Environmental and seasonal controls on riverine dissolved uranium in the Hudson, James, and Ungava bays region, Canada

2012 ◽  
Vol 49 (6) ◽  
pp. 758-771 ◽  
Author(s):  
Eric Rosa ◽  
Claude Hillaire-Marcel ◽  
Bassam Ghaleb ◽  
Terry A. Dick
Keyword(s):  
Flow Control ◽  
Activity Ratio ◽  
Uranium Concentration ◽  
Monitoring Program ◽  
Weighted Average ◽  
Spatiotemporal Variability ◽  
Seasonal Fluctuations ◽  
Study Region ◽  
Field Surveys ◽  
Control Structures

This study documents the spatiotemporal variability of riverine uranium contents and fluxes in rivers discharging into the Hudson, James, and Ungava bays (HJUB). Samples retrieved during a monitoring program of the Koksoak, Great Whale, La Grande, and Nelson rivers were analyzed for dissolved uranium concentration [U] and activity ratio (234U/238U). Field surveys conducted during baseflow and snowmelt in six other rivers of the HJUB basin provided complementary data. It is estimated that altogether, the studied rivers export 3.4 × 105 mol/year of U towards the HJUB, with a discharge weighted average (234U/238U) of 1.27. Two main factors appear to control seasonal fluctuations in dissolved U exports from HJUB rivers: snowmelt and anthropogenic flow control. Under natural hydrological regimes, the dilution of U caused by snowmelt does not compensate for the associated increase in discharge, and riverine U fluxes are intensified during springtime. Contrastingly, the timing of riverine U exports is decoupled from hydroclimatic conditions in rivers affected by flow-control structures. Despite the seasonal variations in riverine U contents, the sampling profiles carried along two of the monitored rivers reveal that within the study region, sample locality is at least as important as sampling time for evaluating riverine U fluxes. In addition, a compilation of data from North American rivers reveals that spatial variations in riverine U contents seem to respond to a prominent lithological control, as rivers draining sedimentary rocks (with abundant carbonates) tend to present overall higher U contents and lower (234U/238U) variability than the rivers of the Canadian Shield.

scholarly journals Detecting spatiotemporal variability in the physicochemical properties of water in the Lower Mearim using remote sensing data

2020 ◽  
Vol 42 ◽  
pp. e32
Author(s):  
George Colares Silva Filho ◽  
Juliana Martins dos Santos ◽  
Paulo Cesar Mendes Villis ◽  
Ingrid Santos Gonçalves ◽  
Isael Coelho Correia ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Water Quality ◽  
Physicochemical Properties ◽  
Monitoring Program ◽  
Remote Sensing Data ◽  
Quality Parameters ◽  
Water Quality Parameters ◽  
Spatiotemporal Variability ◽  
Landsat 8 ◽  
Solids Content

Natural or anthropogenic chemical compounds of different origins often accumulate in estuarine regions. These compounds may alter the water quality. Therefore, It is important to constantly monitor the quality of estuarine regions. A combination of remote sensing and traditional sampling can lead to a better monitoring program for water quality parameters. The objective of this work is to assess the spatiotemporal variability of the physicochemical properties of water in the lower region of the Mearim River and estimate water quality parameters via remote sensing. Samples were collected at 16 points, from Baixo Arari to the mouth of the watershed, using a multiparameter meter and Landsat 8 satellite images. The physicochemical parameters of the water had high salinity levels, between 2.30 and 20.10 parts per trillion; a high total dissolved solids content, between 2.77 and 19.70 g/L; and minimum dissolved oxygen values. Estimating the physicochemical properties of the water via remote sensing proved feasible, particularly in the dry season when there is less cloud cover.

WEIGHTED AVERAGES OF SIRE PROGENY TESTS FOR GROWTH TRAITS IN RECORD OF PERFORMANCE BEEF HERDS

1981 ◽  
Vol 61 (1) ◽  
pp. 35-44 ◽  
Author(s):  
L. R. SCHAEFFER ◽  
J. A. ERIKSSON ◽  
J. W. WILTON
Keyword(s):  
Growth Traits ◽  
Monitoring Program ◽  
Weighted Average ◽  
Test Program ◽  
Weaning Weight ◽  
Declining Enrollment ◽  
Beef Herds ◽  
Progeny Tests ◽  
Annual Trends ◽  
Genetic Trends

Growth records of 281 744 calves born from 1971 to 1978 were used to calculate annual phenotypic and genetic trends for weaning weight and yearling weight. Genetic trends were computed as the weighted average of sire-transmitting abilities obtained from the Record of Performance National Beef Sire Monitoring Program. There were no significant differences between the genetic trends of all calves vs. calves which made a yearling weight for either weaning weight or yearling weight. Annual trends were positive for Angus, Hereford, and Shorthorn breeds, and were negative for Charolais, Limousin, Maine-Anjou and Simmental breeds. The interpretation of annual trends was complicated by the declining enrollment of herds on the test program which could have artificially altered the averages.

Geomorphic and hydrologic consequences of vegetation destruction, Sudbury, Ontario

1976 ◽  
Vol 13 (10) ◽  
pp. 1358-1373 ◽  
Author(s):  
Andrew J. Pearce
Keyword(s):  
Flood Control ◽  
Overland Flow ◽  
Drainage Basin ◽  
Weighted Average ◽  
Design Parameters ◽  
Snowmelt Runoff ◽  
Control Structures ◽  
Denudation Rates ◽  
Complete Destruction ◽  
Erosion Pins

Near-complete destruction of vegetation over 125 km2 near Sudbury, Ontario has increased denudation rates by two orders of magnitude and caused substantial changes in hydrologic regime. Denudation by channeled and unchanneled flow, measured with erosion pins on small plots (2–1000 m2) and a small drainage basin (0.09 km2), averaged 6000 m3/km2 (maximum 24 700 m3/km2) during summer and fall in 1971 and 1972. Maximum denudation occurred during late August to October. Snowmelt runoff in 1972 yielded 1000 m3/km2 of sediment. The weighted average denudation rate, including rates of bedrock disintegration (60–170 m3/km2/y; mean 120 m3/km2/y) is 3700 m3/km2/y.Runoff coefficients average 0.88 for events with return periods between 2 and 10 years; 25% of the May–October rainfall runs off as Hortonian overland flow. Estimated sedimentation rates for three flood-control structures indicate 25% storage depletion over a 50 year period; the return period of floods then able to be retained is reduced to 50 years, compared to the design parameters of 100 year 6 h rainfall (smaller structures) and 100–200 year 12 h rainfall, 6 h P.M.P. (largest structure).

scholarly journals Geostatistical prediction of flow–duration curves in an index-flow framework

2014 ◽  
Vol 18 (9) ◽  
pp. 3801-3816 ◽  
Author(s):  
A. Pugliese ◽  
A. Castellarin ◽  
A. Brath
Keyword(s):  
Cross Validation ◽  
Central Italy ◽  
Weighted Average ◽  
Low Flow ◽  
Mean Annual Precipitation ◽  
Historical Period ◽  
Negative Deviation ◽  
Time Duration ◽  
Study Region ◽  
Flow Duration

Abstract. An empirical period-of-record flow–duration curve (FDC) describes the percentage of time (duration) in which a given streamflow was equaled or exceeded over an historical period of time. In many practical applications one has to construct FDCs in basins that are ungauged or where very few observations are available. We present an application strategy of top-kriging, which makes the geostatistical procedure capable of predicting FDCs in ungauged catchments. Previous applications of top-kriging mainly focused on the prediction of point streamflow indices (e.g. flood quantiles, low-flow indices, etc.); here the procedure is used to predict the entire curve in ungauged sites as a weighted average of standardised empirical FDCs through the traditional linear-weighting scheme of kriging methods. In particular, we propose to standardise empirical FDCs by a reference index-flow value (i.e. mean annual flow, or mean annual precipitation × the drainage area) and to compute the overall negative deviation of the curves from this reference value. We then propose to use these values, which we term total negative deviation (TND), for expressing the hydrological similarity between catchments and for deriving the geostatistical weights. We focus on the prediction of FDCs for 18 unregulated catchments located in central Italy, and we quantify the accuracy of the proposed technique under various operational conditions through an extensive cross-validation and sensitivity analysis. The cross-validation points out that top-kriging is a reliable approach for predicting FDCs with Nash–Sutcliffe efficiency measures ranging from 0.85 to 0.96 (depending on the model settings) very low biases over the entire duration range, and an enhanced representation of the low-flow regime relative to other regionalisation models that were recently developed for the same study region.

scholarly journals Assessment of Precipitation Variability and Trends Based on Satellite Estimations for a Heterogeneous Colombian Region

Hydrology ◽  
2021 ◽  
Vol 8 (3) ◽  
pp. 128
Author(s):  
Enrique Morales-Acuña ◽  
Jean R. Linero-Cueto ◽  
Fausto A. Canales
Keyword(s):  
Sierra Nevada ◽  
Rainfall Variability ◽  
Spatiotemporal Variability ◽  
Monthly Precipitation ◽  
Study Region ◽  
Resources Management ◽  
Heterogeneous Region ◽  
Average Monthly Precipitation

Adequate water resources management includes understanding patterns and spatiotemporal variability of precipitation, as this variable is determinant for ecosystems’ stability, food security, and most human activities. Based on satellite estimations validated through ground measurements from 59 meteorological stations, the objective of this study is to evaluate the long-term spatiotemporal variability and trends of the average monthly precipitation in the Magdalena Department, Colombia, for the 1981–2018 period. This heterogeneous region comprises many different ecoregions in its 23,188 km2 area. The analysis of spatial variability allowed for the determination of four different subregions based on the differences in the average values of precipitation and the degree of rainfall variability. The trend analysis indicates that the current rainfall patterns contradict previous estimates of a progressive decrease in annual averages due to climate change in the study region, as most of the department does not exhibit statistically significant trends, except for the Sierra Nevada de Santa Marta area, where this study found reductions between 10 mm yr−1 and 30 mm yr−1. The findings of this study also suggest the existence of some links between precipitation patterns with regional phenomena of climate variability and solar activity.

scholarly journals Sequential calibration of a water quality model using reach-specific parameter estimates

2017 ◽  
Vol 49 (4) ◽  
pp. 1042-1055 ◽  
Author(s):  
Shushobhit Chaudhary ◽  
C. T. Dhanya ◽  
Arun Kumar
Keyword(s):  
Water Quality ◽  
Oxygen Demand ◽  
Weighted Average ◽  
Sequential Estimation ◽  
Water Quality Model ◽  
Parameter Estimates ◽  
Model Parameters ◽  
Quality Model ◽  
Study Region ◽  
River Stretch

Abstract Calibration is the most critical phase in any water quality modelling process. This study proposes a sequential calibration methodology for any water quality model using reach-specific estimates of model parameters, which would aid in the improved prediction of river water quality characteristics. The proposed methodology accounts for the heterogeneity of river reaches, i.e., diverse characteristics of different reaches on the river stretch. The water quality model, QUAL2K, is coupled with MATLAB, a computing platform, to facilitate sequential estimation of reach-wise model parameters using a grid-based weighted average optimization. The Delhi segment of the Yamuna River is selected as study river stretch. Observations of water quality variables, dissolved oxygen and biochemical oxygen demand are used to calibrate and validate QUAL2K. Desirable performance measures are obtained during the calibration and the validation period. The methodology proves superior to the existing calibration methodologies applied over the study region. The proposed technique also captures the system behaviour effectively, through a systematic, efficient and user-friendly way. The proposed approach is expected to aid decision-makers in formulating better reach-wise management decisions and treatment policies by providing a simpler and efficient way to simulate water quality parameters.

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