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Variabilidade climática nos oceanos e a vazão fluvial no Planalto Brasileiro; Oceans and climate variability in the river flow in Brazilian Pantanal

Silva, Carlos Batista da
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 05/11/2012 PT
Relevância na Pesquisa
66.44%
O objetivo do presente estudo foi avaliar a associação temporal entre a vazão de rios do Pantanal brasileiro com as informações sobre a temperatura da superfície do mar (TSM) dos oceanos globais, índices climáticos e precipitação. A motivação que conduziu esta investigação esteve atrelada aos conhecimentos teóricos trazidos pelas contribuições de Walker (1924 e 1928), Walker e Bliss (1932), Bjerknes (1969), Trop (1965), Hoskins e Karoly (1981), Horel e Wallace (1981), Karoly (1989) e Müller e Ambrizzi (2009) sobre os papéis desempenhados por forçantes oceânicas (aquecimento anômalo das TSM) dentro dos sistemas climáticos. As hipóteses norteadoras para a realização deste trabalho foram de que algumas regiões específicas de TSM dos oceanos, assim como padrões climáticos estabelecidos a partir de alguns índices seriam capazes de influenciar o comportamento fluvial de rios no centro da América do Sul. A partir de levantadas estas hipóteses foram realizadas uma série de cálculos de correlação entre as vazões do rio Miranda e (média regional) do Pantanal, com as séries de dados de TSM, índices climáticos e precipitação. Os testes de correlação foram importantes para a identificação geral de quais áreas de TSM e índices climáticos tinham mais associação estatística com as duas séries de vazões utilizadas. Os primeiros resultados dos testes de correlação em lag entre TSM dos oceanos globais e as vazões dos postos regional do Pantanal e do rio Miranda permitiram a identificação de muito mais áreas de TSM sobre o oceano Pacífico do que sobre o oceano Atlântico. Além deste fato...

Channel-ocean exchange driven by tides and river flow: Espinheiro Channel (Portugal)

Vaz, N.; Leitao, P. C.; Dias, J. M.
Fonte: Coastal Education and Research Foundation Publicador: Coastal Education and Research Foundation
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.28%
A 3D baroclinic model (Mohid) was used to perform hindcast simulations in a tidal channel – Espinheiro Channel (located within Ria de Aveiro, north coast of Portugal) – in order to study its hydrography. The simulations were conducted for four distinct periods where markedly different river discharge and tides occurred and the outputs are compared with synoptic thermohaline data. The model qualitatively reproduces alongchannel thermohaline distributions at three different vertical levels during low-to-medium river inflow, underestimating the salinity stratification under high river inflow (higher than 100 m3 s -1). Once the numerical model is fully implemented, the hydrography of the channel was analysed in terms of two main forcing factors: river discharge and tide. Tidal currents and thermohaline data were analysed at the channel’s inlet and at a mid channel station during two tidal cycles. The stratification and water column stability were found to vary in these stations as a function of the estuarine Richardson number and the buoyancy frequency. Well mixed conditions were found at the lower and mid channel area when the river flow is weak (independently of the tidal regime), turning to highly stratified when the river flow is very high (during neap tide). The residual currents were also analysed revealing an ebb-dominated channel...

Rainfall and river flow trends using Mann–Kendall and Sen’s slope estimator statistical tests in the Cobres River basin

Marques da Silva, Richarde; Santos, Celso A. G.; Moreira, Madalena; Corte-Real, João; Silva, Valeriano C. L.; Medeiros, Isabella C.
Fonte: Natural Hazards Publicador: Natural Hazards
Tipo: Artigo de Revista Científica
POR
Relevância na Pesquisa
46.38%
The main objective of this study is to obtain a better understanding of the spatial and temporal variability and trends of rainfall and river flow in the Cobres River basin, southern Portugal, using statistical tools. The present study is focused on the analysis of the trends in annual precipitations and river flow at a regional scale over 40 years (1960–2000). Datasets of daily precipitation recorded in eight rainfall stations and three river flow stations were analyzed. The nonparametric Mann–Kendall and Sen’s methods were used to determine whether there was a positive or negative trend in rainfall data with their statistical significance. A detailed statistical analysis applied to the river flow and rainfall time series of all gauges indicates that rainfall is highly temporally variable and there is a decrease in the annual rainfall amount for the period studied (1960–2000). Thus, there are signs of significant rainfall reduction in the basin, and in fact, some rain gauges show a small rainfall increase during the recent decades. The annual river flow variation has a cyclic behavior with a period length of approximately 10 years. The results seem integrated to the global and European continental scale findings: Decreasing trends are dominant for almost all indices; most of the calculated slopes are statistically insignificant; the distribution of positive and negative slopes in the area is extremely irregular; and the changes in basin are more significant compared to other studies.

Nutrient Dynamics of Estuarine Invertebrates Are Shaped by Feeding Guild Rather than Seasonal River Flow

Ortega-Cisneros, Kelly; Scharler, Ursula M.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 09/09/2015 EN
Relevância na Pesquisa
46.32%
This study aimed to determine the variability of carbon and nitrogen elemental content, stoichiometry and diet proportions of invertebrates in two sub-tropical estuaries in South Africa experiencing seasonal changes in rainfall and river inflow. The elemental ratios and stable isotopes of abiotic sources, zooplankton and macrozoobenthos taxa were analyzed over a dry/wet seasonal cycle. Nutrient content (C, N) and stoichiometry of suspended particulate matter exhibited significant spatio-temporal variations in both estuaries, which were explained by the variability in river inflow. Sediment particulate matter (%C, %N and C:N) was also influenced by the variability in river flow but to a lesser extent. The nutrient content and ratios of the analyzed invertebrates did not significantly vary among seasons with the exception of the copepod Pseudodiaptomus spp. (C:N) and the tanaid Apseudes digitalis (%N, C:N). These changes did not track the seasonal variations of the suspended or sediment particulate matter. Our results suggest that invertebrates managed to maintain their stoichiometry independent of the seasonality in river flow. A significant variability in nitrogen content among estuarine invertebrates was recorded, with highest % N recorded from predators and lowest %N from detritivores. Due to the otherwise general lack of seasonal differences in elemental content and stoichiometry...

Correlação entre o fator de refletividade do radar e a vazão no rio Mundaú; Correlation between reflectivity factor and flow in the Mundaú river

Barros, Adriano Aubert Silva
Fonte: Universidade Federal de Alagoas; BR; Processos de superfície terrestre; Programa de Pós-Graduação em Meteorologia; UFAL Publicador: Universidade Federal de Alagoas; BR; Processos de superfície terrestre; Programa de Pós-Graduação em Meteorologia; UFAL
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
46.39%
This application aims to identify a possible correlation between the reflectivity factor signal RADAR Weather Radar System of Alagoas (SIRMAL), with the flow of the Rio Mundaú, data obtained fromthe Hydrological Station National Water Agency (ANA) in BoaFortuna, Rio Largo, Alagoas. What is required is a remote monitoring and continuous rate of flow, at one point the river basin Mundaú in order to predict possible flood waves. The floods in the river Mundaú are recurrent, having brought great losses in material resources and human lives for decades, their monitoring is of fundamental importance for better planning and management of these resources. For this we constructed a computer code in object-oriented language, Object Pascal. The program reads the image in jpeg format, generated and provided by SIRMAL on his Internet site, spatially integrates all the values of reflectivity of the microwave pulse on the watershed, determining the volume and then precipitated considered high rainfall area on the Watershed River Mundaú. This value is associated with the reflective state of the basin, at a given time, indicates the amount of precipitated water in the basin for a given period. The high rainfall is related to precipitation over the basin and consequently the flow in river. To verify the correlation with the flow...

A multiobjective ant colony optimization approach for scheduling environmental flow management alternatives with application to the River Murray, Australia

Szemis, J.; Dandy, G.; Maier, H.
Fonte: Amer Geophysical Union Publicador: Amer Geophysical Union
Tipo: Artigo de Revista Científica
Publicado em //2013 EN
Relevância na Pesquisa
46.38%
[1] In regulated river systems, such as the River Murray in Australia, the efficient use of water to preserve and restore biota in the river, wetlands, and floodplains is of concern for water managers. Available management options include the timing of river flow releases and operation of wetland flow control structures. However, the optimal scheduling of these environmental flow management alternatives is a difficult task, since there are generally multiple wetlands and floodplains with a range of species, as well as a large number of management options that need to be considered. Consequently, this problem is a multiobjective optimization problem aimed at maximizing ecological benefit while minimizing water allocations within the infrastructure constraints of the system under consideration. This paper presents a multiobjective optimization framework, which is based on a multiobjective ant colony optimization approach, for developing optimal trade-offs between water allocation and ecological benefit. The framework is applied to a reach of the River Murray in South Australia. Two studies are formulated to assess the impact of (i) upstream system flow constraints and (ii) additional regulators on this trade-off. The results indicate that unless the system flow constraints are relaxed...

Methods to assess environmental flow and groundwater management scenarios for floodplain tree health in the Lower River Murray.

Overton, Ian Clifford
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2013
Relevância na Pesquisa
46.41%
Riparian environments have degraded world-wide as a consequence of human development and climatic change. The native floodplain tree communities of semi-arid river systems are under stress from reduced flooding frequencies as a consequence of water extractions, river regulation and climate change. In regions with saline aquifers, river regulation and land management have also caused soil salinisation, further impacting on floodplain tree health. The lower River Murray in south-eastern Australia is a major ecological asset considered as an area of international significance. The dominant floodplain vegetation is suffering severe decline in health, with approximately 80% of floodplain trees reported as being in poor condition or dead. A reduction in water availability from reduced flooding and soil salinisation, has been identified as the primary cause. This has resulted from large irrigation extractions across the Murray-Darling Basin and elevated saline groundwater levels due to river regulation and land clearance. Management of these ecosystems needs to address both surface and groundwater changes. Increasing flooding regimes from environmental flow management and lowering of groundwater in regions of shallow saline aquifers are the most common scenarios adopted world-wide. Traditionally the assessment of management options for floodplain habitats has focussed on changes in river flow with no consideration given to surface water and groundwater interactions. In addition groundwater has been treated as a single homogenous unit. Wide floodplains have high spatial variability of habitats due to historic meandering anabranch creek systems that cause changing elevations and soil types. This in turn creates a highly variable pattern of surface and groundwater interactions. This thesis investigates the major causes of floodplain tree decline and develops methods for predicting the spatial impacts on floodplain tree health from a range of management scenarios. Surface and groundwater changes are often highly inter-connected but are usually considered separately at regional scales because of the complexity of management and modelling of surface and groundwater interactions over large areas. This thesis addresses the surface and groundwater changes at the regional scale of the lower River Murray. A floodplain inundation model for the River Murray (RiM-FIM) is developed to predict the extent of flooding at various magnitudes of flow and river regulation and a ‘drought index’ was used to indicate the risk to floodplain tree health of changing flow regimes. A floodplain impacts model (FIP) was applied spatially to predict groundwater discharge onto the floodplain and model vegetation risk. At the floodplain scale...

Stability of backwater-influenced river bifurcations: A study of the Mississippi-Atchafalaya system

Edmonds, D.A.
Fonte: American Geophysical Union Publicador: American Geophysical Union
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
46.43%
In this paper I use numerical modeling to show that the hydraulic backwater profile creates a feedback that may stabilize river bifurcations. The numerical model simulates flow and sediment transport in the Mississippi-Atchafalaya River system without the Old River Control Structure. The results show that bifurcation evolution strongly depends on the discharge upstream of the bifurcation. At upstream discharges greater than 12600 $ ext{m}^{3}$ $ ext{s}^{-1}$ the Atchafalaya River discharge increases through time at the expense of the Mississippi River. Interestingly, at upstream discharges lower than 12600 $ ext{m}^{3}$ $ ext{s}^{-1}$ the opposite occurs and the Mississippi River discharge increases at the expense of the Atchafalaya River. The capture direction changes because the backwater profile of each river varies enough at high and low discharge to invert the water surface slope ratio. These results suggest that the capture direction would change at high and low flow, which would have a stabilizing effect by preventing the runaway growth of one channel. Accounting for this, I calculate that in the absence of the Old River Control Structure capture would not happen catastrophically, but rather the Atchafalaya River would capture the Mississippi River in $sim$300 years from present day.

Resilience to Climate Change-Induced Challenges in the Mekong River Basin : The Role of the MRC

Schmeier, Susanne
Fonte: World Bank, Washington, DC Publicador: World Bank, Washington, DC
Tipo: Publications & Research :: Working Paper; Publications & Research
ENGLISH; EN_US
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46.37%
Climate change and its consequences, ranging from increased water variability to more extreme weather events and from sea level rise to ecosystem changes, introduce new challenges to transboundary watercourses, which already face a variety of collective action problems due to their border-crossing nature. Other changes occurring in river basins, such as changing water-use patterns, development of large infrastructure schemes, and changing socioeconomic development levels of riparian states also challenge the institutional capacity of current cooperative management mechanisms. Thus, River Basin Organizations (RBOs), which manage the river basins, must be highly adaptive to ensure not only resilience to change but also long-term sustainable development of the basin and its people. This paper examines the 'adaptation capacity' of the Mekong River Commission (MRC), which manages the Mekong River Basin, a river basin particularly vulnerable to challenges related to climate change as well as to human-caused change. Resilience may be encoded in treaty provisions...

The Zambezi River Basin : A Multi-Sector Investment Opportunities Analysis - Summary Report; A bacia do rio Zambeze : analise das oportunidades de investimento multissectorial

World Bank
Fonte: World Bank Publicador: World Bank
Tipo: Economic & Sector Work :: Investment Climate Assessment (ICA)
ENGLISH
Relevância na Pesquisa
46.4%
The Zambezi River Basin (ZRB) is one of the most diverse and valuable natural resources in Africa. Its waters are critical to sustainable economic growth and poverty reduction in the region. The overall objective of the Zambezi River Multi-Sector Investment Opportunity Analysis (MSIOA) is to illustrate the benefits of cooperation among the riparian countries in the ZRB through a multi-sectoral economic evaluation of water resources development, management options and scenarios from both national and basin-wide perspectives. Better management and cooperative development of the Basin's water resources could significantly increase agricultural yields, hydropower outputs, and economic opportunities. Collaboration has the potential to increase the efficiency of water use, strengthen environmental sustainability, improve regulation of the demands made on natural resources, and enable greater mitigation of the impact of droughts and floods. Seen in this light, cooperative river basin development and management not only provide a mechanism for increasing the productivity and sustainability of the river system...

The Zambezi River Basin : A Multi-Sector Investment Opportunities Analysis - Basin Development Scenarios; A bacia do rio Zambeze : analise das oportunidades de investimento multissectorial

World Bank
Fonte: World Bank Publicador: World Bank
Tipo: Economic & Sector Work :: Investment Climate Assessment (ICA)
ENGLISH
Relevância na Pesquisa
46.43%
The Zambezi River Basin (ZRB) is one of the most diverse and valuable natural resources in Africa. Its waters are critical to sustainable economic growth and poverty reduction in the region. The overall objective of the Zambezi River Multi-Sector Investment Opportunity Analysis (MSIOA) is to illustrate the benefits of cooperation among the riparian countries in the ZRB through a multi-sectoral economic evaluation of water resources development, management options and scenarios from both national and basin-wide perspectives. Better management and cooperative development of the Basin's water resources could significantly increase agricultural yields, hydropower outputs, and economic opportunities. Collaboration has the potential to increase the efficiency of water use, strengthen environmental sustainability, improve regulation of the demands made on natural resources, and enable greater mitigation of the impact of droughts and floods. Seen in this light, cooperative river basin development and management not only provide a mechanism for increasing the productivity and sustainability of the river system...

The Zambezi River Basin : A Multi-Sector Investment Opportunities Analysis - Modeling, Analysis, and Input Data; A bacia do rio Zambeze : analise das oportunidades de investimento multissectorial

World Bank
Fonte: World Bank Publicador: World Bank
Tipo: Economic & Sector Work :: Investment Climate Assessment (ICA)
ENGLISH
Relevância na Pesquisa
46.42%
The Zambezi River Basin (ZRB) is one of the most diverse and valuable natural resources in Africa. Its waters are critical to sustainable economic growth and poverty reduction in the region. The overall objective of the Zambezi River Multi-Sector Investment Opportunity Analysis (MSIOA) is to illustrate the benefits of cooperation among the riparian countries in the ZRB through a multi-sectoral economic evaluation of water resources development, management options and scenarios from both national and basin-wide perspectives. Better management and cooperative development of the Basin's water resources could significantly increase agricultural yields, hydropower outputs, and economic opportunities. Collaboration has the potential to increase the efficiency of water use, strengthen environmental sustainability, improve regulation of the demands made on natural resources, and enable greater mitigation of the impact of droughts and floods. Seen in this light, cooperative river basin development and management not only provide a mechanism for increasing the productivity and sustainability of the river system...

The Zambezi River Basin : A Multi-Sector Investment Opportunities Analysis - State of the Basin; A bacia do rio Zambeze : analise das oportunidades de investimento multissectorial

World Bank
Fonte: World Bank Publicador: World Bank
Tipo: Economic & Sector Work :: Investment Climate Assessment (ICA)
ENGLISH
Relevância na Pesquisa
46.44%
The Zambezi River Basin (ZRB) is one of the most diverse and valuable natural resources in Africa. Its waters are critical to sustainable economic growth and poverty reduction in the region. The overall objective of the Zambezi River Multi-Sector Investment Opportunity Analysis (MSIOA) is to illustrate the benefits of cooperation among the riparian countries in the ZRB through a multi-sectoral economic evaluation of water resources development, management options and scenarios from both national and basin-wide perspectives. Better management and cooperative development of the Basin's water resources could significantly increase agricultural yields, hydropower outputs, and economic opportunities. Collaboration has the potential to increase the efficiency of water use, strengthen environmental sustainability, improve regulation of the demands made on natural resources, and enable greater mitigation of the impact of droughts and floods. Seen in this light, cooperative river basin development and management not only provide a mechanism for increasing the productivity and sustainability of the river system...

The Niger River Basin : A Vision for Sustainable Management

Andersen, Inger; Dione, Ousmane; Jarosewich-Holder, Martha; Olivry, Jean-Claude; Golitzen, Katherin George
Fonte: World Bank, Washington, DC Publicador: World Bank, Washington, DC
Tipo: Publications & Research :: Brief; Publications & Research
ENGLISH
Relevância na Pesquisa
46.29%
The Niger River Basin Authority (NBA) brings together nine countries to promote integrated water resources management across political borders. The nine - Benin, Burkina Faso, Cameroon, Chad, Cote d'Ivoire, Guinea, Mali, Niger, and Nigeria have embraced a shared vision to build institutional capacity, political agreement, and public support for cooperation. The countries agree that sustainable management and development of the basin's water resources are necessary to meet natural and man-made threats to their shared resources, and that progress can be achieved by integrating technical data on the hydrology and geography of the river system with judicious political and economic policy. The Niger river basin, home to 100 million people, is a vital and complex asset of West and Central Africa. The continent's third-longest river, the Niger is more than just a source of water. For the people of the nine countries it is a source of identity, a route for migration and commerce, a source of conflict, and now a catalyst for cooperation. Niger...

Long-term nitrate and phosphate loading of river water in the Upper Manyame Catchment, Zimbabwe

Nyamangara,J; Jeke,N; Rurinda,J
Fonte: Water SA Publicador: Water SA
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2013 EN
Relevância na Pesquisa
46.31%
Urbanisation and agriculture represent a dramatic example of human interference in catchment hydrology. The impact of agricultural, domestic, industrial and municipal activities on river flow and water quality within the Upper Manyame Catchment Area (UMCA) was assessed using 7-year nitrate, phosphate and water flow rate data, collected by the Environmental Management Agency (EMA). Water samples for nitrate and phosphate analysis were collected at 8 points along the Manyame (2 points), Marimba (2 points) and Mukuvisi (4 points) rivers, and runoff volume was recorded at the mouth of each river. Annual runoff of each river was closely related to rainfall amount, with the lowest runoff being recorded during drought years. High nitrate and phosphate concentrations were recorded directly downstream of residential, municipal and industrial areas suggesting that these were the major sources of the pollutants found in the river water. For example, phosphate concentration at 2 sites along Mukuvisi River (downstream of domestic and industrial areas) exceeded the statutory limit (0.5 mg/l) for 'safe' or good quality water ('blue' category) according to the Zimbabwe Water (Waste and Effluent Disposal) Regulations, and ranged from 0.78 mg/l during the dry season to 2.23 mg/l during the wet season. In the Marimba River phosphate concentration at Site 4 (downstream of domestic...

Theoretical and numerical analysis of the influence of the bottom friction formulation in free surface flow modelling

Machiels,O; Erpicum,S; Archambeau,P; Dewals,B; Pirotton,M
Fonte: Water SA Publicador: Water SA
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2011 EN
Relevância na Pesquisa
56.29%
Bottom friction modelling is an important step in river flow computation with 1D or 2D solvers. It is usually performed using energy slope based formulations established for uniform flow conditions, or using a turbulent regime based approach relying on turbulence analysis. However, these formulations are often applied under conditions of relative roughness which lie far outside of their validity fields. Furthermore, the theoretical definition of the roughness coefficients, defined by the different authors of both approaches, is not valid for usual numerical flow modelling, considering numerical approximations. The value of this coefficient becomes generally dependent on the flow conditions. Following the definition of the flow validity field of the main friction formulations proposed in literature, an original formulation has been developed. It combines 2 explicit turbulent regime based formulations smoothly linked by a polynomial expression, providing a continuous formulation covering the wide range of roughness usually encountered in river flows. The formulation is suitable to model, with a unique value of the friction coefficient, river flows with a wide range of hydrodynamic properties (water depth, discharge). The efficiency of this new formulation...

River flow response to changes in vegetation cover in a South African fynbos catchment

Hope,Allen; Burvall,Anders; Germishuyse,Talita; Newby,Terrence
Fonte: Water SA Publicador: Water SA
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2009 EN
Relevância na Pesquisa
56.36%
Mountain fynbos catchments in the Western Cape region of South Africa are prone to substantial changes in land cover due to invasion by exotic tree species (and their clearing), fires, and vegetation response to inter-annual variations in rainfall. While small catchment experiments and modelling studies have pointed to reductions in river flow as catchment biomass increases, there is little empirical evidence of land cover change affecting river flow in large catchments that are important sources of water for the region. Monitoring changes in above-ground green biomass in multiple large catchments is challenging, but may be accomplished using a remotely sensed spectral vegetation index. It was hypothesised in this study that annual river yield (river flow as a fraction of rainfall) in the Molenaars catchment near Paarl, South Africa co-varies with an index of green vegetation cover derived from satellite data (the normalised difference vegetation index, NDVI). The catchment was partitioned into 'upland' and 'lowland' zones and the relationship between annual river yield and summer NDVI was determined for each zone over an 18-year period. There was a statistically significant negative linear relationship between annual river yield and the NDVI of the lowland zone when three outliers were excluded from the analysis. These outliers corresponded to periods with prolonged drought conditions when river yield appeared to be decoupled from vegetation water use in the lowland zone. There was no relationship between river yield and changes in the NDVI in the upland zone where plants were unlikely to have sustained access to adequate soil water for transpiration. The importance of considering the location of land cover changes in a catchment...

Riparian trees as common denominators across the river flow spectrum: are ecophysiological methods useful tools in environmental flow assessments?

Schachtschneider,Klaudia; Reinecke,Karl
Fonte: Water SA Publicador: Water SA
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2014 EN
Relevância na Pesquisa
56.36%
Riparian tree species, growing under different conditions of water availability, can adapt their physiology to maximise their survival chances. Rivers in South Africa may flow perennially, seasonally or ephemerally (episodically). Different riparian species are adapted to survive under each of these different flow regimes by making use of surface, ground, soil, rainwater, or some combination of these. These water sources are available to varying degrees, depending on local climatic, hydrological, geohydrological and geomorphological conditions. This paper tests physiological differences among trees along rivers with varying flow regimes. In this study 3 parameters were selected and tested, namely wood density, specific leaf area and water use efficiency through stable carbon isotope measurements. All three parameters are quick, simple and cheap to determine and as such their value for standard-procedure river monitoring programmes or environmental flow requirement procedures was tested. Acacia erioloba is an arid-adapted riparian tree along the ephemeral Kuiseb (Namibia) and Kuruman (South Africa) Rivers that shows decreasing specific leaf area and increasing wood density correlating with deeper groundwater levels. Intraspecific changes for specific leaf area and carbon isotope values were demonstrated for Acacia mellifera and Croton gratissimus at varying distances from the active channel of the seasonal Mokolo River (South Africa). No significant differences in physiology were noted for Salix mucronata...

Assessment of the contribution of groundwater discharges to rivers using monthly flow statistics and flow seasonality

Le Maitre,David C; Colvin,Christine A
Fonte: Water SA Publicador: Water SA
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/10/2008 EN
Relevância na Pesquisa
56.42%
Groundwater discharge is believed to dominate dry season flows in perennial river systems and to sustain aquatic biodiversity. River flow statistics, extracted from the SPATSIM modelling system, were used to estimate the contribution of groundwater to river flow regimes. The flow statistics were compared for the principal aquifer types (based on major geological formations) in South Africa. This analysis focused on seasonal variation in flows rather than the annual totals or Baseflow Index. Groundwater discharge is expected to reduce flow variability and sustain flows, making flow concentrations lower than rainfall concentrations. Catchments dominated by carbonates have the greatest proportion of baseflow (37%), followed by basement complex (31%) and extrusive aquifer types (31%). The weak relationships between river flow indexes (particularly the Baseflow Index, Coefficient of Variation and Hydrological Index) and the seasonality or concentration statistics imply that catchment storage characteristics and other non-climatic factors play an important role in flow regulation. The geographic distribution of total flow concentrations differs markedly from rainfall concentrations, further evidence that non-climatic factors are important determinants of flow regimes. Karoo dykes and sills...

Optimisation of Bacillus thuringiensis var. israelensis (Vectobac®) applications for the blackfly control programme on the Orange River, South Africa

Rivers-Moore,NA; Bangay,S; Palmer,RW
Fonte: Water SA Publicador: Water SA
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2008 EN
Relevância na Pesquisa
46.3%
The Orange River, South Africa's largest river, is a critical water resource for the country. In spite of the clear economic benefits of regulating river flows through a series of impoundments, one of the significant undesirable ecological consequences of this regulation has been the regular outbreaks of the pest blackfly species Simulium chutteri and S. damnosum s.l. (Diptera: Simuliidae). The current control programme, carried out by the South African National Department of Agriculture, uses regular applications, by helicopter, of the target-specific bacterial larvicide Bacillus thuringiensis var. israelensis. While cost-benefit analyses show significant benefits to the control programme, benefits could potentially be further increased through applying smaller volumes of larvicide in an optimised manner, which incorporates upstream residual amounts of pesticide through downstream carry. Using an optimisation technique applied in the West African Onchocerciasis Control Programme, to a 136 km stretch of the Orange River which includes 31 blackfly breeding sites, we demonstrate that 28.5% less larvicide could be used to potentially achieve the same control of blackfly. This translates into potential annual savings of between R540 000 and R1 800 000. A comparison of larvicide volumes estimated using traditional vs. optimised approaches at different discharges...