Major River Systems Research Articles

Irrigated area determination: a case study in the Province of San Juan, Argentina

Much of the central-western region of Argentina, where San Juan Province is located, experiences arid to semi-arid climatic conditions with low average annual rainfall accompanied by substantial evapotranspiration. Consequently, a viable crop industry depends to a large extent upon irrigation from major river systems. Increasing demand for water in the lower basin of the San Juan River is emphasizing the need for more accurate estimates of water used for irrigation. Since the water demand for a particular crop is very closely related to crop area, monitoring the area of crop under irrigation is considered a proxy for the amount of water used. Landsat 5 imagery for the growing season, field data and aerial photographs were used to evaluate crop area.

Estimating the performance of international regulatory regimes: Methodology and empirical application to international water management in the Naryn/Syr Darya basin

We develop a methodology for estimating the performance of international regulatory regimes in the context of transboundary surface waters. Our performance metric relies on assessments, over time, of actual performance, counterfactual performance, and optimal performance. The metric is of practical relevance as a diagnostic tool for policy evaluation. Thus it provides a starting point for policy improvement. To demonstrate the empirical relevance of this methodology we examine international water management in the Naryn/Syr Darya basin, a major international river system in Central Asia. The emphasis is on the Toktogul reservoir, the main reservoir in the Naryn/Syr Darya basin, and its downstream effects. The biggest policy challenge in this case has been to design and implement international trade‐offs among water releases for upstream hydropower production in winter and water releases for downstream irrigation in summer. We find that the international regime in place since 1998 is characterized by low average performance and high variability.

Fluvial networks of the Iberian Peninsula: a chronological framework

Knowledge of the evolution of Spanish fluvial networks has improved during recent years as more river systems have been studied and more geochronological data has become available. However, the chronological framework is a major issue as the range of applications is limited by methodological constraints and spatial coverage is sparse. Integration of ‘absolute’ dating methods with biostratigraphy and palaeomagnetism permits the recent evolution of these river systems to be reviewed. The timing of incision from the Late Neogene to the present varies between the major Iberian fluvial systems, depending on the substrata and tectonic settings. Early Pleistocene and older fluvial sequences in the core areas of the Iberian Peninsula provide a more extensive record of fluvial evolution and are better preserved than the terrace flights in the coastal lowlands. Middle Pleistocene sequences are well developed in most of the major river systems in Iberia, particularly those of the Tajo, Guadalquivir and Aguas River, and frequently represent the principal climatic cycles of that period, although tectonic and sea-level effects can also be seen. For Late Pleistocene to Holocene times, the scheme becomes more complex. Our review suggests that each river system has responded differently to local and regional climate control, glacial and periglacial processes in headwaters in high mountain areas, glacio-eustatic sea-level changes and local and regional tectonic patterns.

Low mitochondrial divergence indicates a rapid expansion across Europe in the weather loach, Misgurnus fossilis (L.)

Several phylogeographic studies using mtDNA sequence data have revealed an expressed geographic structure in nearly every European freshwater fish species studied. The authors present a phylogeographic study of Misgurnus fossilis on the base of 43 specimens from 17 localities across a major part of the known distribution area of M. fossilis. Despite the large geographic distance between the sampling points and their origin from different major European river systems, only eight closely related haplotypes in the sequences of the whole mitochondrial cytochrome b were detected. The most common haplotype I included more than 60% of specimens and occurred in the North Sea basin in northern Germany, in the Danube and Elbe basins in the Czech Republic, in the Nieman basin in Poland and in the Dniester and Vistula basins in the Ukraine. Since the highest number of haplotypes (six out of eight) and the most divergent haplotypes were found in the Danube, the authors tentatively consider the Danube to have acted as a refuge area for Misgurnus during the glaciation maxima in the Pleistocene. From this refuge, the species presumably recolonized Central and Eastern Europe but failed to stretch to Western Europe.

‘Like the Drifting Grains of Sand’:1 Vulnerability, Security and Adjustment by Communities in the Charlands of the Damodar River, India

Charlands are islands formed in major river systems particularly in the flat deltaic plains such as those in the Bengal delta in eastern India and Bangladesh. The charlands in the lower reaches of the Damodar River in India are prone to frequent floods, shifting river channels and consequent riverbank erosion. In spite of these risks posed by the environment, migrant communities from Bihar and Bangladesh settle in the charlands because the soils are fertile, and because being untitled, they are relatively cheaper than legal lands. This paper explores the mental maps or perceptions that the chouras—the charland inhabitants—have of their places of living. We ask: How do the chouras see their fragile environment? Our findings are as follows: first of all, we agree that the perceptions of vulnerability and insecurity are subjective, and may differ widely between different communities or groups living in the charlands. Secondly, we note that ‘adaptation’ might be too broad a term; the specific process is more contingent than a long-term adaptation and best described as ‘adjustment’. Finally, we note that in light of our study into the livelihoods that people keep pursuing in marginal environments such as that of chars, a felt need has arisen to redefine categories such as ‘resilience’, ‘vulnerability’ or ‘security’. 1 Quote from our informant Naren Sarkar.

River plume patterns and dynamics within the Southern California Bight

Stormwater river plumes are important vectors of marine contaminants and pathogens in the Southern California Bight. Here we report the results of a multi-institution investigation of the river plumes across eight major river systems of southern California. We use in situ water samples from multi-day cruises in combination with MODIS satellite remote sensing, buoy meteorological observations, drifters, and HF radar current measurements to evaluate the dispersal patterns and dynamics of the freshwater plumes. River discharge was exceptionally episodic, and the majority of storm discharge occurred in a few hours. The combined plume observing techniques revealed that plumes commonly detach from the coast and turn to the left, which is the opposite direction of Coriolis influence. Although initial offshore velocity of the buoyant plumes was ∼50 cm/s and was influenced by river discharge inertia (i.e., the direct momentum of the river flux) and buoyancy, subsequent advection of the plumes was largely observed in an alongshore direction and dominated by local winds. Due to the multiple day upwelling wind conditions that commonly follow discharge events, plumes were observed to flow from their respective river mouths to down-coast waters at rates of 20–40 km/d. Lastly, we note that suspended-sediment concentration and beam-attenuation were poorly correlated with plume salinity across and within the sampled plumes (mean r 2=0.12 and 0.25, respectively), while colored dissolved organic matter (CDOM) fluorescence was well correlated (mean r 2=0.56), suggesting that CDOM may serve as a good tracer of the discharged freshwater in subsequent remote sensing and monitoring efforts of plumes.

The variation of discharge entering the Niger Delta system, 1951–2000, and estimates of change under global warming

AbstractA simple and effective statistical scheme for estimating river discharges on the River Niger has been derived using catchment rainfall data. Observed station annual average discharges at two locations were correlated with averaged annual rainfall data in recent years (1951–2000). A comparison of the estimated discharge and the observed discharge showed good agreement. The upstream station of Gaya on the border of Niger and Nigeria, with more extensive records, was used to validate the technique. A more limited discharge record at Lokoja, at the focal point of the Niger Delta, is used to reconstruct the discharge over 1951–2000. Despite the extensive dam construction on the Upper Niger during this period the main determinant of flow into the Delta has remained upstream rainfall. The relationship between the past rainfall data and river discharges at Lokoja are used to predict flows in the 2070s using rainfall values derived from various scenarios of a set of coupled climate model simulations. While there is uncertainty even over the sign of future change in west African rainfall, the river flow inferred from those models predicting increased rainfall over the coming century is at a level consistent with rapid change in channel position, as observed during the 1990s. This technique could be applied more widely to forecast future discharges from major river systems. Copyright © 2007 Royal Meteorological Society

Geomorphic constraints on the active tectonics of southern Taiwan

SUMMARY Taiwan is a region of rapid active tectonics, yet the study of the tectonic processes that shape the interior of the island is difficult due to the high rates of erosion and dense vegetation. We use digital topography to look for indications of active deformation preserved in the local geomorphology. In particular, anomalies in the regional pattern of drainage are used to infer zones of enhanced tectonic activity. The apparent anticlockwise rotation of major river systems in plan view indicates the presence of a diffuse zone of left-lateral shear running down the southeastern side of Taiwan. Asymmetries in the catchments of individual drainage basins show the influence of varying rates of uplift across southern Taiwan, with the most rapid uplift close to Taitung at the indentation point of the Luzon arc with the Chinese continental margin. Our interpretations, though based predominantly on remote-sensing observations, are consistent with the available field evidence. This study demonstrates the usefulness of drainage basins as tectonic markers in the quantification of regional strain and uplift, which may have wider applicability in other deforming parts of the world.

Spatial and temporal patterns in microsatellite DNA variation of wild Atlantic salmon, Salmo salar, in Irish rivers

Abstract Two sequential year classes of Atlantic salmon parr, Salmo salar L., from 13 rivers throughout Ireland, genotyped at four widely used microsatellite loci, displayed comparable levels of intra‐sample genetic variability to elsewhere in the species range. Temporal allele frequency differences were observed in only one riverine sample, whereas significant spatial differences were evident in all cases, with an overall FST value of 0.03. These spatial differences imply a high degree of natal homing. Two tributaries of a single major river system displayed variability comparable with that within the entire study, suggesting that large rivers may contain several separate tributary populations. Isolation‐by‐distance analysis suggests the presence of regional structure, which may have been obscured by inclusion of samples from some smaller rivers in Donegal Bay in the north west that are probably affected by incursions of cultured salmon from a nearby ranching operation. Although limited by the small number of loci screened, individual assignment analysis gave levels of self‐assignment which would suggest that mixed stock analysis would be feasible as a management tool in Irish salmon fisheries, given the inclusion of larger numbers of microsatellite loci and more extensive coverage of salmon producing rivers.

A review of sinuous channel avulsion patterns in some major deep-sea fans and factors controlling them

This paper reviews side-scan sonar, multi- and single-beam echo-sounder, and high-resolution seismic reflection data, and discusses the anatomy and patterns of the most recent sinuous channel avulsions in the Amazon, Zaire, Indus and Bengal Fans, all located along passive continental margins and all fed by major river systems. Channel patterns formed by fore- (seaward) or back- (landward) stepping avulsions are common in the western Amazon Fan and in the Northern and Axial Zaire Fan. However, channels in the Indus and Bengal Fans, and in the Southern Zaire Fan, appear to form radial patterns, with most of the main avulsions having occurred in relatively restricted areas (avulsion nodes). High degrees of development of channel instabilities or avulsion-threshold conditions (e.g. channel sinuosity increase and lengthening, channel thalweg aggradation, differential channel fill and decrease in channel relief, slumping and channel plugging, bank cohesion), and increased peak volumes and speeds of turbidity currents, determined where avulsions occurred in the fan channels. During the Late Quaternary intervals considered here, several global sea-level falls and rises occurred and these, along with climatic changes, are likely to have influenced sediment-gravity flows and may have thus timed many, if not all, significant avulsions. However, available data do not allow documentation of this timing in many cases. The main differences between fan areas with (1) fore-and back-stepping and (2) radial channel avulsion patterns are that, in the former case, fan gradients are steeper with frequent slope breaks, and channel thalweg aggradation occurs along much of the depositional profile. In the latter case, downdip of avulsion nodes, fan gradients are either flat or possibly have no breaks, and channels are incised below the fan surface with no thalweg aggradation in the middle and lower fan regions. These characteristics may have caused differences in avulsion-triggering turbidity flow volumes and avulsion threshold conditions that, in turn, may have resulted in different channel avulsion patterns.

Mixed method approaches to the investigation and mapping of buried Quaternary deposits: examples from southern England

AbstractThe lower reaches of major river valleys usually present archaeologists with considerable problems where thick sequences of stratified alluvium bury archaeology. These situations are typical of the lower reaches of major river systems that are currently under intense pressure from urban development where the archaeological resource is consequently at risk. Here we demonstrate how mixed method approaches, utilizing a range of borehole methods, cone penetration testing and surface and subsurface geophysics coupled with microfossil assessment (Foraminifera/Ostracoda), can be used to model these deposits and predict locations and depths at which important archaeological remains may be located. The novelty of this approach is not in the application of individual techniques to the problem but in the combined methodology, which enables a structured and cost effective programme of works to be formulated and provides the best chance to understand the subsurface. Although this approach has been developed to facilitate the location of archaeological sites buried at depth within the route corridor of development projects it is also suitable for locating fossil‐bearing sequences and mapping stratigraphical units in Quaternary science. We demonstrate the approach using two examples from southern England. Copyright © 2007 John Wiley & Sons, Ltd.

Registro de ocorrência de duas espécies de potamotrigonídeos na região do Alto Rio Paraná e algumas considerações sobre sua biologia

A distribuição geográfica das raias da família Potamotrygonidae é restrita aos principais sistemas fluviais da América do Sul. No Brasil, a ocorrência de potamotrigonídeos é conhecida em toda a Bacia Amazônica, em alguns rios da região Nordeste e na Bacia Paraguai-Paraná. O alto curso do Rio Paraná, separado no passado dos trechos médio e baixo pelas Cachoeiras de Sete-Quedas, hoje está conectado a essas áreas devido ao represamento de grande parte de seu curso. A construção das barragens destruiu obstáculos naturais, possibilitando a dispersão de diversas espécies de organismos aquáticos rumo ao alto curso do Rio Paraná. Reportamos aqui o registro da ocorrência de duas espécies de raias no Alto Rio Paraná, as quais não faziam parte da fauna nativa da região há pouco mais de duas décadas atrás.

Dissolved rare earth elements in river waters draining karst terrains in Guizhou Province, China

Winter seasonal concentrations of dissolved rare earth elements (REE) of two major river systems (the Wujiang River system and the Yuanjiang River system) in karst-dominated regions in winter were measured by using a method involving solvent extraction and back-extraction and subsequent ICP-MS measurements. The dissolved REE concentrations in the rivers and their tributaries are lower than those in most of the large rivers in the world. High pH and high cation (i.e., Na+ + Ca2+) concentrations of the rivers are the most important factors controlling the concentrations of dissolved REE in the river water.

Indiana Bats in the Midwest: The Importance of Hydric Habitats

The endangered Indiana bat (Myotis sodalis) requires very specific habitats to provide necessary day-roosting and foraging resources during the spring and summer months throughout its distribution in the eastern United States. Maternity colonies of Indiana bats are almost always found under the exfoliating bark of dead or dying trees. Furthermore, they switch frequently among multiple roosts within large but still somewhat local areas. Therefore, habitats with large numbers of snags or decadent trees are needed to support Indiana bat maternity colonies. These habitats arise naturally and anthropogenically in a variety of ways. However, these conditions often are rare relative to other forest conditions. In the Midwest, such as southern and central Illinois, USA, maternity colonies are more commonly associated with bottomland, riparian, wetland, or other hydric forest types. It is unclear if this occurs because areas with large numbers of snags are more common in these habitats, if maternity colonies prefer these habitats for their foraging resources, or if decades of intensive agriculture have restricted colonies to these habitats. Because many large maternity colonies have been observed in hydric habitats of the Midwest, I hypothesize that these are preferred maternity habitats. Moreover, very few large maternity colonies have been located using upland forest habitats within the region. Elsewhere, such as in the central and southern Appalachians, maternity colonies have been located in upland areas where bottomland habitats are less extensive. However, these colonies are usually characterized by small numbers of bats and ephemeral persistence. Future conservation efforts for the Indiana bat should focus on protecting and regenerating bottomland habitats along the major river systems of the midwestern United States. It is within these bottomland and riparian habitats that future large and long-term maternity colonies will be established.

Changing River Courses in North India: Calamities, Bounties, Strategies—Sixteenth to Early Nineteenth Centuries

Disaster is a multidimensional social phenomenon. Scholars, cutting across different disciplines, have yet to reach a common understanding or a consensus on the definition of disaster. To understand natural disaster and catastrophe, this article will study the nature of changing river courses and their impact on the environment and on human-environment relations. It will focus on the corrosive power of rivers, the destructive as well as beneficent effects of their impetuous trajectories and the social implications of this process. Our analysis is based on a case study of one of the major river systems in South Asia, i.e. river Ganga (Ganges) and its tributaries in north India.

Afghanistan: An Overview of Ground Water Resources and Challenges

Afghanistan: An Overview of Ground Water Resources and Challenges

Late Quaternary river drainage and fish evolution, Southland, New Zealand

Late Quaternary to Holocene landscape evolution in southern New Zealand was dominated by glacial outwash processes. Evolution of the drainage network on a regional scale was punctuated by numerous river capture events associated with outwash transport and deposition. River capture events can be inferred from geological and topographic observations throughout the region. Independent evidence for river capture and drainage reorientation can be obtained from genetic studies of a freshwater-limited fish ( Galaxias ‘southern’, informal name). Regionally extensive interlinking of principal rivers (Mataura, Oreti, Aparima) via coalescence of alluvial plains onshore, and offshore at sea level lowstands, has resulted in a widespread genetic homogenisation of fish populations (< 0.9% mtDNA divergence). Genetically similar populations of G. ‘southern’ are present in an adjacent catchment (Von) that was captured episodically by the neighbouring major river system (Clutha). The low degree of genetic divergence between Oreti and Von catchments (< 0.15% mtDNA divergence) demonstrates that genetic interaction between fish populations was severed recently, probably during the early Holocene. This is in accord with radiocarbon dating (11–13 ka) of the youngest gravel level within the intervening divide. In contrast, morphologically similar fish in another adjacent major river (Waiau) have a minimum mtDNA divergence of 2.4% from the fish in the Mataura, Oreti, and Aparima Rivers. This genetic separation occurred at ca. 145–240 ka, based on the late Quaternary outwash terrace dating, in agreement with “molecular clock” estimates. Geological and genetic data in combination provide powerful tools for the elucidation of local and regional geomorphic evolution where river capture is an important process. The potential is strong for genetic data alone to provide information on the relative and absolute timing of river capture events, but must be interpreted in the context of severance of water connections between catchments and subsequent isolation of freshwater-limited populations.

Evaluation of the Hydrological Cycle in the ECHAM5 Model

Abstract This study investigates the impact of model resolution on the hydrological cycle in a suite of model simulations using a new version of the Max Planck Institute for Meteorology atmospheric general circulation model (AGCM). Special attention is paid to the evaluation of precipitation on the regional scale by comparing model simulations with observational data in a number of catchments representing the major river systems on the earth in different climate zones. It is found that an increased vertical resolution, from 19 to 31 atmospheric layers, has a beneficial effect on simulated precipitation with respect to both the annual mean and the annual cycle. On the other hand, the influence of increased horizontal resolution, from T63 to T106, is comparatively small. Most of the improvements at higher vertical resolution, on the scale of a catchment, are due to large-scale moisture transport, whereas the impact of local water recycling through evapotranspiration is somewhat smaller. At high horizontal and vertical resolution (T106L31) the model captures most features of the observed hydrological cycle over land, and also the local and remote precipitation response to El Niño–Southern Oscillation (ENSO) events. Major deficiencies are the overestimation of precipitation over the oceans, especially at higher vertical resolution, along steep mountain slopes and during the Asian summer monsoon season, whereas a dry bias exists over Australia. In addition, the model fails to reproduce the observed precipitation response to ENSO variability in the Indian Ocean and Africa. This might be related to missing coupled air–sea feedbacks in an AGCM forced with observed sea surface temperatures.

INCORPORATING KNOWN SOURCES OF UNCERTAINTY TO DETERMINE PRECAUTIONARY HARVESTS OF SALTWATER CROCODILES

It has been demonstrated repeatedly that the degree to which regulation operates and the magnitude of environmental variation in an exploited population will together dictate the type of sustainable harvest achievable. Yet typically, harvest models fail to incorporate uncertainty in the underlying dynamics of the target population by assuming a particular (unknown) form of endogenous control. We use a novel approach to estimate the sustainable yield of saltwater crocodile (Crocodylus porosus) populations from major river systems in the Northern Territory, Australia, as an example of a system with high uncertainty. We used multimodel inference to incorporate three levels of uncertainty in yield estimation: (1) uncertainty in the choice of the underlying model(s) used to describe population dynamics, (2) the error associated with the precision and bias of model parameter estimation, and (3) environmental fluctuation (process error). We demonstrate varying strength of evidence for density regulation (1.3-96.7%) for crocodiles among 19 river systems by applying a continuum of five dynamical models (density-independent with and without drift and three alternative density-dependent models) to time series of density estimates. Evidence for density dependence increased with the number of yearly transitions over which each river system was monitored. Deterministic proportional maximum sustainable yield (PMSY) models varied widely among river systems (0.042-0.611), and there was strong evidence for an increasing PMSY as support for density dependence rose. However, there was also a large discrepancy between PMSY values and those produced by the full stochastic simulation projection incorporating all forms of uncertainty, which can be explained by the contribution of process error to estimates of sustainable harvest. We also determined that a fixed-quota harvest strategy (up to 0.2K, where K is the carrying capacity) reduces population size much more rapidly than proportional harvest (the latter strategy requiring temporal monitoring of population size to adjust harvest quotas) and greatly inflates the risk of resource depletion. Using an iconic species recovering from recent extreme overexploitation to examine the potential for renewed sustainable harvest, we have demonstrated that incorporating major forms of uncertainty into a single quantitative framework provides a robust approach to modeling the dynamics of exploited populations.

Sr and 87Sr/ 86Sr in waters and sediments of the Brahmaputra river system: Silicate weathering, CO 2 consumption and Sr flux

The Brahmaputra is a major river system draining the Himalaya. The concentration of Sr and its 87Sr/ 86Sr have been measured in dissolved and particulate phases of the Brahmaputra and its tributaries in India to trace the sources of dissolved Sr. Dissolved Sr ranges from 250 to 1050 nM with 87Sr/ 86Sr from 0.71298 to 0.75975. The Sr data along with the available concentrations of major ions in the samples show that major contributors of Sr in the Brahmaputra system are the silicates and carbonates of the Himalaya and the Transhimalaya and carbonates and evaporites of the Tibetan basin. Silicate Sr in the Brahmaputra river system ranges from 20% to 80% with an average of ∼ 45%. The silicate component of Sr in the Brahmaputra system is similar or marginally higher than that in the Ganga system due to contribution from the Transhimalayan calc-alkaline plutonic rocks which have higher concentration of Sr. Evaporites of the Tibetan sub-basin and hot springs along the Indus Tsangpo Suture could be the other significant contributors to the dissolved Sr budget of the Brahmaputra. Contribution from evaporite dissolution decouples the total dissolved Sr flux from the Tibetan basin from atmospheric CO 2 consumption. Radiogenic Sr of the Brahmaputra system is derived from the Himalayan silicates whereas other Sr sources tend to dilute its radiogenic signature. The 87Sr/ 86Sr of the dissolved phase shows significant correlation with indices of silicate weathering, indicating that 87Sr/ 86Sr can serve as a proxy of silicate weathering. At their outflow, the Brahmaputra is less radiogenic (∼ 0.72) compared to the Ganga (∼ 0.73), however, the flux of 87Sr from the Brahmaputra is similar to that of the Ganga.