Weir Construction Research Articles

First Gut Content Analysis of 4th Instar Midge Larvae (Diptera: Chronomidae) In Large-Scale Weirs Using a DNA Meta-Barcoding Approach.

Chironomidae larvae play an important role in the food chain of river ecosystems in Korea, where it is dominant. However, detailed information on the diet of Chironomidae larvae are still lacking. The purpose of this study was to identify the gut contents of 4th instar larvae of a Chironomidae inhabiting four large-scale weirs (Sejong Weir, Juksan Weir, Gangjeong-Goryeong Weir, and Dalseong Weir) using a DNA meta-barcoding approach. We found that dominant Operational Taxonomic Unit (OUT) was assigned to Paractinolaimus sp. (Nematoda), and the sub-dominant OTU was assigned to Dicrotendipes fumidus (Chironomidae). The most common OTUs among the individuals included phytoplankton, such as Tetrahymena sp., D. armatus, Pseudopediastrum sp., Tetradesmus dimorphus, Biddulphia tridens, and Desmodesmus spp. We calculated the selectivity index (E’) and provided scientific evidence that Chironomidae larvae have a significant preference (E’ > 0.5) for Desmodesmus armatus, E. minima, and T. dimorphus, while it does not show preference for other species found in its gut. Differences in physico-chemical factors, such as water quality, nutrients, Chl-a, and carbon concentrations, resulting from anthropogenic impacts (i.e., construction of large-scale weirs) as well as the particle size of prey organisms (small-sized single cell) and effects of chemicals (chemokinesis) could affect the feeding behavior of Chironomidae larvae.

Study of quality maintenance of fish habitats in small- and medium-sized mountain rivers with low flow rate

Many large-scale southwestern mountain rivers have intensive hydropower development in China, and it is difficult for the mainstream habitats to meet the needs of fish; thus, the replacement of tributary habitats has become an effective measure for river ecological protection. Appropriate ecological flow is an important tool used to repair fish habitats and plays an important role in the ecological protection of tributaries, but this practice has caused conflicts with the economic interests of hydropower owners, which has made the implementation of restoration work more difficult; therefore, it is imperative to ease the contradiction between the two. Based on field investigation and monitoring, this paper designs remedial measures for the horizontal and vertical sections of the river section, namely, dredging the river horizontally and constructing a water-retaining weir and underwater dam vertically. A two-dimensional hydrodynamic model was used to numerically simulate the hydrodynamic conditions before and after different ecological restoration measures, and the corresponding weighted usable area (WUA) was calculated to evaluate the different restoration effects on habitats. The results show that the suitable ecological flow rate of the study section is 16.80 m3/s (35% average annual flow), and the WUA increased by 317.37% compared with the initial state of 2.39 m3/s (5% average annual flow); when discharge flow is 4.80 m3/s (10% average annual flow), the improvement measures of habitat quality include the combination of river dredging and the construction of water-retaining weir, construction of water-retaining weir, construction of underwater dam, and river dredging. The initial state increased by 129.96%, 177.19%, 226.51% and 329.21%, respectively. The partial excavation and dredging have a complementary effect with the construction of the water trap, and the increase in the WUA caused by the combination of the two exceeds the increase caused by the appropriate ecological flow. In summary, targeted restoration measures can achieve the goal of maintaining a high level of habitat quality at lower flow levels.

Flow Characteristics Of Tigris River Within Baghdad City During Drought

The main source of water supply in Iraq is the surface water, especially Tigris and Euphrates Rivers and their tributaries. In the recent years there was a great drop in the water levels of Tigris River within Baghdad City which had affected the operation of twelve water supply projects located on the banks of Tigris River in Baghdad City, due to significant climate changes, and the expansion of hydraulic construction (dams) and implementation of new irrigation projects in Turkey, these factors have greatly reduced the water flowrates of river by about 46%. In the present study the flow characteristics of Tigris River within Baghdad City was studied, the reach involved was about 49km in which it represents the urban zone beginning from the north of the Baghdad City at Al-Muthana Bridge to the confluence of Tigris River with the Diyala River south of Baghdad, using steady flow one-dimensional hydraulic model to achieve raising of water levels within this reach during drought periods. This model was implemented using HEC-RAS software.Three sets of observation data were used to calibrate the model to estimate suitable Manning roughness coefficient (n) considering the root mean square error (RSME) as an accurate indicator. The results showed that n of value 0.032 for the main river bed and 0.040 for flood banks of the river gave the best results with minimum RMSE of 0.076. Several treatments were suggested such as construction of barrage, inflatable weir, and the use of obstruction for the purpose of raising water levels. Moreover, selection of the suitable site of these treatments or hydraulic structures was studied, as well as their cost was analyzed. The results show that the proper solution for maintain the required water levels that ensure continuous operation of water supply project was the construction of an inflatable weirs, due to low initial cost, simplicity of operation, their ability to inflate and deflate quickly and easily to prevent upstream flooding, and offering a high level of control and easy method for recapturing water.

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.

Groundwater chemistry and demarcation of seawater intrusion zones in the Thamirabarani delta of south India based on geochemical signatures.

Sub-surface water samples from the delta of Thamirabarani River of south India were evaluated for human health risks and seawater intrusion using the geochemical signatures. Electrical conductivity (EC), total dissolved solids (TDS), pH and the concentrations of major cations and anions in 40 samples collected during the winter (January) and summer (July) of 2018 show comparable values. Subsequently, the results were verified with respect to the international drinking water quality standards. The piper trilinear diagram shows mixed Ca-Mg-Cl, Na-Cl, Ca-HCO3 and mixed Ca-Na-HCO3 facies in the samples. Similarly, the plenteous of cations are sequenced as Na+ > Ca2+ > Mg2+ > K+ and the plenteous of anions are sequenced as Cl- > SO42- > HCO3->Br- > NO3- > PO4-. Gibbs plots illustrate that rock-water interaction and evaporation control the geochemistry of sub-surface water. More than 40% of the samples are unsuitable for drinking, and their higher EC and TDS values reflected the seawater intrusion, in addition to the anthropogenic activities (salt panning). Interrelationship between ions of sub-surface water was used to get a better insight into the saline water intrusion in the study area. To mitigate the river water salinization and seawater incursion in the aquifers, engineering solution such as weir construction across the Thamirabarani River near Mukkani village has been proposed. After construction of the weir, freshwater in the river can be diverted to the salt-affected and seawater-intruded areas to improve the scenario.

Study on flow regime change due to weir construction plan in Batang Asai River, Sarolangun, Province of Jambi

The weir design process not only considers the location, dimensions, strength, and durability of the weir structure, but must also be consider the effect on the flow characteristics in the river after the weir, especially related to the flow velocity characteristic around the weir. The water level will rise and affect the flow velocity downstream of the weir. Because of the fall of water, the velocity will greatly increase and the river can erode. The weir construction on the Batang Asai River, specifically located in Sarolangun, Province of Jambi, has unique conditions that cause the velocity of water after the weir to increase. Several alternatives will be analysed as solutions to deal with changes in flow velocity. The alternatives are groundsill, riverbed normalization, and river crossing widening. It was found that the alternative of river widening showed a significant reduction in flow velocity.

Comparison of the habitat distribution characteristics of Aquatic Oligochaeta according to the construction of weirs in four major rivers in South Korea

Comparison of the habitat distribution characteristics of Aquatic Oligochaeta according to the construction of weirs in four major rivers in South Korea

Study of impact sheet pile and Franki NG pile driving on weir construction

The proper quality and the safe execution of geotechnical works imposes the necessity of monitoring techniques to prevent the threats arising from the vibrations. This work presents authors experience gained during sheet piling and Franki pile driving in time of construction of water power plant. Dynamic impact of foundation works can be perceptible by humans and can affect structures and technical devices. The immediate reason for the dynamic analysis was the occurrence of clearly perceivable vibration of the weir. The measurements were performed during sheet wall installation and Franki pile driving at various measuring points. Wave parameter measurements and recording of shocks and vibrations in the close vicinity of the construction site were juxtaposed for different installation phases and measuring points. A comparison of the two technologies shows that the largest vibrations occur during formation of the cast-in-situ (over)expanded Franki pile base. Sheet pile wall installation supported by additional processes such as pre-boring turned out to be as less harmful.

Possibility on Contamination of Upper MUSI Ground Water for Flow Water at River End

The musi river historically provided farmers downstream of hyderabad with irrigation water for the cultivation of paddy for the duration of and after the monsoon rains. Through the construction of weirs, river water is retained in large and small reservoirs on the river from wherein it is diverted thru irrigation canals to village tanks and agricultural fields. This paper focuses on the sample description and corrective requirements after the survey samples at unique black points alongside musi. The presence heavy metals and microbiological pollutants have made the groundwater dangerous for consuming at diverse places in hyderabad. It has also proved that there is large issue of city groundwater recharge in this region. The internet urban recharge factor of groundwater in this region changed into anticipated to be about 567. 51 mm/a and natural recharge element turned into observed to be 52. 78 mm/a. The combination of tools carried out, the outcomes received and the recommendations provided in this have a look at will be helpful for neighborhood planners and selection makers to shield and restore the water assets on this location. The existing work also makes a speciality of the scope of infection by float water immersion at 2d part of musi river in ground as nicely agriculture. The consequences taken into consideration from 2017 june to may additionally 2019 for the actual identifications, the parameters are y18 and y19 for graphical enter.

Combined influence of weir construction and sea-level rise on freshwater resources of a coastal aquifer in northern Germany

A significant volume of an aquifer along the coastline in the German Bight is salinized by seawater intrusion. The mean sea-level rise (MSLR) is expected to continue in the future due to global climatic change, subsequently degrading the fresh groundwater resources. To impede further salinization in the future, a solution is proposed based on weir construction in an existing canal hydraulically connected to the aquifer. The effect is twofold: (1) the elevated groundwater level can upgrade present fresh groundwater resources by shifting the saltwater–freshwater interface position further seaward, or by inhibiting its landward movement, and (2) the inland water level can be elevated, expanding surface water ponds. A fully coupled three-dimensional numerical surface-subsurface model (a modified HydroGeoSphere code) was used to simulate the effects of variable weir construction heights under different MSLR rates, and to quantify the gain of aquifer freshwater volume and loss of usable land due to surface ponding. Construction of a higher weir increases the desalinized aquifer volume and decreases the newly salinized aquifer volume under future MSLR. A minimum height of a weir was determined under a certain MSLR rate to maintain the present freshwater resource. Both weir construction and MSLR can cause the loss of land usage. Computed loss-gain ratio curves can be utilized to determine the optimal weir height, meeting the economic requirements of coastal land management under future MSLR.

Morphological Changes of the Lower Ping and Chao Phraya Rivers, North and Central Thailand: Flood and Coastal Equilibrium Analyses

Abstract The Chao Phraya River flows in the largest river basin of Thailand and represents one of the important agricultural and industrial areas in Southeast Asia. The Ping River is one major upstream branch flowing down slope southwardly, joining the Chao Phraya River in the low-lying central plain and ending its course at the Gulf of Thailand. Surprisingly, the overflow occurs frequently and rapidly at the Lower Ping River where channel slope is high, and in particular area, sand-choked is extensively observed, even in normal rainfall condition. In contrary, at the downstream part, the erosion of river bank and shoreline around the mouth of Chao Phraya River has been spatially increasing in place where there should be a massive sediment supply to form a delta. Here we use Landsat imageries taken in 1987, 1997, 2007 and 2017 to analyze geomorphological changes of rivers. Results show that both rivers have undergone the rapid decreasing of water storage capacity and increasing of sand bar areas in river embayment. The total emerged sand bar area in the Lower Ping River increases from 1987 to 2017 up to 28.8 km2. The excessive trapped bed sediments deposition along the upper reaches is responsible for the shallower of river embankment leading to rapid overflow during flooding. At the Chao Phraya River mouth, a total of 18.8 km2 of the coastal area has been eroded from 1987 to 2017.This is caused by the reducing of sediment supply leading to non-equilibrium in the deltaic zone of the upper Gulf of Thailand. There are several possibility implications from this study involving construction of weir, in-channel sand mining, reservoir sedimentation and coastal erosion management.

Model-based evaluation of restoration measures efficiency in the anastomosing section of the River Narew

Multi-channel rivers support diverse and productive ecological communities, and their rareness in the developed world places a great importance on their conservation. The design of side channel restoration projects remains poorly informed by theory or empirical observations. One of the last examples of anastomosing rivers in Europe is a stretch of River Narew in Poland protected as a national park. Park Authorities face a problem of side channels extinction in last few decades and therefore a dedicated plan of protection measures (submerged weir construction, dredging and mowing of side channels) was established aimed at anastomosing system conservation. The objective of this study was an ex-ante assessment of the impact of proposed protection measures on discharge distribution, flow velocity and sediment transport potential in the anastomosing section of the river, using a hydraulic, one-dimensional model. Among the tested measures, more invasive dredging and damming were significantly more efficient than less invasive vegetation removal. Compared to other restoration projects of multi-channel rivers (Narew and Rhône cases), supported by extensive post-restoration monitoring, efficiency level was comparable reaching on maximum tenfold increase in discharge and fivefold increase in reach-averaged flow velocity in restored side channels. Post-conservation alterations of hydraulic properties in the anabranches resulted in a significant increase in sediment transport potential for measures changing channel geometry. Such change could potentially ensure the stability of restoration eliminating the main cause of channels extinction i.e. excessive sediment deposition.

Passage performance and behaviour of wild and stocked cyprinid fish at a sloping weir with a Low Cost Baffle fishway

Weir construction has fragmented many rivers, resulting in the exclusion of some fish populations from suitable habitat. A cheap retrofit fishway for small, sloping weirs is the Low Cost Baffle (LCB) solution – A series of notched baffles perpendicular to flow on the downstream weir face, generating an angled passage route across the weir face. To test the degree to which LCBs can pass upstream-moving, lowland-river fish at steep weirs, LCBs were fitted onto a 1:3.3-sloping gauging-weir face, in an urban tributary of the River Thames, England. The study also compared the passage of wild and stocked fish (the latter are employed to facilitate population recovery in restored English rivers). Passive Integrated Transponder (PIT) antennas were positioned on the weir to record the upstream movement of PIT-tagged barbel (Barbus barbus; nstock = 120), chub (Squalius cephalus; nstock = 119; nwild = 194), dace (Leuciscus leuciscus; nwild = 50), and roach (Rutilus rutilus; nwild = 30). Over six months, more stocked fish attempted passage (58.9%) than wild (14.6%; χ21 = 26.7, p < 0.001), but there was no difference in successful passage of those that attempted (stock = 34.0%; wild = 40.0%; χ21 = 0.5, p = 0.49). Successful passage was achieved under a range of flow conditions. This study finds that LCBs have the potential to facilitate passage for cyprinid fishes at steep urban weirs that cannot readily be removed, but there is need for design improvements. This study also indicates that stocked and wild fish exhibited similar passage success, a finding with important management implications for achieving dispersal of stocked fish as a rehabilitation measure.

Minimizing the hydraulic side effects of weirs construction by using labyrinth weirs

It is no doubt that weirs are one of the most important hydraulic structures that play a vital role in irrigation project. So, it is necessary to minimize the hydraulic side effects of weirs. Throughout this paper, experiments were conducted to investigate the suitable dimensions and shape of weir's crest to increase head loss, decrease upstream bank level upstream weir and get the most economic structure. Various crest angles of labyrinth weir were tested under different flow conditions. Also back water curve upstream weir was studied according to different weir crest angles. A case of linear weir crest was also included in the test program. The experimental results indicated that labyrinth weirs have lower operating heads and longer crest length compared with a linear weir having the same lateral space and the same discharge. Results showed that the crest weir angle of 60° is the best angle of weir crest. It reduces water level above crested level and the relative jump depth by 18% and 20%, respectively. In addition, it increase the average values of the dissipated energy and the discharge coefficient by 15% and 14%, respectively. It also gave maximum reduction in backwater curve profile by about 17%. Furthermore, the model was verified using CFD numerical model. The numerical results agreed with the experimental results.

Influence of Weir Construction on Chemical Water Quality, Physical Habitat, and Biological Integrity of Fish in the Geum River, South Korea

Influence of Weir Construction on Chemical Water Quality, Physical Habitat, and Biological Integrity of Fish in the Geum River, South Korea

Suspended sediment source tracing at the Juksan Weir in the Yeongsan River using composite fingerprints

Since 2008, the Yeongsan River in South Korea has experienced significant environmental changes, such as the dredging of its riverbed and the construction of large weirs. The quantity and quality of the fine sediments that provide adsorptive surfaces for pollutants has an influence on water quality, human health, and aquatic organisms. To determine the dominant contributors and seasonal variation in suspended sediment at the Juksan Weir in the Yeongsan River, reservoir sediments were obtained at monthly intervals using a time-integrated suspended sediment sampler. We applied a fingerprinting procedure combined with a multivariate mixing model to discriminate between different types of land use and to apportion sediment sources. Cropland topsoils, forest topsoils and channel bank materials were selected as end-members, and fallout radionuclides, geochemical elemental concentrations and the magnetic properties of each source material were used as diagnostic tracer properties. According to the mixing model results, channel bank materials were the dominant source of reservoir sediment during the entire monitoring period. In winter, there was a slight increase in the contribution from forest topsoils, which could have been influenced by freeze–thaw processes. Despite the high proportion of agricultural land use in the study catchment and its proximity to the river, there was a small sediment contribution from the cropland topsoils. There were uncertainties resulting from an imperfect classification due to the spatial distributions of forest and cropland and the combination of the mixing model with the fingerprinting procedure. The results provide the basis for developing strategies for sediment control and reservoir management.

Ecological Niche Space of Fish Communities in Impounded Sections of Large Rivers: Its Application to Assessment of the Impact of Weirs on River Ecosystems

To estimate the impact of weirs on large river fish communities, we applied the ecological niche space (ENS) measured quantitatively using carbon and nitrogen stable isotope ratios to the monitoring of effects of weirs constructed on four major rivers in Korea. ENS was calculated using the Bayesian stable isotope in R statistics. The ENS of fish communities showed persistent differences between upstream and downstream areas of all studied weirs. The ENSs of omnivores were larger in upstream impounded areas but the ENSs of predator species, both endemic (Erythroculter erythropterus) and exotic (Micropterus salmoides) predators had decreased ENSs in upstream areas. E. erythropterus showed horizontal variations in a wide range of carbon stable isotopes, whereas M. salmoides showed vertical variations in nitrogen stable isotopes. The results suggest that weir construction may have species-specific impact on the ENS of fish community by impoundment and increase niche overlap in upstream areas of the weir. The measured ENS of fish community was significantly correlated with the relative abundance of tolerant species negatively, whereas correlated with that of endemic species positively, suggesting that the ENS can be used as a comprehensive indicator of habitat conditions.

Physiological Responses of Cultured Seaweed Pyropia yezoensis to Phosphorous Limitation in the Nakdong River Estuary, Korea

Pyropia yezoensis cultured in the estuary of the Nakdong River in Korea is an important fisheries resource for the local economy. Over the past few decades, the environmental conditions of this estuary have undergone marked changes due to coastal development, and particularly so since the construction of weirs in the main stream of the Nakdong River in 2012, which has resulted in changes in seawater nutrient concentrations. Although the production of P. yezoensis has declined notably since 2012, little is known regarding the relationship between this decline and the environmental changes. In this study, during the period from February to March 2017, we investigated environmental parameters and physiological characteristics of the cultured P. yezoensis in the Nakdong River Estuary in order to determine the factors limiting the growth of this macroalga. Water temperature, salinity, and irradiance at estuary sites were found to be favorable for Pyropia culture. High nitrogen (N) and low phosphorus (P) concentrations were measured in the sea water, which has led to a high N:P ratio. Comparable trends were observed in the N, P, and photosynthetic pigment contents of P. yezoensis tissues. Our results indicate that a deficiency in P might be a factor limiting the growth of Pyropia cultured in the Nakdong River Estuary. This study provides valuable information for gaining an understanding of the impact of environmental changes on the production of Pyropia culture in the Nakdong River Estuary.

Transformations in the water relations in the Wieczno Południowe lake catchment (Chełmno Lakeland, Poland)

Abstract The research involved a detailed analysis of transformations in water relations in the Wieczno Południowe (Wieczno South) lake drainage basin in central Poland, in the physical geographical region of the Chełmno Lakeland. Significant changes were identified in the water relations in the catchment, which were caused by a number of anthropogenic factors. The most significant factors include land development works, changes in land use (a decrease in wetland area in favour of arable land), and the extraction of water from Lake Wieczno South (for irrigation purposes) and the creation of a weir construction on its outflow. It has been shown that in recent years the drainage basin’s water resources have been affected by climate fluctuations manifested as an increase in sums of evaporation. As a result of the deterioration of water relations in the catchment, the hydrological type of some lakes (Płużnica, Wieczno North and Wieczno South) have changed, which unexpectedly resulted in an improvement of their water quality. Taking into account the forecasts for further climate change, this factor will probably have a decisive influence on the water relations of the studied area in the coming years.

Responses of fish assemblage structure to large-scale weir construction in riverine ecosystems

Worldwide, increasing amounts of dams and weirs have been established in rivers in recent decades, often with drastic effects on their ecosystems. Between late 2009 and 2011, 16 large-scale dams were built in the main channels of the four largest rivers in South Korea, eight of these along the main channel of Nakdong River (300 km, 520 km in total). We studied the effect of these constructions on the fish community in the riparian zone based on intensive fish field surveys conducted in the littoral zone during 2007–2017, analysis of fishermen's catch data and molecular analysis of the diet of the keystone species, largemouth bass (Micropterus salmoides). Our results, based on RDA and GLM analyses, showed that environmental characteristics and fish species composition changed significantly with dam construction. Total fish abundance and biomass decreased after the start of the weir construction and fish richness decreased with time. The abundance and biomass of exotic fish decreased during construction but recovered afterwards, leading to higher proportions of exotics. Dominance and Shannon indices did not change significantly from before to after construction, while the Evenness index showed a significant decreasing trend. A comparison of the diet composition of largemouth bass showed decreasing genetic variation after construction. The changes in Functional Feeding Group (FFG) of the benthic communities at the study sites did not coincide with FFG changes in the prey items of largemouth bass, indicating a transition in feeding mode from before to after construction. In conclusion, the endemic and native fish species were most sensitive and showed lower resilience to disturbance by the large-scale dam construction than the translocated and exotic species, and the lake-like ecosystems after construction markedly improved the competitive capacity of these exotic fish over the native and endemic species in the riparian zone of the river.