Great River Research Articles

Grand Canal, Great River: The Travel Diary of a Twelfth-Century Poet (review)

Grand Canal, Great River: The Travel Diary of a Twelfth-Century Poet (review)

Trans-crustal Advections and In-situ Biogeochemical Processes of Global Sub-seafloor Aquifer: The Sub-seafloor “TAIGA”

Since the discovery of rich microbial communities at and around seafloor hydrothermal sites, their extension towards the oceanic crust beneath the seafloor is of great interest not only for microbial physiology/ecology but also for a wide range of Earth and planetary sciences. How can the communities survive in such an extreme environment? What kinds of metabolism are in action? It is proposed that the sub-seafloor ecosystems are characterized by different kinds of chemosynthetic primary production (carbon fixation), all of which are supported by chemical energy supplied from the sub-seafloor aquifers. We designate the unseen aquifers as sub-seafloor TAIGAs (great rivers) which are responsible for a geochemical flux equivalent to or even larger than that of terrestrial river runoff (e.g. Wheat and Mottl, 2000). Besides, they are responsible for supplying nutrients to microbes beneath the seafloor. We hypothesize that there are four representative TAIGAs based on the chemical energy of compounds of sulfur, carbon (methane), iron, and hydrogen, all of which are supported by the TAIGAs. It is important to note that the sub-seafloor ecosystems are controlled extensively by or are mutually related to the types of TAIGA that flow at the site. The hypothesis can be tested through cooperative research among microbiologists, geochemists, geophysicists, and geologists.

Two Questions about Moby-Dick

Two Questions about Moby-Dick Cyrus R.K. Patell (bio) I have two questions about Herman Melville's Moby-Dick that seem, at first, to be unrelated. The first is: Why does Melville begin the narrative of the novel in Manhattan? The second is: Why does the novel's narrator Ishmael insist in his chapter on "Cetology" that the whale should be considered a fish, going against the classification recommended by almost all 19th-century zoologists? In fact, these two questions turn out to be alternative ways of approaching one of the novel's central concerns: how to deal with difference. Because our forum's point of departure is Graham Burnett's Trying Leviathan, let's take the second question first. Melville scholars have shown that Melville made extensive use of the article on whales from The Penny Cyclopedia (published between 1833 and 1843) when composing the famous "Cetology" chapter of Moby-Dick. There he would have found this definition: "WHALES—Cetacea—an order of aquatic mammals with fin-like anterior extremities, the posterior extremities being absent, or rather, having their place supplied by a large horizontal caudal fin or tail, without an external ear, without hair on their external integument, and the cervical bones so compressed as to leave the animal without any outward appearance of a neck." The article then goes on immediately to address the question of the classification of the whale: "The cetacious mammals, whose abode is either in the sea or the great rivers resemble the Fishes so closely in external appearance, that it is hardly to be wondered at that not only the vulgar, but even some of the earlier zoologists looked upon them as belonging to that class." So why does Melville choose to have his narrator, Ishmael, align himself with "the vulgar" and insist that we should call the whale a "fish"? Because it isn't only the "vulgar"—broadly construed to mean "the common people"—who persist in calling the whale a fish, but also those who are most intimately acquainted with the habits of the leviathan: the whalemen. The Cyclopedia continues: "This notion is kept alive to the present day in the announcements of the comparative success of those ships which are employed in the Whale Fishery; for not only is it conveyed by that general term for the capture of whales, but by statements that one ship has arrived with three fish, another with four fish, a third with one fish, &c." The Cyclopedia thus sets science against both popular opinion and the opinions of those who practice whaling. For Ishmael, practice trumps theory. He objects in the "Cetology" chapter to the procedure followed by many naturalists of making "endless subdivisions based upon the most inconclusive differences," which leads "some departments of natural history [to] become so repellingly intricate." He faults what he calls "book naturalists" for promulgating many errors about the sperm whale. After making a joke about the fact that fish continue to swim in the same ocean with the whale in defiance of Linnaeus's edict that they should be "separated," Ishmael submits Linnaeus's rationale for considering the whales as separate from the fish to a higher court of appeal: two of his whaling buddies, Simeon Macey and Charley Coffin. Click for larger view View full resolution From Henry Theodore Cheever, The Whale and His Captors; Or, The Whaleman's Adventures (New York, 1850). Both of these men pronounce Linnaeus's reasons "insufficient," with "Charley profanely hint[ing] they were humbug." As is often the case in Moby-Dick, Ishmael seeks to forge consensus. He begins—unlike the naturalists—not with difference, but with sameness. He subscribes to the traditional view that the whale is a fish, but then asks how the whale differs from other fish. For the internal differences, Ishmael is happy to use Linnaeus as an authority, citing the whale's "lungs and warm blood; whereas, all other fish are lungless and cold blooded." To help those of us who want to be able to classify a whale without cutting him open, Ishmael provides this definition: "a whale is a spouting fish with a horizontal tail." What has Ishmael done here? He...

Influence of severe freshwater flooding during the rainy season on the coral community around Khang Khao Island in the inner Gulf of Tahiland

We observed a severe reduction in salinity around Khang Khao Island at the end of the rainy season in September and October, 1995, caused by the most serious freshwater flooding in Thailand in recent 15 years. During low tide, corals around Khang Khao Island were exposed to 23‰ at three meters depth, and 25‰ at five meters. As a result, Pocillopora damicornis and a few species of Acropora showed colony bleaching or partial or complete colony death in the field. On the other hand, Porites spp., the dominant corals of this area, did not show any conspicuous effects. Porites lutea could survive five days of experimental exposure to 17‰, the critical salinity for other corals. The chlorophyll-a concentration of P. lutea that become partially bleached after seven days exposure to 20‰ was higher than in normal control fragments. These phenomena suggest that P. lutea has a compensation mechanism against salinity reduction. Both field observations and experiments suggest that lowered salinity caused by runoff during the rainy season is an important factor besides turbidity in establishing the characteristics of the coral community structure around Khang Khao Island. A detailed study of the process of coral community formation in this area may contribute to an understanding of not only the negative effects of continental great rivers on the establishment of coral reefs around tropical continental shores but also the influence of the heavy rainfall on a coral community in the coral reef region by the global climate change.

Spectroscopy of sediments in the Ganges–Brahmaputra delta: Spectral effects of moisture, grain size and lithology

The lithologic composition and grain size distribution of sediments are primary determinants of their inherent reflectance properties. However, moisture content is also known to have a strong influence on reflectances of soils and sediments. If the effects of sediment composition, grain size and moisture content could be distinguished spectrally, it might be possible to map these properties at synoptic scales using hyperspectral, or perhaps even broadband, remote sensing. Mapping the spatiotemporal distribution of sediment composition and moisture content could provide unique constraints on both the processes by which the sediments are deposited as well as the constraints they may impose on subsequent water flow and sediment transport. The Ganges–Brahmaputra delta (GBD) is formed by the convergence of these two great rivers and is superlative in both size and geologic activity. Sediment redistribution and channel migration associated with the annual floods disrupt the lives of hundreds of thousands of people living on the GBD but is also critical for maintaining the delta area fertile and above sea level. The 30+ year archive of Landsat imagery could provide a basis for spatiotemporal analysis of these fluvial dynamics if sediment properties could be inferred or measured from reflectance spectra. However, before confronting the challenge of broadband detection we must understand the spectral properties of the sediments under more controlled laboratory conditions. Bidirectional reflectance spectroscopy of 109 sediment samples from the GBD yields a spectral mixing space that appears to be structured by variations in moisture content, grain size and possibly lithology. Although the individual Empirical Orthogonal Functions of the Principal Components do not correspond to unique absorption features, clustering within the mixing space is clearly influenced by moisture content and grain size. Laboratory spectra of sediment reflectance measured under varying moisture content yield distinct trajectories through the spectral mixing space for different grain size distributions of sieved sediments. These variations in moisture content account for > 98% of spectral variance observed in these samples. Drying trajectories of coarse, fine and mixed sediments are distinct and suggest that moisture and grain size might be spectrally distinguishable. These results are consistent with Angstrom's hypothesis of moisture-driven spectral absorption but more controlled experiments are necessary to test the hypothesis rigorously.

A combined acoustic and electromagnetic wave-based techniques for bathymetry and subbottom profiling in shallow waters

Acoustic-wave based sub-bottom profiler (SBP) and electromagnetic-wave based ground penetrating radar (GPR) are two complementary geophysical tools that were used to map bathymetry and sediment sublayers in shallow waters. Near shore regions in Great Lakes, inland lakes, and rivers in Wisconsin, USA were examined using both geophysical tools. In areas with high silt and clay contents, such as Lake Superior, the SBP was able to image the sediment sublayers, whereas in the areas with sand cover and vegetation, the GPR provided sediment stratigraphic information. The higher vertical and horizontal resolutions of the SBP surveys provided more accurate and detailed bathymetry information than GPR surveys. In the Yahara River, SBP surveys imaged blurring contrasts between sublayers due to the gradual deposition of sediments; however, GPR provided sharp delineations of sediment layers but was only able to image the top two sublayers because of the high silt and clay electromagnetic wave attenuation. To confirm these findings, Shelby tubes and hydraulic jetting were used to collect ground-truth information. Sublayer thicknesses are estimated by evaluating acoustic and electromagnetic wave velocities using a mixture-based equation. In Lake Michigan, both techniques show similar sediment stratigraphy, indicating that the average sediment particle size ranges between silt and fine sand. Three-dimensional maps of bathymetry and subbottom sediments are also constructed. Overall it is shown that the combination of GPR and SBP techniques compensates each survey's strengths in an effective methodology for imaging bathymetry and sub-bottom profiles in shallow water environments.

Using stressor gradients to determine reference expectations for great river fish assemblages

Abstract We describe a simple empirical modeling approach for determining least-disturbed conditions for the great rivers of the Upper Mississippi River basin: Missouri, Upper Mississippi, and Ohio Rivers. We used multivariate analysis to identify reference strata (reaches for which a single reference expectation was appropriate) on each river. Strata included the Upper Missouri, Lower Missouri, impounded Upper Mississippi, unimpounded Upper Mississippi, and the Ohio River. We created a multimetric stressor gradient for each stratum using a suite of site- and landscape-scale metrics. Site-scale metrics included water chemistry, aquatic and riparian habitat, and human disturbance metrics. Landscape-scale metrics included land use, land cover, and proximity to human disturbance. The gradient was scaled from 0 (least stressed) to 1 (most stressed). Multimetric indices of condition based on fish assemblages for the Lower Missouri and Upper Mississippi River were responsive to stressor gradients based on 18–24 abiotic stressor metrics. Ohio River fish assemblages were responsive to a hand-picked three-metric gradient. We used the y -intercept of quantile regression to predict the fish index value for a stressor gradient value of 0 (the fish index value at a site with the lowest mean stressor gradient score in the reference stratum) which we designated as least-disturbed condition for the fish index for that stratum. We trisected the difference between predicted least-disturbed condition (ceiling value) and a floor value set at the 5th percentile of the sample to create thresholds for three condition classes: least-disturbed, intermediate, and most-disturbed. Based on the derived condition class thresholds for the fish index, 10% (by length) of the Lower Missouri was in least-disturbed condition, compared to 14% of the Ohio River and 19% of the impounded Upper Mississippi River. The index of condition exhibited longitudinal variation that was associated with the location of major urban areas along each river. We conclude that empirical modeling based on an abiotic stressor gradient can provide an alternative approach for deriving internal reference expectations for great rivers with few, if any, minimally disturbed sites.

Pellagra and the blues song 'Cornbread, meat and black molasses'.

Prisoners, black and white, across the Deep South of the USA were aware of Joseph Goldberger’s experiments, which were designed to find the cause of pellagra by assessing and modifying the diets of prisoners at Rankin Prison Farm, Mississippi. The archives of the State of Mississippi hold evidence of the extensive public controversy, involving outraged victims of the crimes of these inmates, the general public and Governor Brewer, who had sanctioned Goldberger’s experiment and the offer of pardon to the volunteers. In the early 1900s, pellagra affected an estimated 50,000 people in the southern USA and killed 7000 poor blacks and whites. Goldberger believed that pellagra was caused by a dietary deficiency, not by an infection, as was widely believed. He was so strong in this belief that he had tested the hypothesis on himself, his wife and other members of the American public health service. To test the assumed infectiousness of pellagra, they had variously inoculated themselves with skin squames and nasal secretions and eaten faeces from pellagrins. Goldberger’s experiments feeding volunteer prisoners cornbread, fat meat and black molasses induced pellagra, which was alleviated by variations including peas, beans, cabbage greens and wheat bread. By 1926, Goldberger proposed yeast extract supplements to combat the disease and arranged distribution through the Red Cross Stores that were supplying food handouts, canned grapefruit juice (vitamin C – in Champion Jack Dupree’s Warehouseman Blues), clothes and blankets. This dietary support did reduce the frequency of pellagra. However, poor blacks felt stigmatized by handouts and the Red Cross Stores themselves carried a bitter reputation. Oliver describes how, after the great floods of 1927, ‘Negroes who entered the Red Cross food stations were seized and put into forced labour. Negro refugees under armed guards did the entire work on the Vicksburg levees and the treatment of the suffering homeless people was less than human.’ Many did not return from this latter-day slavery. Many collapsed exhausted, to be buried in the earth mounds of the great river – hence, in Red Cross Store Blues, Alabama Sam sings:

Trans-Zab Jewish Neo-Aramaic

AbstractThe present article seeks to describe a major group of Jewish North-Eastern Neo-Aramaic (NENA) dialects located across the Great Zab river in the eastern and south-eastern parts of the dialectological map of NENA, hence the term “Trans-Zab Jewish Neo-Aramaic” (“Trans-Zab”, for short) chosen for this dialect group. A large set of phonological, morphophonological, morphological and lexical innovations, shared by all members of this group, is presented. Each of the Trans-Zab features is compared with contrastive parallel features in other, selected NENA varieties. Finally, an internal classification of Trans-Zab into three subdivisions is proposed, based on a comparison of three respective paradigms of the positive present copula.

Seasonal and provenance controls on Nd–Sr isotopic compositions of Amazon rivers suspended sediments and implications for Nd and Sr fluxes exported to the Atlantic Ocean

This study reports daily water discharge and suspended sediment load concentrations and Sm–Nd and Rb–Sr isotopic systematics and major and trace elements concentrations of twelve monthly sampled suspended load sediments of the Solimões and Madeira rivers, the two major Andean tributaries of the Amazon, during the year 2004. As observed in other long-term monitoring studies of Amazon Rivers, the maximum of suspended sediment load occurs before or during the rising water period (i.e. during the rainy season). In 2004, the Solimões River exported ∼ 289 × 10 6 tonnes of suspended sediments and the Madeira River 294 × 10 6 tonnes which correspond to erosion rates of 129 and 214 T/km 2/yr for the Solimoes and Madeira rivers basins, respectively. Both the Solimoes and Madeira suspended sediments are enriched in LREE over HREE and exhibit similar MREE enrichment; the difference being that the Madeira sediments are more fractionated than the Solimoes ones. When plotted in Al 2O 3–CaO + Na 2O–K 2O diagram, the suspended sediments of the Solimoes and Madeira rivers exhibit two different weathering trends which suggests that these sediments evolved along two different trends starting from felsic rocks with different chemical compositions. The Nd isotopic compositions (εNd) of the Solimoes sediments (− 8.9 to 9.9) are slightly more radiogenic than the corresponding values of the Madeira sediments (− 10.8 to − 12.1). The 87Sr/ 86Sr isotopic compositions of the Madeira sediments (0.728 to 0.740) are significantly more radiogenic than those of the Solimoes (0.713 to 0.717). Together with other major elements and REE evidences, these isotopic compositions suggest that the Solimoes sediments are more influenced by Andean volcanic arc detritus than the Madeira sediments that might be due to input of young basaltic products owing to strong volcanic activity in Ecuador. Mineralogical compositions as well as Nd isotopic compositions do not vary seasonally. Based on our data set and on previous published studies, we have calculated that the Nd suspended sediment flux dominates the Nd total flux (i.e., dissolved + suspended sediment) exported to the Atlantic Ocean by the Amazon River representing ∼ 98% of the Nd total flux and having a global εNd isotopic composition of − 10.3. Contrary to Nd isotopic compositions, Sr isotopic compositions vary seasonally in both rivers. The explanation for this variation remains unclear. We suspect increasing physical weathering during the rainy season to be the main cause of this seasonal control in favouring landslides and river bank erosion that might induce input of more radiogenic sediments not easily mobilized during low water level. We calculated that the Sr isotopic composition of the dissolved load exported by the Amazon River to the Atlantic Ocean is not seasonally dependent and remain fairly constant (0.715–0.716) By contrast, the Sr isotopic composition of the suspended load is strongly affected by the seasonal variation varying from 0.714 in the dry season to 0.730 in the rainy season. Consequently the total Sr isotopic composition (dissolved + suspended sediment) is also seasonally controlled varying from 0.716 to 0.722. We finally suggest that large seasonally controlled Sr isotopic variations of great river is a phenomenon that has been underestimated in previous paleo-climatic and paleo-oceanic studies and should be taken into account in further studies.

Expansion of Existing Monitoring System on Great Man-Made River Project Using Acoustic Fibre Optic Technology

Acoustic monitoring has played a major role in the management of one of the world's largest civil engineering projects. After experiencing failures on their pipeline between 1999 and 2001, the Great Man-Made River Authority (GMRA) undertook an aggressive condition assessment program. This program led to the development of a comprehensive Pipeline Risk Management System (PRMS), making the Great Man-Made River Project one of the best managed pipelines in the world. The planned expansion of the existing acoustic monitoring system, a key component of the PRMS, will allow for monitoring of over 700km of pipeline. This paper will discuss steps taken to-date, the acoustic monitoring technology and the expansion of this key component to the management strategy for the pipeline.

Clay mineral distributions in and around the Mississippi River watershed and Northern Gulf of Mexico: sources and transport patterns

Maps of the distributions of the four major clay minerals (smectite, illite, kaolinite and chlorite) in and around the Mississippi River drainage basin and in the Northern Gulf of Mexico have been produced using newly acquired data from erodible/alluvial terrestrial sediments and marine surface sediments, as well as from previously published data. East of the Rockies, North America can be divided into four, large, clay-mineral provinces: (1) the north-western Mississippi River watershed (smectite rich), (2) the Great Lakes area and eastern Mississippi River watershed (illite and chlorite rich), (3) the south-eastern United States (kaolinite rich) and (4) the Brazos River and south-western Mississippi River watersheds (illite and kaolinite rich). The clay mineral distributions in surface sediments of the present-day Gulf of Mexico are strongly influenced by three main factors: (1) by relative fluvial contributions: the Mississippi River delivers the bulk of the clay input to the Northern Gulf of Mexico whereas the Apalachicola, Mobile, Brazos and Rio Grande rivers inputs have more local influences; (2) by differential settling of various clay mineral species, which is identified for the first time in Northern Gulf of Mexico sediments; and (3) by oceanic current transport: the Gulf of Mexico surface and subsurface circulation distributes the clay-rich sediments from river mouth sources throughout the Northern Gulf of Mexico.

‘Taken captive by the mystery of the Great River’: towards an historical geography of British geography and Atlantic slavery

By examining the case of James MacQueen (1778–1870), this paper initiates a research agenda that contributes to what David N. Livingstone has argued remains the most pressing task for historians of geography: to write ‘the historical geography of geography’. Born in Scotland in 1778, MacQueen was one of the many ‘arm-chair’ geographers whose efforts at synthesising contemporary and historical sources were a significant feature of the encounter between Europe and the rest of the world. Indeed, although he never visited Africa, his speculations about the course and termination of the River Niger turned out to be broadly correct. What makes MacQueen a particularly significant figure was the original source of his theory: enslaved Africans in a Caribbean plantation-colony. In this light, a remark that MacQueen's imagination was ‘taken captive by the mystery of the Great River’ carries a dark double-meaning, because ‘captive’ knowledge was the very source of MacQueen's interest in African geography. Beginning with MacQueen's time in Grenada, the paper explores a series of personal relations, textual traces and West African ethno-histories to reveal how his geographical knowledge and expertise were bound up with Atlantic slavery. This shows not only how the colonial economy, centred on the Caribbean, underwrote the production of geographical knowledge about Africa, but also how British geographical discourse and practice might be probed for traces of Atlantic slavery and enslaved African lives. More generally, the case of James MacQueen illuminates a broader field of relationships between Atlantic slavery, West African exploration, and the development of modern British geography in the late eighteenth and first half of the nineteenth centuries. Examining these relationships is key to writing a ‘historical geography of British geography and Atlantic slavery’ and contributes to postcolonial histories of the discipline by revealing the tangled relationships that bound geography and slavery, knowledge and subjugation, that which ‘captivates’ and those held ‘captive’.

Impact of winter flow regulation on pest-level populations of blackfly (Diptera: Simuliidae) and non-target faunal communities in a South African river

The mid-reaches of the Great Fish River in the Eastern Cape Province of South Africa experience regular outbreaks of the pest blackfly Simulium chutteri as a direct consequence of increased flows caused by an inter-basin transfer scheme. There are opportunities to control these outbreaks through flow manipulation by using an upstream impoundment that has an annual shutdown period for maintenance. In this study, the stones-in-current biotope was surveyed at five sites prior to, and immediately succeeding, a flow shutdown. Changes in aquatic macroinvertebrate community composition and densities of larval and pupal blackfly were assessed and related to changes in hydraulic habitat due to the flow reductions. Although flows at those sites where blackfly densities were highest did not decrease to the levels desired for effective pest control, results from two sites indicated that flow reduction can lead to reductions in densities of larval blackfly without detrimental impacts on non-target macroinvertebrates. Simulations using a blackfly outbreak model indicate that flow reduction from an average of over 7 m3 s−1 to below 2 m3 s−1 for three to four weeks would effectively control blackfly outbreaks. Such an approach could be achieved through negotiations among affected Farmers' Associations, Irrigation Boards and the regional Department of Water Affairs and Forestry.

Seasonal Occurrence of Vibrios in Water and Shellfish Obtained from the Great Kwa River Estuary, Calabar, Nigeria

The prevalence of Vibrio species in shellfish and their seasonal variability in the Great Kwa River estuary (GKWE) were examined. Results revealed a trimodal peak in Vibrio counts, coinciding with meteorological changes and the hot periods of the year. The estuary was constantly faecally polluted, coupled with high rates of infection of shellfish by V. parahaemolyticus 42 (13.6%), V. cholerae non-01 29 (9.4%) and V. alginolyticus 22 (7.1%), thus posing a health risk. The observed seasonal variability and prevalence of Vibrio species infection are of epidemiological significance, and provide a guide for effective control of associated cholera epidemics.

Monitoring programme revision highlights long-term salinity changes in selected South African rivers and the value of comprehensive long-term data sets

Determination of data adequacy for detection of long-term salinity changes was an important task in the revision of the South African National Chemical Monitoring Programme (NCMP). The NCMP has been running for more than 30 years with several hundred active monitoring sites. Twenty-five sites on major rivers had sufficient continuous data for the estimation of salinity changes over a 25-year period and statistically significant upward or downward trends occurred at 17 of the 25 sites. Most sites were too far apart for detailed analysis of whole river systems, though an upward trend is apparent in the Lower Orange River and a downward trend in the Great Fish River. Salinity in the Tugela River remained stable, well below the 70 mS m( - 1) guideline for drinking water. The results underline the importance of long-term data sets for assessing and managing aquatic systems and provide the impetus to continue building and maintaining long-term sampling programmes.

Challenges of optimal implementation of formal water rights systems for irrigation in the Great Ruaha River Catchment in Tanzania

In many countries around the world, increasing attention is being directed to the need to improve water rights systems. This paper is based on a recent study undertaken to investigate challenges facing optimal implementation of formal water rights systems for irrigation purposes in the Great Ruaha River Catchment in Tanzania. The study integrated social survey, hydrologic, water abstraction and water use data, and Geographical Information System techniques. The results showed that all the canals studied, except one, abstracted water throughout the year, provided there was water in the rivers irrespective of the conditions spelt out in their formal water rights. The formal water rights were also found to be problematic as the quantities to be abstracted were much higher compared to the actual water requirements and the actual river flows. This resulted in over-abstraction of water and increased water shortages for downstream users. The study concludes that although formal water rights are meant to control and regulate the use of water, they are also subject to abuse if not managed and monitored closely. The basin authorities in Tanzania therefore need to be equipped adequately and collaborate more closely with local water users in order to attain high levels of supervision and monitoring essential for optimal implementation of formal water rights systems.

A bioassessment approach for mid-continent great rivers: the Upper Mississippi, Missouri, and Ohio (USA)

The objectives of the Environmental Monitoring and Assessment Program for Great River Ecosystems (EMAP-GRE) are to (1) develop and demonstrate, in collaboration with states, an assessment program yielding spatially unbiased estimates of the condition of mid-continent great rivers; (2) evaluate environmental indicators for assessing great rivers; and (3) assess the current condition of selected great river resources. The purpose of this paper is to describe EMAP-GRE using examples based on data collected in 2004-2006 with emphasis on an approach to determining reference conditions. EMAP-GRE includes the Upper Mississippi River, the Missouri River, and the Ohio River. Indicators include biotic assemblages (fish, macroinvertebrates, plankton, algae), water chemistry, and aquatic and riparian physical habitat. Reference strata (river reaches for which a single reference expectation is appropriate) were determined by ordination of the fish assemblage and examination of spatial variation in environmental variables. Least disturbed condition of fish assemblages for reference strata was determined by empirical modeling in which we related fish assemblage metrics to a multimetric stressor gradient. We inferred least disturbed condition from the y-intercept, the predicted condition when stress was least. Thresholds for dividing the resource into management-relevant condition classes for biotic indicators were derived using predicted least disturbed condition to set the upper bound on the least disturbed condition class. Also discussed are the outputs of EMAP-GRE, including the assessment document, multimetric indices of condition, and unbiased data supporting state and tribal Clean Water Act reporting, adaptive management, and river restoration.

Water for irrigation or hydropower generation?—Complex questions regarding water allocation in Tanzania

The need for achieving efficient, equitable and sustainable use of water resources to meet water demands of different sectors is pressing, particularly in areas where water resources are dwindling. Along with this is the quest for having a good understanding of the value of water in its different uses. Using a simplified model derived from the residual imputation approach (the Change in Net Income Model) we assess the value of water in irrigated paddy and hydropower generation in the Great Ruaha River Catchment (GRRC) in Tanzania. The estimated productivity of water (PW) in irrigated paddy ranges from 0.059 to 0.250 kg/m 3 (for withdrawn water) and 0.126 to 0.265 kg/m 3 (for consumed water). The PW in hydropower generation is estimated to range from 0.45 to 1.68 kWh/m 3. In monetary terms the value of water in irrigated paddy is estimated at 15.3 Tanzanian shilling (Tsh)/m 3 (for water withdrawn) and 0.19 Tsh/m 3 (for water consumed). The values of water for hydropower generation are relatively higher than for irrigated paddy, ranging from 59 to 226 Tsh/m 3. Yet, irrigated paddy also supports livelihoods of about 30,000 agrarian families in the GRRC, with gross revenue of about Tsh 15.9 million per annum and GRCC paddy contributes about 14–24% of national rice production. We conclude that understanding the value of water in its alternative uses is key to fostering informed debate on water management and allocation, identifying the basis for making ‘agreeable’ trade-offs, the potential for improvement and creating linkages with water allocation options particularly in agricultural-based economies, where agriculture competes with other sectors and where water re-allocation decisions may involve large transfers of water from the sector generating the highest pro-poor returns (agriculture for this case) to the sectors generating the highest economic returns (hydropower generation and industrial uses).

Recent habitat association and the historical decline of Notropis simus pecosensis

AbstractSmall‐bodied, riverine minnows that historically characterized fish assemblages of Great Plains rivers in North America have declined because of river fragmentation, dewatering, river channel degradation, river salinization and nonnative species introductions. The Pecos bluntnose shiner Notropis simus pecosensis, a member of this guild, persists in one segment of the Pecos River, New Mexico, USA. We characterized habitat associations for the species at two spatial scales. In general, N. s. pecosensis associated with fluvial habitats, but velocity association depended on body size, with larger individuals using swifter habitats. All N. s. pecosensis associated with relatively low depths (3–51 cm), which were most abundant in sites with relatively wide river channels (>25 m), especially when discharge was between 0.5 and 4.0 m3 s−1. The Pecos River sub‐segment that is occupied by the core population of N. s. pecosensis (V‐ii) had a unique combination of being buffered from direct dam effects by intervening segments and sub‐segments, high sub‐segment length, substantial sediment inputs from numerous uncontrolled tributaries, substantial base flow provided by irrigation return flows and groundwater inflows, high channel width in relation to discharge and low salinity. Although no unoccupied Pecos River segment appears to be suitable for N. s. pecosensis, habitat restoration opportunities exist within all occupied sub‐segments (V‐i, V‐ii and V‐iii) via base flow enhancement and river channel restoration. Restoration that offsets chronic effects of dams may be necessary to conserve the species. Restoration would also benefit other rare riverine minnows that coexist with N. s. pecosensis. Copyright © 2008 John Wiley & Sons, Ltd.