River Discharge

Over the last century, large-scale water development of the upper Rio Grande in the U.S. and Mexico, and of the Rio Conchos in Mexico, has resulted in progressive channel narrowing of the lower Rio Grande in the Big Bend region. We used methods operating at multiple spatial and temporal scales to analyze the rate, magnitude, and processes responsible for channel narrowing. These methods included: hydrologic analysis of historic stream gage data, analysis of notes of measured discharges, historic oblique and aerial photograph analysis, and stratigraphic and dendrogeomorphic analysis of inset floodplain deposits. Our analyses indicate that frequent large floods between 1900 and the mid-1940s acted as a negative feedback mechanism and maintained a wide, sandy, multi-threaded river. Declines in mean and peak flow in the mid-1940s resulted in progressive channel narrowing. Channel narrowing has been temporarily interrupted by occasional large floods that widened the channel, however, channel narrowing has always resumed. After large floods in 1990 and 1991, the active channel width of the lower Rio Grande has narrowed by 36-52%. Narrowing has occurred by the vertical accretion of fine-grained deposits on top of sand and gravel bars, inset within natural levees. Channel narrowing by vertical accretion occurred simultaneously with a rapid invasion of non-native riparian vegetation (Tamarix spp., Arundo donax) which created a positive feedback and exacerbated the processes of channel narrowing and vertical accretion. In two floodplain trenches, we measured 2.75 and 3.5 m of vertical accretion between 1993 and 2008. In some localities, nearly 90% of bare, active channel bars were converted to vegetated floodplain during the same period. Upward shifts of stage-discharge relations occurred resulting in over-bank flooding at lower discharges, and continued vertical accretion despite a progressive reduction in stream flow. Thus, although the magnitude of the average annual flood was reduced between 40 and 50%, over-bank flooding continued. These changes reflect a shift in the geomorphic nature of the Rio Grande from a wide, laterally unstable, multi-thread river, to a laterally stable, single-thread channel with cohesive, vertical banks, and few active in-channel bars.

Using a simple conceptual dynamic river water quality model, the effects of different basin-wide water quality management options on downstream water quality improvements in a semi-arid river, the Crocodile River (South Africa) were investigated. When a river is impacted by high rates of freshwater withdrawal (in its upstream reaches), and receives polluted side-stream inflows and wastewater effluent discharges (in the middle reaches), river water quality can deteriorate seriously over time. This study focused on two water quality problems: Progressive increases in the concentrations of total dissolved solids (TDS) as a measure of salinity, and the concentrations of nitrate-plus-nitrite and ammonia (as inorganic nitrogen) as a measure of eutrophication. Based on a lowflow analysis for the period prior to construction of the Kwena Dam (1960 to 1979), the 7d low flows that could be expected to occur every 10 years (7Q10) are generally very low (< 0.5 m 3 •s-1), both in the upstream (Montrose Weir) and the downstream (Kruger National Park) sections of the Crocodile River. During such critical periods of low river flow, very low effluent standard limits would be required to prevent adverse river water quality. However, these options are not economically feasible. Furthermore, inflows from the highly polluted tributary stream, the Kaap River, which drains an area where considerable gold mining takes place, govern water quality in the Crocodile River downstream of the Crocodile-Kaap confluence. Subsequently, two additional water quality control options (setting limits for maximum water withdrawal and low-flow augmentation) were analysed. The results show that a decrease in maximum water withdrawal could reduce the TDS concentration. Furthermore, controlling water release patterns from a dam at the Montrose Weir can have a remarkably positive effect on the downstream river water quality. On the basis of the 1989/90 monitoring data, a minimum flow of 5 m 3 •s-1 at the Montrose Weir can reduce concentrations of TDS and ammonia nitrogen by about 20% and 60%, respectively, in the Kruger National Park (at the downstream point of the considered river). However, this management option does not reduce nitrate nitrogen concentrations. The proposed model used in this study is relatively simple and can be used as a tool for the evaluation of short-term (monthly) basin-wide water quality management options.

A 10-layered, finite-volume advection-dispersion model with real-time meteorological and freshwater runoff drivers investigated the interannual differences in the transport of Downs herring Clupea harengus L. larvae in the southern North Sea. Simulations were carried out for the winters of 1989 and 1996 to 2003. As they grew, the concentrations of herring larvae developed vertical behaviour. Meteorological forcing transported Downs herring larvae to the nursery grounds in the eastern North Sea with large interannual differences. Diel vertical movement was relatively unimportant in the transport of larvae in the hydrographically mixed southern North Sea. Year classes with less transport of larvae from the hatching area (which was generally warmer) were associated with greater abundances of young Downs herring in the ICES International Bottom Trawl Survey. This implies that retention, rather than dispersal or delivery of larvae to nursery grounds, is associated with the determination of year class strength in Downs herring.

. Geographic and hydrodynamic characteristics of shallow coastal lagoons. In: L.G. Ward and G.M. Ashley (Editors), Physical Processes and Sedimentology of Siliciclastic-Dominated Lagoonal Systems. Mar. Geol.,. Coastal lagoons can be conveniently separated based on geomorphology into leaky, restricted or choked systems. This subdivision orders coastal lagoons hydrodynamically according to water exchange with the coastal ocean. Leaky systems have the shortest turnover time, restricted lagoons have a longer turnover time, and choked lagoons have the longest turnover time. In leaky coastal lagoons, oscillating tidal currents account for most of the flow variance and mask residual currents due to wind-and freshwater-induced density gradients. In restricted lagoons, tides, winds, and freshwater runoff drive components of the circulation. Winds are usually dominant in causing circulation and mixing in choked lagoons, and water exchange with the coastal ocean largely depends on the hydrologic cycle. Coastal lagoons are usually well mixed, but can exhibit significant horizontal gradients due to freshwater runoff and vertical gradients due to solar radiation or surface cooling. In general, river inflow and heat balance induce stratification in coastal lagoons, whereas winds and tides cause mixing. Coastal lagoons usually trap inorganic sediment and organic matter, thus serving as material sinks. On a geologic time scale, they are short-lived landscape features, with an existence intrinsically linked to filtering efficiency and relative sea-level change as a result of glacioeustatic cycles and local tectonic activity.

This paper presents a quantitative estimation of the impact of reservoirs on discharge and irrigation water supply during the 20th century at global, continental, and river basin scale. Compared to a natural situation the combined effect of reservoir operation and irrigation extractions decreased mean annual discharge to oceans and significantly changed the timing of this discharge. For example, in Europe, May discharge decreased by 10%, while in February it increased by 8%. At the end of the 20th century, reservoir operations and irrigation extractions decreased annual global discharge by about 2.1% (930 km 3 yr À1). Simulation results show that reservoirs contribute significantly to irrigation water supply in many regions. Basins that rely heavily on reservoir water are the Colorado and Columbia River basins in the United States and several large basins in India, China, and central Asia (e.g., in the Krishna and Huang He basins, reservoirs more than doubled surface water supply). Continents gaining the most are North America, Africa, and Asia, where reservoirs supplied 57, 22, and 360 km 3 yr À1 respectively between 1981-2000, which is in all cases 40% more than the availability in the situation without reservoirs. Globally, the irrigation water supply from reservoirs increased from around 18 km 3 yr À1 (adding 5% to surface water supply) at the beginning of the 20th century to 460 km 3 yr À1 (adding almost 40% to surface water supply) at the end of the 20th century. The analysis is performed using a newly developed and validated reservoir operation scheme within a global-scale hydrology and vegetation model (LPJmL).

With improved observation methods, increased winter navigation, and increased awareness of the climate and environmental changes, research on the Baltic Sea ice conditions has become increasingly active. Sea ice has been recognized as a sensitive indicator for changes in climate. Although the interannual variability in the ice conditions is large, a change towards milder ice winters has been detected from the time series of the maximum annual extent of sea ice and the length of the ice season. On the basis of the ice extent, the shift towards a warmer climate took place in the latter half of the 19th century. On the other hand, data on the ice thickness, which are mostly limited to the land-fast ice zone, basically do not show clear trends during the 20th century, except that during the last 20 years the thickness of land-fast ice has decreased. Due to difficulties in measuring the pack-ice thickness, the total mass of sea ice in the Baltic Sea is, however, still poorly known. The ice extent and length of the ice season depend on the indices of the Arctic Oscillation and North Atlantic Oscillation. Sea ice dynamics, thermodynamics, structure, and properties strongly interact with each other, as well as with the atmosphere and the sea. The surface conditions over the ice-covered Baltic Sea show high spatial variability, which cannot be described by two surface types (such as ice and open water) only. The variability is strongly reflected to the radiative and turbulent surface fluxes. The Baltic Sea has served as a testbed for several developments in the theory of sea ice dynamics. Experiences with advanced models have increased our understanding on sea ice dynamics, which depends on the ice thickness distribution, and in turn redistributes the ice thickness. During the latest decade, advance has been made in studies on sea ice structure, surface albedo, penetration of solar radiation, sub-surface melting, and formation of superimposed ice and snow ice. A high vertical resolution has been found as a prerequisite to successfully model thermodynamic processes during the spring melt period. A few observations have demonstrated how the river discharge and ice melt affect the stratification of the oceanic boundary layer below the ice and the oceanic heat flux to the ice bottom. In general, process studies on ice-ocean interaction have been rare. In the future, increasingly multidisciplinary studies are needed with close links between sea ice physics, geochemistry and biology.

The objective of this paper is to determine the most appropriate data collection strategy and analysis techniques which should be used to assess the low flow regime of a catchment. The data used were: a) synchronous discharge measurements during low flow periods, and b) continuous daily flow records. The analyses based on both types of data were able to distinguish different low flow regimes within a 114 km2 Danish catchment. Despite the limited spatial variation in climate and geomorphology there was a high spatial variability in low flows caused by differences in the lithology of sediments. This demonstrates the difficulties in using simple indices of catchment geology in regional low flow estimation. The results highlight the benefits of using synchronous discharge measurements, both for estimating low flows at ungauged sites, and for understanding groundwater flow paths. Analyses of daily flow records from six gauging stations in the catchment showed that a baseflow index was more useful than the flow duration curve for classifying low flow regimes when only short records were available. The paper illustrates the importance of estimating the uncertainty of discharge measurements when interpreting low flow data.

Observations over the last 20 yr of the development of pelagic and benthic communities of a western European coastal ecosystem (Bay of Brest) provide complementary hypotheses to the 'silicic acid pump' hypothesis. An increase in nitrogen inputs, independent of silicic acid levels, has lowered the Si:N molar ratios during the last 20 yr in river discharges. Since 1981, maximum concentrations of chlorophyll a during the first spring bloom of the annual cycle have decreased, in contrast to the subsequent spring and summer blooms. Concomitantly, extensive spreading of an exotic gastropod Crepidula fornicata has modified the trophic structure of benthic communities by increasing suspension-feeder biomass. The following hypotheses on ecosystem functioning are made: (1) the decrease of chlorophyll biomass during the first spring bloom results from silicic acid limitation and increased suspension feeder activity, (2) benthic filtration and biodeposition activities enhance biogenic silica retention at the sediment-water interface, and (3) recycling of trapped biogenic silica maintains diatom populations by providing silicic acid in summer and reduces primary production seasonality. These hypotheses suggest that benthic organisms control the export rate of biogenic silica towards the open-water ocean and thus the specific composition of secondary phytoplankton blooms in the Bay.

ABSTRACT River water cleaning from microorganisms using electrohydraulic discharges and ozonation was investigated. The processed water was highly polluted with the total number of microorganisms (70 400 cfu/mL) and total Escherichia coli bacteria (280 cfu/mL). The processing was conducted in a tube reactor with a hollow needle-rod electrode configuration. A 400-mL sample of river water was treated at different flow rates. Ozonation was performed in a washing bottle with an ozone concentration of 20 g/m3. The corona discharge treatment showed a steady decrease of bacteria and microorganisms but did not kill them completely. Spark discharge killed the bacteria and microorganisms completely; however, its energy efficiency was much lower than that of ozonation. The ozone treatment decreased the concentration of microorganisms and coli bacteria down to 785 and 10 cfu/mL, respectively, in 45 s which resulted in higher energy efficiency than processing using corona and spark discharges. The NPOC analysis of the treated samples showed its concentration of 5 ± 0, 4 ppm in all samples.

This research aim to analyse how big topography factor, land ground, forest closing, non forest closing, and rainfall influence to discharge of Mamasa River, and formulating link model. This research was executed in DAS Mamasa, taking place during 12 months, December 2006 up to December 2007. Method used in research is survey method that is measurement river discharge at 12 river branch as sample and analysing the Rupa Bumi Indonesia Mapping to know the topography (wide per slope level), land ground (wide per land ground type), wide of forest and non forest closing. Result of research indicate that the topography factor (wide per slope level), wide per land ground type, wide of forest closing, wide of non forest closing and rainfall have an effect on very significant to river discharge. Has model the Q=F(TP,TH, HT, NH, CH), each with the value R2 =

The biotic composition, structure, and function of aquatic, wetland, and riparian ecosystem depend largely on the hydrological regime (Poff, N.L., Ward, J.V., 1990. Implications of streamflow variability and predictability for lotic community structure: a regional analysis of streamflow patterns. Can. J. Fisheries Aquat. Sci. 46, 1805-1818; Richter, B.D., Baumgartner, J.V., Wiginton, R., Braun, D.P., 1997 How much water does a river need? Freshwater Biol. 37, 231-249). Available flow data for many rivers in the world can be used to validate these ecological theories. There is a demand for studies that use hydrological indices to establish criteria, which serve to group together regime types at a local level. Once this has been done, these hydrologically similar groups can be used to identify communities of living organisms that are linked to specific aspects of the river's behaviour.

An examination of Dutch local and regional spatial plans adopted in 2005 has shown that water safety is hardly an issue in Dutch local and regional planning practices. In the light of Dutch climate change scenarios, projecting sea level rise, land subsidence in the peat areas and an increase in extremely high river discharges of the largest Dutch river systems this is at the very least striking. In this paper, it was explored why flooding from the sea or rivers is not considered in Dutch spatial planning at the local and regional level. Dutch flood management policy turned out to be mainly focused on flood prevention through the construction and maintenance of water defences. If the water defences meet the legal safety criteria, spatial developments within the dike-ring, the area protected by water defences, are formally legitimate and additional spatial planning measures to mitigate the residual risk are not compulsory. As a result, flood risk issues are hardly considered in spatial planning practices. In the light of this established prevention practices, it was a striking finding that another discourse appeared in spatial planning practices. In this discourse, additional spatial flood mitigation measures in the dike-ring area were considered to reduce the residual flood risk in the dike-ring area. Four factors have been distinguished that lead to this different consideration of flood risks in spatial planning practices: the conceptualisation of flood risks, the felt public concerns, the felt responsibilities and the felt necessity to legitimise spatial developments.

Daily stage data measured at the closing section of the Po River (Northern Italy), collected from historical archives of the “Hydrological Office of the Po River—Parma”, allowed to estimate daily discharges for the period 1807–1916, therefore to extend the time series of Po River discharges for 110 years before the actually published time series. This paper provides a detailed description of the stage–discharge conversion and of the tests performed for checking homogeneity of reconstructed data. In particular, monthly discharge data were compared with approximated catchment-average data of precipitation and evapotranspiration for the period 1831–2003, which were estimated, respectively, from monthly data of local precipitation (at Milan, Turin and Parma) and local air temperature (at Milan and Turin). It emerges that estimated values of precipitation, evapotranspiration and discharge provide a coherent picture of the hydrological dynamics in the basin throughout the study period. Specifically, an apparent progressive depletion of basin reservoirs is observed since 1920, i.e., when concomitant sudden changes (regime shifts) occurred in precipitation (downward shift) and evapotranspiration (upward shift). The 1920-shift is amongst the likely causes of the fact that prolonged drought periods as those observed in the 1940s and since 2003 are not observed in the pre-shift period, when accumulation of reservoirs occurred. The increase in peak-flow discharges observed in recent decades, with values well above the maximum discharge estimated for the nineteenth century as well as for the early twentieth century, is apparently the result of the massive levee works along the river network that were completed in the 1960s. On decadal time scales, discharge variability is found to essentially reflect the changes in precipitation patterns. In particular, peaks of comparable magnitude are found in the 128-month (∼11 years) wavelet spectra of precipitation and discharge. Furthermore, concurrent changes are observed in the persistence (i.e., autocorrelation) of precipitation and discharge data. Since the red-noise background spectrum of discharge is much lower than that of precipitation, river discharge is the likely hydrological variable to be preferred for assessing the basin’s response to the background climatic variability occurring at the decadal and multi-decadal time scales, notwithstanding the fact that changes in water management and other anthropogenic impacts can be important on long time scales. Concerning the seasonal to interannual response to climatic forcing, a robust dependence of wintertime precipitation and discharges on the state of the NAO was observed. This dependence results in stronger (weaker) precipitation and higher (lower) discharges during negative (positive) anomalies of the NAO index.

Water quantity and quality are considered to be the main driving forces of the reservoir operation. Barra Bonita reservoir, located in the southeast region of Brazil, is chosen as the case study for the application of the proposed methodology. Herein, optimization and artificial intelligence (AI) techniques are applied in the simulation and operation of the reservoir. A fuzzy stochastic dynamic programming model (FSDP) is developed for calculating the optimal operation procedures. Optimization is applied to achieve multiple fuzzy objectives. Markov chain technique is applied to handle the stochastic characteristics of river flow. Water quality analysis is carried out using an artificial neural network model. Organic matter and nutrient loads are modeled as a function of river discharge through the application of a fuzzy regression model based on fuzzy performance functions. The obtained results show that the proposed methodology provides an effective and useful tool for reservoir operation.

The effect of river runoff in the Bay of Bengal is examined using a reduced gravity primitive equation ocean model coupled to an atmospheric boundary layer model. Model simulations are carried out by including river discharges as surface freshwater forcing at the mouths of the rivers. To assess the effect of river inputs on the dynamics and thermodynamics of the tropical Indian Ocean, parallel simulations are carried out by neglecting the river inputs. Additionally, another set of parallel runs without penetrative radiation loss through the mixed layer is carried out. The freshwater flux due to rivers results in lower salinities and shallower mixed layers, as expected. However, the influence of this additional freshwater flux into the bay is rather counterintuitive. With the inclusion of river discharges more heat is absorbed by the ocean, but sea surface temperatures are slightly cooler in the bay because of enhanced entrainment cooling of the shallower mixed layer, enhanced penetrative radiation, and an enhanced effect of latent heat loss on the temperature tendency. This is despite the greater latent heat loss when river input is neglected. Conversley, neglect of penetrative radiation results in a shallower but slightly warmer mixed layer with river input. River input and penetrative radiation each affect the mixed layer depths, the salinity and temperature structure, and currents in the Bay of Bengal, but they have a small effect on SST. Annual SST, averaged over the Bay of Bengal, is only 0.1øC colder with river input. Neglecting penetrative radiation in the river run results in an increase of only 0.2øC for the annual SST. The lack of persistence of a barrier layer in the bay helps regulate SST even in the presence of enhanced buoyancy forcing due to river input. Averaged over the bay, a barrier layer forms as mixed layer detrainment occurs, and the thermocline deepens just after the southwest monsoon and the northeast monsoon. The barrier layer is short-lived in each case it is eroded by mixing. The effect of riverine input in the bay is not confined to the surface waters. A pool of cold anomaly (-1øC) and freshet waters is centered near 100 m depth in the bay with riverine input. This cold pool beneath the mixed layer allows entrainment cooling of the mixed layer to be more effective, even though mass entrainment is lower relative to the case neglecting river input. The more diffuse thermocline in the bay is consistent with enhanced vertical mixing despite the large positive buoyancy forcing. 1. Introduction The Bay of Bengal is the freshest region in the Indian Ocean by virtue of both direct monsoonal rainfall and by large rivefine input. The onset of the summer monsoon rainfall occurs on the eastern side of the bay (near to the outflow of the Irrawaddy River) and over parts of Burma and Thailand and then spreads toward the northwest [Ramage et al., 1972]. During the

The objective of the present work is to analyze the role of landscape for environmental security in the Yantra River Basin, exploring its relationships with river-water quality and flood hazard. The relationship between landscape and river-water quality is analyzed on the basis of landscape indicators and assessment tools like Automated Geospatial Watershed Assessment (AGWA) and Analytical Tools Interface for Landscape Assessment (ATtILA). The relationship between landscape and flood hazard is explored using set of floodhazard indicators and the Soil and Water Assessment Tool (SWAT). The results from ATtILA implementation show that the main sources of nitrogen loading are the agricultural landscapes and the urban areas in the river basin. The SWAT simulation is done for three scenarios in which land cover (forest lands) changes are related to flood hazard. For the most unfavorable scenario, decreasing forest lands, a significant increase of the river discharge is predicted. The degr...

In this paper, we develop and apply a framework for estimating the potential global-scale impact of reservoir construction on riverine sediment transport to the ocean. Using this framework, we discern a large, global-scale, and growing impact from anthropogenic impoundment. Our study links information on 633 of the world's largest reservoirs (LRs) ( z 0.5 km 3 maximum storage capacity) to the geography of continental discharge and uses statistical inferences to assess the potential impact of the remaining >44,000 smaller reservoirs (SRs). Information on the LRs was linked to a digitized river network at 30V (latitude  longitude) spatial resolution. A residence time change (Ds R ) for otherwise free-flowing river water is determined locally for each reservoir and used with a sediment retention function to predict the proportion of incident sediment flux trapped within each impoundment. The discharge-weighted mean Ds R for individual impoundments distributed across the globe is 0.21 years for LRs and 0.011 years for SRs. More than 40% of global river discharge is intercepted locally by the LRs analyzed here, and a significant proportion ( c 70%) of this discharge maintains a theoretical sediment trapping efficiency in excess of 50%. Half of all discharge entering LRs shows a local sediment trapping efficiency of 80% or more. Analysis of the recent history of river impoundment reveals that between 1950 and 1968, there was tripling from 5% to 15% in global LR sediment trapping, another doubling to 30% by 1985, and stabilization thereafter. Several large basins such as the Colorado and Nile show nearly complete trapping due to large reservoir construction and flow diversion. From the standpoint of sediment retention rates, the most heavily regulated drainage basins reside in Europe. North America, Africa, and Australia/Oceania are also strongly affected by LRs. Globally, greater than 50% of basin-scale sediment flux in regulated basins is potentially trapped in artificial impoundments, with a discharge-weighted sediment trapping due to LRs of 30%, and an additional contribution of 23% from SRs. If we consider both regulated and unregulated basins, the interception of global sediment flux by all registered reservoirs 0921-8181/03/$ -see front matter D Global and Planetary Change 39 (2003) 169 -190 (n c 45,000) is conservatively placed at 4 -5 Gt year À 1 or 25 -30% of the total. There is an additional but unknown impact due to still smaller unregistered impoundments (n c 800,000). Our results demonstrate that river impoundment should now be considered explicitly in global elemental flux studies, such as for water, sediment, carbon, and nutrients. From a global change perspective, the long-term impact of such hydraulic engineering works on the world's coastal zone appears to be significant but has yet to be fully elucidated. D

A regionalization of flood data in British Columbia reveals a common scaling with drainage area over the range 0Ð5 ð 10 2 < A d < 10 4 km 2 . This scaling is not a function of flood return period, which implies that simple scaling-consistent with a snowmelt-dominated flow regime-applies to the province. The observed scale relation takes the form Q / A 0Ð75 d , similar to values reported in previous studies. The scaling relation identified was used to define the regional pattern of hydroclimatic variability for flood flows in British Columbia after discounting the effect of drainage area. The pattern was determined by kriging a scale-independent runoff factor k for the mean annual flood, 5 year flood and 20 year flood. The analysis permits quantification of uncertainty of the estimates, which can be used in conjunction with the mapped k-fields to calculate a mean and range for floods with the identified return period for ungauged basins. Owing to the sparsity of data, the precision is relatively poor. The standard error is generally less than 75% of the estimate in the southern half of the province, whereas in the northern half it is often between 75 and 100%. Examination of the relative increase in flood magnitude with increasing return period reveals spatially consistent but statistically insignificant differences. Flood magnitude tends to increase more rapidly in the western regions, where rain events may contribute to flood generation. The relative increase in flood magnitude with return period is consistently lower in the eastern mountain ranges, where snowmelt dominates the flood flow regime.

Semarang is one of the biggest cities in Indonesia and is nowadays suffering from coastal flooding. Land subsidences, high water tide, and inadequate structural measures play important roles in the coastal inundations. Structural and non-structural methods for controlling coastal flooding including dykes, drainage systems, pump stations, polder systems, coastal-land reclamations, coastal planning and management, public education, as well as the establishment of an institutional framework for disaster management have been implemented in the Semarang coastal area. Although some improvements have been made, the current flood management system has generally failed to address a wide range of coastal inundation problems. Some improvement actions have been proposed including stakeholders involvement on the disaster mitigation. For a long period coastal management, accelerated sea level rises due to global warming should also be taken into account.

As a consequence of increasing winter rainfall totals and intensities over the second half of the 20th century, signs of increased flooding probability in many areas of the Rhine and Meuse basins have been documented. These changes affecting rainfall characteristics are most evidently due to an increase in westerly atmospheric circulation types. Land use changes, particularly urbanization, can have significant local effects in small basins (headwaters) with respect to flooding, especially during heavy local rainstorms, but no evidence exists that land use change has had significant effects on peak flows in the rivers Rhine and Meuse.

An organic-walled dinoagellate cyst analysis was carried out on 53 surface sediment samples from West Africa (17-6°N) to obtain insight in the relationship between their spatial distribution and hydrological conditions in the upper water column as well as marine productivity in the study area. Multivariate analysis of the dinoagellate cyst relative abundances and environmental parameters of the water column shows that sea-surface temperature, salinity, marine productivity and bottom water oxygen are the factors that relate signicantly to the distribution patterns of individual species in the region. The composition of cyst assemblages and dinoagellate cyst concentrations allows the identication of four hydrographic regimes; 1) the northern regime between 17 and 14°N characterized by high productivity associated with seasonal coastal upwelling, 2) the southern regime between 12 and 6°N associated with high-nutrient waters inuenced by river discharge 3) the intermediate regime between 14 and 12°N inuenced mainly by seasonal coastal upwelling additionally associated with uvial input of terrestrial nutrients and 4) the offshore regime characterized by low chlorophyll-a concentrations in upper waters and high bottom water oxygen concentrations. Our data show that cysts of Polykrikos kofoidii, Selenopemphix quanta, Dubridinium spp., Echinidinium species, cysts of Protoperidinium monospinum and Spiniferites pachydermus are the best proxies to reconstruct the boundary between the NE trade winds and the monsoon winds in the subtropical eastern Atlantic Ocean. The association of Bitectatodinium spongium, Lejeunecysta oliva, Quinquecuspis concreta, Selenopemphix nephroides, Trinovantedinium applanatum can be used to reconstruct past river outow variations within this region.

Generalized additive models are proposed for a better understanding of the underlying mechanisms for anchovy variations in abundance. Environmental variables derived from satellite imagery (surface chlorophyll, sea surface temperature and wind-mixing index), river discharge (Rhône River and Ebre River) and anchovy landings (landings per unit of effort) as proxy for abundance were used, and three fishing zones were defined along the Catalan Coast. A time shift among wind index mixing, sea surface temperature and chlorophyll was observed for these variables to be significantly correlated with anchovy. Results pointed out to processes that appear to greatly influence species abundance and affect different life stages of anchovy (conditions preceding reproduction, larvae growth and survival and recruits growth). A high proportion of anchovy LPUE variability could be explained by environmental variables. Thus, some univariate models explained deviance are more than 50%, even up to around 70% of anchovy variability. In several cases the deviance explained by a given variable was even higher at the longer time-lags. Among all univariate and bivariate models fitted, the model that best explained anchovy LPUE variability, 79% of total deviance, was a model proposed for the central zone, based on the additive effect of surface chlorophyll and Rhône River discharge, considering time lags of 15 and 18 months, respectively, for each variable.

Floodplains may be transformed when environmental changes or human activity causes alluvial systems to cross channel pattern thresholds. Thresholds between pattern states based on occurrence fields are only available for some pattern distinctions, and these may not encompass the alluvial contexts and range of dynamic factors involved. Pattern changes now known from the UK Holocene are reviewed as a basis for appreciating the potential for future transformations in a changing environment. These involved episodic boulder and gravel spreads in upland environments, and braiding $ meandering, anastomosing ! meandering and active $ inactive transformations in more lowland contexts. Concern for possible impacts of climatic change need to be grounded in an appreciation of the nature and scale of these past changes. Some potential future changes may be relatively predictable in location (braiding $ meandering); others are more difficult given both present knowledge and the varying, modified and inheritance-rich 'contexts of vulnerability' that floodplains now represent. Implications for management are discussed.

1] The Snowball Earth hypothesis explains the development of glaciation at low latitudes in the Neoproterozoic, as well as the associated iron formations and cap carbonates, in terms of a runaway ice-albedo feedback leading to a global glaciation followed by an extreme greenhouse climate. The initiation of a snowball glaciation is linked to a variety of unusual perturbations of the carbon cycle operating over different timescales, as evidenced by unusual patterns in the carbon isotopic composition of marine carbonate. Thus a theory for why multiple glaciations happened at this time, and not in the Phanerozoic nor earlier in the Proterozoic, requires a reexamination of the carbon cycle and the controls on climate stability. We propose that the concentration of continental area in the tropics was a critical boundary condition necessary for the onset of glaciation, both because the existence of substantial continental area at high latitudes may prevent atmospheric carbon dioxide from getting too low and because a tropical concentration of continental area may lead to more efficient burial of organic carbon through increased tropical river discharge. Efficient organic carbon burial sustained over tens of millions of years, required by the high carbon isotopic compositions of preglacial carbonate, may lead to the buildup of enormous quantities of methane, presumably in hydrate reservoirs. We examine how the slow release of this methane may explain the drop in d 13 C values immediately before the glaciation. Moreover, the accumulation of methane in the atmosphere coupled with the response of silicate weathering to the additional greenhouse forcing can lead to a climate with methane as the major greenhouse gas. This situation is unstable because methane is not buffered by a large ocean reservoir like carbon dioxide, and so the collapse of the methane source may provide a trigger for the onset of a runaway ice-albedo feedback. A simple model of the carbon cycle is used to explore the boundary conditions that would allow this to occur.

Among the large rivers rising on the Tibetan Plateau and adjacent high mountains, the discharge and suspended sediment load of the Ayeyarwady (Irrawaddy) River are the least well known. Data collected between 1969 and 1996 at Pyay (Prome) are analysed to provide the best available modern estimate of discharge (379 š 47 ð 10 9 m 3 /year) and suspended sediment load (325 š 57 ð 10 6 t/year) for the river upstream of the delta head. A statistical comparison with data collected in the nineteenth century (1871 to 1879) shows discharge has significantly decreased in the last ¾100 years. Regression and correlation analyses between discharge in the modern period and indices of El Niño-Southern Oscillation (ENSO) show a relationship.

Freshwater availability has been recognized as a global issue, and its consistent quantification not only in individual river basins but also at the global scale is required to support the sustainable use of water. The WaterGAP Global Hydrology Model WGHM, which is a submodel of the global water use and availability model WaterGAP 2, computes surface runoff, groundwater recharge and river discharge at a spatial resolution of 0.58. WGHM is based on the best global data sets currently available, and simulates the reduction of river discharge by human water consumption. In order to obtain a reliable estimate of water availability, it is tuned against observed discharge at 724 gauging stations, which represent 50% of the global land area and 70% of the actively discharging area. For 50% of these stations, the tuning of one model parameter was sufficient to achieve that simulated and observed long-term average discharges agree within 1%. For the rest, however, additional corrections had to be applied to the simulated runoff and discharge values. WGHM not only computes the long-term average water resources of a country or a drainage basin but also water availability indicators that take into account the interannual and seasonal variability of runoff and discharge. The reliability of the modeling results is assessed by comparing observed and simulated discharges at the tuning stations and at selected other stations. The comparison shows that WGHM is able to calculate reliable and meaningful indicators of water availability at a high spatial resolution. In particular, the 90% reliable monthly discharge is simulated well. Therefore, WGHM is suited for application in global assessments related to water security, food security and freshwater ecosystems. q

Greater Cook Strait (GCS) lies between the North and the South Islands of New Zealand. Its location at the convergence of the Pacific and Indo-Australian tectonic plates leads to interesting bathymetry with an adjacent shallow shelf and deep ocean trench as well as numerous crossing faults and complex shoreline geometry. Our purpose in this study is to examine tides and currents in GCS and, in particular, identify the major forcing mechanisms for the residual currents. Toward this end, we use an unstructured-grid numerical model to reproduce the tides and currents, verify these results with observations and then use the model to separate the various forcing mechanisms.

Sixteen water quality parameters have been monitored at four stations located along the Maroon River during 1989–2008. The trend analysis was performed on seasonal and annual timescales using the Mann–Kendall test, the Sen’s slope estimator and the linear regression. The relationships of the water quality parameters to river discharge were also investigated. The statistical methods showed both positive and negative trends in annual water quality data. However, significant trends were detected by the statistical methods only in calcium, magnesium, sodium absorption ratio, pH, and turbidity series. The results indicated that the concentrations of the water quality parameters increased in spring and winter seasons, while the concentrations were diluted in summer and autumn seasons in the last two decades. Moreover, the highest numbers of significant trends were found in the spring and summer series, respectively. According to the regression analysis, most of the water quality parameters were negatively correlated with river discharge.were negatively correlated with river discharge.

Studies that relate changes in land cover with changes in river discharge at the small scale (, 1 km 2 ) are abundant. These studies generally indicate that deforestation causes an increase in the annual mean discharge. However, previous studies that evaluated the effects of changes in land cover in larger river basins (.100 km 2 ) usually have not found similar relationships. Here we analyse a 50-year long time series of discharge of a tropical river, the Tocantins River at Porto Nacional (175,360 km 2 ), as well as precipitation over this drainage area, during a period where substantial changes in land cover occurred in the basin (1949 -1998). Based on agricultural census data, we estimate that, in 1960, about 30% of the basin was used for agriculture. Previous work indicates that by 1995, agriculture had increased substantially, with about 49% of the basin land used as cropland and pastures. Initially, we compare one period with little changes in land cover (period 1-1949 -1968) with another with more intense changes in land cover (period 2-1979 -1998). Our analysis indicates that, while precipitation over the basin is not statistically different between period 1 and period 2 ða ¼ 0:05Þ; annual mean discharge in period 2 is 24% greater than in period 1 ðP , 0:02Þ; and the high-flow season discharge is greater by 28% ðP , 0:01Þ: Further analyses present additional evidence that the change in vegetation cover altered the hydrological response of this region. As the pressure for changes in land cover in that region continue to increase, one can expect important further changes in the hydrological regime of the Tocantins River. q

The Danube catchment basin (817 000 km 2 , 76 10 6 inhabitants) is the major freshwater contributor to the Black Sea (6300 m 3 s 1 , 80% of the annual river discharge into the north-western Black Sea). The aim of the modelling approach developed for the Danube River, is to establish how land use and management of the whole watershed are linked to nutrient (N, P, Si) delivery and retention by the river. The approach uses an adaptation of the RIVERSTRAHLER model, which is based on a schematic representation of the drainage network deduced from geomorphological analysis by stream orders. The whole catchment was divided into 10 sub-basins and one branch, to provide a description satisfying both the need to take into account the heterogeneity of the system and the availability of constraints and validation data. On the basis of this description, a hydrological model was developed, which adequately simulated the seasonal variations of the discharge measured at the outlet of the basin. The model itself resulted from the coupling of the hydrological model with a biogeochemical model (RIVE), which takes into account the main ecological processes. It established a link between microscopic processes, their controlling factors and their macroscopic manifestations in terms of nutrient cycling and ecological functioning at the scale of the whole drainage network. The model was validated for the period from 1988 to 1991 on the basis of available observations of the major water-quality variables involved in the eutrophication processes (inorganic nutrients, phytoplankton biomass, dissolved oxygen, etc.). A reasonable agreement was found between the simulations of the model and the observations. Nutrient fluxes to the Black Sea, calculated for our reference period, are in the same range as those obtained via other approaches. Si/P and N/P ratios suggest silicon, rather than phosphorus, limitation for diatoms and phosphorus, rather than nitrogen, limitation for overall phytoplankton in the coastal zone of the Black Sea. The sharp drop in N and P delivery to the Black Sea, observed since 1991, was simulated with a scenario constructed to reproduce new constraints based on documented modifications of human activity in the watershed. Due to the scarcity of data, there is a need for further validation of the model. Nevertheless, the structure of the model allows the specificity of each sub-basin to be taken into account in future management plans.

The rate of recession of Niagara Falls (Horseshoe and American Falls) in northeastern North America has been documented since the 19th century; it shows a decreasing trend from ca. 1 m y − 1 a century ago to ca. 0.1 m y − 1 at present. Reduction of the flow volume in the Niagara River due to diversion into bypassing hydroelectric schemes has often been taken to be the factor responsible, but other factors such as changes in the waterfall shape could play a role and call for a quantitative study. Here, we examine the effect of physical factors on the historically varying recession rates of Niagara Falls, using an empirical equation which has previously been proposed based on a non-dimensional multiparametric model which incorporates flow volume, waterfall shape and bedrock strength. The changes in recession rates of Niagara Falls in the last century are successfully modeled by this empirical equation; these changes are caused by variations in flow volume and lip length. This result supports the validity of the empirical equation for waterfalls in rivers carrying little transported sediment. Our analysis also suggests that the decrease in the recession rate of Horseshoe Falls is related to both artificial reduction in river discharge and natural increase in waterfall lip length, whereas that of American Falls is solely due to the reduction in flow volume.

Drowned reefs, fossil reefs or paleo-reefs, are important ecologically as areas of high biodiversity, foraging, shelter environment, and as areas supporting the spawning aggregations of economically important reef fish species. This is particularly significant when the structures are situated in a wide soft-bottom continental shelf. The presence of limestone structures, fossil reefs and pinnacles dating from circa 8 to 9 ka, to the north of the Paria Peninsula in north-eastern Venezuela, has been known to local fishermen for decades. Using echograms obtained during acoustic fisheries evaluations and the scarce previously available information, an improved location map of hard-bottom structures was made. Benthic samples to study macromolluscs were taken at depths between 54 and 93 m using an unmodified 2-m beam trawl. Four trawl samples were located over fossil reef areas while another four were situated in soft-bottom valleys between limestone structures. Fossil reefs in the area showed a highly patchy distribution. A total of 91 species from 43 Bivalvia, Gastropoda and Scaphopoda families were found, Gastropoda being the dominant class with 49 species. Paleo-reef-covered areas showed higher species richness and only 21% of the species found were common to both substrates. Gastropods Tonna maculosa and Polystira albida were the most abundant species and occurred in both substrate types. Bivalve life habits, a mixture of organismesubstrate relationships, shell fixation, mobility and feeding type, differed significantly according to bottom type. Six species are recorded for the first time for eastern Venezuelan waters. Bottom heterogeneity plays an important role in marine ecosystems, providing shelter to fish populations and may be significant as breeding and nursery areas. Its presence in a region with biogeographical interest, situated in the confluence of three major provinces and with oceanographic conditions varying seasonally from upwelling dominated to Orinoco River discharges, makes this the area of interest and it should be evaluated as a possible Marine Protected Area.

In the present day world, the problems of too much, too little or too polluted water are increasing at a rapid rate. These problems have become particularly severe for the developing countries, adversely affecting their agriculture, drinking water supply and sanitation. Water recourse management is no more just a challenger it is a declared crises. Water resources in Kosova are relatively small, total amount of water in our country is small around 1600m 3 / inhabitant /year. Territory of Kosova is separated in four river basins: Drini i Bardhë, Ibri, Morava e Binqës and Lepenci. Drini i Bardhë river basin is in the western part of Kosovo, it is the biggest river basin with surface of 4.289 km 2 . Drini i Bardhë discharges its water to Albania and finally to the Adriatic Sea. The area consist of several small stream from the mountains, water flows into tributaries and Drini i Bardhë river. The mean run-off in the area is 141 l/s/km 2, but it varies considerably (5 to 50 l/s/km 2 ), precipitation varies from 600 to 1400 mm/a. Protecting from pollution is a very important issue having in consideration that this river discharges its water and outside the territory. Hydrometeorology Institute of Kosova is in charge for monitoring of water quality.

A systematic comparison of two basic types of neural network, static and dynamic, is presented in this study. Two backpropagation (BP) learning optimization algorithms, the standard BP and conjugate gradient (CG) method, are used for the static network, and the real-time recurrent learning (RTRL) algorithm is used for the dynamic-feedback network. Twenty-three storm-events, about 1632 rainfall and runoff data sets, of the Lan-Yang River in Taiwan are used to demonstrate the efficiency and practicability of the neural networks for one hour ahead streamflow forecasting. In a comparison of searching algorithms for a static network, the results show that the CG method is superior to the standard BP method in terms of the efficiency and effectiveness of the constructed network's performance. For a comparison of the static neural network using the CG algorithm with the dynamic neural network using RTRL, the results show that (1) the static-feedforward neural network could produce satisfactory results only when there is a sufficient and adequate training data set, (2) the dynamic neural network generally could produce better and more stable flow forecasting than the static network, and (3) the RTRL algorithm helps to continually update the dynamic network for learning-this feature is especially important for the extraordinary time-varying characteristics of rainfall -runoff processes. q

An overview of the discharge and sediment load of eight important rivers of North West Frontier Province is presented with a view to analyse the available surface water resource potential of this region most of which is originated from the northern Indus basin. The amount of total suspended solid being very high in most of the rivers have resulted in rapid silting and subsequent loss in the storage capacity ofthe existing reservoirs and it is time that priority is given to the construction of new dams.

In the Segara Anakan lagoon, Java, 21 tree species and 5 understorey genera have been identified. Average tree density is 0.80 ± 0.99 Ind./m² with 48.71% seedlings and an average basal area of 9.86 ± 10.54 cm²/m². Tree density and diversity are high in the eastern part of the lagoon, located near the city of Cilacap. There, the dominant tree species are Aegiceras corniculatum, Nypa fruticans and Rhizophora apiculata, of which the two latter are characteristic for mature forests. By contrast, understorey species and the pioneer species (Avicennia alba, Aegiceras corniculatum and Sonneratia caseolaris) dominate the central lagoon where several rivers discharge. Compared to former studies, seedling density and tree diameter in the central lagoon has declined considerably and tree species dominance has changed. The high sedimentation rates and deforestation are likely to prevent the formation of a mature forest there. Tree communities are more equilibrated in the eastern lagoon which points to a more stable and less disturbed mangrove forest.

A process-based facies model for asymmetric wave-influenced deltas predicts significant river-borne muds with potentially lower quality reservoir facies in prodelta and downdrift areas, and better quality sand in updrift areas. Many ancient barrier-lagoon systems and 'offshore bars' may be better reinterpreted as components of large-scale asymmetric wave-influenced deltaic systems. The proposed model is based on a re-evaluation of several modern examples. An asymmetry index A is defined as the ratio between the net longshore transport rate at the mouth (in m 3 year )1 ) and river discharge (in 10 6 m 3 month )1 ). Symmetry is favoured in deltas with an index below 200 (e.g. Tiber, lobes of the Godavari delta, Rosetta lobe of the Nile, Ebro), whereas deltas with a higher index are asymmetric (e.g. Danube -Sf. Gheorghe lobe, Brazos, Damietta lobe of the Nile). Periodic deflection of the river mouth for significant distances in the downdrift direction occurs in extreme cases of littoral drift dominance (e.g. Mahanadi), resulting in a series of randomly distributed, quasi-parallel series of sand spits and channel fills. Asymmetric deltas show variable proportions of river-, wave-and tide-dominated facies both among and within their lobes. Bayhead deltas, lagoons and barrier islands form naturally in prograding asymmetric deltas and are not necessarily associated with transgressive systems. This complexity underlines the necessity of interpreting ancient depositional systems in a larger palaeogeographic context.

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Flood prediction Uncertainty Ensemble prediction system Streamflow Numerical weather prediction s u m m a r y Operational medium range flood forecasting systems are increasingly moving towards the adoption of ensembles of numerical weather predictions (NWP), known as ensemble prediction systems (EPS), to drive their predictions. We review the scientific drivers of this shift towards such 'ensemble flood forecasting' and discuss several of the questions surrounding best practice in using EPS in flood forecasting systems. We also review the literature evidence of the 'added value' of flood forecasts based on EPS and point to remaining key challenges in using EPS successfully.

Problem statement: A sediment analysis study was conducted at the Chini River on 16 and 31 August 2008. This study was conducted to review the formation of suspended sediment load in the Lake Chini catchment area, which flows into the Pahang River via the Chini River. Approach: Three sampling stations were chosen, the first one at upstream Chini River (S1), mid-stream Chini River (S2) and downstream Chini River (S3). Three parameters were quantified for this study, namely: distribution of sediment grain size (g), concentration of suspended sediment (mg L −1 ) and river discharge values (in m 3 sec −1 ). Results: The findings of the study show that the sizes of sediment fall between phi Ø-1.00 and phi Ø-2.00 with very rough particle sizes falling between phi-1.00 and phi 0.00. At the study area, the daily discharge value is estimated at 722, 304, 00 L day −1 . The average suspended sediment concentration recorded for each station shows varying values for both timelines. The values were 27.33 mg L −1 on 16/08/08 and 2.233 mg L −1 on 31/08/08. Conclusion: The average value for all stations calculated based on the formation of suspended sediment load per day falls between 16,480.4627 kg day −1 on 16/08/08 and 1,540.43 kg day −1 on 31/08/08. Overall, when this number was extrapolated to every square kilometre, the result showed that the estimated average sediment that flows out of Lake Chini is 73.22 tonnes km −2 year −1 .