia quanto a ocorrÃncia de variabilidade, tratando-se de sÃries de vazÃes obtidas pelo SMAP inicializado com evaporaÃÃes estimadas, as rodadas dos modelos MIROC3_2_MEDRES relatou aumentos de variabilidade para o sÃculo XXI em relaÃÃo ao sÃculo XX. Quando a inicializaÃÃo no SMAP ocorre por meio de evaporaÃÃes fornecidas pelo INMET ocorre uma grande diversificaÃÃo nos valores de variabilidade. Ainda na anÃlise interanual, a curva de funÃÃo de distribuiÃÃo acumulada (CDF) demonstrou que dos 8 modelos analisados (modelos inicializados com evaporaÃÃes estimadas pelo mÃtodo de Penann-Motheith modificado) 3 apresentam maior freqÃÃncia de eventos secos, 3 apresentam uma freqÃÃncia de eventos mais Ãmidos e 2 modelos nÃo apresentando anÃlises significativas aproximando-se da curva gerada pela sÃrie de vazÃo observada. Quanto à anÃlise sazonal das vazÃes à observado que quando se utiliza o mÃtodo de Penann Motheith modificado para evaporaÃÃo (na inicializaÃÃo do SMAP) os valores de vazÃes tornam-se menores do que os valores obtidos por sÃries geradas pelo modelo hidrolÃgico inicializado com evaporaÃÃes fornecidas pelo INMET, relacionando o sÃculo XXI com o sÃculo XX. / In the present work flow projections for the basin Ãros (CearÃ) were obtained using the precipitation of global models of the fourth report of the Intergovernmental Panel on Climate Change (IPCC-AR4) for the period 2010 to 2099 the A1B scenario. The flows were generated by the hydrologic model Soil Moisture Account Procedure (SMAP). To obtain these, the precipitations were statistically corrected from the observed data, considering the distributions of the type series range. The evaporation model input rainfall-runoff were two considerations, the first consideration obtained by using flow hydrologic model initialized with SMAP evaporation provided by INMET and considers that the second boot occur by evaporation estimated by the method of Penann Mothieth. For the analysis of interannual variations were observed the characteristics of trends of the series (using the classical method of Mann-Kendall-Sen), the changing patterns of variation (analysis of the mean and coefficient of variation of the series) and the analysis of extremes (compared cumulative distribution curves of the twentieth century and XXI). For seasonal analysis considered the climate anomaly in the middle of the XXI century models over the twentieth century. For analysis it was observed that interannual hydrologic model initialization SMAP with evaporation estimated by the modified Penann Motheith can arise as an implementation for the hypothesis test of Mann Kendall Sen. The calculation of the coefficient of variation showed that despite the short confrontation over the occurrence of variability, in the case of streamflow series obtained by SMAP initialized with estimated evaporation, the rounds of the models MIROC3_2_MEDRES reported increases in variability for the XXI century in relation to the twentieth century. When booting into SMAP occurs through evaporation provided by INMET is a great diversification in the values of variability. Although the interannual analysis, the curve of cumulative distribution function (CDF) showed that eight of the analyzed models (models initialized with evaporation estimated by the method of Penann Motheith-modified) 3 have a higher frequency of dry events, have a third event frequency wet and two models showing no meaningful analyzes approaching the curve generated by the series of observed flows. As for seasonal analysis of the flow is observed that when using the method of Penann Motheith modified to evaporation (initialization SMAP) values of flow rates become smaller than the values obtained by series generated by the hydrologic model initialized with evaporation provided by INMET , relating the new century, the twentieth century.

Historically, hydrologic models have been available only on mainframe computers and have therefore not been used by local water managers to support daily decisions. The development of the microcomputer presents an opportunity for that to change. Mathematical models of soil moisture and river routing are selected, developed and tested for use on a microcomputer as an aid to local water management. The models are then integrated with an appropriate data base in a computer program written for a microcomputer. The result is a Decision Support System for local water managers. In order to evaluate the feasibility of using the Decision Support System, an application of the program to a small hypothetical river and irrigation system is carried out. The speed of execution indicates that the use of the Decision Support System on this class of computer under the present configuration may be possible if software or hardware changes can reduce data transfer times to and from disk.

"May 2002" Includes list of papers published during this study Errata slip inserted inside back cover of v. 1 Includes bibliographical references (leaves 331-357) V. 1. [Text} -- v. 2. Appendices Develops an alternative design flood estimation methodology. Establishing a relationship between catchment characteristics and the rainfall excess frequency duration proportions enables the definition of these proportions for generic catchment types, increasing the potential for translation to catchments with limited data but similar hydrographic properties, thereby improving design process.