1st Order Streams Research Articles

Impacts of bridge constructions on channel dynamics and sediment aggradation: An integrated discussion, West Bengal, India

Channel dynamics, including channel migration, erosion, and deposition, is a significant geomorphological phenomenon. It has been noted that the Gish River exists with its widest extension between 1913 and 2021, causing a bottleneck situation. The section G4 (Gish-4) experienced the most significant squeezing character over time. The catchment landslide-induced sediments, mostly transported in the monsoon by 1st and 2nd order streams, deposited at the beds near the rail and road bridges of the rivers Lish, Gish, and Chel. Landslide susceptibility mapping (LSM) and sediment transport index (STI) maps specify the zones of sediment generation and aggradation. Results of low ‘b” value 0.77 + /−0.04 specify active tectonics and instability of the area. A petrographic analysis of landslide samples and river bed sediments justifies that the landslide connected streams are continuously transported and deposited in the river bed. In the Himalayan foothill rivers like Lish, Gish, and Chel, channel planform dynamics may be the result of landslide occurrences, that induce huge sediments in the rivers and sediment transport index indicates the deposition of the sediments near rail and road bridges in spatio-temporal scale.

Geochemical Survey and Estimation of Baseline Concentrations of Major and Trace Elements in Stream Water, Uttar Pradesh, India: Implication for Environmental Studies

Abstract Stream water plays an important role in the development of habitats. It is one of the important sources of water used for drinking and irrigation in the region. Before using, it is necessary to test the quality of all types of surface water available for various use. A geochemical study of stream water has been conducted in parts of Pratapgarh, Raebareli, and Allahabad districts of Uttar Pradesh to assess its suitability for domestic purposes and establish the baseline concentration of major ions, trace and REEs. 20 samples of stream water from different locations of 1st or 2nd order streams were collected during post-monsoon period, from 18th to 31st October 2021. Different hydrochemical parameters such as pH, electrical conductivity (EC), temperature, dissolved oxygen (DO), salinity, total dissolved solids (TDS), major cations and anions were analysed. In order to obtain maximum quality and purity of water, the stream water samples were analyzed by ICP-MS analytical method in the chemical lab for 47 trace elements including REEs contents. The obtained values of each parameter have been compared with the standard values recommended by BIS and WHO. The value of each element except uranium has been found to be within the desirable and permissible limits prescribed by BIS (2012) and WHO (2006). Selenium and arsenic have been found to be marginally exceed the permissible limits. The pH values of all stream waters in the study area range from 7.14 to 8.86 with an average value of 7.86 indicating an alkaline nature of stream water. The concentration of uranium in stream water varied from 1.5 ppb to 48.67 ppb with a mean value of 7.9 ppb. It is observed that wherever concentration of uranium in the samples increased, the pH as well as the bicarbonate level increased accordingly. Correlation coefficient revealed that uranium is strongly correlated with bicarbonate (r=0.67), moderately with sodium (r=6.1), and low positively correlated with the concentration of pH (r=0.34), EC (r=0.52), and salinity (r=0.52), indicates the same origin. Water quality index (WQI) of water was determined for suitability of drinking purpose, revealed that 65% water samples fall in excellent category and 30% water samples fall in good category while only 5% water sample are in poor category. Trilinear plot of sample shows that most of the stream water samples are Ca-Mg-HCO3 type.

Aquatic Systems of the Wichita State University Biological Field Station: Youngmeyer Ranch, Elk County, Kansas

Intermittent streams and rivers account for over half of the world's waterways and yet they are still vastly understudied compared to permanent streams and rivers. Wichita State University Biological Field Station: Youngmeyer Ranch presents an opportunity to study intermittent streams and stream pools across 1902 hectares of Flint Hills tall grass prairie ecosystems. We used a freely available satellite imagery program (Google Earth Pro©) to map and provide an initial inventory of streams, intermittent stream pools, and cattle ponds. We also used historic images to create connectivity (percent of downstream length with water) and hydroperiod indices (number of years out of four that pools held water). In total, we mapped 58.2 km of major (2nd to 3rd order) and minor (1st order) streams, and 13 cattle pond impoundments on the property. We used a systematic random sample to select a subset of seven stream reaches (out of 83) within the property for on-the-ground surveys of intermittent stream pools. Within selected streams, a subset of 117 stream pools were sampled in the summer of 2020 and data was collected on the average stream pool width, max depth, length, volume, and biological communities. Stream pools averaged 6.5 ± 9.7 m3 (mean ± SD) in volume, 12.50 ± 9.3 m in length, 2.97 ± 1.7 m in width, and 0.38 ± 0.26 m in depth. Stream and stream pool permanence varied widely across the landscape with pools holding water 3.2 ± 0.8 out of the four years with high resolution satellite imagery. We provided an initial baseline of aquatic systems at Youngmeyer Ranch and characterized representative intermittent stream pools in the Flint Hills and the Great Plains. We also demonstrated the viability of using Google Earth Pro© for mapping and taking inventory of aquatic systems without proprietary software or on-site access.

Predicting physical and geomorphic habitat associated with historical lake whitefish and cisco spawning locations in Lakes Erie and Ontario

The Great Lakes basin was historically populated by multiple, coevolved coregonine species, but much of that diversity has been lost. In Lakes Erie and Ontario, both lake whitefish (Coregonus clupeaformis) and cisco (Coregonus artedi) occurred in high numbers before habitat degradation, overfishing, invasive species, and other factors caused significant declines. There is growing interest in restoring these populations, and suggested actions include restoration of critical habitats such as spawning habitat. Unfortunately, our current understanding of lake whitefish and cisco spawning habitat characteristics and locations in these lakes is limited. To highlight areas of potential importance for conservation and restoration, we used random forest models and data on historical spawning locations to predict lake whitefish and cisco spawning habitats based on hypothesized key factors including wind fetch, ice cover duration, distance from 1st and 6th order tributaries, and lake bottom substrate. Our model accurately predicted spawning habitat locations for 71% and 54% of cases for lake whitefish and cisco, respectively. Fetch was the most important variable in the lake whitefish model, with spawning habitats being most likely to occur in regions of low to moderate fetch. Cisco spawning habitats were most likely to occur in areas of relatively low fetch near a 1st order stream. We used these models to predict spawning habitat locations for both species across Lakes Erie, Ontario, and St. Clair. Our results improve our understanding of lake whitefish and cisco spawning habitat characteristics and will aid in the spatial prioritization of actions to restore these native fishes.

Land Use Overrides Stream Order and Season in Driving Dissolved Organic Matter Dynamics Throughout the Year in a River Network.

Anthropogenic land use has increased nutrient concentrations and altered dissolved organic matter (DOM) character and its bioavailability. Despite widespread recognition that DOM character and its reactivity can vary temporally, the relative influence of land use and stream order on DOM characteristics is poorly understood across seasons and the entire flow regime. We examined DOM character and 28-day bioavailable dissolved organic carbon (BDOC) across a river network to determine the relative roles of land use and stream order in driving variability in DOM character and bioavailability throughout the year. DOM in 1st-order streams was distinct from higher stream orders with lower DOC concentrations, less aromatic (specific ultraviolet absorbance at 254 nm (SUVA254)), more autochthonous (fluorescence index), and more recently produced (β/α) DOM. Across all months, variability in DOM character was primarily explained by land use, rather than stream order or season. Land use and stream order explained the most DOM variation in transitional and winter months and the least during dry months. BDOC was greater in watersheds with less aromatic (SUVA254) and more recent allochthonous DOM (β/α) and more development and impervious surface. With continued development, the bioavailability of DOM in the smallest and most impacted watersheds is expected to increase.

Analysis of confluence angle of drainages and its relation to morphometric properties of drainage basins in the Zagros Simply Folded Belt, Iran

Quantitative analysis of drainage network properties plays an important role in the identification of active tectonics and their spatial variations. The purpose of this study is to analyze the drainage's confluence angle (α) in relation to tectonic activity and morphometric characteristics of drainage basins. A total of 23 drainage basins in the Zagros Simply Folded Belt were selected and then the values of α were calculated for 7829 drainage junctions. The relationship between α and other morphometric indexes such as basin area, perimeter, slope, asymmetry factor, shape, circularity, drainage density, ratio of the 1st-order streams to the total number of streams of all orders, and density of drainage's hierarchical anomaly were analyzed. Results show that mean of α increases as the order of stream junctions increases. Basins with higher values of elongation, the ratio of the 1st-order streams to the total number of streams of all orders, and density of drainage's hierarchical anomaly have higher α values. Results also show that the lateral and vertical growth of anticlines, axes of anticlines, trends of faults and drainage patterns influenced by folds growth strongly control the confluence angles of drainage channels in the studied basins.

Contrasting stream water temperature responses to global change in the Mid-Atlantic Region of the United States: A process-based modeling study

The accurate estimation of stream water temperature is essential for understanding environmental controls on the structure and functioning of aquatic ecosystems. Few studies have coupled soil and stream water temperatures to capture the synergy of thermal balances between terrestrial and riverine systems. As a result, little is known about how multiple environmental stresses have affected water temperature, particularly for different orders of streams. Here we incorporated a new water transport scheme into the Dynamic Land Ecosystem Model (DLEM) to predict water temperature in 1st order and higher-order streams (>1st order). Driven by a 4-km geo-referenced dataset of multiple environmental factors, our new water temperature model was utilized to predict the spatiotemporal variations of water temperature in the U.S. Mid-Atlantic Region during 1900–2015. Results revealed that water temperature during 1970–2015 increased significantly (p < 0.05), and the rate of increase of the 1st order streams 0.32 °C∙decade−1 is higher than that of higher-order streams 0.28 °C ∙ decade −1. The buffering effect of groundwater on water temperature in 1st order streams diminished under the context of climate warming. Factorial analysis showed that climate change and variability explain most of the changes (~80%) in stream water temperature since 1900. Land-use conversions (mostly from cropland to forest), CO2 fertilization, and land nitrogen management collectively explained a greater percent of change in water temperature in 1st order streams (24%) than higher-order streams (9%), implying that 1st order streams are particularly vulnerable to human activities.

Spatial Groundwater Modelling of Micro Watersheds – A case study at Junewani watershed, Hingna Taluk, Nagpur, Maharashtra

A model is a simplified representation of the complex natural world. The groundwater model provides a quantitative framework for synthesizing field information and for conceptualizing hydrogeological purposes. The present study aims to utilize remotely sensed data, Geographical Information System (GIS), and limited flow modeling to identify the groundwater recharge management practices carried out in the Junewani watershed of the Nagpur district. In this study, Modflow-NWT, in conjunction with spatial analyses, is used for modeling Groundwater flow in Junewani Watershed located at 78.90°E and 21.03°N in Nagpur District, Maharashtra. Since minimal data on flow parameters are available and aquifer systems are also heterogeneous, water level data observed from dug wells has also been used to generate the groundwater flow directions. The study area consists of 1st, 2nd and 3rd order streams and is covered with Black cotton soil and Vesicular Basalt underneath. Watershed boundary conditions, elevation details, drainage patterns, layer properties, permeability values, average rainfall, etc. are given as input for the model. The initial input data has been procured from GSDA Nagpur and through field observations. This study discusses the micro watershed groundwater modeling carried out mainly in a spatial environment supported by results of limited flow modelling, but the results and insights from this study will help in better understanding the GW flow regime after the recharge decisions were taken and the recharge practices were operated. It has been observed that recharge practices in surface dams and desilting have been beneficial at some places, while groundwater has decreased at other places. Thus it helps in decision making regarding the development of GW recharge and utilization.

ÇORUH NEHRİ HAVZASINA BAĞLI OLTU MİKROHAVZASINDA KANAL VE OYUNTU EROZYONUYLA GERÇEKLEŞEN TOPRAK KAYBININ “EROZYON ÇUBUK YÖNTEMİYLE” BELİRLENMESİ

Water erosion is an important erosion type that erodes and transports the most. With the effects of stream water, both streambank and gully erosions cause even more soil transport and debris accumulation resulting more flood events and associated loss of life and properties, as well as increasing the deposition of sediment in dam reservoirs that shorten the economic lifespan of these dams. This study was carried out in 14 different bank erosion sites (stream reach) in the Oltu Micro Catchment (OMC), one of the sub-watershed of the Coruh River Basin, to measure gully and streambank erosions over five-year long study period using “erosion pin method”. Oltu Micro Catchment has arid and semi-arid climate and has a 37% slope degree with a rugged structure. Over the five-year study period, the annual gully and streambank erosion rates were ranged from 1.25 to 8.79 cm/yr and the five-year average was measured as 4.43 cm/yr. The five-year soil losses were ranged from 30.5 to 190.8 tons/km/yr, and the five-year average was measured as 83.9 tons/km/yr. Compared to 1st and 2nd order streams, most of these measured soil losses were due to gully erosion (78%). In addition, it was determined that very large increase in bank erosion was occurred due to increase in rainfall in this semi-arid region showing that these types of watersheds are sensitive to bank erosions. As a conclusion, streambank and gully erosions are dynamic processes effected by the spatial and temporal scale differences under varying climate settings. Additionally, this study is a pioneer one in the region that identifies a need for the conservation practices (particularly for the gullies) to reduce the soil losses and deposited sediment in the whole channel system and eventually in dam reservoirs.

Geo-morphometric prioritization of Aglar micro watershed in Lesser Himalaya using GIS approach

Lesser Himalayan watersheds are most susceptible to conservational deprivation, that needs to accurate management and planning of available natural resources such as soil and water which are pre-requisites for sustainable growth of the watershed in the mountains regions. The analysis of watershed through morphometric together with geomorphic maps i.e., soil distribution, land cover, and slope map can play a role in forecasting to understand the behavior of hydrological processes in a Himalayan watershed. An attempt has been made to quantify the geo-morphometric parameters and their characteristics for watershed prioritization using remote sensing (RS) and geographical information system (GIS) approach and linked the geomorphologic parameters with the hydrological characteristics of the watershed. The sub-catchment Aglar UP (SC-1), Paligaad (SC-2), and Balganga (SC-3), located in the lesser Himalayas in Jaunpur block of Uttarakhand state having elevation between (670–2975 m). The sub-watershed (SC-1) and (SC-2) are third order and (SC-3) is a 1st order stream, having a dendritic drainage pattern with low drainage density < 0.5 km per km2, indicates the impact of lithology and topography on drainage pattern. The average bifurcation ratio of (SC-1) is combatively less than (SC-2) which shows a high infiltration rate with low overland flow and presence of strong structural control on the drainage pattern. Lower values of circularity ratio and elongation ratio of < 0.5 advocated elongated shape of the watershed with lesser peak flows for an extended time. The less value of the form factor in the elongated type of watershed suggested about flatter peak flow. Based on the obtained morphometry parameters of linear and shape, watershed prioritization has been carried out for erosion risk. Based on weight and ranking, (SC-2) got the highest priority, is the most susceptible to erosion, whereas (SC-1) receives the least priority which means the least erosion. The results from this study helps to understand the hydrological behavior and soil erosion factors of lesser Himalayan watersheds that would be useful to water resource conservation to the planners, policy makers and agriculturists. The study gets the attentions from the scientists, researchers, involved in their respective fields.

DATA MINING APPLIED FOR DETERMINING STREAM FLOW PERMANENCE

Abstract. Streamflow permanence is an aspect of great legal importance in Brazil, because streams, depending on their flow regime, are protected or not by law. Various methods, from field methods to computational methods, are used to determine the flow regime of streams, however some are too time spending and computational methods usually need gaging information as input. Furthermore, computational methods used to extract drainage networks do not identify the flow regimes of streams, and modelled drainage networks always need to be refined manually, as some authors indicate that up to 55% of modelled drainage length is ephemeral in some cases. This work proposes a semi-automatic computational method to determine the flow regime of first order streams, which uses 11 morphometric attributes of the mini drainage basins of these streams to develop a classification model using decision tree algorithms. WEKA package was used to perform the data mining process, which resulted on the development of a compact 8 node decision tree. Ten-fold stratified cross-validation was used to validate the model, which obtained an accuracy rate of 70%. The drainage network of the study area extracted with the classical approach was refined after the result of the classification was obtained. Quantitative analysis of channel length by Strahler order shows an overall reduction of 25% in channel length after refinement was undertaken, and for 1st order streams, as much as 31% were classified as ephemeral. Modelling the drainage areas of headwater streams represents a new approach to determining stream flow permanence, and inclusion of new attributes in the model may yield better results in future research.

How human interference changes the drainage network operating during heavy rainfalls in a medium-high relief flysch mountain catchment? The case study of the Bystrzanka catchment (Outer Carpathians, Poland)

This study demonstrates a human impact on the development of active drainage network (ADN) operating during heavy rainfall in a medium-high relief flysch catchment. The ADN was reconstructed with the use of ALS-LiDAR data. The results have revealed that the density of the ADN (11.2 km∙km−2) is c.a. 5 times higher compared to the river system (2.2 km∙km−2) and c.a. 25% of the ADN constitutes man-origin elements (roads, ditches and plough furrows), which are incorporated into the drainage system. The Hortonian’s type of analysis has revealed that man-origin elements significantly change the structure of a natural, river drainage system, and man-origin elements are predominantly attributed to 1st and 2nd order streams, which drain the upper part of the hillslopes. Roughly up to 37% of 1st and 2nd order streams are the man-origin elements of the ADN and those streams drain c.a. 22% of the catchment area. Quantification of the changes in the ADN gave the opportunity to analyze the hydrological response of a catchment. The results have revealed that the reconstruction of flood wave parameters by rainfall-runoff (SCS-CN and GIUH models) hydrological models is more accurate when the Horton’s parameters describe ADN operating during heavy rainfall. It has been revealed that alteration of the ADN influences the flood wave peak predominantly, increasing it up to 11%.

Morphometry of drainage basins and stream networks as an indicator of active fold growth (Gorm anticline, Fars Province, Iran)

The Zagros Folded belt, as one of the most tectonically active areas in the world, contains NW–SE trending whaleback anticlines that are growing vertically and laterally. Morphometric indices are widely used in tectonic geomorphological research because of their low cost and relative ease of application. Drainage basins and their networks adapt to tectonically induced changes in surface slope, and hence their qualitative and quantitative analysis can reveal aspects of active anticlinal growth. This study evaluates the morphometric properties of drainage basins and their networks developed on the fold limbs, using this quantitative data to detect lateral propagation of the Gorm anticline in the Zagros Simply Folded Belt (ZSFB). The Gorm anticline was considered to be suitable for this approach because of the variability of drainage basins and their networks along the axis of the anticline and also transversely across its forelimb and backlimb. The morphometric properties of stream networks including drainage density (Dd), drainage frequency (Df), ratio of 1st-order streams to the total number of streams of all orders (N1/N), length of 1st-order streams (L1), spacing ratio (R)of main streams on flanks, and drainage patterns were analyzed in three zones of the anticline (southeastern (SE), central, and northwestern (NW)). Also, the morphometric indices of drainage basins such as basin area (Ba), shape (Bs), asymmetry factor (AF), hypsometric integral (HI), a new proposed crescentness index (CI), and sinuosity of anticline divide (SAD) were evaluated. Results show that an increase in N1/N ratio and L1 from the center towards both the southeastern and northwestern fold noses suggests lateral growth of the anticline towards the southeast and northwest. The SE and NW zones are characterized by the smaller, elongated and crescent-shaped basins, lower elevations, lower dip slopes, higher hypsometric integral, and lower sinuosity of anticline ridge. These results collectively suggest that the southeastern and northwestern fold noses are younger, less eroded and laterally growing. The formation of crescent-shaped basins with asymmetric forked drainages developed in the SE and NW zones are considered to be useful indicators of lateral growth of the Gorm anticline. Although higher values of Ba, SAD, Df and S indexes in the central part of the fold can be attributed to the older relative age of this area, the activity of the Nezamabad Fault and the exposure of some weak rocks also play some roles in explaining the increase the values of parameters. Overall, the N1/N, L1, CI, SAD indexes, as well as the fan-shaped and asymmetric forked drainage pattern are the most useful tectonic geomorphological criteria to detect lateral propagation of anticlines.

Spatial and temporal variation of the diet of the flag tetra Hyphessobrycon heterorhabdus (Characiformes: Characidae) in streams of the Eastern Amazon

ABSTRACT Spatial and temporal variations in streams promote large fluctuations of resource availability, thus affecting the diet of fishes. We evaluated the effects of hydrological periods and stream order within periods on the diet of the flag tetra Hyphessobrycon heterorhabdus. We analyzed 160 stomachs in eight streams ranging from 1st to 3rd order between dry and flood period. Sampled streams belonged to a well-preserved area in the Eastern Amazon. The flag tetra is omnivorous, with a tendency towards insectivory. During the dry period, the species exhibited a higher amount of autochthonous than allochthonous items. Fish consumed more allochthonous items in 1st and 2nd order streams in the dry period and in 1st and 3rd order streams in the flood period. These results reflect the interactions between temporal and longitudinal factors on resource availability and its influence on fish diet. This pattern is probably dependent on the extensive riparian vegetation as a direct and indirect source of food for stream fish.

Qurain AL-Thamad Valley Hydrological Aspects Extraction Using Remote Sensing and GIS Techniques

In the arid to semi-arid lands the extracted hydrological features are essential ones, since their effect on water projects managing, agricultural projects administrating, and animals grazing, so that this research is considered to be vital research because the climate of Qurain AL-Thamad basin is arid climate and basin region inhabited by many tribes who works in agricultural and grazing fields. The illustration of hydrological features using morphometric analyses is optimum since the quantization issue of basin factors, in the past this would be difficult using classical procedures (i.e. using paper topographic maps and planmeter). Recently as in this work modern procedures has been used (i.e. satellite imagery DEM as ancillary image and Arc GIS 10.5 as geo-measuring and spatio-analyzing program).&#x0D; The pattern of Qurain AL-Thamad basin's drainage network shows dendritic configuration in low orders streams and parallel configuration in the high order streams. The spatial analysis using GIS environment categorize basin's shape parameters into three categories: firstly one is the linear parameters with streams divided into 1st order streams with (611.587 km) length, 2nd order streams with (384.015 km) length, 3rd order streams with (181.868 km) length, and 4th order streams with (103.674 km) length. Bifurcation ratios were calculated, Rb1 is (2.046), Rb2 is (1.869), and Rb3 is (1.624), with (1.852) Rb mean value. Secondly categorize deals with areal parameters; The longitudinal drainage density was (0.259 km??), the drainage frequency was (0.035 stream /km²), Drainage Texture value was (0.338 stream / km ), the elongation ratio was (0.483), the circularity ratio value was (0.244), the form factor was (0.183) , and the relief ratio was (0.447). according to these quantitative results the flood hazard in the basin main stream is absent, basin soil is high permeable and region rainfall rate is very low, there is significant differences in region geological structures solidity, land steepness and relief ratio are low valued yielding a few water erosion power, sediment yield, and runoff flood peak in the basin water catchment area.

Stream loss in an urbanized and agricultural watershed in China

Stream losses are extensively observed due to human activities in the world, and the patterns of stream loss vary in different land use types. However, relationship between stream loss pattern and land use covers is poorly understood. We select the lower Taihu watershed (LTWS) within Yangtze River Delta (YRD), which is dominated by agricultural and urban covers and a typical case of most urbanized watersheds in China. In this study, we measured the stream loss of LTWS from 1960s to 2010s and investigated its relation to different land use covers and impervious area percentage (IAP) in order to figure out the main factor of stream loss in this area. The results show that urban area has tripled with fractional contribution from 10.3% to 33.18% in the form of conversion from agriculture to urban area during 1990–2015. 12.5% of all the streams are lost and 1st-order streams contribute most (91.8%) to the total stream loss. Urban cover contribute most (76%) to total streams loss compared to other land use types. We find that 1st-order streams have highest stream loss intensity, which is mainly caused by urban expansion, but preferred protections are given to highest-order streams. The linear model of correlation of pixel-level streams loss and IAP shows that the streams loss is statistically significant positive with IAP of cells (R2 = 0.91). Tradeoffs between city expansion and river network make small channels sacrifice for the urbanization. Urgent measures including legislation must be taken to protect small streams during urbanization nowadays and in future.

Reintroduced Beavers Rapidly Influence the Storage and Biogeochemistry of Sediments in Headwater Streams (Methow River, Washington)

North American beavers (Castor canadensis) were targeted within North American headwater landscapes by European loggers and fur traders in the 19th century, reducing beaver populations to near extinction by 1900. The extirpation of beavers from river networks has had profound effects on riparian zones, including channel geomorphology, temperature regimes, sediment storage, channel-floodplain connectivity, carbon storage and nutrient dynamics. Consequently, reintroducing beavers has been provisionally implemented as a restoration approach within some watersheds. We characterized how reintroduced beavers influence the short-term dynamics of organic material accumulation within the sediments of 1st and 2nd order streams within the Methow River watershed of Washington State. In collaboration with the Methow Beaver Project, we identified four creeks where they had reintroduced beavers within the past five years, as well as a control non-beaver pond. At each site, we collected shallow sediment cores from upstream, downstream, and within beaver ponds, and then measured organic material via elemental analyses of sediment carbon (%C) and nitrogen (%N) content. We compared those samples to sediments accumulated in local pond areas not created by beaver activity. Our results show greater organic C and N content of sediments in beaver ponds than non-beaver ponds. C/N ratios indicate elevated accumulation of allochthonous organic material in beaver impoundment sediments that would otherwise not be integrated into headwater streams from the terrestrial landscape. These findings suggest that the reintroduction of beavers could be an effective means to promote restoration of whole ecosystem function.

Diurnal chemistry of two contrasting stream types, Taylor Valley, McMurdo Dry Valley Region, Antarctica

Numerous ephemeral streams flow within the McMurdo Dry Valley Region of Antarctica that transport glacial meltwater to perennially ice-covered, closed-basin lakes during the austral summer. The diurnal behavior for two Taylor Valley streams of different character was examined during the summer of 2010-11. Andersen Creek is a short, 1st-order proglacial stream, whereas Von Guerard Stream is a long, high-order stream with an extensive hyporheic zone that has a substantial cyanobacterial algal mat community in its middle reaches. Both streams display strong daily cycles for temperature, electrical conductivity, dissolved oxygen, and pH. Conductivity varies in concert with flow, with solute dilution occurring during the daily high-flow pulse. Dissolved oxygen co-varies strongly with pH at Andersen Creek but not for Von Guerard Stream. Each stream has a distinct geochemical character that for Andersen Creek is a direct reflection of its glacial source, unmodified by secondary effects, whereas that for Von Guerard Stream is modulated by its resident algal mat community and through extensive hyporheic zone interaction and exchange.

Spatio-temporal diel DOC cycles in a wet, low energy, northern catchment: Highlighting and questioning the sub-daily rhythms of catchment functioning

Sub-daily variations in the rates and dominance of the main controls of stream dissolved organic carbon (DOC) concentration (production, mobility and instream processes) have the potential to create a subtle sub-daily rhythm of DOC variation in streams. We used high-frequency data, covering the spring-summer-autumn period, which included discharge, specific conductivity, pH, groundwater levels, temperature, evapotranspiration and solar radiation to investigate the interplay between factors potentially driving diel DOC cycles in northern catchments. We focused on a peatland dominated 1st order stream (0.65 km2) before investigating the propagation of the signals downstream to a 2nd order stream (3.2 km2), with a lower percentage of peat fringing the stream channel. DOC cycles in the 1st order stream had a median peak time of 14:00 h and temporally varying amplitude, with a median of 0.61 mg l−1. Results supported the hypothesis that diel DOC cycles at the site are driven by hydrological processes, specifically the viscosity-effect theory: viscosity-driven increases in flow from the riparian area in the afternoon flush DOC from the peat to the stream. The temporal variability in the amplitude of the diel DOC cycle was controlled by antecedent temperature. Downstream, the diel DOC signal was weaker, with around 4-fold lower amplitudes and minima in the afternoon. The lower proportion of riparian peat downstream appeared to reduce the influence of terrestrial processes on DOC cycles. In-stream photodegradation and decomposition likely became more dominant as connectivity between DOC sources and stream reduced. The study highlighted that even in climates such as the Scottish Highlands, where energy input is relatively low and precipitation frequent, sub-daily hydrological and biogeochemical rhythms occur. Unravelling the intricacy of such diel cycles is fundamental to fully understanding stream functioning and the global carbon cycle.

Trophic dynamics of macroinvertebrate communities of a subtropical river in China

This study was the first attempt to resolve both spatial and temporal patterns of macroinvertebrate trophic dynamics in a Chinese subtropical river continuum, the Shengli River, from 1st to 4th order. Gut content analysis was adopted to assess the trophic basis and consumption rates of communities. Furthermore, annual energy flow food webs were constructed. Trophic basis analyses showed that 34–79% of the diet of macrozoobenthos in the Shengli River and its tributaries was amorphous detritus. Leaf litter was the second most important food source, followed by animal material. Filamentous algae, diatoms, and fungi served only as subsidies, contributing no more than 5% to total consumption. The macroinvertebrates in 1st and 3rd order streams appeared to show seasonal consumption patterns of different food types, while the communities in 2nd and 4th order streams had the same diet composition throughout the year. Total consumption rates of the communities increased from 1st to 3rd order streams, and declined in 4th order streams. The energy flow food web of 1st order streams was simpler than those of higher‐order streams. With increasing stream order, the food webs increased in complexity until 3rd order, and became simpler again in 4th order streams.