River Location Research Articles

Can the river location within a fjord explain the density of Atlantic salmon and sea trout?

The rivers that drain into the Hardangerfjord were historically known to have numerous populations of both sea trout (Salmo trutta) and Atlantic salmon (Salmo salar). After a decline in catches during the last decades many of the rivers have been closed for fishing. In this study we use snorkelling observations from rivers and catch statistics from 2004 to 2011 to describe the current situation and analyse the patterns of density of wild salmon, sea trout and escaped farmed salmon in the Hardangerfjord rivers. We hypothesize that some of the variance in density of salmon and sea trout can be explained by the location of the river in the fjord, with fish from rivers with a longer fjord exposure having a lower density. A median number of 3.5 salmon×ha−1 and 14.9 sea trout×ha−1 were observed in the rivers. Farmed salmon were observed in all rivers and constituted on average 23.3% of the total number of observed salmon. For salmon, there was an inverse log-linear relationship between density in the river and migration distance to coast, with a higher density in rivers with a shorter migration distance. For sea trout there was no evident relationship with location within the fjord. We suggest that the spatial patterns observed for salmon and sea trout can be related to the species-specific differences in habitat use within the fjord system.

River network completion without height samples using geometry-based induced terrain

We present an improved method for connecting broken river segments by incorporating segment geometry into the induced terrain approach. The reconnection problem is important in aerial photography. Canopies and clouds cover parts of rivers, and a complete river network is necessary for transportation, land-use planning, and floodplain control. Our previously presented induced terrain approach guarantees that the global network topology is hydrologically consistent. However, it assumes many reliable height samples, which may be unavailable because of extensive view obstacles or gentle surfaces, to reconstruct the induced terrain surface. In this paper, we exploit river segment geometries to generate the induced terrain. We assign lowest heights to the known river locations, and higher and higher heights for locations further and further away. Since areas radiating from segment tips tend to be where a river is broken, we assign relatively small heights to these areas, so as to favor water flow toward them in the subsequent river derivation. On average, such a tip-biased model improves reconnection accuracy by five percentage points (which is 40% of what we would have been corrected if we had had rich height samples covering 10% of the terrain cells) over the intuitive baseline model in which the height of a location increases with its distance from the respective nearest river location, without considering the potential effect of segment tips as the tip-biased approach.

Linking the restoration of rivers and riparian zones/wetlands in Europe: Sharing knowledge through case studies

Floodplains in Europe are heavily impacted by human intervention and often disconnected from the main river channel. Restoring lateral hydraulic connectivity between wetlands, fringe habitats and riparian land with the adjacent river channel is extremely important to maintain natural functioning of floodplain wetlands. However, there is no simple solution to restoring and rehabilitating rivers and their floodplains, particularly in terms of long-term sustainability. Floodplains are often the most fertile and productive part of the landscape, in terms of both agricultural production and natural ecosystems. Restoration projects must be able to balance conflicting needs and interests. Flood management is one of the most powerful drivers of developing strategies for floodplain restoration. Appropriate restoration management of floodplains is vital for the conservation of unique bio-diverse systems and for sustainable agricultural productivity. By developing strategies that better incorporate floodplain restoration in the context of the basin scale, it will become more feasible to develop the most effective restoration actions for a specific river type and location. Within this context we must not forget that successful natural resource management is much more than developing good science; it requires working with landowners, meeting deadlines, securing funding, supervising staff, and cooperating with politicians. Furthermore, the benefits of floodplain restoration must be equally demonstrated for multiple purposes including a range of ecosystem services. This paper explores the various interactions associated with floodplain dynamics. Through case studies it explores the various approaches that have been taken across Europe to forward the restoration of these fragile and important ecosystems and embeds these in the context of current European environmental policy and directives.

Beyond ‘Earlygold’: Juice Color and Quality of Additional Early-Maturing Sweet Orange Selections

This publication summarizes 5 years of juice quality information about 15 early-maturing sweet orange selections introduced to Florida and evaluated after ‘Earlygold’ became available. The trees were grown at a central Florida and Indian River location for about 10 years. Also presented are observations on tree development summarized across both locations and two rootstocks. This 8-page fact sheet was written by William S. Castle and published by the UF Department of Horticultural Sciences, January 2013.
 http://edis.ifas.ufl.edu/hs1209

Towards a publicly available, map-based regional software tool to estimate unregulated daily streamflow at ungauged rivers

Abstract. Streamflow information is critical for addressing any number of hydrologic problems. Often, streamflow information is needed at locations that are ungauged and, therefore, have no observations on which to base water management decisions. Furthermore, there has been increasing need for daily streamflow time series to manage rivers for both human and ecological functions. To facilitate negotiation between human and ecological demands for water, this paper presents the first publicly available, map-based, regional software tool to estimate historical, unregulated, daily streamflow time series (streamflow not affected by human alteration such as dams or water withdrawals) at any user-selected ungauged river location. The map interface allows users to locate and click on a river location, which then links to a spreadsheet-based program that computes estimates of daily streamflow for the river location selected. For a demonstration region in the northeast United States, daily streamflow was, in general, shown to be reliably estimated by the software tool. Estimating the highest and lowest streamflows that occurred in the demonstration region over the period from 1960 through 2004 also was accomplished but with more difficulty and limitations. The software tool provides a general framework that can be applied to other regions for which daily streamflow estimates are needed.

Tunnel Inflow Monitoring in Permeable Rocks Nearby Cannero River, Piedmont (Northern Italy)

Analytical methods used in engineering practice for a preliminary tunneling design do not adequately account for the domain limitation due to a river. In order to forecast the flow rate that has to be extracted to reach a sustainable water head in tunnel, the design must consider the changes of river hydrometric level and their consequences on piezometric head. The river is taken in account and the constraints of analytical solutions are discussed assuming isotropic and infinite domain. In particular, the study develops a formulation considering the variation of hydrograph in the river and different location of tunnel in the aquifer nearby the stream. Then, this equation was applied to a preliminary tunneling design in Cannero Valley, Northern Italy (Piedmont). The results, compared with analytical model’s ones show that the analytical approach leads to a good estimation of the tunnel inflow and, the analytical to a preliminary evaluation of its most suitable location.

4次元変分データ同化法を用いた密度分布と水質の再現性向上

Assimilation of 3D observed salinity and temperature data obtained by steady observation stations using 4D-Var (four dimensional variational method) are applied and tested in Osaka Bay. Data assimilation becomes fully effective after around 8 hour calculation. Appropriate horizontal and vertical correlation scales are found to be 10km and more than 3m by calibration with the consideration of density distribution under the influence of river plume and location of the observation stations. Water quality model is modified to represent hypoxia better and run with 4dvar flow model. Without direct data assimilation of dissolved oxygen, the improvement of density profiles has an effect on that of DO profiles.

A GIS approach for explanation of fish assemblage structure in a large river

Although using Geographic Information Systems (GIS) has become common in ecology, few river stud- ies incorporate this technology into examining habitat variables and use of habitat by individual fishes. Our goal was to demonstrate these GIS techniques and to test for the ability to predict fish and habitat relationships using the same data in a multivariate analysis. We collected channel bathymetry, water velocity, and streambed composition using an Acoustic Doppler Current Profiler (ADCP) deployed from a USGS boat and interfaced with a Differential Global Positioning System (DGPS) receiver, for a 10-km study reach of the Wabash River. Individual fishes were collected the following week and assigned spatial coordinates for latitude and longitude. We tested for the ability of a multi- variate technique to explain fish assemblage variation using environmental variables collected in a GIS context. We tested at which of three resolutions the environmental variables explained the highest proportion of fish assemblage variation. For this 10-km reach of the Wabash River, fish assemblages were best explained at a 10 by 10 m resolution with water velocity, water depth, river location, woody debris, and substrate composition. At a lower resolution (30 by 30 m) the same habitat variables provided similar but lower explanation of variation. However, at the highest resolution of 4 by 4 m, environmental variables provided relatively little explanation of fish assemblage structure. We suggest and recommend additional applications of a GIS approach to test temporal and spatial hypotheses of stream fish assemblage structure.

Morphologic evolution of the Central Andes of Peru

In this paper, we analyze the morphology of the Andes of Peru and its evolution based on the geometry of river channels, their bedrock profiles, stream gradient indices and the relation between thrust faults and morphology. The rivers of the Pacific Basin incised Mesozoic sediments of the Marañon thrust belt, Cenozoic volcanics and the granitic rocks of the Coastal Batholith. They are mainly bedrock channels with convex upward shapes and show signs of active ongoing incision. The changes in lithology do not correlate with breaks in slope of the channels (or knick points) such that the high gradient indices (K) with values between 2,000–3,000 and higher than 3,000 suggest that incision is controlled by tectonic activity. Our analysis reveals that many of the ranges of the Western Cordillera were uplifted to the actual elevations where peaks reach to 6,000 m above sea level by thrusting along steeply dipping faults. We correlate this uplift with the Quechua Phase of Neogene age documented for the Subandean thrust belt. The rivers of the Amazonas Basin have steep slopes and high gradient indices of 2,000–3,000 and locally more than 3,000 in those segments where the rivers flow over the crystalline basement of the Eastern Cordillera affected by vertical faulting. Gradient indices decrease to 1,000–2,000 within the east-vergent thrust belt of the Subandean Zone. Here a correlation between breaks in river channel slopes and location of thrust faults can be established, suggesting that the young, Quechua Phase thrust faults of the Subandean thrust belt, which involve Neogene sediments, influenced the channel geometry. In the eastern lowlands, these rivers become meandering and flow parallel to anticlines that formed in the hanging wall of Quechua Phase thrust faults, suggesting that the river courses were actively displaced outward into the foreland.

Microhabitat use and seasonal movements of hatchery-reared and wild shortnose sturgeon in the Savannah River, South Carolina - Georgia

Summary Radio and acoustic telemetry were used to monitor the seasonal movement of hatchery-reared and wild shortnose sturgeon (622–927 mm total length) in the Savannah River. Diploid, and sterile hatchery-reared shortnose sturgeon, and wild shortnose sturgeon showed apparent similar seasonal patterns of movement within the river. We were unable to detect any significant differences in the seasonal mean river location, minimum daily distance moved, absolute distance moved, displacement or mean territory size among treatments. Fish moved throughout the brackish and freshwater interface area of the Savannah River during the summer months. Coinciding with decreasing fall temperatures, fish of all treatment groups moved downriver into brackish areas of the upper estuary, residing in the Front, Middle, and Back Rivers, where they remained through winter. Upriver movements of some hatchery-reared and wild groups began in early February as river temperatures began to increase. Shortnose sturgeon from each group selected apparent similar thermal, salinity and water depth conditions throughout the year. Hatchery-reared fish may be useful as surrogates for wild fish in behavioural studies. Triploid or surgically-sterilized fish may be used in situ behavioural studies where genetic contamination is a concern. It may be possible to monitor habitats used by released hatchery-reared fish to locate or verify remnant populations of rare or endangered species in systems where they are thought to be extirpated.

Estimating river flow effects on water ages by hydrodynamic modeling in Little Manatee River estuary, Florida, USA

The water age in a tidal river in Florida, Little Manatee River, has been investigated in this study by the application of a three-dimensional hydrodynamic model. In response to a pulse dye release in the upper end of the river boundary, the hydrodynamic model determines the water age for a given location by recording the time for the dye to reach the given river location. The hydrodynamic model uses horizontal curvilinear orthogonal grids to represent the complex river system that includes several bayous and tributaries. The model has was calibrated and verified in previous study by using two continuous data sets for a 6 month period. Satisfactory model verifications indicate that the hydrodynamic model is capable of quantifying the mixing and transport process for calculating the water age in the tidal river. For 17 freshwater inflow scenarios in the Little Manatee River, the hydrodynamic model was applied to simulate water ages along the main channel of the river at 2-km interval. Flow rates in the 17 scenarios varying from 0.26 to 76.56 m3/s cover the range of the observed flows in the Little Manatee River. Water ages from model predictions range from the minimum 1.2 days under the maximum 76.56 m3/s inflow condition to the 50 days under the minimum 0.26 m3/s inflow condition. Empirical regression equations at three selected stations, with the correlation coefficient R2 above 0.96, were derived from numerical model simulations to correlate water ages to freshwater inflows. The empirical water-age equation derived from hydrodynamic model simulations can be used to provide quick and low-cost estimations of water ages in response to various inflow scenarios for studying physical–chemical and biological processes in the river.

Validation of ecological status concepts in UK rivers using historic diatom samples

We assessed the feasibility of using herbarium specimens to validate reference conditions in the UK by comparing diatom community composition of river sites with both recent and historic diatom samples. The question of substrate specificity was addressed by comparing epilithon (stone-derived) and epiphyton (plant-derived) samples from a number of rivers. No significant differences were found between the Trophic Diatom Index (TDI), species richness, species diversity, and percentage of motile valves between paired diatom samples (epilithic and epiphytic) from contemporary samples. Significant differences were recorded between a number of indices derived from analysis of the historic diatom samples on plant material sampled pre-1930 compared with diatoms from stones collected post-1990 from the same river location. The TDI, mean species richness, and species diversity and percentage of motile valves and nutrient tolerant valves were all significantly greater in the contemporary samples ( p ≤ 0.05). The percentage of nutrient sensitive valves was significantly lower in the contemporary samples ( p ≤ 0.05). The relative abundance of Achnanthidium minutissimum and Cocconeis placentula var. lineata was significantly greater on the herbarium material compared to matched contemporary samples. Calculated values for the TDI (43 ± 3) expected at reference conditions were similar to the observed TDI values derived from herbarium material (44 ± 12) showing no significant deviation in ecological status.

Factors influencing wetland plant communities during a flood-drawdown cycle in the Peace-Athabasca Delta, Northern Alberta, Canada

ABSTRACT I analyzed two sets of the same 583 vegetation plots (0.25–10 m2) and 97 plant taxa sampled in 1993 and 2001 in the Peace-Athabasca Delta (PAD), northern Alberta, Canada. Cluster analyses and Bray-Curtis ordinations were used to examine relationships between environmental and biological factors and wetland community changes over a flood-drawdown cycle. While water regime was key to explaining variation in the vegetation, the vegetation gradients were complex. Vegetation structure, bison grazing, and landscape attributes such as distance to nearest major river, relative elevation, and geographic location within the PAD also played significant roles in explaining variation in the vegetation. Autocorrelations among physical and biological factors indicate that the physical and biological regimes were integrated. The importance of environmental and biological variables in explaining vegetation variation changed from pre- to post-flood. The 1993 and 2001 vegetation matrices were positively associated,...

A Water Quality Index Applied to an International Shared River Basin: The Case of the Douro River

A Water Quality Index (WQI) is a numeric expression used to evaluate the quality of a given water body and to be easily understood by managers. In this study, a modified nine-parameter Scottish WQI was used to assess the monthly water quality of the Douro River during a 10-year period (1992-2001), scaled from zero (lowest) to 100% (highest). The 98,000 km(2) of the Douro River international watershed is the largest in the Iberian Peninsula, split between upstream Spain (80%) and downstream Portugal (20%). Three locations were surveyed: at the Portuguese-Spanish border, 350 km from the river mouth; 180 km from the mouth, where the river becomes exclusively Portuguese; and 21 km from the mouth. The water received by Portugal from Spain showed the poorest quality (WQI 47.3 +/- 0.7%); quality increased steadily downstream, up to 61.7 +/- 0.7%. In general, the water quality at all three sites was medium to poor. Seasonally, water quality decreased from winter to summer, but no statistical relationship between quality and discharge rate could be established. Depending on the location, different parameters were responsible for the episodic decline of quality: high conductivity and low oxygen content in the uppermost reservoir, and fecal coliform contamination downstream. This study shows the need to enforce the existing international bilateral agreements and to implement the European Water Quality Directive in order to improve the water quantity and quality received by the downstream country of a shared watershed, especially because two million inhabitants use the water from the last river location as their only source of drinking water.

Geographic variation, genetic structure, and conservation unit designation in the Larch Mountain salamander (Plethodon larselli)

The Larch Mountain salamander (Plethodon larselli Burns, 1954) is an endemic species in the Pacific northwestern United States facing threats related to habitat destruction. To facilitate development of conservation strategies, we used DNA sequences and RAPDs (random amplified polymorphic DNA) to examine differences among populations of this species. Phylogenetic analyses of cytochrome b revealed a clade of haplotypes from populations north of the Columbia River derived from a clade containing haplotypes from the river's southwestern region. Haplotypes from southeastern populations formed a separate clade. Nucleotide diversity was reduced in northern populations relative to southern populations. These results were corroborated by analyses of RAPD loci, which revealed similar patterns of clustering and diversity. Network analyses suggested that northern populations were colonized following a range expansion mediated by individuals from populations located southwest of the river. Changes in the Columbia River's location during the Pliocene and Pleistocene likely released distributional constraints on this species, permitting their northern range expansion. Based on the barrier presented by the Columbia River's present location and differences in haplotype diversity and population structure observed between northern and southern populations, we suggest that designation of separate management units encompassing each region may assist with mitigating different threats to this species.

Fish community structure and environmental correlates in the highly altered southern Sacramento-San Joaquin Delta

We sampled 11 sites in the southern Sacramento-San Joaquin Delta from 1992–1999, to characterize fish communities and their associations with environmental variables. Riparian habitats were dominated by rock-reinforced levees, and large water diversion facilities greatly influenced local hydrodynamics and water quality. We captured 33 different taxa, only eight of which were native. None of the native species represented more than 0.5% of the total number of individuals collected. The abundance of native species was consistently low but typically peaked during high outflow periods. Fish communities were predominantly structured along environmental gradients of water temperature and river flow. Native species (tule perch, Hysterocarpus traski, & Sacramento sucker, Catostomus occidentalis) were associated with conditions of high river flow and turbidity, while the majority of the non-native species were associated with either warm water temperature or low river flow conditions. The exceptions were the non-native striped bass, Morone saxatilis, and white catfish, Ameiurus catus, which were positively associated with relatively high river flow. Variation in fish community structure was greater among river locations within years than within river locations among years, thus fish communities at each river location were consistently different each year. Differences in fish communities among river locations were correlated with river flow and turbidity. We predict that the fish communities of this region will remain numerically dominated by non-native species if the environmental conditions we observed persist in the future.

Effect of Hook Style, Bait Type, and River Location on Trotline Catches of Flathead and Channel Catfish

Abstract Trotlines can be used to provide data on catfish populations, but better understanding of trotline selectivity is needed. We compared differences in the presence or absence of channel catfish Ictalurus punctatus and flathead catfish Pylodictis olivaris caught on trotlines among hook types, bait types, substrate types, channel types, water depths, and woody debris complexities in two South Dakota rivers. Channel catfish were 3.5 times more likely to be caught on hooks baited with cut common carp Cyprinus carpio, and flathead catfish were 28 times more likely to be caught on hooks baited with live black bullheads Ameiurus melas. Sea-circle hooks caught fewer catfish of either species than O'Shaughnessy or modified circle hooks. Channel type, water depth, and substrate type affected catches of flathead and channel catfish from the Big Sioux River, but did not influence catches of either species on the James River. The Big Sioux River had greater habitat variability, thereby increasing our chances of...

Use of indirect conductimetry to establish predictive no effect concentrations of oxytetracycline and oxolinic acid in aquatic sediments

A method based on indirect conductimetry was developed for detecting the minimum effect concentration (MEC) of oxytetracycline and oxolinic acid on the metabolic activity of the microflora of freshwater sediments. For each agent, three repeat examinations of separate samples collected from the same river location generated identical MEC values (20 mg/kg for oxytetracycline and 0.63 mg/kg for oxolinic acid). Sediment microcosms were employed to determine the impact of these agents on the frequency of resistance in the culturable microflora. The minimum concentration capable of selecting for increased frequencies of resistance (MSC) was determined from resistance profiles constructed by measuring the percentage of resistant colony forming units over a range of selective concentrations. For each agent, the MSC values calculated in three independent analyses were identical to the previously determined MEC values. Comparisons of the resistance profiles generated from impacted and unimpacted microcosms allowed the establishment of empirically justifiable breakpoint concentrations for incorporation into Iso-Sensitest agar. These were 12.5 mg/l for oxytetracycline and 1.56 mg/l for oxolinic acid. Arguments are presented that the determination of MEC values for any sediment will allow the determination of no-effect concentrations that can be used in predictive environmental impact studies.

Risk Perception in Context: The Savannah River Site Stakeholder Study

Environmental managers are increasingly charged with involving the public in the development and modification of policies regarding risks to huma health and the environment. Involving the public in environmental decision making first requires a broad understanding of how and why the public perceives various risks. The Savannah River Stakeholder Study was conducted withthe purpose of investigating individual, economic, and social characteristics of risk perceptions among those living near the Savannah River Nuclear Weapons Site. A number of factors were found to impact risk perceptions among those living near the site. One's estimated proximity to the site and relative river location surfaced as strong determinants of risk perceptions among SRS residents. Additionally, living in a quality neighborhood and demonstrating a willingness to accept health risks for economic gain strongly abated heightened risk perceptions.

Citizen Participation in Water Management

If rivers are to be managed sustainably, and the potential to resolve conflicts of use realised, the general public must be more involved in their management. Participation in water management in England and Wales occurs at three levels: formal consultation; public involvement; or actual direct participation by the public. Formal consultations often leave the public in the role of the “objector” and ignore the “silent majority” focusing on the more vociferous minority of the population. Public involvement is less formal and can take a variety of forms. Although not allowing the public to be directly involved in the decision making processes, it provides the public with the opportunity to comment upon plans for river works or the re-development of a river location, or to indicate what they want from the rivers that flow through their own local area and which they use for recreation and amenity. True participation is where the public are actively involved in the decision making processes. Citizen participation at all three levels provides environmental education, however, personal experience promotes a greater environmental awareness and understanding by the public. This paper reflects upon approaches to citizen participation in the UK and provides examples of specific projects involving both formal organisations and the general public.