Master of Engineering in Applied Hydrology
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- item: Thesis-AbstractEvaluation of hydro power potential in Uma Oya basinSiriwardena, WADLW; Kariyawasam, HC; Wickramasooriya, SA substantial quantity of untapped hydro energy will still exist in Sri Lanka, even after the completion of the Accelerated Mahaweli Programme, as still a number of rivers and tributaries will remain unexploited. Hence it is imperative to launch a project on formulating a methodology to calculate the quantity of technically feasible hydro energy of a river basin as accurately as possible. The actual hydropower available depends on technical, economical, political and physiographic factors. This dissertation formulates a methodology to evaluate available hydropower potential in the Uma Oya basin, which is a sub catchment of the river Mahaweli, at four different levels of gross and net potentials. They are, (a) Gross precipitation potential (b) Gross surface runoff potential (c) Gross river potential (d) Net potential with individual reservoirs The relationships between different levels of gross and net potentials are analysed and the technical feasibility of the Uma Oya basin for the development of hydropower is examine
- item: Thesis-AbstractComparison of some techniques for design flood estimationBatuwitage, LP; Wickramasuriya, S; Manchanayake, PSri Lanka, a country with abundant water resources, has a predominantly agriculture oriented economy. Hence, hydrological development plays an important role, not only in the vast irrigation development efforts, but also in meeting the energy requirements of the country through hydro-power. Many hydrologic design problems require simply an estimation of the peak flow rate generated by a river system under specific conditions. Several methods are available for the estimation of peak flow rate, but many of these are quite inadequate to produce results which are consistent within the accuracy required for hydrologic analysis and design. In this study several different flood estimation methods have been considered for sixteen catchments to determine their applicability to Sri Lankan catchments. A frequency analysis is also carried out for each of the catchments and their flood peaks are compared with the design floods obtained by different methods. It is observed that the findings of this thesis lead to various research areas, for further detailed studies with regard to some of the methods of analysis.
- item: Thesis-AbstractRainfall runoff model for Uma-Oya basinEkanayake, STBThe Rainfall-Runoff model presented here could be used to predict the monthly runoff values at the unengaged site of Uma Oya confluence, "and hence monthly runoff values at the Mnipe anicut in the Mahaweli river.'These estimated, monthly runoff values are needed for the operation of the control gates of Minipe right bank and left bank main canals in order to divert water to system B,C and E respectively. Although there are long periods of rain fall records over the Uma Oya basin the availability of runoff records is limited and are available for the two upstream gauging stations at Welimada and Talawa kanda across the Uma Oya . As the location of the Uma Oya confluence is different from the locations of the river gauging stations the model parameters need to be renationalized so that the runoff at any location of the Uma Oya river could be estimated. A deterministic black-box regression model for rainfall-runoff simulation in the two sub-basins at Welimada & Talawakanda is developed. The model is mathematically expressed as; Qp.t = nt [∑_(1=0)^k▒〖a 〗t2l Pip1t] I = 01I………K t = 1.2 …….12 The model structure depends on two key parameters which are; 1. An Order parameter- K (an integer, greater than or equal to 1) 2. A Memory parameter- nt ( t = l,2,3........12) An order parameter K, characterizes the runoff behavior of the Das in .ie. When K=l, the catchment is linear and for K >1, the catchment is non-linear. A memory parameter nt characterizes the memory of the rainfall-runoff process The order parameter K is determined from monthly rainfa 11-runoff functional relationships and the model coefficients 0t,1 are estimated for the same functional relationships by the least-square technique for both sub basins. Finally the model coefficients are regionalized over the Uma Oya basin, so that the model can be used to estimate monthly runoff at the unqauged site of Uma Oya confluence. These estimated runoff values have been compared with the runoff values of observed differences between . Rantambe and Randenigala of Mahaweli river, before application of the model.
- item: Thesis-AbstractAnalysis of pumping test results of North West aquifer using numerical techniquesHangilipola, RMPTB; Senerath, DCHThis report is intended to analyze the pumping test results of North west aquifer using nu1nerical techniqu-2s. The pumping test results were taken from Water Resources Board , Sri Lanka. These pump tests were carried out during the period March l980- m arch l98l. in analyzing the flow to a pumped well, the radial flow can be represented by a differential equation, which is derived from Darcy's law. There are various approaches to solve this differential equation of radial flov1 to an aquifer. These methods are dependent on the type of aquifer and the condition of flow. Therefore suitable method should be selected for particular problem. Most of these approaches are graphical methods. A numerical method was introduced by K.!{. Ruston (Ruston, K.R. & Chan, Y.K. ~976). In graphical methods, the differential equation of radial flov1 are solved using analytical expressions. Generally these analytical expressions contain-~ infinite integrals and summations of higher transcendental functions. Therefore the evaluation of these analytical expressions is sometimes difficult. But the values of aquifer parameters can be obtai;1ed by matching the theoretical curves derived from analytical expressions with the field data. The same differential equation can be solved by using numerical techniques. In one such technique a discrete space -discrete time model is introduced to represent the radial flovJ in an aquifer. Thus, the saoe differential equation for radial flow can be replaced by the discrete space- discrete time numerical mode1 • The number of assumptions can be reduced in using numerical technique compared to the graphical methods. In addition to that, most of the actual field conditions can be included in to a single numerical solution. These field conditions are leakage, variable saturated depth
- item: Thesis-AbstractA preliminary study of the spatial variation of rainfall and its effect on water management in the dry zoneRavindra, PS; Kumaraswamy, NIncorporating effective rainfall in irrigation water is an important task in water management. Understanding the climatic conditions is necessary to plan a raingauge network. The occurrence of thunderstorms is a main feature in the intermonsoonal periods. These convective storms are often highly localized and usually tend to be less than 8 km in width. Thus a fairly dense network of raingauges is necessary to get an accurate representation of the rainfall during these periods. However, when the rainfall is widespread, the maintenance of such a dense raingauge network is not essential. Paddy production in Sri Lanka is more influenced by rainfall in the Maha (October to February) season than in the Yala (May to August), as there is hardly any rain in the Yala season in most of the paddy growing areas. For the Maha crop, land preparation usually starts in October. About 28 percent of the annual rainfall occurs in October and November (second intermonsoonal period) and is mostly of the convective type. With a proper understanding of the areal rainfall distribution during this period conserving irrigation water is possible. The use of isohyetal patterns, correlation coefficient vs. distance diagrams and correlation linkage diagrams could be used to assess an optimum spacing between the raingauges. Using a triangular storm model, it can be shown that negative correlation values between pairs of raingauges, are due to smaller storm cells. Further, it can be shown when the storm width is approximately three times the width of the gauged area then no negative correlation can occur between the raingauges. A square grid of raingauges at about 2 km intervals is necessary during the period of the convective storms while a 14 km grid is required for the widespread monsoonal storm period. This study indicates an area where more research work is required for better water management and it is possible to achieve this within the normal level of management and would also yield considerable economic benefits.
- item: Thesis-AbstractHydrology of Mahakanadarawa schemeGunasekara, TAG; Kariyawasam, CHarnessing the nature's gift of water resources abundantly available, has been the daunting task of Sri Lankan life over hundreds of generations. Evidence of great historical hydraulic developments are standing monuments of golden eras scattered along the long history of this island country, better known as the paradise of South-East Asia. The country is once again experiencing another chapter of intensive water resources development. Present day engineers are faced with the challenge of putting their sound theoretical knowledge into useful practice, with the primary objective of transforming the gift of naturally available water resources into invaluable sources of socio economic development of the nation. In an effort of further supplementing this task, .University of Moratuwa offer & opportunities for the young engineers to do Post-Graduate studies in the field of water resources. Author of this dissertation is one of such fortunate students, who was a participant in the Post Graduate Diploma/ Master of Engineering degree course in Applied Hydrology, commenced in October 1982. This dissertation titled "HYDHOLOGY OF MAHAHAKANADARAWA SCHEME" is submitted in partial fulfilment of Masters degree requirements in Engineering. Mahakanadarawa, another major irrigation scheme of the golden history of Sri Lanka, has been restored once again by the government just after the independence in 1948. However the project poses serious problems owing to its continuous water shortages. Preliminary studies suggested that excessive exploitation of the catchment by restoring large numbers of minor tanks may be a basic reason for such shortages of water in the major tank. This problem had been common to few other reservoirs in the dry zone of Sri Lanka, as well. An effort has been made in this dissertation to analyse this situation in detail, through a computerised water balance analysis, integrating all the minor tanks in the catchment. A generalised computer programme has been developed for the water balance study. Once the cause is first established, further effort has been made to suggest remedial measures such as augmenting the Mahakanadarawa tank through additional sources of water either from nearby catchments or from the Mahaweli waters diverted to the dry North Central regions of the country. Author wishes to note his sincere gratitude to all those who assisted him in his challenging task o£ making this dissertation a success in every aspect o£ it. Details o£ the particular assistance given by them are mentioned under title "ACKNOWLEDGEMENT" next. It is hoped that the finding of this dissertation will eventually bring about desired results and constitute another significant contribution to the gigantic water resources development e££ort aimed at building an economically strong, prosperous Sri Lanka.
- item: Thesis-AbstractApplication of the probability matrix method to the Labugama & Kalatuwawa reservoirsSiriwardane, LS; Wickramasuriya, SSThe research considers the application probability Matrix Method to Labugama and of the Kalatuwawa reservoirs and storage-draft-probability of failure relationships have been derived. The study shows that preliminary design procedures using the Mass Curve Method/Residual Mass Curve Method also give useful results which can be used in the Probability Matrix Method. The Probability Matrix Method requires a relatively large computational effort. It has been observed that for satisfactory results a large number of zones are needed in the analysis without which the hunting effect arises.