Higher Order Streams Research Articles

Stream macroinvertebrate assemblage uniformity and drivers in a tropical bioregion

Summary Understanding spatial and environmental drivers of undisturbed stream assemblages is important for separating natural and human‐induced changes, but has rarely been attempted for an entire tropical bioregion. We sampled riffle macroinvertebrate assemblages and measured associated biophysical variables in post‐wet and dry seasons from 68 streams of orders 1–5 across the Australian Wet Tropics, a small bioregion (18 497 km2) defined by its warm moist climate and closed‐forest vegetation. As climate and landscape were relatively uniform across the bioregion, we predicted that assemblages would be similar, with turnover (beta diversity) unrelated to distance, and with composition determined mainly by habitat. We identified 93 higher taxa. Density and richness of macroinvertebrates were greatest in the dry season because of habitat contraction and minimal flow disturbance. Richness was greatest in higher order streams. Relative abundance and richness of functional groups showed minor effects of catchment, lithology and stream order, and a positive relationship with altitude for richness of collectors, predators and shredders, and for abundance of shredders. Distance‐based linear modelling showed that among‐assemblage differences were explained by landscape‐scale variables (9.5% of the variation), stream size (13.0%), riparian characteristics (9.6%), water quality (4.6%), substratum (21.1%) and organic resources (22.4%); for models of individual taxa and functional groups, habitat and organic‐resource variables also predominated. Similarities among site assemblages differed little among catchments and there was no relationship between pairwise similarities of catchments and their geographical distances. Nestedness analysis confirmed that samples and catchment groupings were nested subsets of the total set of samples. Across the Australian Wet Tropics, uniformity of assemblages (identified to family or above) conformed to the bioregional classification, probably as a result of the great age of the region. The habitat variables that most influenced macroinvertebrate assemblages support the idea that a suite of biophysical influences is common to stream macroinvertebrate assemblages globally.

Scenario analysis for assessing the impact of hydraulic fracturing on stream low flows using the SWAT model

ABSTRACTScientists and water users are concerned about the potential impact on water resources, particularly during low-flow periods, of freshwater withdrawals for hydraulic fracturing (fracking). Therefore, the objective of this paper is to assess the potential impact of hydraulic fracturing on water resources in the Muskingum watershed of Eastern Ohio, USA, especially due to the trend of increased withdrawals for hydraulic fracking during drought years. The Statistical Downscaling Model (SDSM) was used to generate 30 years of plausible future daily weather series in order to capture the possible dry periods. The data generated were incorporated in the Soil and Water Assessment Tool (SWAT) to examine the level of impact due to fracking at various scales. Analyses showed that water withdrawal due to hydraulic fracking had a noticeable impact, especially during low-flow periods. Clear changes in the 7-day minimum flows were detected among baseline, current and future scenarios when the worst-case scenario was implemented. The headwater streams in the sub-watersheds were highly affected, with significant decrease in 7-day low flows. The flow alteration in hydrologically-based (7Q10, i.e. 7-day 10-year low flow) or biologically-based (4B3 and 1B3) design flows due to hydraulic fracking increased with decrease in the drainage area, indicating that the relative impact may not be as great for higher order streams. Nevertheless, change in the annual mean flow was limited to 10%.

Morphometric analysis of Seonath river of Chhattisgarh using remote sensing and Geographical Information System (GIS) Technique

The delineation of drainage system is importance in understanding hydrological system of an area, water resource management and it's planning in an effective manner. Remote sensing, Geographical Information System has proved to be an efficient tool in delineation of drainage pattern and water resources management and it's planning. The study has demonstrated the potential use of remotely sensed data and Geographical Information Systems (GIS) in evaluation of linear, relief and areal morphometric parameters of Seonath river. Strahler's method of stream ordering is the most commonly used method has been followed for the present study. The Seonath river of Chhattisgarh covers an area of about 30868 km2 and is 7th order drainage basin with mainly dendritic drainage pattern. The numbers of lower order streams are more than the higher order streams and the bifurcation ratio of the study area was low value. The low values of bifurcation ratio indicate that the drainage of the basin has suffered less structural disturbances and drainage pattern has been distorted. The basin has low drainage density of 0.49km−1 and is elongated in shape. Stream length decreases with the order increases and the length of overland flow values of the basin was 0.25. These studies are significant for soil erosion prevention and land and soil management practices.

The Effect of Beaver Ponds on Water Quality in Rural Coastal Plain Streams

We compared water-quality effects of 13 beaver ponds on adjacent free-flowing control reaches in the Coastal Plain of rural North Carolina. We measured concentrations of nitrate, ammonium, soluble reactive phosphorus (SRP), and suspended sediment (SS) upstream and downstream of paired ponds and control reaches. Nitrate and SS concentrations decreased, ammonium concentrations increased, and SRP concentrations were unaffected downstream of the ponds and relative to the control reaches. The pond effect on nitrate concentration was a reduction of 112 ± 55 μg-N/L (19%) compared to a control-reach—influenced reduction of 28 ± 17 μg-N/L. The pond effect on ammonium concentration was an increase of 9.47 ± 10.9 μg-N/L (59%) compared to the control-reach—influenced reduction of 1.49 ± 1.37 μg-N/L. The pond effect on SS concentration was a decrease of 3.41 ± 1.68 mg/L (40%) compared to a control-reach—influenced increase of 0.56 ± 0.27 mg/L. Ponds on lower-order streams reduced nitrate concentrations by greater amounts compared to those in higher-order streams. Older ponds reduced SS concentrations by greater amounts compared to younger ponds. The findings of this study indicate that beaver ponds provide water-quality benefits to rural Coastal Plain streams by reducing concentrations of nitrate and suspended sediment.

Order classification of river watershed divides based on processing digital elevation models

The principles and the algorithm of order classification of river watershed divides are outlined. It is shown that a formal application of any available order classification procedures for river watershed divides is not theoretically grounded as well as being impractical, because the physical mechanisms for formation of watershed divide network are different from those operating in the river network. We have formulated the basic principle of determining the watershed divides order on the basis of a serial sequence of sections constituting the travel path of an arbitrary water drop from the watershed divide to the outlet section of the basin. It is suggested that the order N should be assigned to the section of the watershed divide belonging to the full divide line of the N-order basin only if the travel path from it to the N-order stream is “full” in the topological sense, i.e. includes sections of all orders, from 1 to N. Also, we present a variant of determining the order on the basis of so-called higher-order triplets, incomplete sequences of sections of three neighboring orders along the travel path, with the higher of them determining the watershed divide order. The use of triplets is a subjective procedure of generalization that eliminates the influence of recent random erosional incisions on the forms of stable high-order watersheds. We outline the variants of the technique for identifying the network of watershed divides and calculating their orders, based on processing the digital elevation models (DEM) through the use of standard GIS ArcMap tools. Results are obtained in the form of a correlated classification of river and watershed networks which are rationally interpreted and hold promise for investigating the structure, functioning and evolution of river systems. The study revealed the existence of formation “cores” of river systems, i.e. regions within which the system reaches a higher stream order and which are bounded by watersheds of the same order.

Drainage network extraction and morphometric analysis using remote sensing and GIS mapping techniques (Lesser Zab River Basin, Iraq and Iran)

The Lesser Zab River, in the northeast of Iraq and northwest of Iran, is the largest tributary inside Iraq supplying water to the Tigris River. The majority of the basin lies inside Iraq. The important goals of this study are to estimate the erodibility and flash flood hazard of the Lesser Zab River Basin (LZRB). The present research highlights sub-basins that should be prioritized for conservation and flood risk schemes. The morphometric analysis reveals that the most important sub-basins are Sb1 and Sb2, in terms of water contribution to the main river. They are characterized by higher stream order, larger area, high elevation, low drainage density, low drainage texture, and low relative relief. Because of the relatively high relief in the upper part of the LZRB, the sub-basins are characterized by low drainage density, which indicates more surface runoff compared to the main basin in the lower part. The very fine drainage texture in the upper part of the LZRB reflects low infiltration and higher runoff relative to the lower part. The sub-basins in the upper part of the LZRB, which have a low bifurcation ratio, produce flood hydrographs with marked discharge peaks, while the sub-basins in the lower part, which have high ratios, produce low peaks over a long time period. Various morphometric parameters have been used for each sub-basin to calculate compound parameters for the final ranking of the sub-basins. Based on utilization of morphometric parameters for the erodibility hazard assessment, sub-basins were divided into seven prioritization classes: critical, very high to critical, high to very high, medium to high, low to medium, very low to low, and lowest. Furthermore, the resultant hazard map indicates that 18 sub-basins have moderate to low risk of flash flooding and 29 sub-basins have low possibility of flash flooding.

Studies on eucrenal-hypocrenal zonation of springs along the river mainstream: A case study of a karst canyon in Bosnia and Herzegovina

AbstractThe canyons in Dinaric karst are known to harbour a diverse aquatic fauna living in springs along the river mainstream. However, the knowledge on the ecology of these springs and also on the springs in mountainous areas of the Balkan Peninsula in general is poor. This study is focused on the macroinvertebrate assemblages of three different types of springs along the Cvrcka River (Republic of Srpska, Bosnia and Herzegovina). The aim of this study was to check whether existing criteria for regional spring zonations in Central Europe are applicable also for riparian springs with short springbrooks bordering high order streams. The macroinvertebrates were collected seasonally for one year at two different distances from the source: at the source, and approximately 2–3 m from the source (“springbrook”). At the spring sources, we found 59 species and higher taxa while in the springbrooks 61 species and higher taxa were recorded. Diptera represented the most abundant taxon, followed by Amphipoda and Trichoptera. No strong trend for the Margalef’s index for the spring source and springbrook was detected, while the Shannon’s diversity index increased in the springbrook of the studied springs. Our analysis did not prove significant differences between the macroinvertebrate assemblages from the source and springbrook. Based on faunistic data we suggest that small riparian springs with a short outflow likely do not exhibit true spring zonation but may show a “quasi-zonation” defined as a possible hidden differentiation between spring source and springbrook. Our study shows that criteria for spring zonation are not suitable for riparian springs bordering high order streams.

Impact of Global Climate Change on Stream Low Flows in a Hydraulic Fracking Affected Watershed

The impact of fresh water withdrawals for hydraulic fracturing has concerned water resource scientists and communities interested in sustainable water resource management. Specifically, low flow conditions in watersheds may be further reduced due to global climate change, as it has the potential to decrease streamflow. Since an earlier study found that the current rate of fracking had some impact on water availability, this study was conducted in order to ascertain whether or not the current fracking trend will have an impact in stream low flow in the future. This study was conducted on the Muskingum watershed in Eastern Ohio, which has been subjected to the rapid expansion of hydraulic fracking. The watershed model, Soil and Water Assessment Tool (SWAT), was used for watershed simulation using the climate output of Coupled Model Intercomparison Project Phase 5 (CMIP5). Precipitation and temperatures outputs from Max Planck Institute Earth System Model (MPI-ESM) were used to evaluate the variation in streamflow during the 21 st century using three Representative Concentration Pathways (RCP) scenarios: RCP 2.6; RCP 4.5; and RCP 8.5. Three future periods, namely, 2035s (2021-2050), 2055s (2051-2070) and 2085s (2070-2099) were set against the baseline condition (1995-2009). Lowest flow was projected to increase across the watershed during 2035s period compared to the remaining 50 years period, under the highest forced climate scenario (RCP8.5). Similarly, mean flow also could be expected to decrease during 2035s in the eastern, north-western and south western portion of the watershed. Additionally, the streamflow was simulated using current fracking scenarios and 2035s climate output in order to assess the impact of water withdrawal for a continuous trend of current fracking rates. A modest effect on stream low flow was detected, when extreme scenario (RCP 8.5) was considered, especially in the headwater streams. While results indicate that 14 of 32 subbasins were affected, with maximum difference up to 55% in lowest 7 days minimum low flow (considered lowest value from each year), negligible impact was detected on mean monthly and annual streamflow. Analysis with RCP 2.6 and RCP 4.5 indicated that stream low flow would not be affected especially in higher order streams. Even though a localized effect of hydraulic fracking to reduce the environmental flow was detected; this research indicated that future climate change may not have additional adverse impacts if hydraulic fracking trends are stable.

Endangered Golden mahseer Tor putitora Hamilton: a review of natural history

Golden mahseer, Tor putitora Hamilton, one of the largest freshwater fish of the Indian sub-continent, inhabits mainly Himalayan rivers in the foothills. Among numerous freshwater fishes of the sub-continent, Golden mahseer is the most striking due to its large size, attractive golden colour, sustenance and sporting values. Tor putitora is known by various common names such as king mahseer, mighty mahseer and the tiger of water. Being a migratory fish, Golden mahseer undertakes periodic upstream migration during pre-monsoon and monsoon seasons from large rivers and higher order streams in the foothills to lower order streams for spawning. In recent years, conservationists, anglers and commercial fishermen have expressed concern over the declining populations of Golden mahseer due to indiscriminate fishing of brooders and juveniles besides the adverse effects of dams. Despite its ecological and economic importance, specific conservation measures by way of protective legal provisos are lacking for Golden mahseer in India. In view of its physical features, ecology and vulnerable conservation status, there is an exigent need to promote the Golden mahseer as a flagship conservation species of the Himalayan rivers. In view of the recent reports of unprecedented river regulation projects on the Himalayan rivers and need to draw global attention of conservationists, we review various aspects of ecology, life history, interesting features, traits and threats associated with the reduced chances of survival of Golden mahseer.

Changes in runoff regime. The Lomnice catchment case study

Water distribution in landscape is essentially influenced by the nature of the catchment rainfall-runoff process. Firstly, this paper presents an analysis of trends in the rainfall-runoff regime of the Lomnice river basin (South Bohemia, Czech Republic), using a single and double mass curve method. Secondly, the analysis of the rainfall-runoff regime is supplemented by an analysis of the evolution of temperature and snow conditions. Finally, a water balance analysis is performed for three selected years, using the Bilan hydrological model. The aim of the present paper was to find out (1) whether any changes have occurred in the trend of the rainfall-runoff regime of the catchment since 1970, and (2) to what extent these changes may have been caused by anthropogenic activities in the catchment. The results show several changes in the runoff scheme that are not related to the amount of precipitation. This statement follows from the comparison of single mass curves of precipitation and discharges. A comparison of the hydrological balance data for the Lomnice river basin, and the Otava and the Upper Vltava (a higher order stream) river basins led to the following conclusions: (1) There has been a change in the trend of the Lomnice river runoff regime. (2) The runoff regime of the Lomnice river basin differs from the regime of the higher order river basin (the Otava, the Upper Vltava). (3) The changes in the runoff regime in the Lomnice river basin were probably caused mainly by anthropogenic activities, the influence of which disappears within the larger basin (a higher order catchment area). Therefore, when planning sustainable water resources management, it is necessary to consider the impact of human activities not only globally, but also at the local scale.

Effects of water flow regulation on ecosystem functioning in a Mediterranean river network assessed by wood decomposition

Mediterranean rivers are extensively modified by flow regulation practises along their courses. An important part of the river impoundment in this area is related to the presence of small dams constructed mainly for water abstraction purposes. These projects drastically modified the ecosystem morphology, transforming lotic into lentic reaches and increasing their alternation along the river. Hydro-morphologial differences between these reaches indicate that flow regulation can trigger important changes in the ecosystem functioning. Decomposition of organic matter is an integrative process and this complexity makes it a good indicator of changes in the ecosystem. The aim of this study was to assess the effect caused by flow regulation on ecosystem functioning at the river network scale, using wood decomposition as a functional indicator. We studied the mass loss from wood sticks during three months in different lotic and lentic reaches located along a Mediterranean river basin, in both winter and summer. Additionally, we identified the environmental factors affecting decomposition rates along the river orders. The results revealed differences in decomposition rates between sites in both seasons that were principally related to the differences between stream orders. The rates were mainly related to temperature, nutrient concentrations (NO2−, NO32−) and water residence time. High-order streams with higher temperature and nutrient concentrations exhibited higher decomposition rates compared with low-order streams. The effect of the flow regulation on the decomposition rates only appeared to be significant in high orders, especially in winter, when the hydrological characteristics of lotic and lentic habitats widely varied. Lotic reaches with lower water residence time exhibited greater decomposition rates compared with lentic reaches probably due to more physical abrasion and differences in the microbial assemblages. Overall, our study revealed that in high orders the reduction of flow caused by flow regulation affects the wood decomposition indicating changes in ecosystem functioning.

Geomorphological Variables that Determine the Magnitude of Stream Floods in Wadi Al-Hasa - South Jordan

The study aims to analyze the geomorphological variables that determine the magnitude of stream floods in Wadi Al-Hasa through the analysis of the characteristics of rainfall; the shape and areal dimensions of the basin; the topography of the surface; the gradient of the Valley; the characteristics of water discharge network; and the morphology and capacity of the channel. To achieve the objectives of the study, the Analytical Approach was adopted when examining stream floods. This approach is based on the analysis of the climatic information and the hydrological data available on stream floods in Wadi Al-Hasa; and the analysis of the morphometric, hydrological and vegetation measurements that have been extracted from the topographic maps, aerial photographs and field work. The study found several results including: the increasing likelihood of frequent flooding in the sub-reaches of Wadi Al-Hasa with the increase in their stream orders, as a result of the increase in the amount of water discharge. Moreover, the results of the statistical analysis of the stepwise regression showed the importance of the following variables: (the stream order, the gradient, the width of the river channel and vegetation) in explaining the variation in the volume of the water discharge of the river tributaries in the basin, as these variables interpreted about (53%) of the total variation. The study also found that there are three areas with increased likelihood of flooding in the basin, namely: the estuaries of the eastern tributaries in Qa' Al-Jinz area; the areas where western tributaries meet with higher stream orders; and the estuary area of the mainstream of ??Valley.

A hydrogeomorphic river network model predicts where and why hyporheic exchange is important in large basins

Hyporheic exchange has been hypothesized to have basin-scale consequences; however, predictions throughout river networks are limited by available geomorphic and hydrogeologic data and by models that can analyze and aggregate hyporheic exchange flows across large spatial scales. We developed a parsimonious but physically based model of hyporheic flow for application in large river basins: Networks with EXchange and Subsurface Storage (NEXSS). We applied NEXSS across a broad range of geomorphic diversity in river reaches and synthetic river networks. NEXSS demonstrates that vertical exchange beneath submerged bed forms rather than lateral exchange through meanders dominates hyporheic fluxes and turnover rates along river corridors. Per kilometer, low-order streams have a biogeochemical potential at least 2 orders of magnitude larger than higher-order streams. However, when biogeochemical potential is examined per average length of each stream order, low- and high-order streams were often found to be comparable. As a result, the hyporheic zone's intrinsic potential for biogeochemical transformations is comparable across different stream orders, but the greater river miles and larger total streambed area of lower order streams result in the highest cumulative impact from low-order streams. Lateral exchange through meander banks may be important in some cases but generally only in large rivers.

Nitrate uptake dynamics of surface transient storage in stream channels and fluvial wetlands

River systems are important regulators of anthropogenic nitrogen flux between land and ocean. Nitrogen dynamics in small headwater streams have been extensively measured, whereas less is known about contributions of other components of stream networks to nitrogen removal, including larger streams or fluvial wetlands. Here, we quantified nitrate reaction rates in higher-order stream channels and in surface transient storage (STS) zones (sub-systems with greater water residence time than the main channel) of the Ipswich River watershed, a temperate basin characterized by suburban development. We characterized uptake in STS both within higher-order stream channels and in fluvial wetlands that remain connected to advective fluxes but not constrained within channels. We compare reaction rates in these systems to those previously measured in headwater streams in the same basin. We found that (1) nitrate reaction rates (as uptake velocity, υf) in higher-order streams (n = 2) differed from each other but were consistent with previous estimates from headwater streams, (2) nitrate reaction rates in STS zones within higher-order stream channels (n = 2) were higher than rates estimated at the whole-stream scale, (3) ambient nitrate reaction rates in fluvial wetland STS (n = 7) were high but comparable to headwater streams with low nitrate concentration, (4) nitrate reaction rates were higher in fluvial wetland STS compared to headwater stream channels at elevated nitrate concentration, and (5) efficiency loss (EL) similar to that found in headwater streams was also apparent in fluvial wetlands. These results indicate that STS are potential hotspots of biogeochemical activity and should be explicitly integrated into network scale biogeochemical models. Further, experimental evidence of EL in fluvial wetlands suggests that the effectiveness of STS to retain N may decline if N loading increases.

Rock-derived Micronutrient Transport in the Tropics: Molybdenum Cycling in Deeply-weathered Panama Soils

The rock-derived micronutrient Molybdenum (Mo) is important in both terrestrial and ocean ecosystems as an essential cofactor in nitrogenase, the enzyme used by microorganisms to fix atmospheric nitrogen. As global nitrogen fixation rates respond to increasing atmospheric pCO2, the weathering, transport, and availability of this micronutrient becomes essential, because Mo limitation on nitrogen fixation has been documented in diverse ecosystems, including tropical soils in Panama. Therefore, a thorough understanding of the carbon and nitrogen cycles may depend more on the availability of trace metals such as Mo than previously realized, but the weathering and cycling of these elements as they pass across ecosystem boundaries remains poorly understood. This work explores the sources and sinks of Mo in small (36-176ha) single land cover catchments in tropical Panama. Water samples were collected from precipitation, canopy throughfall, soil water, groundwater, soil seeps, and first- order through higher-order streams. Though Mo is considered a “rock-derived” micronutrient, concentrations were higher in precipitation and shallow soil water than in the groundwater and stream waters in contact with underlying rocks and weathered saprolite. Event-based mass balance suggests that Mo is being retained within the catchment ecosystem. The source of Mo in tropical forests may have important implications as the amount of nitrogen fixation changes during tropical forest recovery from a previous land use.

The groundwater recharge response and hydrologic services of tropical humid forest ecosystems to use and reforestation: Support for the “infiltration-evapotranspiration trade-off hypothesis”

Summary The hydrologic effects of forest use and reforestation of degraded lands in the humid tropics has implications for local and regional hydrologic services but such issues have been relatively less studied when compared to the impacts of forest conversion. In particular, the “infiltration-evapotranspiration trade-off” hypothesis which predicts a net gain or loss to baseflow and dry-season flow under both, forest degradation or reforestation depending on conditions has not been tested adequately. In the Western Ghats of India, we examined the hydrologic responses and groundwater recharge and hydrologic services linked with three ecosystems, (1) remnant tropical evergreen forest (NF), (2) heavily-used former evergreen forest which now has been converted to tree savanna, known as degraded forest(DF), and (3) exotic Acacia plantations (AC, Acacia auriculiformis) on degraded former forest land. Instrumented catchments ranging from 7 to 23 ha representing these three land-covers (3 NF, 4 AC and 4 DF, in total 11 basins), were established and maintained between 2003 and 2005 at three sites in two geomorphological zones, Coastal and Up-Ghat (Malnaad). Four larger (1–2 km2) catchments downstream of the head-water catchments in the Malnaad with varying proportions of different land-cover and providing irrigation water for areca-nut and paddy rice were also measured for post-monsoon baseflow. Daily hydrological and climate data was available at all the sites. In addition, 36 min data was available at the Coastal site for 41 days as part of the opening phase of the summer monsoon, June–July 2005. Low potential and actual evapotranspiration rates during the monsoon that are similar across all land-cover ensures that the main control on the extent of groundwater recharge during the south-west monsoon is the proportion of rainfall that is converted into quick flow rather than differences in evapotranspiration between the different land cover types. The Flow duration curves demonstrated a higher frequency and longer duration of low flows under NF when compared to the other more disturbed land covers in both the Coastal and Malnaad basins. Groundwater recharge estimated using water balance during the wet-season in the Coastal basins under NF, AC and DF was estimated to be 50%, 46% and 35% respectively and in the Malnaad it was 61%, 55% and 36% respectively. Soil Water Infiltration and Movement (SWIM) based recharge estimates also support the pattern (46% in NF; 39% in AC and 14% in DF). Furey–Gupta filter based estimates associated with the Coastal basins also suggest similar groundwater recharge values and trends across the respective land-covers: 69% in NF, 49% in AC, and 42% in DF. Soil water potential profiles using zero flux plane methods suggest that during the dry-season, natural forests depend on deep soil moisture and groundwater. Catchments with higher proportion of forest cover upstream were observed to sustain flow longer into the dry-season. These hydrologic responses provide some support towards the “infiltration-evapotranspiration trade-off” hypothesis in which differences in infiltration between land-cover rather than evapotranspiration determines the differences in groundwater recharge, low flows and dry-season flow. Groundwater recharge is the most temporally stable under natural forest, although substantial recharge occurs under all three ecosystems, which helps to sustain dry-season flow downstream in higher order streams that sustain local communities and agro-ecosystems. In addition to spatial scale effects, greater attention also needs to be given to the role of hydrogeology within the context of the above hypothesis and its implications for hydrologic services.

Nongame Fish Species Distribution and Habitat Associations in the Snake River Basin of Southern Idaho

The distribution and abundance of game fish populations are commonly monitored closely, whereas sampling of nongame species is often neglected. We used a broad-scale salmonid sampling project both to simultaneously assess the distribution and relative abundance of nongame fish species in small streams (i.e., ≤15 m wetted width) in the Snake River basin of southern Idaho and to relate the distribution and abundance of nongame species to abiotic and biotic stream conditions in the study area. Of the 1738 reaches surveyed, 34% were dry or contained too little water to support fish, and an additional 21% had flowing water but were still absent of fish. At least one species of nongame fish was captured at 30% of the reaches surveyed, and all 18 native nongame fish species believed present in study area streams were captured. The most widely distributed species was speckled dace Rhinichthys osculus (present in 21% of surveyed reaches, excluding dry and nearly dry reaches), followed by bridgelip sucker Catostomus columbianus (19%), Paiute sculpin Cottus beldingi (15%), and redside shiner Richardsonius balteatus (13%). The species least often present (≤ 1%) were leopard dace Rhinichthys falcatus and peamouth Mylocheilus caurinus. Common carp Cyprinus carpio (captured at 3 locations) and oriental weatherfish Misgurnus anguillicaudatus (2 locations) were the only nonnative nongame species encountered. Catostomids and cyprinids generally formed a composite fish assemblage that was associated with higher stream order (i.e., farther from headwaters), lower elevation, and lower-gradient reaches where streams were wider and deeper. Stream order was the strongest loading factor for canonical correlations constructed for study reaches both above and below Shoshone Falls, suggesting that the increased abundance of catostomids and cyprinids generally occurred on a longitudinal downstream gradient. Biologists sampling game fish populations in streams should also record data on nongame species to more closely monitor their status through time.

Wetlands in agricultural landscapes for nitrogen attenuation and biodiversity enhancement: Opportunities and limitations

Riparian zones along streams and other small wetlands perform important ecosystem services in agricultural landscapes. They improve water quality by retaining nutrients and sediment from through-flowing water, sequester carbon and attenuate flood peaks at high discharge. At the same time, they have been shown to enhance biodiversity at the landscape as well as regional scale. However, there is concern about loss of biodiversity and enhanced greenhouse gas emissions where wetlands have become overloaded with nutrient-rich surface water or groundwater. This paper discusses conditions for the best performance of riparian zones and other small wetlands in agricultural landscapes in terms of nutrient and greenhouse gas retention and biodiversity.High nitrous oxide emissions have been identified in riparian zones used for N removal and could be a concern which would diminish their overall environmental benefit. However, it has been shown in riparian zones in the Rhine and Scheldt catchment that nitrous oxide emissions mainly occur when soil pH values are lower than 5. Such conditions occur mostly in stream headwater areas only where sandy sediments have a low buffering capacity, whereas higher-order streams and their riparian zones often have fine silty clay or loam sediments with higher pH values, supporting effective denitrification with low nitrous oxide emission.The question whether the nutrient attenuation service comes at the expense of biodiversity losses should be answered differently for existing, (semi-)natural wetlands and for new wetlands created in the agricultural landscape. Existing wetlands are quite vulnerable for nutrient loading, depending on their natural nutrient richness. Oligotrophic and mesotrophic wetlands such as bogs and fens are negatively affected by nutrient loadings>4gNm−2y−1 and 0.5gPm−2y−1, which lead to loss of diversity and characteristic species. Wetlands in riparian zones are naturally more nutrient-rich and can tolerate much higher nutrient loadings without consequences for ecosystem health and diversity, their loading limits are 50gNm−2y−1 and 4gPm−2y−1. For nitrogen the relatively high limit is explained by significant denitrification activities in wetlands, transforming nitrate to mostly inert elemental nitrogen gas. There are also indications that only one of the major nutrients needs to be in short supply (i.e. below the limits indicated) in order to avoid major eutrophication problems. In agricultural areas where large numbers of wetlands have been created for N removal and biodiversity enhancement, the experience of this ‘dual purpose’ are generally positive, particularly in landscapes where not much of the original wetland resource remains.

Global abundance and size distribution of streams and rivers

To better integrate lotic ecosystems into global cycles and budgets, we provide approximations of the size-distribution and areal extent of streams and rivers. One approach we used was to employ stream network theory combined with data on stream width. We also used detailed stream networks on 2 continents to estimate the fraction of continental area occupied by streams worldwide and corrected remote sensing stream inventories for unresolved small streams. Our estimates of global fluvial area are 485 000 to 662 000 km2 and are +30–300% of published appraisals. Moderately sized rivers (orders 5–9) seem to comprise the greatest global area, with less area covered by low and high order streams, while global stream length, and therefore the riparian interface, is dominated by 1st order streams. Rivers and streams are likely to cover 0.30–0.56% of the land surface and make contributions to global processes and greenhouse gas emissions that may be +20–200% greater than those implied by previous estimates.

Fresh waters and fish diversity: distribution, protection and disturbance in tropical Australia.

BackgroundGiven the globally poor protection of fresh waters for their intrinsic ecological values, assessments are needed to determine how well fresh waters and supported fish species are incidentally protected within existing terrestrial protected-area networks, and to identify their vulnerability to human-induced disturbances. To date, gaps in data have severely constrained any attempt to explore the representation of fresh waters in tropical regions.Methodology and ResultsWe determined the distribution of fresh waters and fish diversity in the Wet Tropics of Queensland, Australia. We then used distribution data of fresh waters, fish species, human-induced disturbances, and the terrestrial protected-area network to assess the effectiveness of terrestrial protected areas for fresh waters and fish species. We also identified human-induced disturbances likely to influence the effectiveness of freshwater protection and evaluated the vulnerability of fresh waters to these disturbances within and outside protected areas. The representation of fresh waters and fish species in the protected areas of the Wet Tropics is poor: 83% of stream types defined by order, 75% of wetland types, and 89% of fish species have less than 20% of their total Wet Tropics length, area or distribution completely within IUCN category II protected areas. Numerous disturbances affect fresh waters both within and outside of protected areas despite the high level of protection afforded to terrestrial areas in the Wet Tropics (>60% of the region). High-order streams and associated wetlands are influenced by the greatest number of human-induced disturbances and are also the least protected. Thirty-two percent of stream length upstream of protected areas has at least one human-induced disturbance present.Conclusions/SignificanceWe demonstrate the need for greater consideration of explicit protection and off-reserve management for fresh waters and supported biodiversity by showing that, even in a region where terrestrial protection is high, it does not adequately capture fresh waters.