Submitted by Caroline Falcao (caroline.rfalcao@ufpe.br) on 2017-05-22T17:18:22Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação.pdf_Diego Lira dos Anjos.pdf: 2042388 bytes, checksum: 0eaa06622a1c9f131bff88e150e338ab (MD5) / Made available in DSpace on 2017-05-22T17:18:23Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação.pdf_Diego Lira dos Anjos.pdf: 2042388 bytes, checksum: 0eaa06622a1c9f131bff88e150e338ab (MD5) Previous issue date: 2012-05-31 / A presente pesquisa teve como objetivo efetuar uma análise espaço-temporal da estrutura da comunidade fitoplanctônica, biomassa e parâmetros hidrológicos no estuário do rio Capibaribe (Recife, Pernambuco, Brasil). As coletas foram realizadas em três pontos fixos durante o período de estiagem (outubro, novembro e dezembro de 2010) e chuvoso (maio, junho e julho de 2011) abrangendo dois ciclos de marés (baixa- mar e preamar). As amostras de microfitoplâncton foram coletadas com auxílio de uma rede de plâncton com abertura de malha de 64μm. Os dados de pluviometria foram fornecidos pelo Instituto Nacional de Meteorologia - 3° Distrito de Meteorologia (INMET - 3° DISME), provenientes da Estação Meteorológica. Foram aferidos in situ dados sobre as variáveis abióticas: profundidade local, temperatura e transparência da água; concomitantemente, foram coletadas amostras de água, com garrafa oceanográfica do tipo Kitahara, para análise da salinidade e clorofila a. Foram identificados 96 táxons, distribuídos entre os filos Ochrophyta (61,46%), Chlorophyta (12,50%), Cianobacteria (11,46%), Myzozoa (7,29%), Euglenozoa (4,17%) e Charophyta (3,12%), sequenciados em ordem de riqueza taxonômica e abundância, destacando-se como dominantes: as cianobactérias Oscillatoria sp e Planktothrix sp; e as ochrophytas (diatomáceas) Aulacoseira granulata, Cyclotella glomerata, Cyclotella sp, Cylindrotheca closterium, Helicotheca thamesis, Skeletonema costatum e Thalassiosira sp. A biomassa fitoplanctônica variou de 0,66 a 52,69mg.m-3 , com média geral de 13,46mg.m-3 e juntamente com a salinidade, temperatura e transparência da água apresentaram maiores valores no período de estiagem. Foram registrados valores de salinidade, temperatura e transparência da água mais elevados nas preamares e biomassa fitoplanctônica nas baixa-mares. Os resultados obtidos indicam uma variação sazonal bem definida da biomassa fitoplanctônica e composição florística do microfitoplâncton, influenciada pelo efeito sinergético dos parâmetros climatológicos e hidrológicos, notadamente com relação à penetração da luz solar no ambiente. Conclui-se que, a região estuarina do rio Capibaribe é um ambiente eutrófico, e que o ciclo de maré foi o fator determinante na variação da biomassa fitoplanctônica e composição do microfitoplâncton. / This study aimed to perform an analysis of the spatio-temporal structure of phytoplankton, biomass and hydrological data in the estuary of the river Capibaribe (Recife, Pernambuco, Brazil). Samples were collected at three fixed points during the dry season (october, november and december 2010) and rainy (may, june and july 2011) covering two tidal cycles (low tide and high tide). Microphytoplankton samples were collected with the aid of plankton net with mesh size of 64μm. The rainfall data were provided by the National Institute of Meteorology - 3° District of Meteorology (INMET - 3° DISME) from the meteorological station of Recife and located in the neighborhood of the Várzea. Were measured in situ data on abiotic variables: local depth, temperature and water clarity, concomitantly, water samples were collected with Kitahara bottle oceanographic type for analysis of salinity and chlorophyll a. Phytoplankton presented 96 taxa, distributed among phyla Ochrophyta (61,46%), Chlorophyta (12,50%), cyanobacteria (11,46%), Myzozoa (7,29%), Euglenozoa (4,17%) and Charophyta (3,12%), sequenced in order of abundance and taxonomic richness, standing out as dominant: the cyanobacteria Oscillatoria sp and Planktothrix sp; and ochrophytas (diatoms) Aulacoseira granulata, Cyclotella glomerata, Cyclotella sp, Cylindrotheca closterium, Helicotheca thamesis, Skeletonema costatum and Thalassiosira sp. Phytoplankton biomass ranged from 0,66 to 52,69mg.m-3 , with overall average of 13,46mg.m-3 and with the salinity, temperature and water transparency showed higher values in the dry season. Recorded values of salinity, temperature and water transparency in higher high tides and phytoplankton biomass in the low tides. The results indicate a clear seasonal variation of phytoplankton biomass and floristic composition of microphytoplankton, influenced by the synergistic effect of climatological and hydrological parameters, especially with respect to the penetration of sunlight in the environment. Concluded that, the estuary of the river Capibaribe is a eutrophic environment, and the tide was the determining factor in the variation of phytoplankton biomass and composition of microphytoplankton.

Alternativamente ao preenchimento de falhas, buscou-se neste estudo apresentar uma metodologia para a geração de séries de precipitações mensais médias apenas com os dados observados disponíveis nas estações pluviométricas presentes na área de estudo e seu entorno. Neste caso, para cada época da série, somente os dados disponíveis foram utilizados para o cálculo da precipitação média, assim em cada época admitiu-se que uma combinação diferente de postos pluviométricos fosse utilizada para o seu cálculo. Para isso foi desenvolvida uma ferramenta computacional em ambiente SIG para automatizar todas as etapas do estudo. Os resultados das séries de precipitação mensal média para uma bacia hidrográfica calculados segundo a metodologia alternativa apresentada foram comparados a dois métodos de preenchimento de falhas comumente utilizados nos estudos hidrológicos. Posteriormente foram avaliados os impactos do quantitativo de falhas nas séries. Também foram avaliados os reflexos na aplicação das séries na modelagem chuva-vazão e por fim a metodologia foi aplicada a um caso concreto. Os resultados encontrados e os testes estatísticos apontam resultados satisfatórios e equivalentes nas condições testadas. Verificou-se uma degradação na correlação entre a série gerada a partir dos dados sem falhas e as séries geradas com os dados com as imposições das falhas com o aumento do número de falhas impostas. As séries de vazões médias mensais geradas utilizando-se o modelo mensal SMAP quando da aplicação das séries de precipitação calculadas pela metodologia alternativa também se mostraram equivalentes, segundo os testes estatísticos realizados, às séries geradas de dados de precipitação sem falhas ou com as falhas preenchidas. As diferenças encontradas entre as séries foram pequenas o que se refletiu nos Índices de Nash-Sutcliffe que foram próximos. / In this study, we proposed a methodology for the generation of average monthly rainfall series only with the observed data available in the rainfall stations present in the study area and its surroundings. In this case, for each season of the series only the available data were used for the calculation of the average precipitation, so in each season it was admitted that a different combination of pluviometric stations was used for its calculation. For this, a computational tool was developed with a GIS approach to automate all stages of the study. The results of the average monthly rainfall series for a river basin calculated according to the alternative methodology presented were compared to two methods of filling gaps commonly used in hydrological studies. Subsequently, the impacts of the number of failures in the series were evaluated. We also evaluated the reflexes in the application of the series in the rainfall-flow modeling and finally the methodology was applied to a case study. The results found and the statistical tests show satisfactory and equivalent results under the conditions tested. There was a degradation in the correlation between the series generated from the data without fail and the series generated with the data with the impositions of the failures with the increase of the gaps imposed. The series of monthly average flows generated using the SMAP monthly model when applying the rainfall series calculated by the alternative methodology were also shown to be equivalent, according to the statistical tests carried out, to the series generated of data of precipitation without gaps or with the gaps fulfilled. The differences found between the series were small, which was reflected in the Nash-Sutcliffe Indices that were close.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / A presenÃa de Ãgua à um fator determinante na disponibilidade de fontes de alimento e/ou de sÃtios de nidificaÃÃo, e Ã, portanto, potencialmente importante para as comunidades de invertebrados terrestres, particularmente para animais com ninhos fixos/perenes e vivendo em ambientes marcados por uma forte sazonalidade pluviomÃtrica. O objetivo deste trabalho foi obter informaÃÃes sobre os padrÃes sazonais de estrutura de uma assemblÃia de formigas de solo da Caatinga e investigar como a diversidade e a composiÃÃo dessa assemblÃia variam com a sazonalidade pluviomÃtrica. O estudo foi realizado em uma Ãrea de Caatinga arbÃrea localizada em Pentecoste - CE. Um transecto de 200 metros com 20 unidades amostrais espaÃadas entre si por 10 metros foi estabelecido. A amostragem no transecto foi realizada uma vez por mÃs durante 12 meses, no perÃodo 08/2008 â 08/2009. Em cada unidade amostral, uma armadilha de solo (13 cm de altura; 12 cm de diÃmetro) com soluÃÃo de etanol/etilenoglicol foi instalada no inÃcio de cada mÃs e ficou operacional durante uma semana. A estrutura taxonÃmica da fauna amostrada e a distribuiÃÃo de freqÃÃncia (relativa) das espÃcies seguem os padrÃes geralmente encontrados nas regiÃes neotropicais. Foram coletadas 41 espÃcies (40 na estaÃÃo seca, 30 na estaÃÃo chuvosa), pertencentes a seis subfamÃlias e 20 gÃneros, sendo a subfamÃlia Myrmicinae (21 spp.) e os gÃnero Pheidole (10 spp.) e Camponotus (8 spp.) com maior riqueza em espeÃies. A maioria das espÃcies foi pouco abundante, sendo capturada em menos de 10% das unidades amostrais de todo o perÃodo de coleta. Apenas cinco espÃcies foram coletadas em mais de 50% das unidades amostrais. A coleta da espÃcie relativamente rara Thaumatomyrmex mutilatus representa o segundo registro dessa espÃcie para o Nordeste semi-Ãrido, enquanto a coleta de uma nova espÃcie, em fase de descriÃÃo, do gÃnero Platythyrea representa o primeiro registro para o CearÃ. Das 41 espÃcies, 12 foram exclusivas da estaÃÃo seca e uma (Strumigenys elongata) da estaÃÃo chuvosa. As curvas de acumulaÃÃo de espÃcies (observadas e estimadas) demonstraram que a suficiÃncia amostral foi atingida, bem como indicam que em torno de 90% da riqueza estimada foi coletada. Tanto o Ãndice de diversidade de Shannon como o de Simpson, foi menor na estaÃÃo chuvosa em relaÃÃo à estaÃÃo seca (Hâ: 2,91 versus 2,78; 1/D: 13,83 versus 12,8), e houve correlaÃÃo negativa entre os Ãndices de diversidade mensais de Shannon e Simpson, e os Ãndices pluviomÃtricos. A relaÃÃo inversa foi constatada para os Ãndices de equabilidade (equabilidade de Pielou: 0,79 versus 0,83; equabilidade de Simpson: 0,35 versus 0,44), com existÃncia de uma correlaÃÃo positiva significativa entre os Ãndices de equabilidade mensais de Simpson e os Ãndices pluviomÃtricos. Os Ãndices de ―turnover‖ foram baixos, com mÃdia de 0,23 entre os meses consecutivos do perÃodo de coleta, e com valor de 0,19 na comparaÃÃo dos dois perÃodos (seco e chuvoso). A similaridade de fauna (Ãndice de Jaccard) entre as coletas mensais (mÃdia de 0,61) e entre os dois perÃodos (0,67) foi relativamente elevada. A anÃlise de agrupamento (UPGMA) nÃo permitiu detectar a existÃncias de dois grupos claramente definidos em relaÃÃo aos dois perÃodos (seco e chuvoso). A riqueza em espÃcies foi considerada baixa, comparativamente a outros biomas brasileiros, e os resultados sugerem que o perÃodo seco na Caatinga nÃo à um fator limitante para as comunidades de formigas. Entretanto, a reduÃÃo de diversidade observada na estaÃÃo chuvosa poderia ser o reflexo de uma importante reduÃÃo das atividades das formigas decorrente de um quadro chuvoso atÃpico/excepcional do ano 2009. A biodiversidade reduzida em relaÃÃo a outros biomas brasileiros poderia resultar da falta permanente ou sazonal de serrapilheira, importante para as espÃcies predadoras de solo especialistas, e da possÃvel limitaÃÃo sazonal de carboidratos (nÃctar e ―honeydew‖) / Presence of water is a determinant factor for food sources and/or nest sites availability, and is therefore potentially important for terrestrial invertebrate communities, particularly for those with fixed/perennial nests and that live in environments marked by strong rainfall seasonality. The aim of this work was to obtain informations about the seasonal patterns of a soil ant assembly structure of a Caatinga area, and to investigate how diversity and species composition of that assembly vary with rainfall seasonality. The study was performed in a Caatinga area localized at Pentecoste-CE. A 200 meters transect with 20 sampling points at 10 meters intervals was established. Transect sampling was performed once a month during 12 months, in the period 08/2008 â 08/2009. At each sampling point, a pitfall trap (height: 13 cm; diameter: 12 cm) filled with a ethanol/ethylenoglicol solution was placed at the beginning of each month and remained in the field for seven days. The taxonomic structure of the sampled fauna as well as the species (relative) frequency distribution followed the patterns generally found in neotropical regions. Forty-one species (40 in the dry season; 30 in the rainy season) belonging to six subfamilies and 20 genera were collected, with Myrmicinae (21 spp.), Pheidole (10 ssp) and Camponotus (8 spp) as the most specious taxa. Most species showed low (relative) abundance, being found in less than 10% of all the sampling units used in the whole sampling period. Only five species were collected in more than 50% of the sampling units. The collect of the relatively rare species Thaumatomyrmex mutilatus represents the second record of that species for the semi-arid northeastern region, whereas the collect of a new species, actually being described, of the Platythyrea genus represents the first record for the Cearà state. Of the 41 collected species, 12 and 1 (Strumigenys elongata) were found only during the dry and the rainy season respectively. The species-accumulation curves (observed and estimated) indicated that the sampling sufficiency was attained, and that about 90% of the estimated fauna had been collected. The Shannon and the Simpson diversity indexes for the rainy season were both lower compared to the dry season (Hâ: 2,91 versus 2,78; 1/D: 13,83 versus 12,8), and there was a negative correlation between the monthly Shannon and Simpson diversity indexes and the pluviometric indexes. A reverse relationship was observed with the equability indexes (Pielou equability index and Simpson equability index) (Pielou equability: 0,79 versus 0,83; Simpson equability: 0,35 versus 0,44), with a significant positive correlation between the monthly Simpson equability indexes and the pluviometric indexes. The turnover indexes were low, with a mean of 0,23 between the consecutive months of the sampling period, and a value of 0,19 when comparing the two periods (dry and rainy). The average fauna similarity (JaccardÂs index) for the monthly samplings (0,61) and the fauna similarity for two periods (dry and rainy) (0,67) were high. The group analysis with the hierarchical clustering method (UPGMA) did not allow the detection of two clear-cut groups corresponding to the two periods (dry and rainy). Compared to other Brazilian biomes, the ant species richness found in the study was low, and the results suggest that the dry season is not a limiting factor for the ant communities of the Caatinga biome. Nevertheless, the diversity reduction observed in the rainy season could result from an important reduction of ant activity in response to an atypical/exceptional rainy period in the 2009 year. The reduced biodiversity, when compared to other Brazilian biomes, could result from the permanent or seasonal lack of leaf-litter, an important factor for the specialized soil ant predators, and from the possible carbohydrates seasonal limitation (nectar, honeydew)

Computer modeling is the powerful tool for simulating nature’s behavior; however, still more efforts are need for reaching perfect simulation with computer models (especially in the hydrological field of study). In this Master’s thesis, the accuracy of the HEC-HMS computer model for long term rainfall-runoff simulation was evaluated across Sweden. Five different catchments from north to south of Sweden were selected and then simulation have done for 34 years of available data. Simulation was conducted using daily, monthly and yearly time scale resolutions. Results from the north to the south of Sweden were completely different. Simulated runoff and observed runoff in northern catchments followed the same pattern over different time scales but in the southern part of Sweden the results had different patterns in space and time. The best results with HEC-HMS were found in the northern catchments with steep main river slopes. In the southern catchments the model could not predict runoff in any realistic manner at any time and space scale. In total the HEC-HMS model cannot simulate the rainfall runoff for long periods of simulation across Sweden. This is especially true in southern parts of the country dominate with low elevation catchments. However, with regards to its ability for event-based simulation HEC-HMS could be a suitable tool to simulate flood event discharges that are needed for road or other hydraulic structures designs. But, this would require significant amounts of calibration and model development.

The objectives of the study are to review and evaluate four basic risk models that are commonly used in investment science; statistically investigate the risk factor in Capital Asset Pricing Model (CAPM) that is used to reflect the safety of an investment decision in stocks; explore the statistical distribution of monthly precipitation in Belize and to forecast tourist arrivals using statistical time series modelling techniques. The risk models are the Capital Asset Pricing Model (Sharpe-Linter Version), Capital Asset Pricing Model (Conditional Version), Arbitrage Pricing Theory, and Fama–French three-factor model adopted in empirical investigations of asset pricing. The underlying assumptions of using these models are reviewed, and the statistical procedures to evaluate their robustness are reviewed. It will be shown that the present manner of determining this risk factor is quite sensitive and misleading. We introduce a statistical procedure for obtaining a more robust measure of the risk factor commonly referred to as CAPM beta. Changes in the hydrological cycle will generate repercussions in all sectors. It is therefore imperative that Belize’s water resources be managed in an integrated manner, responding to the requirements of all sectors. Daily rainfall data have been collected for a period of 51 years (1960– 2011) from The National Meteorological Service of Belize. The Wakeby distribution adequately fit the monthly rainfall data producing a suitable model based on the Kolmogorov – Smirnov test. Tourism is vitally important to the entire Belize’s economy, contributing 50% of Belize's gross domestic product in 2015. It is the foremost foreign exchange earner in this small economy, followed by exports of marine products, citrus, cane sugar, bananas, and garments. The tourist sector is not without its vulnerabilities and is subject to international economic vagaries. In order to meet the expected future demands on the industry in terms of service delivery it is important that the sector understands the significance of forecasting.

M.Sc. (Geography) / Hailstorms are well-known phenomena in the summer rainfall region of southern Africa where they cause extensive damage - especially in the agricultural sector. This thesis examines the geography and climatology of hail in the Transvaal. It deals with three main issues, namely a) the spatial and temporal characteristics of hail days (HDs); b) rainfall and atmospheric conditions prevailing during hail events; and c) the geography of hail damage as it pertains to maize. In the Transvaal, hail day frequency (HDF) increases with altitude and latitude in a non-linear (exponential) manner. Variations in altitude, as reflected in the diverse physiography of the area, account for most of the spatial and temporal variations in hail occurrence. Seven hail regions can be distinguished which differ from one another in terms of the onset times of hail, its seasonal occurrence and annual HDF patterns. In general, most hailstorms occur during November with the peak onset time varying between 16:00 and 20:00. The most notable finding concerning rain - hail interrelationships, is that rainfall and HDF appear to be inversely related, years/months with high hail incidence being dry and vice versa. Daily and seasonal precipitation characteristics also differ between 'high hail years' (HHYs; dry) and 'low hail years' (LHYs; wet). For instance, during HHYs, the peak hail season is delayed while the rain season peaks earlier. Moreover, while the frequency of convective systems remains nearly the same during HHYs as in 'normal' years, the average precipitation area and the volumetric production decreases significantly. These anomalies appear to be the result of changes in the large-scale circulation patterns (as reflected by the transition from baroclinic to quasi-barotropic conditions) which influence the precipitation from mesoscale convective systems. It is likely that the Southern Oscillation plays a role in these changes, particularly during November and December. However, although these Southern Oscillation Index (SOl) - HDF associations are weak, they are appreciably stronger than those between the SOl and rainfall. Rainfall characteristics on HDs differ from those of non-hail rain days in that, on HDs, more rain falls and the rain-bearing systems are more extensive. In general, atmospheric conditions are less stable, and the humidity level is higher, on HDs than on other days. Furthermore, HDs are characterized by warm north easterly winds near the surface but cold, dry south westerlies at the 600 hPa level. Above this the south westerlies become progressively stronger

Les sols sableux peuvent constituer une réserve potentielle de sols cultivables mais leur mise en valeur entraîne toujours des dégradations de la structure et une baisse du potentiel agricole. Une dégradation très fréquente est l’affaissement des couches labourées sous l’action de la pluie, ou slumping. Notre objectif était d’identifier les mécanismes et les facteurs déterminants du slumping afin de proposer des techniques de prévention. L’étude a été conduite sous pluies naturelles (au champ) et simulées (au laboratoire). Au champ, la cinétique d’évolution des caractéristiques hydriques et physiques du sol a été suivie après un labour à 20 ou à 40 cm de profondeur, dans un sol sableux tropical Thaïlande. Au laboratoire, un sol cultivé modèle a été élaboré dans un cylindre (h et Ø = 20 cm) à partir i) du sol prélevé dans le champ expérimental, ii) de la fraction sable (> 50 μm) extraite de ce même sol. Les sols modèles ont subi des pluies d’intensité variable (de 20 à 120 mm/h) après mise en place sur une table à succion (20 à 90 hPa). Le slumping se produit lorsque deux conditions sont réunies: (1) l’eau doit atteindre un potentiel proche de 0 hPa ce qui réduit la cohésion et aboutit à un équilibre fragile du sol comme décrit par la physique des milieux granulaires; (2) ce potentiel doit être maintenu assez longtemps pour qu’une instabilité se produise et entraine une brusque et importante diminution de la cohésion, donc l’effondrement du matériau. Si la fraction fine (<50 μm) est retirée du sol, aucun effondrement n’est observé, démontrant l’importance de cette fraction limonoargileuse, pourtant minoritaire (<10-15 % en masse), dans l’instabilisation et le slumping. La prévention du slumping et la gestion des sols sableux sont discutées en guise de conclusion. / The sandy soil can serve as a potential reserve for cultivation. However, they are often considered as marginal because prone to have low productivity and problems of structure degradation. One of the degradations is compaction caused by rainfall or irrigation, which is called slumping. Our objective is to identify the processes and factors that affect slumping. The study had been done under natural conditions (field) and simulated conditions (laboratory) respectively. In the field, a tropical sandy soil in Thailand was selected. After 20 cm and 40 cm depth tillage, the dynamic of hydraulic and physical characteristics were measured. In laboratory, a cultivated soil model was build in a cylinder (height and diameter was 20 cm). We used two materials: 1) the original soil from the experiment field site, and 2) the sand fraction (> 50 μm) extracted from this soil. These model soils were submitted to rainfalls with different intensity (20 to 120 mm h-1), combined with different suction (20 to 90 hPa) on a suction table which can support the cylinder. The slumping for soil happens when two conditions were met: 1) the water potential reached a threshold value near 0 hPa. In this value, the soil cohesion decreased and a fragile equilibrium conditions were reached according to granular material theory; 2) the potential value was kept long enough and the cohesion continue decrease until they can no more support the equilibrium, so slumping happens. Surprisingly, in our treatment, when the fine particles (<50 μm) were taken out from the soil, no slumping was observed. This demonstrates the particles of clay and silt are very important to soil stability, even their content were very low as less than 10 percent. The possible ways to prevent slumping and management of sandy soils are also discussed.

Introduction: The Chattahoochee River and its lakes and tributaries are essential resources for metro-Atlanta; however, urbanization and other human impacts near these resources affects the quality of water. The objectives of this study are to describe the spatial and temporal patterns of Escherichia coli (E. coli), and examine the relationship between rainfall and E. coli levels in metro-Atlanta surface waters, including the Chattahoochee River and its lakes and tributaries. Methods: The water quality data used for the study was originally collected and analyzed by the Chattahoochee Riverkeeper (CRK) Neighborhood Water Watch (NWW) program. For this analysis, sites with a total of 50 samples or more were subjected to descriptive analysis. Results: Twenty-seven of the 36 sites had a mean E. coli concentration exceeding the US EPA’s recreational water quality criteria of 2.37 log Most Probable Number per 100 milliliters. Sites with the highest and lowest mean E. coli levels were located, on average, 2.77 and 20.22 miles from downtown Atlanta, respectively. Spikes in E. coli levels occurred 99 counts of 699 sampling events in the winter, 168/827 spring, 141/877 summer, and 170/950 fall. Seven of the 36 sites were analyzed to examine the relationship between 48-hour rainfall and E. coli levels. Four sites indicated that there was a significant positive correlation between the two variables. (r=0.52, p<.0001; r=0.67, p<.0001; r=0.39, p<.0001; r=0.38, p<.0001) Discussion: The water quality in waterways closer to downtown may be attributable to combined sewer overflows and the urbanization and land use associated with the city. Overall, there was temporal variation in E. coli concentrations, however there was no distinct seasonal pattern. The relationship between 48-hour rainfall and E. coli levels of four of the seven sites analyzed was consistent with other studies.

Magister Scientiae - MSc / The primary origin of this project is due to a high demand for freshwater supply in the Berg Water Management Area (WMA). Most of the Berg WMA`s freshwater supply does not live up to the high ecological standards. This is mainly due to high sediments loading in the Berg River which is one of the water supplies to the Berg WMA. The project was conducted on a small-scale catchment at Langgewens experimental farms in Swartland district. The focus of this study was to address some of the hydrological processes active in the research catchment: infiltration, run-off and sediment mobilization on different soil types under wheat and canola vegetation cover. This was done to investigate the origin of sediments in the Berg River. Considering the results, one might conclude that the decayed root systems from the canola and wheat vegetation covers, organic matter content, soil cracks, slope orientation, and soil composition, all played a major role in influencing the ability of the soil to absorb the simulated rainfall. Because the infiltration was calculated using the difference between the incoming simulated rainfall and the measured run-off, there was an inverse relationship between run-off and infiltration. When run-off was low, the infiltration was high and vice versa. iv Factors that governed sediment mobilisation within the ring area are micro topography within the ring area, the slope gradient and vegetation covers. Considering the results, vegetation cover played a pivotal role and it must be maintained at all times. It is advisable that the land users leave crop residual cover behind after the annual harvest and not expose the land surface in bare form for too long as this will generate more run-off and increase sediment mobilisation. The analyses showed that wheat crop protects the soil from rain drop impact than on canola crop.

Recent droughts in South Africa have highlighted the vulnerability of the economy to water restrictions. However, the degree of surface aridity in southern Africa is not only a function of precipitation, but also one of evaporation. The quantitative assessment of evaporative loss is important since it is a major component of the water budget. For example, in southern Africa, evaporation accounts for 79.5% of the hydrological water budget. As the cost of water resource development increases, so there has been an increasing demand for hydrological modelling to optimise project planning. Reliable estimates of evaporation are essential to significant improvements in the practice of hydrology and particularly in a country like South Africa which is prone to the adverse effects of drought. It is difficult to adequately measure potential evaporation over an area as large and as sparsely populated as southern Africa. Despite the research that has been undertaken to estimate evaporation from related meteorological and physical variables, generally, the estimation of evaporation in southern Africa has been unsatisfactory. There are a number of methods for estimating potential evaporation. However, a major problem tends to be the incompatibility between the data requirements of some of the more physically-based models, and the actual data that is available and collected on a routine basis at a sufficient number of stations. In existing water resources estimation models, evaporation is often incorporated as a time series input of pan evaporation, using daily or monthly values. The lack of a nearby record of pan evaporation often necessitates the use of published regionalised mean monthly pan values. This technique of using the mean monthly evaporation values in water resources estimation models tends to overestimate or underestimate the actual evaporation that is occurring, depending on the actual amount of rain occurring in a specific month. This is because no attempt has been made to correct these mean evaporation values for the amount of rainfall that occurs in a specific month, in a specific region. The regional rainfall/evaporation relationships (that vary spatially and temporally) are not taken into account. A need was identified for an assessment of the value of grouping data by rainfall as a better tool for estimating evaporation. Here, the monthly evaporation and the mean monthly evaporation for a specific rainfall group category will be estimated using daily data. Due to data availability, the most appropriate time scale to use is one day. Therefore, in this study an attempt has been made to relate rainfall amounts to evaporation values and to develop rainfall/evaporation relationships, identifying variations by season and region. It is important to identify and quantify these relationships and assess the possibility of incorporating these variations into existing Water Resource Estimation Models. The ability to derive and develop meaningful relationships between daily rainfall and daily evaporation for each season, and for a number of sites considered representative of the climatological zones for southern Africa was assessed. The first approach was to compare daily evaporation plotted against daily rainfall, and in the process develop a quantitative rainfall/evaporation relationship. Unfortunately, no direct linear relationships were identified. The second approach was to test the performance of the water resource estimation model using the following possible choices, (i) a real daily input (COREVAP1) - here the estimated monthly evaporation is the sum of the product number of days within each month * mean daily evaporation for each specified raingroup category, (ii) a distributed mean monthly input (COREVAP2) - here evaporation is estimated using a random sampling procedure to draw samples from a restricted part of the daily evaporation distribution for each raingroup and is defined by the mean and standard deviation, and (iii) a distributed mean monthly input and correction (COREVAP3) - here samples are drawn from the full distribution of daily evaporation for each raingroup category. The performance of the COREVAP programs was analyzed in terms of the improvement effected by estimating evaporation using the mean monthly evaporation regardless of rain. COREVAP1 produced the best simulations of monthly evaporation. This was expected as the program uses the straight-forward mean evaporation value multiplied by the number of days to simulate the monthly evaporation values. However, the COREVAP programs did not perform well when using the monthly evaporation data based on daily infilled values using the transformed parameters. Any regionalisation of parameter files would mean that a range of parameters in a region would now be represented by a single value. The need to assess the effect of this change from a regional range of values to a single representative value was identified. This was done by conducting a sensitivity analysis, in terms of what effect a percentage increase or decrease in the lambda, mean evaporation and mean rainfall values would have on the resultant simulated monthly evaporation and coefficient of efficiency values. A sensitivity analysis was conducted on COREVAP1 to determine which parameters of the model had the greatest influence on the simulations. This was done with reference to the percentage error of monthly evaporation and the monthly and accumulative coefficient of efficiency values. Generally, the percentage increase/decrease in mean evaporation values that are acceptable for the representative stations are low. In contrast, fairly high percentage changes in mean rainfall values are tolerated. The objective of the regionalisation of parameters was to determine whether general characteristics can be applied to some stations that are significantly different compared to other stations, so that the stations may be combined to represent a separate region. The demarcation of regions was conducted on the basis of the regional relative mean evaporation values (per raingroup, per season), the daily mean evaporation values per month and the average number of days within each raingroup, per season. Intra-station and inter-region variability was analysed using the Kruskal-Wallis H test and the Friedman Fr test. The regional parameters were then used as input into the COREVAP programs and the simulation results were analysed in terms of whether the simulations still produce positive accumulative coefficient of efficiency values. The results obtained when substituting the regional parameters were not good. Based on these results, it has been concluded that the hypothesis that grouping data by rainfall may be a better tool for estimating evaporation compared to simply using the mean monthly evaporation, may be rejected.