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Published Article / A stream flow at an outlet of a catchment can be entirely a base flow or direct flow or a combination of both. The base flow component of a stream is mainly contributed from the ground water storage which often is an open aquifer whereas the direct flow component is mainly the result of a direct response of a rainfall event. The Upper Modder river basin catchment is considered to be the origin of the Modder River which supplies water to Rustfontein Dam, situated at the outlet of the C52A with an area of 928 km2. Nine years of daily stream flow showed a continuous none zero discharge throughout the year. During the rainy season the discharge of the stream increases significantly. Thus, it is necessary to separate the direct and base flow of the stream in order to understand the important component that is more likely to be affected by different land use changes in a catchment. The Modder river daily mean flow at the inlet of Rustfontein dam (in Central South Africa) was analysed using four base flow separation methods, the Nathan & McMahon (N&M), the Chapman, Smakhtin & Watkins (S&W) method and the frequency duration analysis. All the methods gave higher percentage of the low flow component, except for the S&W method which underestimated it. The N&M filtering equation gave base flow components greater than 66% in 1999 and increased to 84% in 2007 while the Chapman equation revealed 65% and 74% in 1999 and 2007, respectively. Similarly, the frequency duration analysis gave 62% in 1999 and increased to 79% in 2007. The frequency duration analysis gave up to 13% lower percentage than the N&M (1990) filtering equation. The nine year base flow averages are 69%, 69% and 75% for frequency duration analysis, Chapman (1999) and N&M (1990) filtering equations, respectively. The result revealed that the Modder River is largely supplied by the ground water discharge. The result seemed to concur with the fact that for a semi-arid catchment such as the Modder river basin, with an average annual runoff coefficient of approximately 6%, the contribution of annual rainfall to direct runoff is very minimal.

No description available.

This study examines the relationship between baseflow and urbanization over time with the help of spatial analysis using Geographic Information Systems. The urbanization parameters used were population and urban land use. Five urban and three non-urban streams were chosen for analysis in the state of Georgia. Four percentile baseflows for each stream were identified and analyzed for trends over time. A correlation analysis was also run to determine how baseflow varies as a function of urbanization. According to the trend analysis, the baseflows over time were considered stable or had no statistically significant trend. The correlation analysis between baseflow and urbanization revealed some scattered relationships though a general conclusion cannot be drawn. The simplicity of the study may have contributed to not capturing all of the baseflow changes with the urbanization parameters.

The slope-area method is a commonly used and widely accepted technique for estimating peak flood flows in rivers where direct discharge measurements could not be obtained during the flood. The method makes multiple assumptions to simplify calculations which include assuming uniform flow conditions between surveyed cross sections, and that losses of energy in the reach occur only due to bank friction. Even though flows in nature do not always exhibit these simplified conditions, this method has been proven to provide adequate results when compared to direct measurements and thus, has become the go-to approach. To conduct a slope-area computation, the hydrologist needs to make multiple assumptions in the field based on experience, judgment, and published resources as guides. One of these assumptions is determining where to locate cross sections for the slope-area computation such that they sufficiently represent the cross-sectional area and slope of the channel. Traditional methods suggest to place the cross sections at breaks in the water surface slope. This research focuses on the variability of results of computed discharge values when cross sections are located at many different locations in the reach. What has been found is that many combinations of cross sections in the reach, including sections not located at the breaks in water surface slope, produce similar results when compared to the traditional methods. In fact, 121 of these combinations of cross sections produce peak discharge calculations within plus or minus five percent of the traditional methodology. What also was found was that variability in channel geometry goes unnoticed when using the traditional locating method, and losses due to expansion and contraction of flow area at locations which would not have been traditionally surveyed are occurring at multiple cross sections in the reach. The results suggest that reaches be evaluated for changes in geometry and not overlooked, so that the changes in shape, and subsequent losses in energy, be considered in the computation.

Content removed due to copy right restriction: Dewson, Z.S., Death, R.G. & James, A.B.W. (2003) The effects of water abstractions on invertebrate communities in four small North Island streams. New Zealand natural Sciences 28, 51-65. / Small streams are often used for small-scale water abstractions, but the effects of these water abstractions on the instream environment, invertebrate communities and ecosystem functioning of small permanent streams is poorly understood. This research extends current knowledge by surveying existing water abstractions and completing flow manipulation experiments in the field. Reduced discharge often decreases water velocity, water depth, and wetted channel width and can increase sedimentation, modify the thermal regime and alter water chemistry. In a survey of sites upstream and downstream of existing water abstractions, I found that downstream sites had higher densities of invertebrates, but fewer taxa sensitive to low water quality compared with upstream sites. There were greater differences in physicochemical characteristics such as velocity and conductivity and in invertebrate communities between upstream and downstream sites on streams where a larger proportion of total discharge was abstracted. Using before-after, control-impact (BACI) designed experiments, weirs and diversions were created to experimentally decrease discharge by over 85% in each ot three small streams, ranging from pristine to low water quality. The response of invertebrates to short-term (one-month) discharge reduction was to accumulate in the decreased available area, increasing local invertebrate density. After a year of reduced flow, the density of invertebrates and percentage of mayflies, stoneflies and caddisflies decreased at the pristine site, whereas only taxonomic richness decreased at the mildly polluted stream. Reduced discharge had no affect on the invertebrate community at the stream with the lowest water quality. Reduced discharge had little influence on leaf decomposition rates, but distances travelled by released coarse particulate organic matter (CPOM) increased with increasing discharge. The effects of reduced discharge on primary production were not consistent between streams. Overall, the severity (magnitude/duration) of flow reduction appeared to influence invertebrate responses to water abstraction although the outcomes of water abstraction were dependent on the invertebrate assemblage present in each stream.

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / This study aims to develop a planning system on multiple spatial and temporal scales, and apply it to the Brazilian electric sector and Cearà State, Jaguaribe Metropolitan System. For realization of this proposal, we have been considered some temporal scales: short-term (up to 1 month), short term (up to one year) and medium to long term (1-10 years and 10-30 years, respectively). To obtain estimates of the flow of short-term rainfall forecasts from atmospheric models for later entry in the hydrological rainfall-runoff model are used. To short term scale were considered stochastic and statistical models, as the Periodic Autoregressive type (PAR), Periodic Autoregressive with exogenous variables (PARx) and K-nearest neighbor models, and the use of global atmospheric models as input to hydrological rainfall-runoff model Soil Moisture Accounting Procedure (SMAP). For the range of the medium term were considered auto regressive models (AR) and Fourier and wavelets. We used data from the Coupled Model Intercomparison Project Phase 5 (CMIP5) as input in hydrological rainfall-runoff model for long-term scale. For the weather forecast, as the rain threshold adopted in the construction of the contingency table increases, the quality of the forecasts decreases, except for the adjustment index. Thus, the system of numerical prediction proves efficient in detecting the occurrence of rainfall of less intensity, with most satisfactory results in the North and Northeast regions of Brazil. On seasonal scale the models feature up better than the climatology. Likewise, in the range of medium-term models based on Fourier series and wavelets have better likelihood than the weather. In multi-scale, there are differences in the future shown by the projections of the CMIP5 models that were analyzed for RCP8.5 and RCP4.5 the XXI century scenarios, but in the North sector of the National Interconnected System (SIN), most models indicate negative trend, diverging only in magnitude. / O presente trabalho visa elaborar um sistema de planejamento em mÃltiplas escalas temporais e espaciais e aplicÃ-lo ao setor elÃtrico brasileiro e ao sistema Jaguaribe-Metropolitano do Estado do CearÃ. Para realizaÃÃo desta proposta, foram consideradas algumas escalas temporais: curtÃssimo prazo (atà um mÃs), curto prazo (atà um ano) e mÃdio e longo prazo (1 a 10 anos e atà 30 anos, respectivamente). Para obtenÃÃo das previsÃes de vazÃes de curtÃssimo prazo sÃo utilizadas as previsÃes de precipitaÃÃo a partir de modelos atmosfÃricos, para posterior entrada no modelo hidrolÃgico chuva-vazÃo. Para escala de curto prazo foram considerados modelos estocÃsticos e estatÃsticos, como do tipo PeriÃdico Autorregressivo (PAR), PeriÃdico Autorregressivo com variÃveis exÃgenas (PARx) e K-vizinhos, e o uso de modelos atmosfÃricos globais como entrada do modelo hidrolÃgico chuva-vazÃo Soil Moisture Accounting Procedure (SMAP). Na escala de mÃdio prazo foram considerados modelos autorregressivos (AR) e as transformadas de Fourier e ondeletas. Para escala de longo prazo foram utilizados dados provenientes do Coupled Model Intercomparison Project Phase 5 (CMIP5) como dados de entrada no modelo hidrolÃgico chuva-vazÃo. Quanto à previsÃo de tempo, à medida que o limiar de chuva adotado na construÃÃo da tabela de contingÃncia aumenta, a qualidade das previsÃes diminui, exceto para o Ãndice acerto. Dessa forma, o sistema de previsÃo numÃrica mostra-se eficiente em detectar a ocorrÃncia de chuvas de menor intensidade, apresentando resultados mais satisfatÃrios nas regiÃes Norte e Nordeste do Brasil. Na escala sazonal, os modelos apresentam-se melhor que a climatologia. Da mesma forma, na escala de mÃdio prazo, os modelos baseados na sÃrie de Fourier e ondeletas apresentam melhor verossimilhanÃa do que a climatologia. Na escala plurianual, hà divergÃncias quanto ao futuro mostrado pelas projeÃÃes dos modelos do CMIP5 que foram analisados para os cenÃrios RCP8.5 e RCP4.5 do sÃculo XXI, porÃm no setor Norte do Sistema Interligado Nacional (SIN), a maioria dos modelos sinaliza tendÃncia negativa, divergindo apenas em magnitude.

Submitted by Mario BC (mario@bc.ufrpe.br) on 2016-05-20T16:02:58Z No. of bitstreams: 1 Diego Vicente de Souza Ferreira.pdf: 4348458 bytes, checksum: d170ec08e8b19561b0eff75d6b69c040 (MD5) / Made available in DSpace on 2016-05-20T16:02:58Z (GMT). No. of bitstreams: 1 Diego Vicente de Souza Ferreira.pdf: 4348458 bytes, checksum: d170ec08e8b19561b0eff75d6b69c040 (MD5) Previous issue date: 2016-02-18 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this work we analyze the complexity of stream flow in the São Francisco River and hot-pixels detected in Amazonia, in order to evaluate the effects of human activity. Permutation entropy is employed which takes into account temporal causality by comparing consecutive values within the series. We also use this entropy method to analyze rainfall regime in Pernambuco, Brazil. For the São Francisco River, we analyze the influence of the Sobradinho dam construction on the hydrological regime. The results show that entropy of stream flow increases after the dam’s construction in 1979, which indicates more disordered and less predictable dynamics. For hot-pixels detected in Amazonia, the increase in entropy is related to severe droughts in 2005, 2007, and 2010. For temporal series of precipitation in Pernambuco, entropy values decrease with distance from the coast, indicating more predictability of monthly rainfall in the zona de mata and agreste regions, and less predictable rainfall dynamics in the sertão and vale do São Francisco regions. / Neste trabalho foi analisada a complexidade das séries temporais de vazão do rio São Francisco e de queimadas na Amazônia, para avaliar as alterações causadas pela atividade humana. Utilizou-se o método entropia de permutação (Permutation entropy) que incorpora a relação temporal entre os valores da série analisada, utilizando uma representação simbólica baseada na comparação dos valores consecutivos da série. Este método também foi usado para analisar regime de chuva de Pernambuco. Para a vazão do rio São Francisco avaliou se a influência da construção da barragem Sobradinho no regime hidrológico. Os resultados das análises da série temporal de vazão para o período 1929-2009 mostraram que a entropia aumentou depois da construção da barragem Sobradinho indicando uma dinâmica de vazão mais desordenada e menos previsível neste período. Os resultados obtidos para série temporal diária de queimadas detectadas na Amazônia durante o período 1999-2012, mostraram um aumento da entropia relacionado com secas que ocorreram em 2005, 2007 e 2010. Em relação aos dados de precipitação de Pernambuco, os valores da entropia de permutação diminuem com o aumento da distância das estações do litoral, indicando maior variabilidade e menor previsibilidade das chuvas mensais nas regiões próximas a zona da mata e agreste, e menor variabilidade e maior previsibilidade nas regiões próximas ao sertão e vale do São Francisco.

Climate change and human activities alter the hydrologic systems and exerted global scale impacts on our environment with significant implications for water resources. Climate change can be characterized by the change of precipitation and temperature, and both precipitation pattern change and global warming are associated with the increase in frequency of flooding or drought and low flows. With increasing water demand from domestic, agricultural, commercial, and industrial sectors, humans are increasingly becoming a significant component of the hydrologic cycle. Human activities have transformed hydrologic processes at spatial scales ranging from local to global. Human activities affecting watershed hydrology include land use change, dam construction and reservoir operation, groundwater pumping, surface water withdrawal, irrigation, return flow, and others. In this thesis, the hydromorphology (i.e., the change of coupled hydrologic and human systems) of the Econlockhatchee River (Econ River for short) is studied. Due to the growth of the Orlando metropolitan area the Econ basin has been substantially urbanized with drastic change of the land cover. The land use / land cover change from 1940s to 2000s has been quantified by compiling existing land cover data and digitizing aerial photography images. Rainfall data have been analyzed to determine the extent that climate change has affected the river flow compared to land use change. The changes in stream flow at the annual scale and low flows are analyzed. The Econ River has experienced minimal changes in the amount of annual streamflow but significant changes to the amount of low flows. These changes are due to urbanization and other human interferences.

The design of wetlands to replace those lost to development requires quantitative understanding of the wetland water budget in order to estimate the amount of water available to the wetland over time. Many methods exist to estimate each component of the wetland water budget. In this study, monthly values of the water budget components namely, precipitation, runoff, evapotranspiration, and groundwater seepage were calculated using a water budget model and compared to on-site field measurements for a wetland in Manassas, Prince William County, VA. The monthly precipitation estimated from a weather station 32.18 km from the site differed from the on-site values by as much as 2.9 times. Runoff estimates calculated by the Soil Conservation Service (SCS) method using antecedent moisture condition (AMC) II underpredicted runoff for every month by as high as 100 percent compared to the on-site measured runoff. The choice of AMC greatly affected the SCS runoff estimates. Runoff was the dominant water budget component at the Manassas wetland. The evapotranspiration (ET) estimates using the Thornthwaite method either over or underestimated ET when compared to ET calculated from diurnal cycles of the water table in the wetland. Groundwater seepage losses were calculated using Darcy's equation with an assumed hydraulic gradient of one, and with gradients measured with nested piezometers. Seepage losses at the Manassas wetland were negligible. Overall, the water budget model provided conservative estimates of the available water in the wetland during the 10-month period of observation. / Master of Science