Weir Pool Research Articles

Optimal Band Selection for Airborne Hyperspectral Imagery to Retrieve a Wide Range of Cyanobacterial Pigment Concentration Using a Data-Driven Approach

Understanding the concentration and distribution of cyanobacteria blooms is an important aspect of managing water quality problems and protecting aquatic ecosystems. Airborne hyperspectral imagery (HSI)—which has high temporal, spatial, and spectral resolutions—is widely used to remotely sense cyanobacteria bloom, and it provides the distribution of the bloom over a wide area. In this study, we determined the input spectral bands that were relevant in effectively estimating the main two pigments (PC, Phycocyanin; Chl-a, Chlorophyll-a) of cyanobacteria by applying data-driven algorithms to HSI and then evaluating the change in the spatio-temporal distribution of cyanobacteria. The input variables for the algorithms consisted of reflectance band ratios associated with the optical properties of PC and Chl-a, which were calculated by the selected hyperspectral bands using a feature selection method. The selected input variable was composed of six reflectance bands (465.7–589.6, 603.6–631.8, 641.2–655.35, 664.8–679.0, 698.0–712.3, and 731.4–784.1 nm). The artificial neural network showed the best results for the estimation of the two pigments with average coefficients of determination 0.80 and 0.74. This study proposes relevant input spectral information and an algorithm that can effectively detect the occurrence of cyanobacteria in the weir pool along the Geum river, South Korea. The algorithm is expected to help establish a preemptive response to the formation of cyanobacterial blooms, and to contribute to the preparation of suitable water quality management plans for freshwater environments.

Assessment of the causes and solutions to the significant 2018–19 fish deaths in the Lower Darling River, New South Wales, Australia

In late 2018 to early 2019, three significant fish death events occurred in the Lower Darling River, Australia, with mortality estimates of millions of fish. We examined the proximate and ultimate causes of these events. We determined that not only were the conditions existing at the time a significant contributing factor, but that antecedent conditions, particularly during the period 2010–17, also contributed. The extreme hot and dry climate during 2018, extending into 2019, shaped the conditions that saw a large fish biomass, which had flourished in the Darling River and Menindee Lakes since favourable spawning conditions in 2016, isolated in weir pools, with no means of escaping upstream or downstream. Strong and persistent weir pool stratification created hypoxic conditions in the hypolimnion. A series of sudden cool changes subsequently initiated rapid and sudden mixing of the stratified waters, causing depletion of oxygen throughout the water column and resulting in the fish deaths. The events were also shaped by broader climatic, hydrological and basin management contexts that placed the Lower Darling River at risk of such fish deaths. Our observations have implications for future river management, and we make several suggestions how policy makers and river operators can minimise fish death risks into the future.

Effects of a low-head weir on multi-scaled movement and behavior of three riverine fish species

Despite providing considerable benefits to society, dams and weirs threaten riverine ecosystems by disrupting movement and migration of aquatic animals and degrading riverine habitats. Whilst the ecological impacts of large dams are well studied, the ecological effects of low-head weirs that are periodically drowned out by high flows are less well-understood. Here we examine the effects of a low-head weir on fine- and broad-scale movements, habitat use, and breeding behaviour of three species of native freshwater fish in the Nymboida River in coastal eastern Australia. Acoustic telemetry revealed that eastern freshwater cod (Maccullochella ikei) and eel-tailed catfish (Tandanus tandanus) made few large-scale movements, but Australian bass (Percalates novemaculeata) upstream of the weir were significantly more mobile than those below the weir. Within the weir pool, all three species displayed distinctive patterns in fine-scale movement behaviour that were likely related the deeper lentic environment created by the weir. No individuals of any species crossed the weir during the study period. Tandanus tandanus nesting behaviour varied greatly above and below the weir, where individuals in the more lentic upstream environment nested in potentially sub-optimal habitats. Our results demonstrate the potential effects of low-head weirs on movement and behaviour of freshwater fishes.

Habitat use, movement and activity of two large-bodied native riverine fishes in a regulated lowland weir pool.

The construction of dams and weirs, and associated changes to hydrological and hydraulic (e.g., water level and velocity) characteristics of rivers is a key environmental threat for fish. These multiple stressors potentially can affect fish in a variety of ways, including by causing changes in their movement, habitat use and activity. Understanding how and why these changes occur can inform management efforts to ameliorate these threats. In this context, we used acoustic telemetry to examine habitat use, longitudinal movement and activity of two lowland river fishes, Murray cod Maccullochella peelii and golden perch Macquaria ambigua, in a weir pool environment in south‐eastern Australia. We compared our results to published studies on riverine populations to determine if their behaviours are similar (or not). We show that M. peelii and M. ambigua in a weir pool exhibited some similar behaviours to conspecific riverine populations, such as strong site fidelity and use of woody habitat for M. ambigua. However, some behaviours, such as large‐scale (tens–hundreds of kilometres) movements documented for riverine populations, were rarely observed. These differences potentially reflect flow regulation (e.g., stable water levels, loss of hydraulic cues) in the weir pool. The two species also exhibited contrasting responses to dissolved oxygen conditions in the weir pool, which may reflect differences in their life history. Overall, this study shows that although some aspects of these two native fishes' life history can continue despite flow regulation, other aspects may change in weir pools, potentially impacting on long‐term population persistence.

Comparison of historical and modern river surveys reveal changes to waterhole characteristics in an Australian dryland river

Human activities are known to impact the physical template of river channels. These impacts can result from deliberate, direct modifications as well as via indirect processes linked to broadscale landscape change. This study examined changes in the physical template of the Barwon-Darling River, a dryland river in southeastern Australia. Historical longitudinal profiles from the late 1800s were compared with contemporary profiles derived from high-definition, side scanning sonar. Comparisons focused on characterising waterhole features as they are a critical biophysical component of dryland rivers. The use of historical data presented several challenges related to small sample size and suspected sampling bias in the historical survey. However, this study demonstrates that these issues are not insurmountable providing the limitations and uncertainties with the data are acknowledged and data analyses are limited to parameters that can distinguish genuine landscape change. The findings revealed a dramatic change in the physical template of the Barwon-Darling River over a 120-yr period. Waterhole depths and distances between waterholes have been altered significantly. The magnitude and trajectory of change was found to be scale-dependent, with the greatest observable change aligned with the presence or absence of low-level weirs. Waterholes influenced by low-level weirs have increased in depth because of localised impoundment, whilst the distance between deep waterholes (>4 m in depth) has declined substantially. In contrast, the maximum depths of waterholes located outside the influence of weir pools has declined by 1.6 m and the distance between deep waterholes has more than doubled in several reaches. These declines are likely to be caused by sediment accumulation in waterholes associated with anthropogenic increases in sediment flux and a decline in the river's capacity to entrain and transport sediment throughout the system.

Spatiotemporal and Longitudinal Variability of Hydro-meteorology, Basic Water Quality and Dominant Algal Assemblages in the Eight Weir Pools of Regulated River (Nakdong)

Spatiotemporal and Longitudinal Variability of Hydro-meteorology, Basic Water Quality and Dominant Algal Assemblages in the Eight Weir Pools of Regulated River (Nakdong)

Barriers to dispersal: The effect of a weir on stream insect drift

AbstractDams and weirs degrade river ecosystems, reducing diversity and altering the assemblage composition of aquatic biota. These structures may damage rivers by disrupting longitudinal connectivity, fragmenting rivers, and isolating populations. We tested whether a weir could impede the downstream dispersal of stream insects by comparing drift rates through natural pools and through a weir pool. For three of four of our study taxa (Offadens spp., Austrosimulium spp., and Simsonia spp.), we found the numbers of drifters were consistently reduced by the weir across multiple occasions (reduction ranging from 68 to 98%) to a higher degree than natural pools (reduction ranging from 24 to 41%). Drift of Cheumatopsyche spp. through the weir was greatly reduced in December (−95%) compared with natural pools, but the weir had little effect during April (−9%). There were size‐related patterns in drift through the weir pool for some taxa. In the weir pool, emigrating individuals of Austrosimulium spp. were significantly smaller than immigrating individuals, which was not observed in natural pools. In contrast, significant reductions of Cheumatopsyche spp. drifters through the weir only occurred when individuals were small (December). Within the weir pool, the combined effects of lower average water velocity, multiple large low velocity areas, and the weir wall were likely to be the cause of the reduction in stream insect drift through the weir. The impediment of drift of some taxa by weirs may affect dispersal and colonisation processes. This obstruction of downstream movement could undermine the outcomes of river restoration projects.

Evaluating Use of Environmental Flows to Aerate Streams by Modelling the Counterfactual Case

This paper evaluates an experimental environmental flow manipulation by modeling the counterfactual case that no environmental flow was applied. This is an alternate approach to evaluating the effect of an environmental flow intervention when a before-after or control-impact comparison is not possible. In this case, the flow manipulation is a minimum flow designed to prevent hypoxia in a weir on the low-gradient Broken Creek in south-eastern Australia. At low flows, low reaeration rates and high respiration rates associated with elevated organic matter loading in the weir pool can lead to a decline in dissolved oxygen concentrations with adverse consequences both for water chemistry and aquatic biota. Using a one dimensional oxygen balance model fitted to field measurements, this paper demonstrates that increased flow leads to increases in reaeration rates, presumably because of enhanced turbulence and hence mixing in the surface layers. By comparing the observed dissolved oxygen levels with the modeled counterfactual case, we show that the environmental flow was effective in preventing hypoxia.

Bank instability along a weir pool of the River Murray

ABSTRACTRiver banks are an important transition zone between aquatic and terrestrial environments. This ecotone is highly vulnerable to natural and anthropogenic disturbances. Bank erosion is a common occurrence along the River Murray. Morphological features reflecting river bank instability form a near-continuous pattern along large tracts of the river. This study investigates the character and extent of bank instability along the Torrumbarry Weir Pool. Over 90% of the bank length in this weir pool was assessed as being actively eroding. Notch development was the dominant instability mechanism and it promoted other forms of bank instability. Erosion notches result from stable water levels and inherent soil instability of the river banks along the weir pool. The character and extent of river bank erosion recorded along this section of the River Murray is an artefact of flow regulation and not a reflection of the natural occurrence of bank erosion in river networks. Water level management in the upstream weir pool has significant implications for the management of river banks along regulated reaches of the River Murray.

Applying the environmental flow components approach to the River Murray in South Australia

ABSTRACTRiver regulation has degraded the River Murray’s riverine ecosystems. Environmental flows are now being delivered to restore these ecosystems to a more natural, pre-regulation state. To guide the development of environmental flow recommendations, I calculated 28 Environmental Flow Components for the River Murray in South Australia, comparing simulated flow data for natural and present conditions. Regulation has caused complex changes to the rivers’ hydrology. Under present conditions, the inter-annual frequency of extreme low flows (<4150 ML/day) and high flow pulses (15,000–55,000 ML/day) has increased, whilst for small floods (55,000–100,000 ML/day) and large floods (>100,000 ML/day) frequency has declined. The magnitude of low flows (4150–15,000 ML/day) has been reduced for all months, and extreme low flows and high flow pulses occur later in the year. The duration of high flow pulses, and both small and large floods, have also declined under present conditions. Restoring more natural extreme low flows and high flow pulses will require new events to be engineered, whilst environmental water can be used to enhance monthly low flows and small floods. In addition to providing environmental flows, changes to river operations, particularly instituting weir pool manipulation, is required to maximise ecological outcomes.

Limnological Study on Spring-Bloom of a Green Algae, Eudorina elegans and Weirwater Pulsed-Flows in the Midstream (Seungchon Weir Pool) of the Yeongsan River, Korea

Limnological Study on Spring-Bloom of a Green Algae, Eudorina elegans and Weirwater Pulsed-Flows in the Midstream (Seungchon Weir Pool) of the Yeongsan River, Korea

Effect of Thermal Stratification on Phytoplankton and Nutrient Dynamics in a Regulated River (Saar, Germany)

AbstractThe weir pool Serrig is the deepest one along the impounded river Saar. Damming caused massive changes in the river's hydrodynamics. We analyzed the spatio‐temporal variability of thermal density stratification in the weir pool and its effect on phytoplankton and nutrient dynamics. In the analysis, continuous measurements from the years 2014 and 2015 were combined with three two‐day sampling campaigns in spring 2015. Thermal stratification occurred regularly in the downstream section of the weir pool during spring and summer and showed a diurnal rhythm. Temperature differences &gt;1 K between the 1 and 2 m water layer were observed during 34 out of 217 days (16%) in 2014, with maximum temperature gradients up to 3.71 K. Whereas the influence of thermal stratification on phytoplankton biomass and distribution was low during the algal bloom in early spring, stratification events between May and July promoted temporary algal blooms in the surface layer with chlorophyll a concentrations up to 98 µg Chla l−1 and a maximum difference between the 1 and 2 m water layer of 36 µg Chla l−1. Some of the stratification events resulted in reduced concentrations of dissolved nutrients in the surface layer as a result of increased uptake by algae, with maximum gradients between the surface and the 8 m water layer of 0.070 mg ortho‐PO43‐‐P l−1, 0.136 mg NH4+−N l−1 and 0.24 mg NO3¯−N l−1. These vertical gradients should be considered in sampling protocols for the assessment of the water quality of temporarily stratified river sections. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Model Predictive Control of a Large-scale River Network

This study investigates the use of Model Predictive Control (MPC) for regulation of river flows. During the past decade, MPC has emerged for controlling open water systems, such as irrigation and drainage channels. Compared to a full river network, irrigation and drainage systems are of relatively small scale. The aim of the present work is to investigate MPC as a tool for control of releases from gates and dams in a large-scale river network using the Murrumbidgee River in New South Wales, Australia, as case study. The Murrumbidgee River has around 1300 kilometers of river reaches, and the travel time through the valley is of the order of one month. The research has focused on four points: 1) Configuring linear surrogate models to describe the characteristics of reaches and weir pools; 2) Formulating the control problem and its objectives; 3) Using MPC with a receding horizon to solve the control problem; and 4) Testing the accuracy of the calculated control action, by using it as forcing in a detailed hydraulic model. The tests show that a reliable computation of optimal releases from regulators throughout the river is obtained, despite the linear approximation of the dynamics. The tests also show that the computation time for setting up and solving the optimization problem is no more than a few minutes on today's laptops.

영산강 다기능보 운영에 따른 플러싱 및 조류 배제 효과 모델링

The purpose of this study was to model the effect of flushing discharge on algae removal by multi-purpose weir operation in Yeongsan River (Seungchon Weir) using a 3-dimensional (3D) model. The chlorophyceae Eudorina sp. formed bloom in May 2013. Flushing discharge was conducted in two different ways for algal bloom reduction. To elucidate the spatial variability, a high-resolution 3D model, ELCOM-CAEDYM, was used to simulate the spatial variations of water quality and chl-a over a month. The results showed that ELCOM-CAEDYM could reproduce highly spatially resolved field data at low cost, and showed very good performance in simulating the pattern of algal bloom occurrence. The effect of each flushing discharge operation was analyzed with the results of modeling. The results of case 1, flushing discharge using an open movable weir, showed that the algal bloom between the Seochang Bridge and the Hwangryong River junction is rapidly flushed after operating the movable weir, but the residual algae remained in the weir pool as the discharge decreased. However, the results of case 2, fixed weir overflow with a small hydropower stop, showed that most of the algae was removed after flushing discharge and the effect of algae removal was much bigger than that in case 1, as per modeling results and observed data.

An Unexpected Lack of Response in Lignum (Muehlenbeckia Florulenta Meissn.) to A Managed Rise in the Level of the Lower River Murray, South Australia

Weir-pool surcharge is a method of providing water for the environment by using in-channel weirs to raise the river above its normal operating level, holding it for a period and then restoring it. In the spring and summer of 2005–2006 the level of the Lock 5 and 6 weir pools were surcharged for environmental benefit. the effect of the surcharge on the shrub, tangled lignum (Muehlenbeckia florulenta Meissn.), was assessed at six sites, where all surveyed plants were inundated. From 2004–2008 three categorical parameters: branch greenness, leaves and flowering were assessed from repeatedly measured shrubs. there were few changes in parameter state between surveys, with a change only occurring 32% of the time. Where a change did occur, shrubs tended to move back and forth between adjacent states rather than in one direction. this was unexpected as lignum is known to respond to flooding by producing shoots, flowers and leaves. Possible explanations for this lack of response were that the monitored lignum were not water-stressed; conditions were already favourable and the shrubs did not respond; natural senescence; competition with adjacent plants; high soil or groundwater salinity; or that a minor response occurred but went undetected.

Ecological response of Eucalyptus camaldulensis (river red gum) to extended drought and flooding along the River Murray, South Australia (1997–2011) and implications for environmental flow management

Riparian forest and woodlands of the lower River Murray floodplain are exhibiting deteriorating health as a result of anthropogenic alterations to flow regimes and south-eastern Australia’s long-term ‘Millennium Drought’ from 1997 to 2009. Extensive flooding in 2010/2011 brought the drought to an end, providing an opportunity to monitor ecological floodplain recovery. The relationship between flooding and lateral recharge and condition of the dominant riparian tree species, Eucalyptus camaldulensis, was determined between 2007 and 2011 using the Landsat (LTM5) Normalised Difference Vegetation Index (NDVI). Linking the river hydrograph with the River Murray Floodplain Inundation Model (RiM-FIM) allowed exploration of the relationship between inundation duration and E. camaldulensis water requirements. Results indicate lateral bank recharge is an important mechanism in the maintenance of vegetation condition along the River Murray channel. Higher in-channel irrigation water delivery during summer months was identified as critical to survival of trees adjacent to the channel during the drought. The research suggests that weir pool manipulation to create in-channel flood pulses will aid E. camaldulensis maintenance. Furthermore, release of environmental flows once every 3 to 5 years to create bank-full flow or preferably overbank flows, will increase hydrological connectivity between river banks, wetlands and riparian zones, providing positive ecological benefits to E. camaldulensis and other floodplain and aquatic ecological assets.

Effects of hydrology and river management on the distribution, abundance and persistence of cyanobacterial blooms in the Murray River, Australia

Major cyanobacterial blooms (biovolume>4mm3L−1) occurred in the main water reservoirs on the upper Murray River, Australia during February and March 2010. Cyanobacterial-infested water was released and contaminated rivers downstream. River flow velocities were sufficiently high that in-stream bloom development was unlikely. The location has a temperate climate but experienced drought in 2010, causing river flows that were well below the long-term median values. This coupled with very low bed gradients meant turbulence was insufficient to destroy the cyanobacteria in-stream. Blooms in the upper 500km of the Murray and Edward Rivers persisted for 5 weeks, but in the mid and lower Murray blooms were confined to a small package of water that moved progressively downstream for another 650km. Anabaena circinalis was the dominant species present, confirmed by 16S rRNA gene sequencing, but other potentially toxic species were also present in smaller amounts. Saxitoxin (sxtA), microcystin (mcyE) and cylindrospermopsin (aoaA) biosynthesis genes were also detected, although water sample analysis rarely detected these toxins. River water temperature and nutrient concentrations were optimal for bloom survival. The operational design of weirs and retention times within weir pools, as well as tributary inflows to and diversions from the Murray River all influenced the distribution and persistence of the blooms. Similar flow, water quality and river regulation factors were underlying causes of another bloom in these rivers in 2009. Global climate change is likely to promote future blooms in this and other lowland rivers.

Microeukaryote community composition assessed by pyrosequencing is associated with light availability and phytoplankton primary production along a lowland river

Summary The importance of microeukaryotes (protists, ciliates, fungi, algae and small invertebrates) in riverine food webs is well recognised, but the difficulty in surveying these taxa has meant that monitoring of biodiversity in rivers has focused on larger organisms. Microeukaryote biodiversity was assessed by pyrosequencing of the conserved 18S rRNA gene during summer and autumn at two river sites and a weir pool site that form a flow gradient in the Murray River, Australia. Concurrent measurements were made of phytoplankton concentrations, irradiance conditions, river metabolism and associated water quality attributes. Based on operational taxonomic units derived from the molecular analyses, significant differences were identified in eukaryotes between the river and the weir pool. Taxonomic assignment was possible for 66% of the operational taxonomic units, reflecting the large amount of unsurveyed diversity present. Visual identification of algae corroborated the orders identified in the molecular data set, and more orders were detected using pyrosequencing. Day length, depth of light penetration and phytoplankton biomass and primary productivity were strongly linked to eukaryote community composition suggesting the importance of algae as an energy source. Our finding that microeukaryote biodiversity is linked with environmental characteristics demonstrates the potential of 18S rRNA pyrosequencing for more comprehensive assessment of the condition of an aquatic ecosystem, but further data are required to confirm this potential.

ERRATUM

River Research and ApplicationsVolume 29, Issue 9 p. 1205-1205 ErratumFree Access ERRATUM This article corrects the following: ENVIRONMENTAL GRADIENTS ALONG A LOWLAND WEIR POOL IN THE SOUTHERN MURRAY-DARLING BASIN, AUSTRALIA N. Whiterod, B. Sherman, Volume 28Issue 10River Research and Applications pages: 1680-1694 First Published online: August 3, 2011 First published: 05 April 2013 https://doi.org/10.1002/rra.2657AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat References Whiterod N, Sherman B. 2012. Environmental Gradients Along a Lowland Weir Pool in the Southern Murray–Darling Basin, Australia. River Research and Applications 28(10): 1680– 1694. doi: 10.1002/rra.1563 Wiley Online LibraryWeb of Science®Google Scholar Page 1690, Equations 1–3 should read (1) (2) (3) Volume29, Issue9November 2013Pages 1205-1205 ReferencesRelatedInformation

Use of laser-scan technology to analyse topography and flow in a weir pool

Abstract. The development of laser-scan techniques provides opportunity for detailed terrain analysis in hydrologic studies. Ground based scans were used to model the ground surface elevation in the area of a stream gauge weir over an area of 240 m2 at a resolution of 0.05 m. The terrain model was used to assess the possibility of flow bypassing the weir and to calculate stream flow during filling of the weir pool, prior to flow through the weir notch. The mapped surface shows a subtle low-lying area at the south end of the structure where flow could bypass the weir. The flow calculations quantify low-flows that do not reach the weir notch during small rain events and flow at the beginning of larger events in the ephemeral stream.