Tributaries Research Articles

The Amazon’s 2023 Drought: Sentinel-1 Reveals Extreme Rio Negro River Contraction

The Amazon, the world’s largest rainforest, faces a severe historic drought. The Rio Negro River, one of the major Amazon River tributaries, reached its lowest level in a century in October 2023. Here, we used a U-net deep learning model to map water surfaces in the Rio Negro River basin every 12 days in 2022 and 2023 using 10 m spatial resolution Sentinel-1 satellite radar images. The accuracy of the water surface model was high, with an F1-score of 0.93. A 12-day mosaic time series of the water surface was generated from the Sentinel-1 prediction. The water surface mask demonstrated relatively consistent agreement with the global surface water (GSW) product from the Joint Research Centre (F1-score: 0.708) and with the Brazilian MapBiomas Water initiative (F1-score: 0.686). The main errors of the map were omission errors in flooded woodland, in flooded shrub, and because of clouds. Rio Negro water surfaces reached their lowest level around the 25th of November 2023 and were reduced to 68.1% (9559.9 km2) of the maximum water surfaces observed in the period 2022–2023 (14,036.3 km2). Synthetic aperture radar (SAR) data, in conjunction with deep learning techniques, can significantly improve near-real-time mapping of water surfaces in tropical regions.

Distribution and risk assessment of microplastic pollution in a rural river system near a wastewater treatment plant, hydro-dam, and river confluence

Rivers are the natural drainage system, transporting anthropogenic wastes and pollution, including microplastics (plastic < 5 mm). In a riverine system, microplastics can enter from different sources, and have spatial variance in concentration, physical and chemical properties, and imposed risk to the ecosystem. This pilot study presents an examination of microplastics in water and sediment samples using a single sample collection from the rural Raquette River, NY to evaluate a hypothesis that distinct locations of the river, such as downstream of a wastewater treatment plant, upstream of a hydro-dam, and river confluence, may be locations of higher microplastics concentration. In general, our results revealed the presence of high microplastic concentrations downstream of the wastewater treatment plant (in sediments), upstream of the hydro dam (both water and sediment), and in the river confluence (water sample), compared to other study sites. Moreover, the risk assessment indicates that even in a rural river with most of its drainage basin comprising forested and agricultural land, water, and sediment samples at all three locations are polluted with microplastics (pollution load index, PLI > 1; PLIzone = 1.87 and 1.68 for water and sediment samples respectively), with risk categories between Levels I and IV (“minor” to “danger”). Overall, the river stands in a “considerable” risk category (PRIzone = 134 and 113 for water and sediment samples respectively). The overall objective of this pilot study was to evaluate our hypothesis and advance our understanding of microplastic dynamics in rural river systems, elucidating their introduction from a point source (wastewater treatment plant), transit through an impediment (hydro-dam), and release into a vital transboundary river (confluence of Raquette-St. Lawrence Rivers).

The effects of land use types on microplastics in river water: A case study on the mainstream of the Wei River, China

Microplastics are widely found in rivers and their sediments, which will cause harm to the water ecological environment. The Wei River is a first-class tributary of the Yellow River, the fifth largest river in the world, and has vulnerable ecological environment and most sediment in the world. However, understanding how anthropogenic activities and environmental factors affect the microplastics distribution in this river is not clear. Based on this, the spatiotemporal distribution of microplastics in the Wei River were investigated. The abundance of microplastics ranged from 1033 to 8333 items/m3 and from 120 to 840 items/kg in the water and in the sediment, respectively. Fibers and fragments were the main shapes of Wei River, microplastics less than 500 μm were the main sizes, and black and white/transparent were the main colors. In Wei River, the abundance of microplastics in urban areas was higher than that in agricultural areas and mountainous areas. Furthermore, the correlation analysis revealed that microplastic abundance in the water was related to anthropogenic activities (population density, per capita GDP and distance) and environmental factors (water temperature, NH3-N, ORP), while in the sediments was correlated with anthropogenic activities (per capita GDP) and environmental factors (water temperature and NH3-N). This study reveals new patterns in microplastic pollution in the Wei River, underscoring the need for targeted environmental strategies. Our findings provide novel insights into the characteristics and distribution of microplastics, significantly adding to the current understanding of riverine microplastic pollution.

Occurrence Characteristic and Risk Assessment of Microplastics in Sishui River (Xingyang Section)

Urban rivers are the main receptors and transporters of microplastic pollution. Understanding the occurrence and environmental risk of microplastics in urban rivers can provide theoretical basis for further control of microplastic pollution. The Sishui River, a tributary of the Yellow River, was selected as the research object. A total of nine water samples were collected from sewage outlets of the Sishui River (Xingyang section). The microplastics in the collected samples were characterized by their sizes, shapes, and colors using a microscope. It was found that microplastics were mostly in the form of transparent fibers and fragments in the water body of sewage outlets, of which the size below 500 μm was relatively high. In addition, PET and PE polymers were identified as the main types using a laser infrared imager. The correlation analysis showed that there was a significant correlation between the PET and PE, indicating that they were similar in origin. The results of the environmental risk assessment showed that the type of microplastics was the main factor affecting the assessment results, whereas the risk values of six sewage samples containing PVC were high. However, the value of pollution load index revealed a low risk level of pollutants in the study area.

Spatial and seasonal variation in disinfection byproducts concentrations in a rural public drinking water system: A case study of Martin County, Kentucky, USA.

To increase our understanding of the factors that influence formation of disinfection byproducts (DBPs) in rural drinking systems, we investigated the spatial and seasonal variation in trihalomethane (THM) and haloacetic acid (HAA) concentrations in relation to various chemical and physical variables in a rural public drinking water system in Martin County, Kentucky, USA. We collected drinking water samples from 97 individual homes over the course of one year and analyzed them for temperature, electrical conductivity, pH, free chlorine, total chlorine, THMs (chloroform, bromodichloromethane, dibromochloromethane, dichlorobromomethane, and bromoform) and HAAs (monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, bromoacetic acid, and dibromoacetic acid). Spatial autocorrelation analysis showed only weak overall clustering for HAA concentrations and none for THMs. The relationship between modeled water age and TTHM or HAA5 concentrations varied seasonally. In contrast, there was strong variation for both HAA and THMs, with concentrations of HAA peaking in mid-summer and THMs peaking in early fall. Multiple regression analysis revealed that THM concentrations were strongly correlated with conductivity, while HAA concentrations were more strongly correlated with water temperature. Individual DBP species that only contained chlorine halogen groups were strongly correlated with temperature, while compounds containing bromine were more strongly correlated with conductivity. Further investigation revealed that increased drinking water conductivity associated with low discharge of the Tug Fork River, the source water, is highly correlated with increased concentrations of bromide. Discharge and conductivity of the Tug Fork River changed dramatically through the year contributing to a seasonal peak in bromide concentrations in the late summer and early fall and appeared to be a driver of brominated THM concentrations. Brominated DBPs tend to have higher toxicity than DBPs containing only chlorine, therefore this study provides important insight into the seasonal factors driving risk from exposure to DBPs in rural drinking water systems impacted by bromide.

Zambia–Zimbabwe 2022 hippopotamus (Hippopotamus amphibius) and other species population distribution along Zambezi River

ABSTRACT A hippopotamus and other wildlife species survey were conducted in the Zambezi River between Kariba dam wall and Luangwa River confluence. The main objective of the survey was to establish hippopotamus and other wildlife species population distribution and densities along the Zambezi River. The boat survey method was used on both sides of the river in October 2022 for 262 km. Individual hippopotamus counted were 1769 on the Zambian side and 1424 on the Zimbabwean side. The Zimbabwean side recorded higher hippopotamus pods (138) than the Zambian side (123). Individual hippopotamus density was 26.60/km with a pod density of 0,45/km. There was a significant difference in hippo population between the five Zambezi River sections on the Zambian side ( x 2 = 2345, df = 4, p = 0.01) and Zimbabwean side ( x 2 = 538, df = 4, p = 0.01). The study established areas with high hippo and other wildlife species population distribution and densities, and the study helps to inform management of protected areas’ carrying capacities and management of Human Wildlife Conflicts. The study recommends more studies on hippopotamus migration, population demography, variation in home ranges and regular population surveys in both rivers and inland waterholes.

Health risk assessment and potential sources of metals in riparian soils of the Wujiang River, China.

In order to understand the pollution status of metals in the riparian soils along the Wujiang River, 26 sampling sites in the mainstream and tributary streams were selected for investigation. The geo-accumulation index (Igeo), Nemerow integrated pollution index, and potential ecological risk index were applied to evaluate the contamination status and ecological risks of metals. Results revealed that the average concentrations of As, Cd, Cr, Cu, Mn, Ni, Pb, and Zn were 12.20, 0.51, 84.01, 57.42, 922.57, 38.37, 38.06, and 127.82mg/kg, respectively. The metal contamination degree and ecological risks in the upper reaches were significantly higher than those in the middle and lower reaches of the Wujiang River. Cd was the dominant contamination metal. Significant non-carcinogenic and carcinogenic risks of metals were found in children based on the hazard index and carcinogenic risk. As was the main non-carcinogenic and carcinogenic pollutant metal in both adults and children. According to principal component analysis, hierarchical clustering analysis, and absolute principal component scores-multiple linear regression, anthropogenic sources (mining and agricultural activities) contributed most to Zn, Pb, Cr, Cd, Cu, and Ni, with contribution rates of 89.14, 82.32, 74.46, 72.12, 68.52, and 61.02%, respectively. Natural sources contributed most to Mn, with a contribution rate of 83.07%. Unidentified sources contributed most to As, with a contribution rate of 47.27%.

ASSESSMENT OF CHEMICAL POLLUTION OF THE SURFACE WATER IN VLADIMIR

The results of studies of river water of the Vladimir city district for the content of heavy metals conducted in August 2022 are presented and the anionic-cationic composition of water is analyzed. It is shown that a number of heavy metals (lead, iron, cadmium, zinc, copper and vanadium) and ions (ammonium, magnesium, sulfates, nitrates, fluorides, phosphates) in water samples of the rivers of the city district exceed hygienic and fishery standards, which is due to both human economic activity and regional specifics of the geochemical composition of water-bearing rocks and features of groundwater functioning and feeding. The potassium concentration in water of the Nerl river, which is a drinking water source for Vladimir, corresponds to the lower threshold of physiological competence, which can affect the health of city residents if they use such water for a long time. It is shown that insufficient extraction of biogenic elements at the treatment facilities of enterprises could lead to their ingress into water bodies in concentrations exceeding hygienic and fishery standards. This in turn could contribute to the accumulation of other elements. Strict requirements for the content of chemical elements in fishery water bodies make it necessary to improve the equipment and technological schemes of purification at treatment facilities. Small rivers of cities are vulnerable and poorly protected; therefore they require special attention of environmental authorities. Being tributaries of larger rivers, small rivers form the quality of their waters. If they are used for the household and drinking purposes, they become a factor determining the health of urban residents.

Effect of hydrological variability on suspended sediment load at a river junction: a case study

Abstract Confluences act as crucial intersection in a fluvial system as they regulate the flow, sediment, and geomorphological stability. Two of the natural occurrences that have an effect on hydro-morphological processes that characterize the channel are sediment movement and stream discharge. However, assessments of suspended sediment distribution patterns across channel confluences and functions of tributaries on sediment transfer in downstream streams are still inadequately explored. To fulfil this, a year-long field investigation was conducted around river confluence at various time scales during the hydrological season. The bathymetry of the confluence was performed using digital echo-sounding equipment, electro-magnetic current meter, and differential global positioning equipment. This study uses in situ measurement and empirical techniques to quantify the spatiotemporal distribution of suspended sediment particles. Furthermore, Yang's formula was used to analyze the sediment concentration, and several statistical standards were employed to establish a differentiation between predicted and observed data. The results illustrated that a good agreement has been achieved among the calculated and measured statistics based on the correlation coefficient value. According to the findings, 8% fewer errors in the quantification of suspended sediment were induced in the tributary than in the main river because of the very low flow of the tributary. The present ramifications can help increase our database and understanding of the dynamics of major river confluences.

Robustness of design flood estimates under nonstationary conditions: parameter sensitivity perspective

The changing frequency of flooding in global watersheds, driven by various human and natural factors like land use/cover changes and global warming, necessitates innovative approaches in flood frequency analysis and risk assessment. Nonetheless, the reliability of nonstationary frequency analysis models remains a concern given challenges in accurately measuring the uncertainty introduced by these methods and the impact on design flood values. In this study, deviation-based differential sensitivity indices, including single-parameter (SDDSI) and entire-parameter (EDDSI) measures were developed to assess the influence of parameter uncertainty in nonstationary models using Bayesian statistics and "equivalent reliability" nonstationary design. The Weihe River, the largest tributary of the Yellow River which is experiencing both climate change and heavy impact of human activities, is chosen to be the study area to investigate the impact of precipitation change and land use change on nonstationary flood frequency. Results show that in the One-At-A-Time (OAT) sensitivity analysis under a small uncertainty scenario (SUS) for parameter inputs, the shape parameter stands out as the most influential factor (SDDSI_SUS = 0.347) affecting the 100-year design flood in the Stationary Generalized Extreme Value (SGEV) model. For the Non-Stationary GEV (NGEV) models, the influence of this parameter is less pronounced, with SDDSI_SUS values of 0.095 and 0.093 for the SSP126 and SSP585 scenarios, respectively. Instead, attention turns to the regression coefficient of the grassland area, associated with the GEV scale parameter. In global sensitivity analysis under the posterior uncertainty scenario (PUS) for parameter inputs, the EDDSI_PUS values for SGEV, NGEV_SSP126, and NGEV_SSP585 models were 0.52, 1.41, and 1.30, respectively, inferring heightened sensitivity of NGEV models to perturbations from entire parameters. It is anticipated that incorporating additional evidence, such as historical flood data, is essential for accurate nonstationary hydrological design to mitigating the influence of parameter uncertainty. The sensitivity indices in this study provide significant insights for assessing the robustness of nonstationary hydrological design in flood risk management and applications.

Numerical Simulation of Habitat Restoration for Floating Fish Eggs in the Upper Yangtze River Tributaries

The upper reaches of the Yangtze River not only serve as a crucial waterway in China’s southwestern region but also function as a conservation area for rare fish species. Recognizing the tendency of current navigation channel improvement projects to overlook the impact on aquatic habitats and the limitations of existing habitat assessment systems, this study specifically focuses on the bifurcation section of the upper Yangtze River. To address these issues, a two-dimensional mathematical model is established to simulate and validate various improvement schemes. An analysis of the flow conditions necessary for fish migration and spawning in this section is conducted, determining optimal flow rates and water levels during spawning and migration periods. A suitability assessment system for spawning and migration is then established, utilizing the four major Chinese carps as representative fish species for evaluation. Through a comprehensive analysis of the results, rational improvement schemes are identified. The findings underscore the importance of considering elevation of dam crest during the construction of sub-dams to regulate the navigation channel, particularly regarding its impact on fish habitats during the dry season. In this plan, the weighted available area of the spawning ground increased by 189,251 m2, 165,860 m2, 89,527 m2, 66,542 m2, and 47,182 m2 under five conditions. Additionally, the evaluation indexes PPA, HFI, and CQI showed increases of 5.011%, 4.176%, and 2.901%, respectively. Moreover, this study refines fish habitats based on their reproductive and living habits, thereby enhancing existing habitat assessment models.

Patterns of genetic divergence in the Rio Grande cooter (Pseudemys gorzugi), a riverine turtle inhabiting an arid and anthropogenically modified system.

The lower Rio Grande and Pecos River of the southwest United States have been heavily modified by human activities, profoundly impacting the integrity of their aquatic wildlife. In this context, we focused our study on the population genomics of the Rio Grande Cooter (Pseudemys gorzugi), a freshwater turtle of increasing conservation concern, residing in these two rivers and their tributaries. The genetic data revealed two distinct populations: one in the Pecos and Black Rivers of New Mexico and another in the Rio Grande and Devils River of Texas, with admixed individuals identified at the confluence of the Rio Grande and Pecos River. In addition to having a smaller geographic range, we found lower observed heterozygosity, reduced nucleotide diversity, and a smaller effective population size (Ne) in New Mexico population. Our results depict a significant isolation-by-distance pattern across their distribution, with migration being notably infrequent at river confluences. These findings are pivotal for future conservation and restoration strategies, emphasizing the need to recognize the unique needs of each population.

Spatiotemporal distribution, source apportionment, and ecological risk of bisphenol analogues in a highly urbanized river basin

Bisphenol analogues (BPs), as one of the endocrine disruptors, have received wide attention due to their adverse impacts on ecosystems. However, the seasonal spatiotemporal distribution, source apportionment, and ecological risk of BPs in natural basins are poorly understood. Especially in highly urbanized river basins with the extensive economic development and anthropogenic activities threaten these critical but ecologically fragile regions. In this study, field investigations of BPs in the waters of the entire Qinhuai River Basin (QRB) were conducted in June (before the annual flood period) and August (after the annual flood period) 2023. The Qinhuai River, an important primary tributary of the lower Yangtze River, is located in eastern China and the QRB is characterized by a high population density and dense urbanization. Thirty-two sites were sampled for six types of BPs known to be ubiquitous in the surface water of the QRB. Significant differences in the concentrations of those BPs were found. Specifically, the concentration of total BPs (ΣBPs) was significantly higher before than after the flood period: 20.3–472 ng/L (mean = 146 ng/L) and 14.1–105 ng/L (mean = 35.9 ng/L), respectively. BPA was the main contributor to ΣBPs before the flood, and BPB followed by BPA after the flood. ΣBP concentrations were 12–241 % higher downstream than upstream of wastewater treatment plants (WWTPs). The results of a principal component analysis followed by multiple linear regression (PCA-MLR) suggested that untreated wastewater discharge from the WWTPs is an important source of BPs in the basin, with urban rainfall runoff as another potential source after the flood period. An assessment of the ecological risk of BPs, based on a calculation of the risk quotient, showed that BPA and BPS should be given due attention, and overall ecological risk of BPs pose a low risk to local algae but high and medium risks to invertebrates and fish, respectively.

Zoobentos de arroyos inmisarios del Embalse Río Tercero con especial referencia a la zonación del Río Grande (Calamuchita, ´Córdoba, Argentina)

The structural and functional atributes of zoobenthos in the tributary streams of the Río Tercero reservoir were evaluated. The analysis of Surber samples allows us to determine dominant associations, relative abundance as well as to suggest a tentative approach of trophic structure. The most frequent groups were chironomids and may- flies: Pseudochironomus sp., Pentaneura sp., Baetis sp. and Ephemerella sp. The affinity was high within the same river. In hill stretchs there were more scrapers and in the mouths collectors predominated. It is considered that zonal differentiation of the physiography and physiognomy of each stream basin is expressed in the composition of benthos communities.

Quantifying the contributions of tributaries to large‐river fish populations through mark‐recapture modeling

AbstractObjectiveTributaries may play a vital role in maintaining populations of large river fishes, although the specific contributions of tributaries toward recruitment of river‐wide populations are not often understood. Tributaries may experience fewer cumulative anthropogenic impacts relative to main‐stem rivers and may offer more natural conditions supportive of native fish populations, which may provide opportunities for fish population restoration. Thus, an improved understanding of tributary–main‐stem population dynamics may inform targeted conservation actions for spatially structured populations of large‐river fishes. Colorado River tributaries in the Grand Canyon, Arizona, USA, are a focus of imperiled Humpback Chub Gila cypha conservation, which includes translocations to enhance population redundancy and to expand the overall population. However, the fate of fish dispersed to the main stem has not been thoroughly quantified.MethodsUsing open population mark–recapture models, we quantified the relative contribution of three groups of Humpback Chub, including fish of confirmed tributary origin that were either translocated or produced in situ, and others presumed to be Colorado River main‐stem‐origin fish, to three main‐stem populations. Our specific study objectives were to (1) estimate Colorado River abundances of tributary and main‐stem‐origin fish over time, (2) compare relative group‐specific contributions to three main‐stem populations, and (3) compare group‐specific survival rates of Humpback Chub in the Colorado River and in a tributary where a recent translocation has occurred.ResultTributaries contributed 26% and 43% of the overall abundance in two tributary inflow reach populations and zero in a third, which we attributed to uncharacteristically low tributary survival immediately following translocation. In the main stem, survival of tributary‐origin fish was higher compared to main‐stem‐origin fish, suggesting an advantage of tributary residence.ConclusionOur contrasting results from three different tributary inflow populations highlight the potential role for tributaries in sustaining large‐river fish populations, which may have important implications for long‐term maintenance of river metapopulations.

Seasonal variation of surface water quality and streamflow in Rispana: A tributary of Ganges river, India

AbstractTo evaluate the seasonal changes in quality and quantity of river Rispana (a tributary of river Ganges—Dehradun region of India) water quality index (WQI) was calculated at four major locations by using the weighted arithmetic method. Sixteen samples in all were taken throughout the pre‐monsoon (April 2022), monsoon (July 2022), post‐monsoon (November 2022), and the Winter season (January 2023). The major parameters, namely, temperature, dissolved oxygen (DO), pH, electrical conductivity (EC), and total dissolved solids (TDS), E‐coliform, sulphate, total alkalinity (TA), total hardness (TH), and biochemical oxygen demand (BOD) were considered for calculation of WQI. The WQI varied from minimum 44.53 (good) at site 1 – Kairwaan Gaon during monsoon season to maximum 302.69 (unfit for drinking) at site 4 – Mothrowala during the pre‐monsoon period. In 75% samples quality of water was unfit for domestic purpose and the contributing factors are DO, BOD, and Coliform which exceeds permissible limit in all samples. The major factors attributed for decline in the Rispana water quality are discharge of sewage, commercial sites effluent, and urban runoff. Pre‐monsoon, monsoon, post‐monsoon, and winter had average total coliform levels of 1849.6, 2419.6, 2419.6, and 1546.25, respectively, in MPN units. The average value of E‐coli for the four season vary from 1306.8 to 1888.1 MPN. The pollution load (physico‐chemical parameters and bacteriological factors) increases as the river Rispana flows to downstream in urban locations. Streamflow was observed as very lean except monsoon season (~1500 cfs) due to more extraction of Rispana's fresh water in upstream and unplanned changes in its catchment basin; thus establishes an extensive decline in availability of fresh water sources (Domestic use) in downstream Dehradun city area. In monsoon season, more streamflow (rain water influx) maintains the WQI also in good‐moderate category. The land use/land cover – LULC analysis in Rispana basin area, depicted 71% enhancement in urbanization (24.16%–41.55%) takes place in 15 years’ span (2003–2017). The study establishes the potential causes (natural and anthropogenic) for Rispana deterioration and provides a baseline (quality index) for aquatic and ecological rejuvenation of its watershed by executing a proper management strategy with people participation. This work contributes discernments for effective water resource management to address the smart city objectives and sustainable development goal‐SDG:6, urban and municipal authorities must take cognizance for revival of this domestic water resource.

A 35-Year Record (1987-2022) of Hg Concentrations in Two of the Fish Species Most Consumed by People Living in the Upper Madeira River Basin, Brazilian Amazon Region.

This study presents a 35-year record of total mercury (Hg) concentrations in the detritivore fish Prochilodus nigricans (Curimatã) and the carnivore Cichla pleiozona (Tucunaré), two of the most widely distributed, ecologically important and consumed fish species in the upper Madeira River Basin in the Western Brazilian Amazon. Fish samples from the major Madeira River and marginal lakes and tributaries were compared. Irrespective of site, Hg concentrations were higher in the carnivore fish compared to the detritivore. Hg concentrations increased 5-fold in C. pleiozona in the past three decades, whereas they remained relatively constant in P. nigricans when analyzing the entire 35-year period. When analyzed separately, fish in the main river and marginal lake and tributaries presented the same pattern of Hg variation, with a significant increase in Hg concentrations in the carnivore and in the detritivore in marginal lakes and tributaries but not in the main river. This was in line with the increase in methyl-Hg production in tributaries, mostly associated with deforestation in the past decade in the basin. Although an increase in direct emissions from artisanal gold mining also occurred in the past decade, this caused virtually no impact on fish Hg concentrations, suggesting atmospheric emission and deposition in forests and further export to water systems as an intermediate link with fish Hg concentrations.

Fluvial Response to Environmental Change in Sub-Tropical Australia over the Past 220 Ka

This paper uses a 30 m record of valley alluviation in the Lockyer Creek, a major tributary of the mid-Brisbane River in Southeast Queensland, to document the timing and nature of Quaternary fluvial response. A combination of radiocarbon and optically stimulated luminescence dating reveals a sequence of major cut and fill episodes. The earliest aggradation phase is represented by a basal gravel unit, dating to ~220 ka (marine isotope sub-stage 7d), and although little evidence supports higher fluvial discharges during MIS 5, a MIS 3 fluvial episode characterised by incision and aggradation dates to ~60 ka. A penultimate phase of incision to a depth of 30 m prior to ~14 ka saw the lower Lockyer occupy its current position within the valley floor. The Lockyer Creek shows evidence of only minor fluvial activity during MIS 2, suggesting a drier LGM climate. The appearance of alternating fine- and coarse-grained units at about 2 ka is notable and may represent higher-energy flood conditions associated with a strengthening of El Niño Southern Oscillation activity as observed in the flood of 2011. The aggradation rate for this Holocene floodplain unit is ~11 times higher than the long-term rate.

Progression along the invasion curve: silver carp growth slows temporally in two Missouri River tributaries

Silver carp (Hypophthalmichthys molitrix Valenciennes, 1844) have been invading North American rivers for decades, often altering zooplankton community structure and impacting native fishes. Silver carp invaded eastern South Dakota tributaries of the Missouri River in the early 2000s. Changes in dynamic rate functions can occur as invasive populations move to the latter stages of the invasion curve, but direct temporal assessments of silver carp populations are limited. Our objectives were to compare current growth of silver carp 1) between the Big Sioux and James rivers in South Dakota and 2) with previous growth recorded from the early stages of invasion (2009–2012) in these rivers. We collected silver carp in May and June of 2020–2022 using boat electrofishing and cast netting. We extracted lapilli otoliths for consensus aging from 99 and 82 silver carp from the Big Sioux and James rivers, respectively. We evaluated growth for each population using Bayesian von Bertalanffy models and compared posterior mean length at ages 2–5 to determine the probabilities of differences between rivers and with estimates from the introduction stage. Posterior estimated mean L∞ values were similar between the Big Sioux (714 mm) and James rivers (709 mm); however, the probability that the posterior mean K estimate was greater for silver carp in the James River (0.271) than the Big Sioux River (0.248) was &amp;gt;99.9%. Estimated mean lengths at age 2 were larger in the Big Sioux and James samples than during the introduction stage, but mean lengths at ages 3–5 were smaller. Changes in growth characteristics indicate that growth has slowed in the current establishment stage of invasion from the earlier introduction stage.

Investigating Temporal and Spatial Variations of Nutrient and Trace Metal Loading in Utah Lake (Utah, USA)

Utah Lake is one of the largest freshwater bodies in the West and a valuable resource for agricultural and recreational activities in the region. However, it has suffered elevated trace metal and nutrient levels since the pioneer settlement in 1847. The objectives of this project were as follows: (1) investigate the temporal and spatial variations of trace metal and nutrient concentrations in Utah Lake and its tributaries; (2) model trace metal and nutrient concentrations across the lake using GIS spatial analysis techniques. We collected floc layer sediment samples quarterly as well as monthly water samples for trace metal and nutrient analyses at designated sites. GIS spatial analysis techniques were used to model the trace metal and nutrient concentrations in the lake. Elevated trace metal concentrations in river and lake water samples have been detected, especially in the month of June. The GIS modeling revealed that the highest trace metal and nutrient concentrations were located at the deepest part of the lake and near the Spanish Fork River inlet, respectively. Moreover, the results indicate that Utah Lake is not well mixed horizontally but well mixed vertically. Our findings can help state agencies address issues in water quality and management related to human–environment interactions.