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A method to optimally site river water quality sensors is expanded and applied to a case study river to explore the application of mathematical siting methods to the design of river sampling networks. Fecal coliform contamination due to flooded swine waste lagoons was modeled as it moves downstream, and optimal sensor locations are located by minimizing the objective function of the optimization problem. The results of the simulations are analyzed by varying the number of allowed sampling locations and the simulated contamination event. For the case study application, the model suggests three sampling locations along the modeled river section. These three suggested sensing points did not greatly vary in location for different river flows and contamination events, indicating the robustness of the model results for this specific case study. Generally, the application of mathematical contaminant modeling is a useful and systematic approach to aid the design of river water quality monitoring networks. [ABSTRACT FROM AUTHOR]

In this study, a mass balance model is developed to improve the understanding of phosphorus fluxes (P fluxes) between sediment and water in a river that is strongly influenced by low-head dams and discharges from wastewater-treatment plants (WWTPs). Before this study, recommendations had been made for dredging the river without a complete understanding of the causes and effects of sediment phosphorus flux. This study changed the way the river dynamics are understood and will provide a basis for watershed management and permitting decisions into the future. The analysis presented focuses on sorption processes at the sediment-water interface as a function of the diagenesis flux rate into the sediment, reactions within the sediments with partitioning between dissolved and particulate forms, and the inorganic phosphorus concentration in the overlying waters. The sediment is modeled as two layers with a thin (0.8 mm) surface aerobic layer and an underlying, thicker (10 cm) anaerobic layer. The phosphorus settling and diagenesis flux and the initial phosphorus concentrations in the sediment and water column are varied to simulate seasonal fluctuations and evaluate the effectiveness of different river management scenarios aimed at reducing phosphorus concentrations. This study shows the importance of including such a microanalysis within water-quality studies to enhance overall system understanding when making water management decisions. [ABSTRACT FROM AUTHOR]

A recently rediscovered rock art site at Farm Hornkranz-South in the Khomas Hochland of Namibia presents a close resemblance to the Fallen Rock site at Bushman's Kloof in the Cederberg of South Africa. This discovery may well point to early San migration up the river systems from the Western Cape via Namaqualand and the Orange River to the interior of Namibia. If a migration hypothesis can be archeologically expounded by means of, for instance, pot shards, lithic assemblage, or by linguistics, then the same should be possible by means of rock paintings, especially in the case of ones so convincingly similar as those from the two sites under consideration. It may here be productive to analyse the two sets of paintings, not only in terms of age, placement, symbolism and orientation, but also in terms of artistic style and aesthetics, in order to explore a cultural (art-historical) connection. Although the aesthetic approach may not solve the symbolic problems of ancient rock art, it may well be of use in indicating relatedness between artistic styles, and time/space. Traces of a cultural relationship, as evidenced through styles of art, would then necessitate a closer look at river systems as possible arteries for migration in pre-Historic southern Africa. [ABSTRACT FROM AUTHOR]

The mitochondrial DNA cytochrome b sequences of 36 Schizothorax species from 51 localities in the Yunnan-Guizhou Plateau (YGP) and its adjacent areas were analysed. Maximum parsimony, Maximum likelihood and Bayesian phylogenetic analyses were performed to examine the relationships of Schizothorax species. A hypothesis of the phylogenetic relationships of the species is given. A relaxed molecular clock based on Bayesian evolutionary analysis was used to tentatively calculate the divergence times of Schizothorax. Samples from the YGP were tentatively grouped into three geographically distributed clades: the Tsangpo-Irrawaddy, the Mekong-Salween and the Trans-Jinsha River (including Jinsha, Red, Nanpan and Beipan Rivers). Calibration of the molecular clock revealed that two geological periods, the late Miocene about 10 million years before present (Myr BP) and the Pliocene (4.0 Myr BP), were important times in the vicariant speciation of Schizothorax. The phylogenetic history of the species is congruent with events caused by the uplift of the Tibetan Plateau and the YGP. The divergence of Schizothorax species in YGP began in the Pliocene. Our phylogenetic trees did not support the hypothesis that the paleo Jinsha River was drained through the Yangtze River-Jianchuan Lake-Erhai Lake to the Red River. Schizothorax in the Beipan River were derived from the Jinsha River. [ABSTRACT FROM AUTHOR]

Abstract: The Mesoproterozoic Belt-Purcell Supergroup (BPS) preserves a thickness of 17km of dominantly siliciclastic rocks deposited between 1470 and 1400Ma. The total range of Chemical Index of Alteration (CIA) values, corrected for diagenetic K-addition, are 62–88 for argillites and 55–80 for sandstones, with averages of 72±6 and 68±7, respectively. More intense CIA values, in conjunction with low absolute contents of Sr, Ca and Na, and high Rb/Sr ratios (average 4), reflect an intensely weathered provenance in a hot-wet climate with hot-arid intervals resulting in evaporitic sediments. Covariations of CIA-Eu/Eu* and Sr-Eu/Eu* are consistent with a large catchment area including extensive provenance terranes of weathered recycled sedimentary rocks for the most extreme CIA and Eu/Eu* values, with smaller less intensely weathered juvenile terranes represented by lower CIA values. Accordingly, variations of CIA within the BPS stratigraphic sequence may record some combination of shifting catchment terranes and weathering intensity. Stratigraphic trends in CIA within the Appekunny and Grinnell Formations of 80±6 to 66±4 to 79±5 record the variation in this combination with time. Siliciclastic rocks record a first order trend of CIA values from CIA ∼80–100 in the Mesoarchean, through ∼80–90 in the Neoarchean, and ∼70–85 in the Proterozoic, to ∼72 for global Phanerozoic shales. These values reflect progressive drawdown of greenhouse gases that promote silicate weathering by their sequestration into carbonates and black shales, as preserved in the geologic record. Second order secular peaks in CIA values correlate in time with mantle plumes that emit greenhouse gases, which enhance silicate weathering. Some of the more intense CIA values in the BPS may also stem from release of volcanic gases during magmatism that accompanied rifting of Laurentia during breakup of the Supercontinent Columbia at ∼1.4Ga. Overall, CIA values are within the range of modern humid-temperate and humid-tropical climatic catchment areas drained by large river systems such as the Orinoco, Nile and Amazon rivers. Proterozoic rivers have been viewed as mostly braided systems due to the lack of influence of rooted vegetation, which resulted in fast channel lateral migration, high run-off rates, and low bank stability. Many large-scale Proterozoic siliciclastic basins have been preserved, formed by river systems up to pan-continental scale. However, their significance as archives of continental weathering intensity remains under-explored. This study suggests that BPS CIA values reflect more aggressive chemical weathering, since Proterozoic rivers had less sediment residence times due to a lack of vegetation cover, and therefore faster transport time than their modern counterparts. To achieve high CIA values in shorter periods of time without vegetation cover, more intense chemical weathering conditions must have been present. [Copyright &y& Elsevier]

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Population and economic growth, urbanisation process and advanced technology have transformed many Malaysian river systems. Due to these changes, the function of the riverfront areas had also changed such that the current pattern of riverfront development in Malaysia is now shaped more by mixed development and recreation. This article examines waterfront development practice in Malaysia and its sustainability based on the findings of field interviews conducted with government officers, property developers, and the waterfront community from three waterfront areas of Kuching, Malacca and Glenmarie Cove, Selangor. Questionnaires were mailed and e-mailed to 91 property development companies listed in the Malaysian bourses. The findings indicated that the majority of respondents thought that Malaysia had not achieved the kind of sustainable waterfront development seen in developed countries. Several factors caused this, namely, difficulty in balancing the various social, economic and financial needs of the various stakeholders, insufficient financial resources, lack of human expertise and difficulty in obtaining planning permission. Addressing these shortcomings would contribute to best practices of waterfront development in Malaysia. [ABSTRACT FROM AUTHOR]

This paper presents a detailed modeling of rainfall-runoff processes and flow routing along a complex large-scale region, the Upper Paraguay River Basin (UPRB), encompassing a drainage area of approximately 600;000 km², which extends over Brazil, Paraguay, and Bolivia. Within the UPRB lies the Pantanal, the world's largest wetland, with extraordinary biodiversity and great ecologic value, but which currently is threatened by anthropogenic activities. A conceptual model was applied with two main components: (1) simulation of the basin and part of the Paraguay River tributaries by means of the distributed large-scale hydrological model MGB-IPH using simpler flow routing methods; and (2) simulation of the main drainage network, approximately 4,800 km of river reaches, with a one-dimensional hydrodynamic model. Despite the data scarcity, complexity, and the intricate river drainage network of the region, the coupled model was able to represent the hydrological regime of the basin. Comparisons between observed and calculated hydrographs showed a good model skill in representing the flow regime of the upper Paraguay River and its tributaries, highlighting its value as a tool for understanding and predicting the system behavior. The proposed modeling of the hydrological processes of the UPRB, with a detail never presented before, provides a valuable tool for understanding ecosystem functioning and assessing its resilience to anthropogenic pressure, climate change, and climate variability. [ABSTRACT FROM AUTHOR]

Summary: This study presents gene-expression programming (GEP), which is an extension of genetic programming (GP), as an alternative approach to predict the transverse mixing coefficient in open channel flows. Laboratory data were collected in the present study and also from the literature for the transverse mixing coefficient covering wide range of flow conditions. These data were used for the development and testing of the proposed method. A functional relation for the estimation of transverse mixing coefficient has been developed using GEP. The proposed GEP approach produced satisfactory results compared to the existing predictors for the transverse mixing coefficient. [Copyright &y& Elsevier]

Rapid economic development has led to urban sprawl and threatens river systems. In this paper, we used geographic information system (GIS) techniques to examine the effects of urbanisation on the water resources of the Yanggong River watershed in Lijiang City, and analysed the temporal changes in river systems and their impacts on watershed ecosystem functions. The total length of the river systems in the Yanggong River watershed decreased from 786.9 km in 1995 to 674.2 km in 2009 and is predicted to continue to decrease by 35.5 km in the next 11 years according to various data sources. The decrease in river system density started in the Old Town of Lijiang and gradually spread to the surrounding areas. Our analysis shows that urbanisation is failing to take into account the impacts on river systems and their functions, which could cause a reduction in the size of the river systems and degradation of watershed ecosystem functions in the Yanggong River watershed of Lijiang City. It is suggested that protecting the natural river network and making full use of the advantages of the distinctive terrain in the Yanggong River watershed could contribute to the sustainability of urban development in Lijiang City. [ABSTRACT FROM AUTHOR]

Abstract: Fast-paced watershed change, driven by anthropogenic development, is threatening the sustainability of freshwater resources across the globe. Developments within watersheds interact in a manner that is additive and synergistic over space and time. Such cumulative environmental effects are defined as the results of actions that are individually minor but collectively significant when added to other past, present, and reasonably foreseeable future actions. Cumulative effects assessment (CEA) then is broadly defined as the process of evaluating the potential impacts of such collective actions on the environment and is a requirement in many countries, including in Canada at the federal level under the Canadian Environmental Assessment Act. However, current approaches to CEA for river systems are proving to be ineffective, which is largely attributed to the disconnect between CEA science and practice. We highlight this gap herein by discussing contradictions in the CEA literature, challenges in quantifying cumulative interactions, including overcoming spatiotemporal scale issues, multiple hydrologic and ecological pathways, and lack of predictive analysis. Our analysis shows there is a need for improved CEA for river systems, and in responding to this need we propose a conceptual framework for better integrating science and practice for improved CEA for river systems using one of the most adversely affected rivers basins in Canada, the Athabasca River, as our model. We conclude by addressing the challenges inherent to CEA with the intent of providing scientists with ways to help improve CEA of river systems. [Copyright &y& Elsevier]

Abstract: Over the last decade several computational models, and several types of model, have been developed to simulate the response of river systems to environmental change over time scales of decades to millennia: hydrological models, flood inundation models, channel morphology models, channel network models, models of river meandering and river braiding, alluvial stratigraphy models, and landscape evolution models. Each type of model simulates different aspects of a river''s response to changes in environmental inputs such as climate and land-use — and to changes in these inputs. And each type of model has its abilities, advantages and limitations. We provide an overview of the different types of model that have been developed, and we evaluate their suitability for testing hypotheses about past environmental conditions, as well as for investigating the response of alluvial river systems to future environmental change. Additionally, we discuss the general issues and problems of computational modelling (e.g. scale and resolution, data availability, process representation, process parameterization, model calibration, non-linearity, and uncertainty), and the extent to which these hamper the usefulness of the models as a tool in environmental landscape studies. Finally, we identify trends in computational modelling research to outline possible future directions of the discipline. [Copyright &y& Elsevier]

Kootenai River white sturgeon spawn in an 18-km reach of the Kootenai River, Id. Since completion of Libby Dam upstream from the spawning reach in 1972, 1974 is the only year with documented significant recruitment of juvenile fish. Where successful in other rivers, white sturgeon spawn over clean coarse material of gravel size or larger. The channel substrate in the current (2008) 18-km spawning reach is composed primarily of sand and some buried gravel; within a few kilometers upstream there is an extended reach of clean gravel, cobble, and bedrock. We used a quasi-three-dimensional flow and sediment-transport model along with the locations of collected sturgeon eggs as a proxy for spawning location from 1994 to 2002 to gain insight into spawning-habitat selection in a reach which is currently unsuitable due to the lack of coarse substrate. Spatial correlations between spawning locations and simulated velocity and depth indicate fish select regions of higher velocity and greater depth within any river cross section to spawn. These regions of high velocity and depth occur in the same locations regardless of the discharge magnitude as modeled over a range of pre- and postdam flow conditions. A flow and sediment-transport simulation shows high discharge, and relatively long-duration flow associated with predam flow events is sufficient to scour the fine sediment overburden, periodically exposing existing lenses of gravel and cobble as lag deposits in the current spawning reach. This is corroborated by video observations of bed surface material following a significant flood event in 2006, which show gravel and cobble present in many locations in the current spawning reach. Thus, both modeling and observations suggest that the relative rarity of extremely high flows in the current regulated flow regime is at least partly responsible for the lack of successful spawning; in the predam flow regime, frequent high flows removed the fine sediment overburden, unveiling coarse material and providing suitable substrate in the current spawning reach. [ABSTRACT FROM AUTHOR]

Abstract: Over the past 15 years, artificial neural networks (ANNs) have been used increasingly for prediction and forecasting in water resources and environmental engineering. However, despite this high level of research activity, methods for developing ANN models are not yet well established. In this paper, the steps in the development of ANN models are outlined and taxonomies of approaches are introduced for each of these steps. In order to obtain a snapshot of current practice, ANN development methods are assessed based on these taxonomies for 210 journal papers that were published from 1999 to 2007 and focus on the prediction of water resource variables in river systems. The results obtained indicate that the vast majority of studies focus on flow prediction, with very few applications to water quality. Methods used for determining model inputs, appropriate data subsets and the best model structure are generally obtained in an ad-hoc fashion and require further attention. Although multilayer perceptrons are still the most popular model architecture, other model architectures are also used extensively. In relation to model calibration, gradient based methods are used almost exclusively. In conclusion, despite a significant amount of research activity on the use of ANNs for prediction and forecasting of water resources variables in river systems, little of this is focused on methodological issues. Consequently, there is still a need for the development of robust ANN model development approaches. [Copyright &y& Elsevier]

The Huron-Erie Corridor serves as a major waterway in the Great Lakes and is the connecting channel between Lake Huron and Lake Erie. The system consists of the St. Clair River, Lake St. Clair, and the Detroit River, and serves as a recreational waterway, source of drinking water for Detroit and surrounding cities, as well as the only shipping channel to Lakes Huron, Michigan, and Superior. This paper describes a three-dimensional unsteady model of the combined system and its application to real-time predictions of physical conditions over the corridor. The hydrodynamic model produces nowcasts eight times per day and 48 h forecasts twice a day. Comparisons between model simulations and observed values show average differences of 3 cm for water levels and 12 cm/s for along-channel currents in the St. Clair River (compared to mean current values of 1.7 m/s) for the period of September 2007 to August 2008. Simulations reveal a spatially and temporally variable circulation in Lake St. Clair as well as significant changes in flow rate and distribution through the St. Clair Delta not accounted for in previous models. [ABSTRACT FROM AUTHOR]

Recent research has elucidated the positive ecological roles of large wood (LW) in fish-bearing channels. However, where logjams increase local flooding and bank erosion, LW has negative impacts on public safety and property protection. Although our understanding of reach-scale processes and patterns has increased dramatically in recent years, only a few studies have integrated this knowledge at the watershed scale. Here we review variations in LW dynamics along a gradient of watershed sizes. In small watersheds, a massive amount of LW, resulting from forest dynamics and hillslope processes, remains on the valley floor. These pieces may persist for several decades and are eventually transported during debris flows. In intermediate watersheds, LW is dominantly recruited by bank erosion from adjacent riparian areas. These pieces are continuously transported downstream with LW pieces that are supplied from the upstream watershed by floods because these channels have a greater width and depth than the length and diameter of the pieces, as well as a high stream power. This leads to fragmentation of the LW pieces, which increases their transportability. In large watersheds, LW pieces are frequently recruited at locations where the channel is adjacent to riparian forests. Floated LW pieces can accumulate along channels with wide floodplains. Storage in floodplains can lead to more rapid decay than in an anaerobic environment, resulting in the subsequent removal of LW pieces from the system. Our review presents a generalized view of LW processing at the watershed scale, and is relevant to ecosystem management, disaster prevention and the identification of knowledge gaps. [ABSTRACT FROM AUTHOR]

This study presents a weighted pre-emptive goal programming model formulation for coordinated reservoir operation, with easy inclusion of uncontrolled water flows. The model is combined with a multiple water inflows forecasting model, and can be used for real time reservoir operation. Water flow routing from various upstream sites is accounted by with a single compact equation. Integration of controlled and uncontrolled water flows in the optimization model simplifies the operation model, resulting in accurate computation of the downstream water flow. Multiple objectives with water storage and flow variables are used to derive optimal regulation for a reservoir system under flood conditions. For real time operations, the model can be used to determine optimal water release rates for a current period, on the basis of an optimal water release schedule for an operating horizon ( T). The model is applied to the flood control operation of reservoirs in the Narmada River Basin (India), with three controlled and three uncontrolled water flows affecting the downstream flow at Hoshangabad. Reservoir water storage and downstream control point flows are zoned, with prioritized objectives used to derive the optimal water release rates. Model applications to the 1999 flood event in the Narmada River Basin with observed and forecasted inflows illustrates that, if water inflows were known through a forecasting technique well in advance, the coordinated operation of the reservoirs could substantially reduce the peak water flows at the control points. The study also indicates that uncontrolled channel flows at the damage site were sufficiently high to cause flooding at the damage site. [ABSTRACT FROM AUTHOR]

Abstract: There is a long history of human–riverine interactions throughout the period of agriculture that in some regions of the world started several thousand years ago. These interactions have altered rivers to human dominated systems with often negative impacts on fluvial environments. To achieve a good ecological and chemical status of rivers, as intended in the European Water Framework Directive (WFD), a better understanding of the natural status of rivers and an improved quantification of human–riverine interactions is necessary. Over the last decade the PAGES-LUCIFS (Land Use and Climate Impact on Fluvial Systems) program has been investigating both contemporary and long-term (centuries to millennia) river responses to global change with the principal aims of: 1) quantifying land use and climate change impacts of river-borne fluxes of water, sediment, C, N and P; 2) identification of key controls on these fluxes at the catchment scale; and 3) identification of the feedback on both human society and biogeochemical cycles of long-term changes in the fluxes of these materials. Here, we review recent progress on identifying fluvial system baselines and quantifying the response of long-term sediment budgets, biogeochemical fluxes and flood magnitude and frequency to Holocene global change. Based on this review, we outline the future LUCIFS research agenda within the scope of the PAGES-PHAROS (Past Human-Climate-Ecological Interactions) research program. Key research strategies should be focused on: 1) synthesising the data available from existing case studies; 2) targeting research in data-poor regions; 3) integrating sediment, C, N and P fluxes; 4) quantifying the relative roles of allogenic and autogenic forcing on fluvial regimes, extreme events and sediment fluxes; 5) improving long-term river basin modelling; and 6) integration of LUCIFS with other research communities within PHAROS, namely HITE (land cover) and LIMPACS (water quality and biodiversity). [Copyright &y& Elsevier]

This paper presents a one-dimensional hydrodynamic modeling of a large-scale river network and floodplains. The study site comprises the Upper Paraguay River and its main tributaries (a total of 4,800 km of river reaches) in South American central area, including a complex river network flowing along the Pantanal wetland. The main issues are related to preparing input data for the hydraulic model in a consistent and georeferenced database and to representing different flow regimes. Geographic information systems-based automatic procedures were developed in order to produce cross-sectional profiles that encompass the large floodplains and to link hydraulic data and spatial location. The marked seasonal flow regime and relative smooth hydrographs of Paraguay River were quite well reproduced by the hydraulic model. For the tributaries, it must be mentioned the model’s ability to simulate both cases when the hydrograph does not present a marked peak flow, due to water loss for the floodplain, and when the hydrograph presents a more common shape, with recession and peak flows well defined. [ABSTRACT FROM AUTHOR]

Muskingum method which is covered in most hydraulic engineering courses and textbooks is widely used for hydrologic flood routing in rivers. In this paper, computational and optimization capabilities of Microsoft Excel spreadsheet is used to perform multiple-reach Muskingum flood routing in a river for which observed inflow and outflow hydrographs are available and its storage-discharge relationship is highly non-linear. The employed method is straightforward and results in better accuracy compared with traditional methods. It is also illustrated that the proposed computational procedure in the spreadsheets can be extended to flood routing in more complex river systems such as branched systems. Considering all these, from educational point of view, a main conclusion is that the results of the study significantly improve the methodologies for teaching Muskingum flood routing in complex river systems. © 2009 Wiley Periodicals, Inc. Comput Appl Eng Educ 17: 448–454, 2009; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20234 [ABSTRACT FROM AUTHOR]

The fundamental problem for any scheme of water management that tries to maximise welfare across a river system is that of determining the optimal allocation at every point. The problem cannot, in general, be avoided by trading water rights because the price will not account for the effect of extraction at any one point on all other points. This article interprets the problem in terms of the indeterminacy that results from missing information on the value of water at internal junctions between rivers. It is then solved in an optimal control theory framework. [ABSTRACT FROM AUTHOR]

Choosing a suitable set of cross sections for the representation of the natural geometry of a river is important for the efficiency of one-dimensional (1D) hydraulic models, but only few guidelines are available for the selection of the most suitable distance between cross sections, depending on the hydraulic problem at hand. This issue is investigated by examining models of a ∼55 km reach of the River Po, Italy, and a ∼16 km reach of the River Severn, United Kingdom, for both of which high quality laser scanning altimetry are available. The high-resolution digital terrain models of the two river reaches enabled the construction of a series of hypothetical topographical ground surveys with different spacing between cross sections, which could be used as input to a standard 1D model (UNET). Both historical and synthetic flood events for the two river reaches were simulated, and the results were then analyzed to quantify the accuracy associated with each resolution and to assess how survey resolution impacts the performance of standard 1D models. The study results agree with the available suggestions in the literature and provide useful guidelines for 1D hydrodynamic modeling. [ABSTRACT FROM AUTHOR]

A number of computer models for river basin planning and management have been developed by various agencies and used extensively since the mid-1970s. Most of the early developments have been based on the use of heuristic weight factors to represent priorities of allocation, and specialized optimization algorithms that were based on the use of network flow algorithms (NFAs). While these algorithms were at first considerably faster than the standard Simplex solvers, their handling of flow constraints was simplistic, which eventually led to the use of iterative schemes for handling nonnetwork constraints. This paper critically examines the notion that iterations applied in combination with NFA are a good vehicle for handling nonnetwork constraints. The failures are demonstrated on several variants of a simple problem with two reservoirs in series. [ABSTRACT FROM AUTHOR]

A methodology for determining the optimal spatial distribution of a river pollutant detection network using a geographic information system and genetic algorithms (GAs) is developed. Two case studies are investigated to evaluate the performance of the developed methodology: (1) a hypothesized river system consisting of only 11 reaches; (2) the Logan and Albert Rivers in Southeast Queensland. Plausible results are obtained, encouraging the possibility of applying GAs in designing a river monitoring network. [ABSTRACT FROM AUTHOR]

The Muskingum principle of flood routing is applicable to a single channel reach bounded by two measuring sections with no lateral inflow in the reach. The basic Muskingum model provides a forecasting form that may be used to predict the downstream flow, a finite time ahead on the basis of the current flow rates. To apply the Muskingum principle to a channel network having inflows from different subcatchments that join downstream to form a combined outflow, the inflows from the subcatchments may be substituted by an equivalent single inflow for an ideal Muskingum reach. This paper proposes a new multiple inflows Muskingum model; the parameters in the model can be estimated using channel properties, the model may be used for routing in ungauged river networks. The new model appropriately extends the Muskingum philosophy to multiple inflows routing and can be expressed in single inflow-single outflow form; a Muskingum-Cunge model and forecasting model for multiple inflows similar to the basic model can be defined. The multiple inflows single outflow forecasting model is simple with easy calculations, and permits prediction of common downstream outflow a finite time ahead, using the concurrent flow rates observed at different gauging stations. The model performance is compared with the nonlinear kinematic wave model. Application of the model to the flood events in Narmada Basin, in India, shows that the model performance is satisfactory. [ABSTRACT FROM AUTHOR]

Water quality impacts of zebra mussel metabolism over an infested 15 km reach of the Seneca River, N.Y., are documented, based on vertically and temporally detailed robotic monitoring at the reach boundaries during the summer through early fall intervals of 2 years. Substantial reductions over the study reach are documented for dissolved oxygen (DO), pH, fluorometric chlorophyll a, and turbidity, associated with the metabolism of this invader. Violations of New York State water quality standards for DO that would not be resolved by traditional manual monitoring programs were observed. The loss of assimilative capacity caused by the zebra mussel invasion is confounding rehabilitation efforts for a downstream polluted lake that had considered diversion of municipal effluent to the river. The critical role robotic monitoring units would play in an automated control system for an innovative strategy of time-variable river discharge of the effluent is described. Near-real time robotic monitoring provides a more detailed understanding of the impacts of zebra mussels on water quality than traditional less intensive manual measurements. [ABSTRACT FROM AUTHOR]

The technology of irrigated agriculture has often been controversial. The development agencies would praise its productivity, as only 18% of the world’s cultivated land is irrigated but produces roughly 33% of the world’s human food supply. Environmental and ecological concerns cite the degradation of natural landscapes, elimination of floodplains and wetlands, and profound impacts on wildlife habitats. Dr. Mark Fiege (University of Washington Press, Seattle, 1999) in his book entitled Irrigated Eden: The Making of an Agricultural Landscape in the American West proposes a possible reconciling view—that irrigation should be viewed as a manmade ecological system, in which land and water are modified to increase agricultural production. The reported research has used this ecological approach to study the Middle Rio Grande irrigated landscape, for the purpose of identifying options for water and ecosystem conservation. This article presents research findings related to opportunities in the agricultural sector to reduce water diversions from the river, primarily by changing the practice of continuous canal water delivery to rotational water delivery. Following the research recommendations since 2002, irrigation water users in the Middle Rio Grande Valley have reduced their diversions by more than 30%, which means more water is now available in the river for better ecology in general and for better fish and wildlife habitat in particular. [ABSTRACT FROM AUTHOR]

Patterns of native and exotic species richness and cover were examined together with the composition of species assemblages along a typical Mediterranean river and across its floodplain. Major goals were to characterize species distribution regarding diverse environmental and habitat features, and to explore floodplain landforms relations using plant assemblages and invasion responses as biological indicators of aquatic–terrestrial connectivity. A floristic survey was undertaken during May and early June 1998 in six sites of a southern Iberian basin. Vegetation data were gathered from three transects in three landforms: inundated and frequently flooded banks (FF), infrequently flooded valley floors (IF), and rarely flooded higher floodplains (RF). We used 2×2 m plots to record each species present and visual estimates of percentage cover of each species. Cover of native and exotic species assemblages were also estimated for each plots, for the transects, and for the landforms. The total number of vascular plant species found was 287 of which only 26 were exotic. Despite the high environmental and geomorphological variability, the hierarchical classification showed that species composition varied across the floodplain, rather than along the river. The IF and RF landforms were the most species-rich, both for native and exotic species group, whereas the cover trends of exotic and native plant species were opposed, with exotics being consistently more abundant in FF, and native cover increasing towards RF landforms. We found positive correlations between native and exotic species richness on the floodplain scale, and on a smaller scale in FF and IF landforms, thus supporting the hypothesis that in aquatic and riparian ecosystems of semi-arid landscapes, species-rich communities are preferentially colonized by exotic species. However, this pattern was not consistently coupled with a high cover of exotic species, and it was not sustained for the dry areas of the RF landforms. [ABSTRACT FROM AUTHOR]

Beginning in January 1992, the Bureau of Reclamation (Reclamation) and the US Geological Survey (USGS) formulated plans for the Watershed and River Systems Management Program—a cooperative interagency effort to develop and implement flexible and robust river basin management tools for the benefit of managers and decision makers using a data centered approach. In addition to Reclamation and the USGS, a number of other agencies and universities have made substantial contributions to the success of the program. The result has been the need driven research and development of state-of-the-art technology which benefits water managers and technical specialists in many river basins. [ABSTRACT FROM AUTHOR]

A water availability modeling system was implemented during 1997–2004 by the Texas Commission on Environmental Quality and its contractors, in collaboration with the water management community, under a mandate provided by comprehensive water management legislation enacted by the Texas legislature in 1997. The availability and reliability of water resources are assessed based on simulating river/reservoir system management and water allocation practices using sets of historical naturalized monthly streamflow sequences to represent basin hydrology. The prior appropriation water rights permit system and other institutional mechanisms for allocating streamflow and reservoir storage resources among numerous water users are considered in detail in evaluating basinwide impacts of water management decisions. The generalized modeling system and lessons learned in its implementation in Texas are applicable to river basin management throughout the world. [ABSTRACT FROM AUTHOR]

Abstract: We describe the statistical properties of two large river systems: the Danube and the Mississippi. The properties of the two rivers are compared qualitatively to the general properties of a critical steady-state system. Specifically, we test the recent suggestion by Bramwell et al. (Europhys. Lett. 57 (2002) 310) that a universal probability density function (PDF) exists for the fluctuations in river level, namely the Bramwell–Holdsworth–Pinton (BHP) PDF. The statistical properties investigated in this paper are: the PDF of the river flow and river level; moment scaling with basin area; moment to moment scaling or relative scaling; and power spectral properties of the data. We find that the moments of the flow scale approximately with basin area and that the seasonally adjusted flows exhibit relative moment scaling. Compared to the Mississippi, the Danube shows large deviations from spatial scaling and the power spectra show considerable dependence on system size. This might be due to water use and regulations as well as inhomogeneities in the basin area. We also find that the PDF of level data in some, but not all, cases can be qualitatively approximated by the BHP PDF. [Copyright &y& Elsevier]

Transferable discharge permit (TDP) programs show potential as cost-effective methods of pollution control. Nevertheless, there remain uncertainties that, if not adequately addressed, might impair their success. Concerns include modeling difficulties that might cause erroneous predictions of cost savings and environmental performance. This study focuses on environmental modeling associated with the stochastic environment. The mean-value first-order second-moment (MFOSM) method is extended to demonstrate how changes, due to discharge permit trading, in the environmental quality mean and/or variance of a system will cause the environmental quality reliability of the system to either decrease, increase, or remain unchanged. The Willamette River in Oregon and the Athabasca River in Alberta, Canada, are used as example case studies. These river systems are simulated to predict how they might respond if trading were implemented. In this study, environmental quality reliability is defined as the probability of the minimum dissolved oxygen (DO) concentration over the length of the river meeting a predetermined standard. Generally, for the Willamette River, trading improves the reliability, while for the Athabasca River, trading makes the reliability worse. [ABSTRACT FROM AUTHOR]

A new dynamic model of water quality, Q2, has recently been developed, capable of simulating large branched river systems. This paper describes the application of a generalized sensitivity analysis (GSA) to Q2 for single reaches of the River Thames in southern England. Focusing on the simulation of dissolved oxygen (DO) (since this may be regarded as a proxy for the overall health of a river); the GSA is used to identify key parameters controlling model behavior and provide a probabilistic procedure for model calibration. It is shown that, in the River Thames at least, it is more important to obtain high quality forcing functions than to obtain improved parameter estimates once approximate values have been estimated. Furthermore, there is a need to ensure reasonable simulation of a range of water quality determinands, since a focus only on DO increases predictive uncertainty in the DO simulations. The Q2 model has been applied here to the River Thames, but it has a broad utility for evaluating other systems in Europe and around the world. [ABSTRACT FROM AUTHOR]

A new dynamic model of water quality, Q2, has recently been developed, capable of simulating large branched river systems. This paper describes the application of a generalized sensitivity analysis (GSA) to Q2 for single reaches of the River Thames in southern England. Focusing on the simulation of dissolved oxygen (DO) (since this may be regarded as a proxy for the overall health of a river); the GSA is used to identify key parameters controlling model behavior and provide a probabilistic procedure for model calibration. It is shown that, in the River Thames at least, it is more important to obtain high quality forcing functions than to obtain improved parameter estimates once approximate values have been estimated. Furthermore, there is a need to ensure reasonable simulation of a range of water quality determinands, since a focus only on DO increases predictive uncertainty in the DO simulations. The Q2 model has been applied here to the River Thames, but it has a broad utility for evaluating other systems in Europe and around the world. [ABSTRACT FROM AUTHOR]

As urban and suburban areas expand, the problem of sewage disposal spreads as well. Inappropriate planning of a sewage management system could impair water quality, destroy habitat, and threaten public health. Simply building a sewage interceptor system along the urban river corridor to handle the wastewater effluents without regard to the impacts from combined-sewer overflows (CSOs) in the storm events cannot fulfill the ultimate goal of environmental restoration in the receiving water body. This study therefore carries out a system-based assessment to search for the optimal operating strategy of the interceptor facilities with respect to biocomplexity or biodiversity in an urban river system. In particular, it focuses on the richness of the fish community in the biological systems, the effect of stress on the fish community by storm events, and their capacity for adaptive behavior in response to the CSOs’ impact in the Love River estuarine system, South Taiwan. By integrating the biological indicators in an environmental context, two simulation models describing the quality and quantity of storm water and their impact on the river water quality are calibrated and verified. The interactions of natural systems and engineered systems covering both spatial and temporal aspects can then be explored in terms of the predicted levels of dissoved oxygen (DO) along the river reaches so as to strengthen an ultimate optimal search for the best operational alternative for the interceptor system. In view of the inherent complexity of integrating simulation outputs at various scales to aid in building the optimization step, three regression submodels were derived beforehand. These submodels present a high potential for exhibiting, eliciting, and summarizing the nonlinear behavior between the CSO impacts and the DO levels in the river reaches. With the aid of such findings, this study finally applies a linear programming model to determine the optimal size of a constructed storage pond (i.e., a detention pond), based on several types of storm events in the study area. This is proved essential for minimizing the ecological risk in such a way so as to indirectly improve the biodiversity in the estuarine river system. [ABSTRACT FROM AUTHOR]

A methodology for evaluation of risk for a river water quality management problem is presented. A fuzzy waste load allocation model is solved with a simulation–optimization approach for obtaining optimum fractional removal levels for the dischargers to the river system. With the optimal fractional removal levels, sensitivity analysis and first-order reliability analysis are applied to identify key random variables which influence the water quality simulation model output, and key checkpoints where the model output is more likely to be affected (i.e., has high variability). Frequency distributions of the output variable are obtained at the key checkpoints using Monte Carle simulation with the key random variables as input variables. The event of low water quality at a checkpoint in a river system is considered as a fuzzy event, with appropriate membership functions defined for the fuzzy risk of low water quality. With the help of fuzzy membership functions and frequency distributions, fuzzy risk levels are computed at the key checkpoints. The proposed methodology is demonstrated through a case study of Tunga–Bhadra River in southern India. [ABSTRACT FROM AUTHOR]

A vertical (laterally integrated) two-dimensional numerical model was applied to study the salt water intrusion in the Tanshui River estuarine system, Taiwan. The river system has experienced dramatic changes in the past half century because of human intervention. The construction of two reservoirs and water diversion in the upper reaches of the river system significantly reduces the freshwater inflow. The land subsidence within the Taipei basin and the enlargement of the river constriction at Kuan-Du have lowered the river bed. Both changes have contributed farther to the intrusion of tidal flow and salt water in the upstream direction. The model was reverified with the earliest available hydrographic data measured in 1977. The overall performance of the model is in reasonable agreement with the field data. The model was then used to investigate the change in salt water intrusion as a result of reservoir construction and bathymetric changes in the river system. The model simulation study reveals that significant salinity increases have resulted from the combined changes. It has been speculated by ecological researchers that the long-term increase in salinity might be the driving force altering the aquatic ecosystem structure in the lower reach of the estuary and the Kuan-Du mangrove swamp, particularly the enlargement of the mangrove area and the disappearance of freshwater marshes. However, concrete proof has not been available since no prototype salinity data were available prior to the reservoir construction. This case study offers the first quantitative estimate of the salinity changes due to human interference in this natural system. [ABSTRACT FROM AUTHOR]

The concept of a dominant discharge that governs the cross-sectional and planform characteristics of a channel is used widely in stream restoration practice. This dominant discharge can be based on field measurements, a chosen recurrence interval of flooding or related to the effective discharge. The effective discharge is defined as the flow which transports the most sediment over the period of record. Significant differences in the relation between the computed effective discharge and bankfull discharge have been documented in the literature. Herein, different methods of estimating the effective discharge are described and analytical solutions derived. These analytical solutions are easy to apply and can be used to predict the effective discharge under existing conditions and the historic flow records. These solutions can be used to explain some of the discrepancies between different methods of estimating the effective discharge. In addition, the equations can be used to predict future trends in the effective discharge should the hydrologic, sediment transport or channel characteristics change in the future. The analysis procedures are illustrated with examples at two different scales: The Red River in Idaho and the Russian River in Northern California. [ABSTRACT FROM AUTHOR]

Decisions about water pollution control and management in river systems are increasingly based on predictions made with water quality models. Many uncertainties are associated with the development and calibration of such models and thus affect the model predictions. Therefore it often is necessary to perform a model reliability analysis prior to or as a supplement to model application to water pollution control and planning problems. In this paper, only the effect of parameter uncertainties on model prediction is investigated by applying sensitivity and uncertainty analyses. The Latin hypercube sampling technique in combination with regression and correlation analyses has been applied to the DUFLOW model developed for the Dender River in Belgium. These analyses aim to (1) identify the model parameters that significantly affect the model output uncertainty; (2) define the variables that should be measured for a successful model calibration; and (3) examine how model sensitivity changes with changing level of waste treatment. The results obtained indicate that three parameters related to the algal growth process have the greatest effect on the uncertainty of the simulated dissolved oxygen concentrations in the Dender River. [ABSTRACT FROM AUTHOR]

The problem of waste load allocation (WLA) for water quality management of a river system is addressed with a simulation-optimization approach. The WLA model developed in the study provides the best compromise solutions to the pollution control agency (PCA) responsible for maintaining the water quality and the dischargers disposing pollutants into the river system. A previously developed fuzzy waste load allocation model (FWLAM) is extended to incorporate QUAL2E, a water quality simulation model developed by the U.S. Environmental Protection Agency for modeling the pollutant transport in a river. The imprecision associated with establishing water quality standards and the aspirations of the PCA and dischargers are quantified using fuzzy goals with appropriate membership functions. The membership functions of the fuzzy goals represent the variation of the goal satisfaction in the system. A genetic algorithim (GA) is used as an optimization tool to find optimal fraction removal levels to the dischargers and the corresponding satisfaction level. Because a GA is an unconstrained optimization tool, it is extended to handle constraints by complementing it with homomorphous mapping (HM), a constraint handling method for evolutionary algorithms. The GA directs the decision vector in an encoded form to HM. HM, after a few interactions with QUAL2E, redirects the decoded solution back to the GA. The GA assigns a fitness value to the feasible solution vector and applies operators to refine the solution. This interaction among the GA, HM, and QUAL2E continues until a prespecified criterion for global optimality is met. Application of the model is illustrated with a case study of the Tunga-Bhadra River in South India. [ABSTRACT FROM AUTHOR]

Nitrogen budgets established for large river systems reveal that up to 60% of the nitrate exported from agricultural soils is eliminated, either when crossing riparian wetlands areas before even reaching surface waters, or within the rivers themselves through benthic denitrification. The study of nitrogen isotope ratios of riverine nitrates could offer an elegant means to assess the extent of denitrification and thus confirm these budgets, as it is known that denitrification results in a natural 15N enrichment of residual nitrates. The results reported here, for the Seine river system (France), demonstrate the feasibility of this isotopic approach at the scale of large watersheds. On the basis of in situ observations carried out in a large storage reservoir in the upstream Seine catchment (Der Lake), where intensive benthic denitrification occurs, as well as on the basis of laboratory experiments of denitrification under controlled conditions, it is shown that the isotopic discrimination associated with benthic denitrification is minimal (ℇ of NO3-N ranging from -1.5 to -3.6‰), probably because the rate-limiting step of the process consists of nitrate diffusion through the water-sediment interface. Riparian denitrification on the contrary, when it implies nitrate reduction during convective transfer through reducing environements, causes a much more significant isotopic enrichment of 15N of residual nitrate (ℇ about -18‰). The authors report measurements of nitrogen isotopic composition of nitrate from rivers of various stream orders in the Seine river system under summer conditions. Anomalies in the data with respect to the values expected from the mixture of the various sources of nitrate are here attributed to riparian denitrification. However, the authors show that because of the patchy distribution of actively denitrifying riparian zones within the drainage network, the isotopic signature conferred to residual nitrate in river water intrinsically provides only a minimum estimate of the extent of denitrification. [ABSTRACT FROM AUTHOR]

In order to reduce the environmental and ecological problems induced by water resources development and utilization, this paper proposes a concept of environmental and ecological water requirement. It is defined as the minimum water amount to be consumed by the natural water bodies to conserve its environmental and ecological functions. Based on the definition, the methods on calculating the amount of environmental and ecological water requirement are determined. In the case study on Haihe-Luanhe river system, the water requirement is divided into three parts, i.e., the basic in-stream flow, water requirement for sediment transfer and water consumption by evaporation of the lakes or everglades. The results of the calculation show that the environmental and ecological water requirement in the river system is about 124×108 m3, including 57×108 m3 for basic in-stream flow, 63×108 m3 for sediment transfer and 4×108 m3 for net evaporation loss of lakes. The total amount of environmental and ecological water requirement accounts for 54% of the amount of runoff (228×108 m3). However, it should be realized that the amount of environmental and ecological water requirement must be more than that we have calculated. According to this result, we consider that the rational utilization rate of the runoff in the river systems must not be more than 40%. Since the current utilization rate of the river system, which is over 80%, has been far beyond the limitation, the problems of environment and ecology are quite serious. It is imperative to control and adjust water development and utilization to eliminate the existing problems and to avoid the potential ecological or environmental crisis. [ABSTRACT FROM AUTHOR]

In this paper, a review of a semi-empirical modelling approach for cohesive sediment transport in river systems is presented. The mathematical modelling of cohesive sediment transport is a challenge because of the number of governing parameters controlling the various transport processes involved in cohesive sediment, and hence a semi-empirical approach is a viable option. A semi-empirical model of cohesive sediment called the RIVFLOC model developed by Krishnappan is reviewed and the model parameters that need to be determined using a rotating circular flume are highlighted. The parameters that were determined using a rotating circular flume during the application of the RIVFLOC model to different river systems include the critical shear stress for erosion of the cohesive sediment, critical shear stress for deposition according to the definition of Partheniades, critical shear stress for deposition according to the definition of Krone, the cohesion parameter governing the flocculation of cohesive sediment and a set of empirical parameters that define the density of the floc in terms of the size of the flocs. An examination of the variability of these parameters shows the need for testing site-specific sediments using a rotating circular flume to achieve a reliable prediction of the RIVFLOC model. Application of the model to various river systems has highlighted the need for including the entrapment process in a cohesive sediment transport model. [ABSTRACT FROM AUTHOR]

• Genetic structure was assessed using seven polymorphic SSR markers. • High genetic diversity and the absence of a spatial genetic structuring were detected. • Ecoregion differences might not be responsible for the diversity within Ottelia ulvifolia. • Floodplains and river systems connectivity were likely to contribute to the high gene flow among populations. As vital components of freshwater ecosystems, river systems directly boost the dispersal and gene flow of aquatic species. However, various river systems might also increase the potential for isolation of these species and their genetic differentiation. In Africa, the roles of river systems in shaping the genetic diversity and structures of aquatic species are still poorly studied. In order to assess the influence of river systems in freshwater ecoregions on the genetic variation of Ottelia ulvifolia , we genotyped 307 individuals of 18 populations from Bangweulu-Mweru, Middle Zambezi-Luangwa, and Upper Zambezi Floodplain ecoregions in Zambia using ten microsatellite markers. Our results revealed an overall high genetic diversity (H E = 0.475) and high gene flow (Nm > 1) among the three ecoregions. Notably, a relatively higher diversity (H E = 0.485; I = 0.836) was detected in Bangweulu-Mweru compared to those other ecoregions, which could be contributed by frequent river capture events in the area. STRUCTURE, TESS, PCoA, and NJ analyses identified two distinct clusters that were further divided into five sub-clusters, three in bisexual populations and two in the unisexual populations, respectively. The lower genetic differentiation among 18 populations (Fst = 0.258) in the present study could be attributed to the frequent hybridization among populations via insect pollination and water-mediated seed dispersal. A significant positive correlation between Jost's D/(1-Jost's D) and geographic distance among populations (r = 0.142, P = 0.050) indicated deviation for mutation-drift equilibrium. The current findings, however, do not support the hypothesis that variations within ecoregions drive the genetic variation and population structure of O. ulvifolia in Zambia. Lastly, habitat specialization and floral characteristics are examples of behavioral factors that may promote a genetic difference in O. ulvifolia. Our study provides general knowledge of the genetic variation of O. ulvifolia in tropical Africa and indicates a possible regional alteration of various macrophyte dispersal mechanisms at a vast geographic scale, therefore encouraging the need for further research on the genus. [ABSTRACT FROM AUTHOR]

The development of the Ohře River near Žatec between the Late Glacial Maximum (LGM) and present time was studied to obtain its natural trajectory and thus to understand the role of human impact on floodplain development. The study was based on geomorphic research, sampling and dating fluvial sediments by optically stimulated luminescence (OSL) and anthropogenic contamination by Sn since 16th century. During the LGM and the Pleistocene/Holocene transition (P/H), the river valley was shaped by large, incising meanders creating the entire valley floor. The Holocene river, due to decreased channel forming discharges, only slowly continued the LGM and P/H trajectory by cut-offs of the large palaeomeander necks and channel belt narrowing and incision. The last Holocene incision step was likely triggered by hydrological extremes of the Little Ice Age. The LGM and P/H Ohře River consequently changed from meandering to low sinuous, incised in the valley floor; this incision was completed by river engineering in the 20th century. The Ohře River development can thus be rationalised neither by traditional terrace-step formation model nor by model of the Anthropogenic aggradation. [ABSTRACT FROM AUTHOR]