scholarly journals Trace elements in mussel shells from the Brazos River, Texas: environmental and biological control

2019 ◽  
Author(s):  
Alexander A. VanPlantinga ◽  
Ethan L. Grossman
Keyword(s):  
River Discharge ◽  
Distribution Patterns ◽  
Low Flow ◽  
Clumped Isotopes ◽  
Metabolic Rates ◽  
Brazos River ◽  
Growth Increments ◽  
Shell Chemistry ◽  
Mussel Shells ◽  
Discharge Patterns

Abstract. In sclerochronology, understanding the drivers of shell chemistry is necessary in order to use shells to reconstruct environmental conditions. We measured the Mg, Ca, Sr, Ba, and Mn contents in water samples and in the shells of two freshwater mussels (Amblema plicata and Cyrtonaias tampicoensis) from the Brazos River, Texas to test their reliability as environmental archives. Shells were analyzed along growth increments using age models established with stable and clumped isotopes. Shells were also examined with cathodoluminescence (CL) microscopy to map Mn / Ca distribution patterns. Sr / Ca correlated with Mn / Ca, while Mg / Ca and Ba / Ca showed no clear trends. Mn / Ca correlated inversely with the log of river discharge. Because dissolved and inorganic particulate sources of manganese are low during low flow, peak Mn / Ca values may come from elevated feeding or metabolic rates. Shell Mn / Ca values were used to reconstruct river discharge patterns, which, to our knowledge, has previously only been performed with shell chemistry using oxygen isotopes.

Rapid morphological evolution during beach breaching and closure at a bar-built estuary

2021 ◽  
Author(s):  
Mara Orescanin ◽  
Tyonna McPherson ◽  
Paul Jessen
Keyword(s):  
Sediment Transport ◽  
River Discharge ◽  
Morphological Evolution ◽  
Water Levels ◽  
Low Flow ◽  
Long Term Stability ◽  
Erosion Rates ◽  
Discharge Rates ◽  
Elevation Changes ◽  
Elevated Water

<p>The Carmel River runs 58 km from the Santa Lucia Mountains through the Carmel Valley eventually entering a lagoon at Carmel River State Beach near Carmel, California, USA. During the dry summer months, the lagoon is closed, with no connection to the coastal ocean.  However, during the wet winter months, the river often breaches through the lagoon allowing water to freely flow between the river and Carmel Bay. Sediment transport, in part owing to river discharge and in part owing to ocean forcing (tides and waves), contributes heavily to whether the lagoon is open or closed: when there are low flow conditions, waves and tides can decrease flow rates in the breach, allowing sediment to settle. The sediment budget is expected to be a closed system, owing to the rocky headlands and long-term stability (no yearly regression or transgression) of the shoreline, despite managed attempts to control breach and closure timing. However, it is currently unknown 1) how velocity profiles evolve during breaching, and 2) how much sediment moves during such an event. The hypothesis is that the breach mouth can completely disappear and re-emerge over a single breach-closure cycle, leading to meter-scale daily accretion and erosion rates of berm height if berm elevation is significantly lower than the expected steady-state berm height. Furthermore, it is hypothesized that during active breaching, discharge rates through the breach channel are larger than upstream river discharge rates owing to elevated water levels within the back lagoon. This study uses a RiverSurveyor M9 Acoustic Doppler Profiler to measure outflow discharge and GPS topographic surveys to quantify elevation changes. A velocity profile can be built which will estimate the sediment transport potential within the breach. The information obtained will help identify and better understand the river discharge thresholds which contribute to frequent breaching as well as estimates of morphological evolution during breaching, which are currently unknown, and can assist in determining likelihood of successful managed breaching and closure events. </p>

Changes in Latvian river discharge regime at the turn of the century

2012 ◽  
Vol 44 (3) ◽  
pp. 554-569 ◽  
Author(s):  
Elga Apsīte ◽  
Ilze Rudlapa ◽  
Inese Latkovska ◽  
Didzis Elferts
Keyword(s):  
River Runoff ◽  
River Discharge ◽  
Large Scale ◽  
Hydrological Regime ◽  
Turn Of The Century ◽  
Significant Trend ◽  
Low Flow ◽  
Data Series ◽  
Discharge Data ◽  
Baltic Countries

The study deals with turn-of-the-century changes in the total annual river runoff distribution and high and low flows in Latvia, covering river basins within four hydrological districts which vary according to size and physiographical conditions. Mathematical statistical methods were applied in the analysis of river discharge data series for two study periods of 1951–2009 and 1881–2009. The present results confirm the basic statement concerning the Baltic countries that major significant changes in river runoff during the last two decades have occurred between spring (decrease) and winter (increase) seasons. Mostly insignificant changes in summer runoff and significant/insignificant changes in autumn runoff were found. Analysis shows that a statistically significant trend of increase in low flow for the cold period and a significant trend of decrease in the high discharge and coefficient d of uneven runoff distribution were detected. Changes in river hydrological regime are mainly caused by changes in large-scale atmospheric circulation processes following climate warming, which has taken place. Latvian river hydrography has therefore changed and become more similar to Western European rivers.

scholarly journals Climate change and its impacts on river discharge in two climate regions in China

2015 ◽  
Vol 19 (11) ◽  
pp. 4609-4618 ◽  
Author(s):  
H. Xu ◽  
Y. Luo
Keyword(s):  
Climate Change ◽  
River Discharge ◽  
Climate Change Impacts ◽  
High Flow ◽  
Global Climate Models ◽  
Assessment Tools ◽  
Low Flow ◽  
Climate Projections ◽  
Seasonal Temperature ◽  
Pronounced Increase

Abstract. Understanding the heterogeneity of climate change and its impacts on annual and seasonal discharge and the difference between median flow and extreme flow in different climate regions is of utmost importance to successful water management. To quantify the spatial and temporal heterogeneity of climate change impacts on hydrological processes, this study simulated river discharge in the River Huangfuchuan in semi-arid northern China and in the River Xiangxi in humid southern China. The study assessed the uncertainty in projected discharge for three time periods (2020s, 2050s and 2080s) using seven equally weighted GCMs (global climate models) for the SRES (Special Reports on Emissions Scenarios) A1B scenario. Climate projections that were applied to semi-distributed hydrological models (Soil Water Assessment Tools, SWAT) in both catchments showed trends toward warmer and wetter conditions, particularly for the River Huangfuchuan. Results based on seven GCMs' projections indicated changes from −1.1 to 8.6 °C and 0.3 to 7.0 °C in seasonal temperature and changes from −29 to 139 % and −32 to 85 % in seasonal precipitation in the rivers Huangfuchuan and Xiangxi, respectively. The largest increases in temperature and precipitation in both catchments were projected in the spring and winter seasons. The main projected hydrologic impact was a more pronounced increase in annual discharge in the River Huangfuchuan than in the River Xiangxi. Most of the GCMs projected increased discharge in all seasons, especially in spring, although the magnitude of these increases varied between GCMs. The peak flows were projected to appear earlier than usual in the River Huangfuchuan and later than usual in the River Xiangxi, while the GCMs were fairly consistent in projecting increased extreme flows in both catchments with varying magnitude compared to median flows. For the River Huangfuchuan in the 2080s, median flow changed from −2 to 304 %, compared to a −1 to 145 % change in high flow (Q05 exceedance threshold). For the River Xiangxi, low flow (Q95 exceedance threshold) changed from −1 to 77 % and high flow changed from −1 to 62 %, while median flow changed from −4 to 23 %. The uncertainty analysis provided an improved understanding of future hydrologic behavior in the watershed. Furthermore, this study indicated that the uncertainty constrained by GCMs was critical and should always be considered in analysis of climate change impacts and adaptation.

scholarly journals Multi-variate infilling of missing daily discharge data on the Niger basin

2021 ◽  
Author(s):  
Ganiyu Titilope Oyerinde ◽  
Agnide E. Lawin ◽  
Oluwafemi E. Adeyeri
Keyword(s):  
Missing Data ◽  
River Discharge ◽  
Missing Values ◽  
Spatial Scales ◽  
Gap Filling ◽  
Discharge Data ◽  
Flow Duration ◽  
Daily Discharge ◽  
Flow Duration Curves ◽  
Discharge Patterns

Abstract The Niger basin have experienced historical drought episodes and floods in recent times. Reliable hydrological modelling has been hampered by missing values in daily river discharge data. We assessed the potential of using the Multivariate Imputation by Chained Equations (MICE) to estimate both continuous and discontinuous daily missing data across different spatial scales in the Niger basin. The study was conducted on 22 discharge stations that have missing data ranging from 2% to 70%. Four efficiency metrics were used to determine the effectiveness of MICE. The Flow Duration Curves (FDC) of observed and filled data were compared to determine how MICE captured the discharge patterns. Mann-Kendall, Modified Mann-Kendall, Pettit and Sen's Slope were used to assess the complete discharge trends using the gap-filled data. Results shows that MICE near perfectly filled the missing discharge data with Nash-Sutcliffe Efficiency (NSE) range of 0.94–0.99 for the calibration (1992–1994) period. Good fits were obtained between FDC of observed and gap-filled data in all considered stations. All the catchments showed significantly increasing discharge trend since 1990s after gap filling. Consequently, the use of MICE in handling missing data challenges across spatial scales in the Niger basin was proposed.

Brachiopod Shells: Recorders of the Present and Keys to the Past

2001 ◽  
Vol 7 ◽  
pp. 117-144 ◽  
Author(s):  
Nancy Buening
Keyword(s):  
Time Interval ◽  
Growth Line ◽  
Seasonal Temperature ◽  
Ambient Seawater ◽  
Growth Increments ◽  
Shell Chemistry ◽  
Structural Growth ◽  
History Of ◽  
Shell Carbonate ◽  
The Individual

The Brachiopod shell provides more than protection for the organism dwelling within: it provides a structural record of growth and a chemical record of fluctuations in the environment in which it formed. Typically, a shell formed by an accretionary process will have growth lines visible on the shell surface that can be used to measure chronological age directly. This is common in many fossil and modern bivalve molluscs where growth bands are prominent (see, e.g., Lutz and Rhoads, 1980; Jones, 1983; Tanabe, 1988). However, growth increments are not always so easily identified in other shelled organisms. For instance, growth lines in brachiopod shells are often indistinct, and the time interval represented by each growth line is uncertain. When growth information can't be obtained directly, we must turn to an alternative method (Jones and Gould, 1999). Fortunately, periodicities in the chemical composition of a shell may serve as proxies for age (e.g., Buening and Carlson, 1992). The shell chemistry of brachiopods reflects, for the most part, the changes in chemistry of the surrounding seawater. For instance, partitioning of oxygen isotopes (18O/16O ratio) in shell carbonate is sensitive to temperature (e.g., Hoefs, 1997). Thus, if brachiopods precipitate shells in water that is affected by seasonal temperature variations, then fluctuations of the18O/16O ratio of the shell should provide a record of annual temperature variation in ambient seawater. Consequently, this seasonal record may be used in conjunction with structural growth lines to reconstruct the life history of the individual, as well as the local environmental conditions in which the brachiopod lived.

scholarly journals A water availability and low-flow analysis of the Tagliamento River discharge in Italy under changing climate conditions

2012 ◽  
Vol 16 (3) ◽  
pp. 1033-1045 ◽  
Author(s):  
L. N. Gunawardhana ◽  
S. Kazama
Keyword(s):  
River Discharge ◽  
General Circulation ◽  
Flow Analysis ◽  
Low Flow ◽  
Climate Conditions ◽  
Changing Climate ◽  
Time Period ◽  
Lower Elevation ◽  
Pearson Type ◽  
Tagliamento River

Abstract. This study estimated the effects of projected variations in precipitation and temperature on snowfall-snowmelt processes and subsequent river discharge variations in the Tagliamento River in Italy. A lumped-parameter, non-linear, rainfall-runoff model with 10 general circulation model (GCM) scenarios was used. Spatial and temporal changes in snow cover were assessed using 15 high-quality Landsat images. The 7Q10 low-flow probability distribution approximated by the Log-Pearson type III distribution function was used to examine river discharge variations with respect to climate extremes in the future. On average, the results obtained for 10 scenarios indicate a consistent warming rate for all time periods, which may increase the maximum and minimum temperatures by 2.3 °C (0.6–3.7 °C) and 2.7 °C (1.0–4.0 °C), respectively, by the end of the 21st century compared to the present climate. Consequently, the exponential rate of frost day decrease for 1 °C winter warming in lower-elevation areas is approximately three-fold (262%) higher than that in higher-elevation areas, revealing that snowfall in lower-elevation areas will be more vulnerable under a changing climate. In spite of the relatively minor changes in annual precipitation (−17.4 ~ 1.7% compared to the average of the baseline (1991–2010) period), snowfall will likely decrease by 48–67% during the 2080–2099 time period. The mean river discharges are projected to decrease in all seasons, except winter. The low-flow analysis indicated that while the magnitude of the minimum river discharge will increase (e.g. a 25% increase in the 7Q10 estimations for the winter season in the 2080–2099 time period), the number of annual average low-flow events will also increase (e.g. 16 and 15 more days during the spring and summer seasons, respectively, in the 2080–2099 time period compared to the average during the baseline period), leading to a future with a highly variable river discharge. Moreover, a consistent shift in river discharge timing would eventually cause snowmelt-generated river discharge to occur approximately 12 days earlier during the 2080–2099 time period compared to the baseline climate. These results are expected to raise the concern of policy makers, leading to the development of new water management strategies in the Tagliamento River basin to cope with changing climate conditions.

scholarly journals Changes in water discharges of the Baltic states rivers in the 20th century and its relation to climate change

2007 ◽  
Vol 38 (4-5) ◽  
pp. 401-412 ◽  
Author(s):  
A. Reihan ◽  
T. Koltsova ◽  
J. Kriauciuniene ◽  
L. Lizuma ◽  
D. Meilutyte-Barauskiene
Keyword(s):  
Climate Change ◽  
Air Temperature ◽  
River Discharge ◽  
Water Resource Management ◽  
Global Climate ◽  
Kendall Test ◽  
Low Flow ◽  
Baltic States ◽  
Temperature And Precipitation ◽  
The Baltic

The river discharge changes in three Baltic States and its relation to changes in the main climatic variables such as precipitation and air temperature were analyzed using observed data and methods of empirical statistical analysis. The study is important for the development of efficient water resource management systems and validation of climate change impact models. The application of the Mann-Kendall test reveals that a significant increasing trend in winter air temperature and precipitation was determined for all 3 investigated periods (1923–2003, 1941–2003 and 1961–2003). The same trend was found for the winter and annual discharge time series. No trend was observed for the spring, summer and autumn seasonal streamflow and summer low flow series for most of the Baltic region. In general the relation between the main meteorological and hydrological parameters and the tendency in river discharge trends is common for all of the Baltic States, and might be associated with the regional impacts of global climate change.

scholarly journals A water availability and low-flow analysis of the Tagliamento River discharge in Italy under changing climate conditions

2012 ◽  
Vol 9 (1) ◽  
pp. 139-173 ◽  
Author(s):  
L. N. Gunawardhana ◽  
S. Kazama
Keyword(s):  
River Discharge ◽  
Flow Analysis ◽  
Low Flow ◽  
Present Climate ◽  
Climate Conditions ◽  
Changing Climate ◽  
Time Period ◽  
Lower Elevation ◽  
Tagliamento River ◽  
Time Periods

Abstract. This study estimated the effects of projected variations in precipitation and temperature on snowfall-snowmelt processes and subsequent river discharge variations in the Tagliamento River in Italy. A lumped-parameter, non-linear, rainfall-runoff model with 10 general circulation model (GCM) scenarios was used to capture river response variations attributed to climate-driven changes in 3 future time periods in comparison to the present climate. Spatial and temporal changes in snow cover were assessed using 15 high-quality Landsat images collected during the 2001–2003 time period, which were further used to define different elevation bands to incorporate the elevation effects on snowfall-snowmelt processes. The 7Q10 low-flow probability distribution approximated by the Log-Pearson type III distribution function was used to examine river discharge variations with respect to climate extremes in the future. On average, the results obtained for 10 scenarios indicate a consistent warming rate for all time periods, which may increase the maximum and minimum temperatures by 2.3 °C (0.6–3.7 °C) and 2.7 °C (1.0–4.0 °C), respectively, by the end of the 21st century compared to the present climate. Consequently, the exponential rate of frost day decrease for 1 °C winter warming in lower-elevation areas is approximately three-fold (262%) higher than that in higher-elevation areas, revealing that snowfall in lower-elevation areas will be more vulnerable under a changing climate. In spite of the relatively minor changes in annual precipitation (−17.4 ~ 1.7% compared to the average of the baseline (1991–2010) period), snowfall will likely decrease by 48–67% during the 2080–2099 time period. The accumulated effects of a decrease in winter precipitation and an increase in evapotranspiration demand on winter river discharge will likely be compensated for by early snowmelt runoff due to increases in winter temperatures. Nevertheless, the river discharge in other seasons will decrease significantly, with a 59% decrease in the predicted river discharge in October over 100 yr. The low-flow analysis indicated that while the magnitude of the minimum river discharge will increase (e.g. a 25% increase in the 7Q10 estimations for the winter season in the 2080–2099 time period), the number of annual average low-flow events will also increase (e.g. 16 and 15 more days during the spring and summer seasons, respectively, in the 2080–2099 time period compared to the average during the baseline period), leading to a future with a highly variable river discharge. Moreover, a consistent shift in river discharge timing would eventually cause snowmelt-generated river discharge to occur approximately 12 days earlier during the 2080–2099 time period compared to the baseline climate. These results are expected to raise the concern of policy makers, leading to the development of new water management strategies in the Tagliamento River basin to cope with changing climate conditions.

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