Dissertations / Theses on the topic 'Early water system'
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Baker, Lee. "Evolution of water reservoirs in the early solar system through their oxygen isotopic composition." Thesis, n.p, 2001. http://oro.open.ac.uk/19051/.
Full textMcAdam, Margaret M. "Water in the Early Solar System| Infrared Studies of Aqueously Altered and Minimally Processed Asteroids." Thesis, University of Maryland, College Park, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10623671.
Full textThis thesis investigates connections between low albedo asteroids and carbonaceous chondrite meteorites using spectroscopy. Meteorites and asteroids preserve information about the early solar system including accretion processes and parent body processes active on asteroids at these early times. One process of interest is aqueous alteration. This is the chemical reaction between coaccreted water and silicates producing hydrated minerals. Some carbonaceous chondrites have experienced extensive interactions with water through this process. Since these meteorites and their parent bodies formed close to the beginning of the Solar System, these asteroids and meteorites may provide clues to the distribution, abundance and timing of water in the Solar nebula at these times. Chapter 2 of this thesis investigates the relationships between extensively aqueously altered meteorites and their visible, near and mid-infrared spectral features in a coordinated spectral-mineralogical study. Aqueous alteration is a parent body process where initially accreted anhydrous minerals are converted into hydrated minerals in the presence of coaccreted water. Using samples of meteorites with known bulk properties, it is possible to directly connect changes in mineralogy caused by aqueous alteration with spectral features. Spectral features in the mid-infrared are found to change continuously with increasing amount of hydrated minerals or degree of alteration. Building on this result, the degrees of alteration of asteroids are estimated in a survey of new asteroid data obtained from SOFIA and IRTF as well as archived the Spitzer Space Telescope data. 75 observations of 73 asteroids are analyzed and presented in Chapter 4. Asteroids with hydrated minerals are found throughout the main belt indicating that significant ice must have been present in the disk at the time of carbonaceous asteroid accretion. Finally, some carbonaceous chondrite meteorites preserve amorphous iron-bearing materials that formed through disequilibrium condensation in the disk. These materials are readily destroyed in parent body processes so their presence indicates the meteorite/asteroid has undergone minimal parent body processes since the time of accretion. Presented in Chapter 3 is the spectral signature of meteorites that preserve significant amorphous iron-bearing materials and the identification of an asteroid, (93) Minerva, that also appears to preserve these materials.
Price, Amina, and n/a. "Utilisation of Still-Water Patches by Fish and Shrimp in a Lowland River, With Particular Emphasis on Early-Life Stages." University of Canberra. Applied Science, 2007. http://erl.canberra.edu.au./public/adt-AUC20081202.090600.
Full textTang, Gula. "Research on distributed warning system of water quality in Mudan river based on EFDC and GIS." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAD023/document.
Full textSimulation and Early Warning System (SEWS) is a powerful tool for river water quality monitoring. Mudan River, an important river in northeastern cold regions of China, can run out of China into Russia. Thus, the water quality of Mudan River is highly concerned not only locally andregionally but also internationally. Objective of this study is to establish an excellent SEWS of water quality so that the spatio-temporal distribution of water quality in both open-water and ice-covered periods can be accurately simulated and visualized to understand the spatial variation of pollutants along the river course. The dissertation is structured into 7 chapters, chapter 1 outlines the background of the study and reviews the current progress. Chapter Il compares the main available models for evaluating river water quality so that a better model can be selected as the basis to establish a modeling system for Mudan River. Chapter Ill establishes the model, the required boundary conditions and parameters for the model were verified and calibrated. Chapter IV, a distributed simulation procedure was designed to increase the simulation efficiency. Chapter V discusses more about the programing and operational issues of the distributed simulation. Chapter VI is about the core techniques to implement the system. Chapter VII is the conclusion of the study to summarize the key points and innovations of the study. The study has the following three points as innovation : a two-dimensional environmental fluid dynamics model for Mudan River, an efficient distributed model computational method and a prototype of SEWS, which can greatly improve the capability of monitoring and management of water quality in Mudan River and other similar rivers
TINELLI, SILVIA. "Monitoring, early detection and warning systems for contamination events in water distribution networks." Doctoral thesis, Università degli studi di Pavia, 2018. http://hdl.handle.net/11571/1214885.
Full textBode, Felix [Verfasser], and Wolfgang [Akademischer Betreuer] Nowak. "Early-warning monitoring systems for improved drinking water resource protection / Felix Bode ; Betreuer: Wolfgang Nowak." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2018. http://d-nb.info/1179787218/34.
Full textBrettle, Matthew John. "Sedimentology and high-resolution sequence stratigraphy of shallow water delta systems in the early Marsdenian (Namurian) Pennine Basin, Northern England." Thesis, University of Liverpool, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367677.
Full textDuncan, Andrew Paul. "The analysis and application of artificial neural networks for early warning systems in hydrology and the environment." Thesis, University of Exeter, 2014. http://hdl.handle.net/10871/17569.
Full textAland, Jenny, and n/a. "Art and design education in South Australian Schools, from the early 1880s to the 1920s: the influence of South Kensington and Harry Pelling Gill." University of Canberra. Education, 1992. http://erl.canberra.edu.au./public/adt-AUC20050601.145749.
Full textWitt, Tanja Ivonne [Verfasser], Thomas R. [Akademischer Betreuer] Walter, Bernd [Akademischer Betreuer] Zimanowski, Magnus Tumi [Gutachter] Gudmundsson, and Helge [Gutachter] Gonnermann. "Camera Monitoring at volcanoes : Identification and characterization of lava fountain activity and near-vent processes and their relevance for early warning systems / Tanja Ivonne Witt ; Gutachter: Magnus Tumi Gudmundsson, Helge Gonnermann ; Thomas R. Walter, Bernd Zimanowski." Potsdam : Universität Potsdam, 2018. http://d-nb.info/1218404205/34.
Full textNOTARANGELO, NICLA MARIA. "A Deep Learning approach for monitoring severe rainfall in urban catchments using consumer cameras. Models development and deployment on a case study in Matera (Italy) Un approccio basato sul Deep Learning per monitorare le piogge intense nei bacini urbani utilizzando fotocamere generiche. Sviluppo e implementazione di modelli su un caso di studio a Matera (Italia)." Doctoral thesis, Università degli studi della Basilicata, 2021. http://hdl.handle.net/11563/147016.
Full textNegli ultimi 50 anni, le alluvioni si sono confermate come il disastro naturale più frequente e diffuso a livello globale. Tra gli impatti degli eventi meteorologici estremi, conseguenti ai cambiamenti climatici, rientrano le alterazioni del regime idrogeologico con conseguente incremento del rischio alluvionale. Il monitoraggio delle precipitazioni in tempo quasi reale su scala locale è essenziale per la mitigazione del rischio di alluvione in ambito urbano e periurbano, aree connotate da un'elevata vulnerabilità. Attualmente, la maggior parte dei dati sulle precipitazioni è ottenuta da misurazioni a terra o telerilevamento che forniscono informazioni limitate in termini di risoluzione temporale o spaziale. Ulteriori problemi possono derivare dagli elevati costi. Inoltre i pluviometri sono distribuiti in modo non uniforme e spesso posizionati piuttosto lontano dai centri urbani, comportando criticità e discontinuità nel monitoraggio. In questo contesto, un grande potenziale è rappresentato dall'utilizzo di tecniche innovative per sviluppare sistemi inediti di monitoraggio a basso costo. Nonostante la diversità di scopi, metodi e campi epistemologici, la letteratura sugli effetti visivi della pioggia supporta l'idea di sensori di pioggia basati su telecamera, ma tende ad essere specifica per dispositivo scelto. La presente tesi punta a indagare l'uso di dispositivi fotografici facilmente reperibili come rilevatori-misuratori di pioggia, per sviluppare una fitta rete di sensori a basso costo a supporto dei metodi tradizionali con una soluzione rapida incorporabile in dispositivi intelligenti. A differenza dei lavori esistenti, lo studio si concentra sulla massimizzazione del numero di fonti di immagini (smartphone, telecamere di sorveglianza generiche, telecamere da cruscotto, webcam, telecamere digitali, ecc.). Ciò comprende casi in cui non sia possibile regolare i parametri fotografici o ottenere scatti in timeline o video. Utilizzando un approccio di Deep Learning, la caratterizzazione delle precipitazioni può essere ottenuta attraverso l'analisi degli aspetti percettivi che determinano se e come una fotografia rappresenti una condizione di pioggia. Il primo scenario di interesse per l'apprendimento supervisionato è una classificazione binaria; l'output binario (presenza o assenza di pioggia) consente la rilevazione della presenza di precipitazione: gli apparecchi fotografici fungono da rivelatori di pioggia. Analogamente, il secondo scenario di interesse è una classificazione multi-classe; l'output multi-classe descrive un intervallo di intensità delle precipitazioni quasi istantanee: le fotocamere fungono da misuratori di pioggia. Utilizzando tecniche di Transfer Learning con reti neurali convoluzionali, i modelli sviluppati sono stati compilati, addestrati, convalidati e testati. La preparazione dei classificatori ha incluso la preparazione di un set di dati adeguato con impostazioni verosimili e non vincolate: dati aperti, diversi dati di proprietà del National Research Institute for Earth Science and Disaster Prevention - NIED (telecamere dashboard in Giappone accoppiate con dati radar multiparametrici ad alta precisione) e attività sperimentali condotte nel simulatore di pioggia su larga scala del NIED. I risultati sono stati applicati a uno scenario reale, con la sperimentazione attraverso una telecamera di sorveglianza preesistente che utilizza la connettività 5G fornita da Telecom Italia S.p.A. nella città di Matera (Italia). L'analisi si è svolta su più livelli, fornendo una panoramica sulle questioni relative al paradigma del rischio di alluvione in ambito urbano e questioni territoriali specifiche inerenti al caso di studio. Queste ultime includono diversi aspetti del contesto, l'importante ruolo delle piogge dal guidare l'evoluzione millenaria della morfologia urbana alla determinazione delle criticità attuali, oltre ad alcune componenti di un prototipo Web per la comunicazione del rischio alluvionale su scala locale. I risultati ottenuti e l'implementazione del modello corroborano la possibilità che le tecnologie a basso costo e le capacità locali possano aiutare a caratterizzare la forzante pluviometrica a supporto dei sistemi di allerta precoce basati sull'identificazione di uno stato meteorologico significativo. Il modello binario ha raggiunto un'accuratezza e un F1-score di 85,28% e 0,86 per il set di test e di 83,35% e 0,82 per l'implementazione nel caso di studio. Il modello multi-classe ha raggiunto un'accuratezza media e F1-score medio (macro-average) di 77,71% e 0,73 per il classificatore a 6 vie e 78,05% e 0,81 per quello a 5 classi. Le prestazioni migliori sono state ottenute nelle classi relative a forti precipitazioni e assenza di pioggia, mentre le previsioni errate sono legate a precipitazioni meno estreme. Il metodo proposto richiede requisiti operativi limitati, può essere implementato facilmente e rapidamente in casi d'uso reali, sfruttando dispositivi preesistenti con un uso parsimonioso di risorse economiche e computazionali. La classificazione può essere eseguita su singole fotografie scattate in condizioni disparate da dispositivi di acquisizione di uso comune, ovvero da telecamere statiche o in movimento senza regolazione dei parametri. Questo approccio potrebbe essere particolarmente utile nelle aree urbane in cui i metodi di misurazione come i pluviometri incontrano difficoltà di installazione o limitazioni operative o in contesti in cui non sono disponibili dati di telerilevamento o radar. Il sistema non si adatta a scene che sono fuorvianti anche per la percezione visiva umana. I limiti attuali risiedono nelle approssimazioni intrinseche negli output. Per colmare le lacune evidenti e migliorare l'accuratezza della previsione dell'intensità di precipitazione, sarebbe possibile un'ulteriore raccolta di dati. Sviluppi futuri potrebbero riguardare l'integrazione con ulteriori esperimenti in campo e dati da crowdsourcing, per promuovere comunicazione, partecipazione e dialogo aumentando la resilienza attraverso consapevolezza pubblica e impegno civico in una concezione di comunità smart.
Yang, Kuo-Cheng, and 楊國城. "Early Warning System for Water Chiller Unit and Empirical Study." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/j9vu79.
Full text元智大學
資訊管理學系
106
With the advanced development of information and communication technology, new device has been presented based on the internet of things (IoTs). Integration of IoTs and cloud computing gradually changed the style of operations and productions in modern manufacturing industry. To maintain the normal operation of production equipment and avoid the unexpected failure of downtime, the preventative maintenance (PM) was used for regular testing and manual inspection. However, it’s difficult to monitor the condition of equipment in real time. Predictive maintenance (PDM ) use the sensor data or other information collected from the equipment monitoring system to evaluate the production line equipment before failure, and determine the maintenance schedule adaptively. This study aims to propose an IoTs framework with three-level layers, including hardware sensing layer, the network information layer, and application layer. First, each device via the sensor technology is used to collect sensor data in the hardware perception layer. Second, the sensor data are transferred to the designated equipment or the storage area in the network information layer. Then, long short-term memory model is used for building prediction models. Third, a graphical visual management interface for decision making is constructed in the application layer. To evaluate the validity of the proposed framework, a water chiller unit equipped new sensor device was used for building early-warning decision support system. The results demonstrate how to build the equipment engineering capability with sensor device and thus to improve the efficiency of industrial operation in a smart factory.
Yuan, Lun-Chin, and 袁倫欽. "Studies on Reservoir Water Supply Operation and Drought Early Warning System." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/60770356121383456152.
Full text國立臺灣海洋大學
河海工程學系
93
In practice, “rule curve”generally regulates reservoir operation. In an area of uneven water distribution, reservoir can stabilize the water flow to mitigate water problems. Therefore, a task to operate reservoirs efficiently is essential.However, operating by rule curves can’t fit the demand efficiently during dry season, and the operation of rule curves by single reservoir also works inefficiently. In addition, drought events hit Taiwan frequently in recent years, and which brought immense impacts to people’s daily life. Unfortunately, the drought early warning system in Taiwan is not well developed, and the alert categories are in their infancy and quite vague in their definitions. This study gives an example as the two-parallel joint operation between Feitsui and Shismen reservoir in northern Taiwan. The objectives are:(1)to select the optimum reservoir operating alternative for single use. (2)to develop the joint long-term reservoir operating rule curves for conjunctive use.(3)to build a handy early warning system for drought management to reduce the impacts. In this study, a lexicographic method is used to select the operation alternative for the Feitsui reservoir. Simulation results show that the alternative, the limitation of water supply by Taipei city government during the fight against 2002 drought, would be the best in terms of minimum shortage. On the other hand, the alternative, the new rules after May 31 2004, would be selected in terms of maximum water utilization. However, alternative of new rules need an assistance of the Drought Early Warning System to reduce its high risk of reservoir emptiness. Furthermore, the joint operation between Feitsui and Shihmen reservoir system is selected to demonstrace its applicability of the GA-based simulation model on a complex water resource system. In the multiple reservoir model, simulation results show Feitsui's surplus water can be utilized efficiently to fill Shihmen's deficit water without affecting Feitsui's main purpose as Taipei city's water supply. The optimal joint operation suggests that Feitsui, on average, can provide 650,000 m3/day and 850,000 m3/day to Shihmen during the wet season and dry season, respectively. In this research, a color-coded early warning system is also developed and proposed for drought management on the real-time reservoir operation. The system consists of three essential elements, namely, (a) drought watch, (b) water consumption measure, and (c) policy making. A new Drought Alert Index is used to characterize the alert level of drought severity. For demonstration, the drought warning procedures were effectively applied to historical droughts from dry condition to wet situation. The implementation of such a system proves that the decision support-like system can help the water authorities concerned take a timely action while confronting drought threats.
Lee, Ting-Chuan, and 李庭鵑. "A Long-Term Early Warning System for Climate Change Impacts on Sustainable Water Quality Management." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/17220569199268899528.
Full text國立臺灣大學
生物環境系統工程學研究所
95
Climate Change impacts not only on individual situation but on short-term variation and on long-term gradually changes. This kind characteristic should adopt the suitable environmental management with long-term formulation and short-term operation in sure keeping environmental sustainability as social economy developing using environmental resource. In this article, the climate change assessment has been combined to set up an early warning system for a river, and focus on analyzing climate change impacts on water quality and stream assimilative capacity. The issue of warning period is also discussed, and furthermore, the adaptative strategies are provided and evaluated. However, there is a problem for establishing an early warning system that estimate future climate changes would be faced with high uncertainty. In general, take estimations would use global scale GCMs data but too rough-cut for estimating a smaller region, such a stream area. In order to get over the problem, the statistic downscaling model (SDSM) has been used for regional analysis and the data is applied for Touchen River in North Taiwan. The result shows that after downscaling can display regional characteristics reasonably. Farther, the data analysis also shows that in arid period, the concentration of BOD is growing worse. The BOD assimilative capacity of a river is confronted by decreasing. For understanding when will suffer the risk, not only climate change assessment but also local evolution will include to establish an early warning indicator (EWI) for analyzing the warning period, and then, to estimate the optimal strategy and when should take action. Furthermore, the acting warning will be alerted. For sustainable development, both bioenvironmental sustainability and social economy development are important. How to find a compromising point between human development and natural conservation is crucial. But climate changes impacts throw down the gage to our resource. To avoid the impacts, by impacts assessment we establish an early warning system for early warning what risk is, when risk will happen, and how we choose the optimal strategy for planning the course of management. Hopefully by setting up the framework of early warning system can defend stream area form impacts damaging and in sure the sustainable development.
Swanepoel, Annelie. "Early warning system for the prediction of algal-related impacts on drinking water purification / Annelie Swanepoel." Thesis, 2015. http://hdl.handle.net/10394/15590.
Full textPhD (Botany), North-West University, Potchefstroom Campus, 2015
Lin, Huang-Ming, and 林晃民. "Breeding, Embryology, Early Ontogeny, and Mass-scale Cultivation of The Anemone Fish (Amphiprion ocellaris var.) In Close-circulating Water System." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/tr8h3a.
Full text國立澎湖科技大學
水產資源與養殖研究所
102
Marine ornamental fish industry is considered as one of the six key emerging industries in the future Taiwan. Recently, researches on anemone fish breeding, cultivation, and farming are proliferation worldwide; however, studies on mass-scale cultivation of anemone fish are scarce. The major limitation and obstacle to industrial-scale cultivation of anemone fish is the high mortality resulting from diseases during the process of cultivation. Hence, the ornamental fish industry stagnated in Taiwan. In present study, the innovated closed water circulation system was applied to prevent the anemone fish from diseases, improve the success rate of breeding pairs, and develop technologies of mass-scale cultivation. Based on the technical support, breeding of commercial hybrids and establishing the provenance library of eye-spot anemone fish (Amphipeion ocellaris) significantly sustain the marine ornamental fish industry in Taiwan. In 10 months of cultivation, a total of 23 pairs of black & white clownfish (Amphiprion ocellaris var.) and black & white clownfish (A. ocellaris var.), 3 pairs of black & white clownfish (A. ocellaris var.) and A. ocellaris, 1 pair of black & white clownfish (A. ocellaris var.) and snowflake clownfish (A. ocellaris var.), and 3 pairs of A. ocellaris and A. ocellaris were successfully matched. The survivorship of the fishes maintained up to 90% during the whole cultivation. The numbers of successfully nurtured 3-cm fries of black & white clownfish, new breed of black & white clownfish × snowflake clownfish, black & white clownfish × clownfish, and clownfish × clownfish are 11000, 1200, 250, and 800, respectively. The results provide the fundamentals for commercial production in future clownfish market.
Gillcrist, Ashley. "Impact of Oasis® Supplement and Lysozyme on Incidence of Early Mortality, Digestive System Development, Growth Performance and Behaviour of Turkey Poults with Delayed Access to Feed and Water." Thesis, 2012. http://hdl.handle.net/10222/15706.
Full textChan, Ya-Ting, and 詹雅婷. "Powder behavior upon laser pulses in water and early stage sintering-coarsening-coalescence kinetics of powder in air:A case study of NiO-Al2O3 system." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/50003360756951541562.
Full text國立中山大學
材料與光電科學學系研究所
101
The first part of this thesis is about pulsed laser ablation of micron size NiAl2O4 spinel powder or NiO-Al2O3 powder mixture in water regarding size/phase changes of the powders. The combined X-ray diffraction and transmission electron microscopic observations indicate that upon laser pulses, the stoichiometric nickel aluminate spinel powder were nanosized and decomposed as atom clusters for further nucleation as Al-doped NiO, Ni-doped -Al2O3 and β-Ni(OH)2 whereas the NiO and Al2O3 powder mixture can also become nanosized β-Ni(OH)2, Al-doped NiO, and Ni-doped -Al2O3 for further composition modification as nonstoichiometric nickel aluminate spinel. The colloidal solution containing the nanosized and hydrated phases in the NiO-Al2O3 system have a bimodal minimum band gap around 5 eV and 3 eV according to UV-visible absorption spectrum for potential photocatalytic applications. In the second part, an onset sintering-coarsening-coalescence (SCC) event of submicron NiO and micron NiAl2O4 powders (1:9 molar ratio) by isothermal firing in the 1300-1450oC range in air was characterized by N2 adsorption-desorption hysteresis isotherm and scanning electron microscopy. The apparent activation energy of such a rapid SCC process for the composite powders was estimated as 329±5 kJ/mol based on 50% change of specific surface area with accompanied formation of cylindrical pores. This SCC process was controlled by the relatively small-sized and less refractory NiO particles shedding light on their Brownian rotation kinetics at the NiAl2O4 grain boundaries. The minimum temperature of the SCC process, as of concern to optocatalytic applications of NiO/NiAl2O4 composite nanoparticles, is 1147oC based on the extrapolation of steady specific surface area reduction rates to null.
Mathivha, Fhumulani Innocentia. "Drought in Luvuvhu River Catchment - South Africa: Assessment, Characterisation and Prediction." Thesis, 2020. http://hdl.handle.net/11602/1522.
Full textDepartment of Hydrology and Water Resources
Demand for water resources has been on the increase and is compounded by population growth and related development demands. Thus, numerous sectors are affected by water scarcity and therefore effective management of drought-induced water deficit is of importance. Luvuvhu River Catchment (LRC), a tributary of the Limpopo River Basin in South Africa has witnessed an increasing frequency of drought events over the recent decades. Drought impacts negatively on communities’ livelihoods, development, economy, water resources, and agricultural yields. Drought assessment in terms of frequency and severity using Drought Indices (DI) in different parts of the world has been reported. However, the forecasting and prediction component which is significant in drought preparedness and setting up early warning systems is still inadequate in several regions of the world. This study aimed at characterising, assessing, and predicting drought conditions using DI as a drought quantifying parameter in the LRC. This was achieved through the application of hybrid statistical and machine learning models including predictions via a combination of hybrid models. Rainfall and temperature data were obtained from South African Weather Service, evapotranspiration, streamflow, and reservoir storage data were obtained from the Department of Water and Sanitation while root zone soil moisture data was derived from the NASA earth data Giovanni repository. The Standardised Precipitation Index (SPI), Standardised Precipitation Evapotranspiration Index (SPEI), Standardised Streamflow Index (SSI), and Nonlinear Aggregated Drought Index (NADI) were selected to assess and characterise drought conditions in the LRC. SPI is precipitation based, SPEI is precipitation and evapotranspiration based, SSI is based on streamflow while NADI is a multivariate index based on rainfall, potential evapotranspiration, streamflow, and storage reservoir volume. All indices detected major historical drought events that have occurred and reported over the study area, although the precipitation based indices were the only indices that categorised the 1991/1992 drought as extreme at 6- and 12- month timescales while the streamflow index and multivariate NADI underestimated the event. The most recent 2014/16 drought was also categorised to be extreme by the standardised indices. The study found that the multivariate index underestimates most historical drought events in the catchment. The indices further showed that the most prevalent drought events in the LRC were mild drought. Extreme drought events were the least found at 6.42%, 1.08%, 1.56%, and 4.4% for SPI, SPEI, SSI, and NADI, respectively. Standardised indices and NADI showed negative trends and positive upward trends, respectively. The positive trend showed by NADI depicts a decreased drought severity over the study period. Drought events were characterised based on duration, intensity, severity, and frequency of drought events for each decade of the 30 years considered in this study i.e. between 1986 – 1996, 1996 – 2006, 2006 – 2016. This was done to get finer details of how drought characteristics behaved at a 10-year interval over the study period. An increased drought duration was observed between 1986 - 1996 while the shortest duration was observed between 1996 - 2006 followed by 2006 - 2016. NADI showed an overall lowest catchment duration at 1- month timescale compared to the standardised indices. The relationship between drought severity and duration revealed a strong linear relationship across all indices at all timescales (i.e. an R2 of between 0.6353 and 0.9714, 0.6353 and 0.973, 0.2725 and 0.976 at 1-, 6- and 12- month timescales, respectively). In assessing the overall utilisation of an index, the five decision criteria (robustness, tractability, transparency, sophistication, and extendibility) were assigned a raw score of between one and five. The sum of the weighted scores (i.e. raw scores multiplied by the relative importance factor) was the total for each index. SPEI ranked the highest with a total weight score of 129 followed by the SSI with a score of 125 and then the SPI with a score of 106 while NADI scored the lowest with a weight of 84. Since SPEI ranked the highest of all the four indices evaluated, it is regarded as an index that best describes drought conditions in the LRC and was therefore used in drought prediction. Statistical (GAM-Generalised Additive Models) and machine learning (LSTM-Long Short Term Memory) based techniques were used for drought prediction. The dependent variables were decomposed using Ensemble Empirical Mode Decomposition (EEMD). Model inputs were determined using the gradient boosting, and all variables showing some relative off importance were considered to influence the target values. Rain, temperature, non-linear trend, SPEI at lag1, and 2 were found to be important in predicting SPEI and the IMFs (Intrinsic Mode Functions) at 1, 6- and 12- month timescales. Seven models were applied based on the different learning techniques using the SPEI time series at all timescales. Prediction combinations of GAM performed better at 1- and 6- month timescales while at 12- month, an undecomposed GAM outperformed the decomposition and the combination of predictions with a correlation coefficient of 0.9591. The study also found that the correlation between target values, LSTM, and LSTM-fQRA was the same at 0.9997 at 1- month and 0.9996 at 6- and 12- month timescales. Further statistical evaluations showed that LSTM-fQRA was the better model compared to an undecomposed LSTM (i.e. RMSE of 0.0199 for LSTM-fQRA over 0.0241 for LSTM). The best performing GAM and LSTM based models were used to conduct uncertainty analysis, which was based on the prediction interval. The PICP and PINAW results indicated that LSTM-fQRA was the best model to predict SPEI timeseries at all timescales. The conclusions drawn from drought predictions conducted in this study are that machine learning neural networks are better suited to predict drought conditions in the LRC, while for improved model accuracy, time series decomposition and prediction combinations are also implementable. The applied hybrid machine learning models can be used for operational drought forecasting and further be incorporated into existing early warning systems for drought risk assessment and management in the LRC for better water resources management. Keywords: Decomposition, drought, drought indices, early warning system, frequency, machine learning, prediction intervals, severity, water resources.
NRF
Tyler, John. "A Pragmatic Standard of Legal Validity." Thesis, 2012. http://hdl.handle.net/1969.1/ETD-TAMU-2012-05-10885.
Full text