scholarly journals Identification of the contributing area to river discharge during low-flow periods

2021 ◽  
Vol 25 (12) ◽  
pp. 6261-6281
Author(s):  
Maxime Gillet ◽  
Corinne Le Gal La Salle ◽  
Pierre Alain Ayral ◽  
Somar Khaska ◽  
Philippe Martin ◽  
...  
Keyword(s):  
River Discharge ◽  
Discharge Rate ◽  
Unsupervised Classification ◽  
Mixing Model ◽  
Low Flow ◽  
Geochemical Data ◽  
Main River ◽  
Drying Up ◽  
A Minor ◽  
End Members

Abstract. The increasing severity of hydrological droughts in the Mediterranean basin related to climate change raises the need to understand the processes sustaining low flow. The purpose of this paper is to evaluate simple mixing model approaches, first to identify and then to quantify streamflow contribution during low-water periods. An approach based on the coupling of geochemical data with hydrological data allows the quantification of flow contributions. In addition, monitoring during the low-water period was used to investigate the drying-up trajectory of each geological reservoir individually. Data were collected during the summers of 2018 and 2019 on a Mediterranean river (Gardon de Sainte-Croix). The identification of the end-members was performed after the identification of a groundwater geochemical signature clustered according to the geological nature of the reservoir. Two complementary methods validate further the characterisation: rock-leaching experiments and unsupervised classification (k-means). The use of the end-member mixture analysis (EMMA) coupled with a generalised likelihood uncertainty estimate (GLUE) (G-EMMA) mixing model coupled with hydrological monitoring of the main river discharge rate highlights major disparities in the contribution of the geological units, showing a reservoir with a minor contribution in high flow becoming preponderant during the low-flow period. This finding was revealed to be of the utmost importance for the management of water resources during the dry period.

scholarly journals  Identification of the contributing area to river discharge during low-flow period

2021 ◽  
Author(s):  
Maxime Gillet ◽  
Corinne Le Gal La Salle ◽  
Pierre Alain Ayral ◽  
Somar Khaska ◽  
Philippe Martin ◽  
...  
Keyword(s):  
River Discharge ◽  
Discharge Rate ◽  
Unsupervised Classification ◽  
Mixing Model ◽  
Low Flow ◽  
Geochemical Data ◽  
Main River ◽  
Drying Up ◽  
A Minor ◽  
End Members

Abstract. The increasing severity of hydrological droughts in the Mediterranean basin related to climate change raises the need to understand the processes sustaining low-flow. The purpose of this paper is to trial simple mixing model approaches first to identify and then quantify streamflow contribution during low-water periods. An approach based on the coupling of geochemical data with hydrological data allows quantifying flow contributions. In complement, monitoring during the low water period was used to investigate the drying up the trajectory of each geological reservoir individually. Data were collected during the summer of 2018 and 2019 on a Mediterranean river (Gardon de Sainte Croix). The identification of the end-members was performed after the identification of groundwater geochemical signature clustered according to the geological nature of the reservoir. Two complementary methods validate further the characterisation: rock leaching experiments and unsupervised classification (k-means). The use of G-EMMA mixing model coupled with hydrological monitoring of the main river discharge rate shows major disparities in the contribution of the geological units, showing a reservoir with a minor contribution in high flow becoming preponderant during the low-flow period. This finding revealed to be of the utmost importance for managing water resources during the dry period.

Sources of Chlorophenolic Compounds to the Fraser River Estuary

1988 ◽  
Vol 23 (1) ◽  
pp. 55-68 ◽  
Author(s):  
J. H. Carey ◽  
J. H. Hart
Keyword(s):  
River Flow ◽  
River Estuary ◽  
Low Flow ◽  
Fraser River ◽  
Pulp Mills ◽  
Flow Conditions ◽  
Downstream Site ◽  
Upstream Site ◽  
The North ◽  
Main River

Abstract The identity and concentrations of chlorophenolic compounds in the Fraser River estuary were determined under conditions of high and low river flow at three sites: a site upstream from the trifurcation and at downstream sites for each main river arm. Major chlorophenolics present under both flow regimes were 2,4,6-trichlorophenol (2,4,6-TCP), 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP), pentachlorophenol (PCP), tetrachloroguaiacol (TeCG) and a compound tentatively identified as 3,4,5-trichloroguaiacol (3,4,5-TCG). Under high flow conditions, concentrations of the guaiacols were higher than any of the Chlorophenols and concentrations of all five chlorophenolics appeared to correlate. Under low flow conditions, concentrations of chloroguaiacols were higher than Chlorophenols at the upstream site and at the downstream site on the Main Arm, whereas at the downstream site on the North Arm, concentrations of 2,3,4,6-TeCP and PCP were higher than the chloroguaiacols in some samples. Overall, the results indicate that pulp mills upstream from the estuary are important sources of chlorophenolics to the estuary under all flow conditions. Additional episodic inputs of 2,3,4,6-TeCP and PCP from lumber mills occur along the North Arm. When these inputs occur, they can cause the concentrations of Chlorophenols in the North Arm to exceed provisional objectives. If chloroguaiacols are included as part of the objective, concentrations of total chlorophenolics in water entering the estuary can approach and exceed these objectives, especially under low flow conditions.

Pengaruh Curah Hujan dan Debit Air Terhadap Produktivitas Energi Listrik yang Dihasilkan Pada Pembangkit Listrik Tenaga Air (Studi Kasus: Sub Unit PLTA Kracak, Kabupaten Bogor Jawa Barat)

2020 ◽  
Vol 5 (1) ◽  
pp. 56-60
Author(s):  
Wildan Gunawan ◽  
Suyitno Muslim ◽  
Imam Arif Rahardjo
Keyword(s):  
River Discharge ◽  
Research Method ◽  
Rainfall Intensity ◽  
Discharge Rate ◽  
Electrical Power ◽  
Electric Energy ◽  
Energy Productivity ◽  
Rain Fall ◽  
Average Rain

This research is aimed to understand the effects of  rain fall and discharge rate towards hydro electric power plant productivity (case study at Kracak Sub Unit HPP, Bogor Regency Jawa Barat). Multiple regression tecnique analysis is used as research method with quantitative approach for describing the effects of rain fall and discharge rate towards hydro electric energy productivity. Based on Sub Unit PLTA Kracak during a highest down pour in June 2018 has gained electrical power about 173,583 kWh for 15,84 mm rain fall and the lowest rain fall in July 2018 is 0,86 mm only obtain 49,772 kWh electrical power with the average rain fall record in three stations is 8,9592 mm. Mean while, for the highest river discharge rate happened in February is 10,08 m3/detik which produce 198,296 kWh electrical power and the lowest in June that only gained 3,53 m3/detik which produce 49,772 kWh electrical power with the average of river discharge rate in 2018 is only 7,9858 m3/detik. The average of electrical power it self is only 156,0105 kWh for 8,9592 mm of rainfall and 7,9858 m3/detik river discharge rate record in 2018. The conclusion oh this research is the discharge rate in headwaters area is affected by rainfall intensity, but not necessarily affected to hydro electric energy productivity.   ABSTRAK Tujuan dari penelitian ini adalah untuk mengetahui pengaruh curah hujan dan debit air terhadap produktivitas energi listrik yang dihasilkan pada pembangkit listrik tenaga air (Studi Kasus: Sub Unit PLTA Kracak, Kabupaten Bogor Jawa Barat). Metode yang digunakan dalam penelitian ini adalah metode deskriptif dengan pendekatan kuantitatif teknik analisis data regresi berganda untuk mendiskripsikan data penelitian curah hujan dan debit air terhadap produktivitas energi listrik yang dihasilkan. Berdasarkan data hasil penelitian yang diperoleh di Sub Unit PLTA Kracak data curah hujan tertinggi pada tahun 2018 di Bulan Juni sebesar 15,84 mm dapat menghasilkan energi listrik sebesar 173,593 kWh dan terendah di Bulan Juli sebesar 0,86 mm dapat menghasilkan energi listrik sebesar  49,772 kWh dengan rata-rata pertahun 2018 yaitu sebesar 8,9592 mm di tiga stasiun. Sedangkan data debit air pada tahun 2018 tertinggi di Bulan Februari sebesar 10,08 m3/detik dapat menghasilkan energi listrik sebesar 198,296 kWh dan terendah di Bulan Juli sebesar 3,53 m3/detik dapat menghasilkan energi listrik sebesar 49,772 dengan rata-rata pertahun 2018 debit air sebesar 7,9858 m3/detik. Dengan rata-rata curah hujan 8,9592 mm dan debit air 7,9858 m3/detik dapat menghasilkan energi listrik rata-rata pertahun 2018 sebesar 156,0105 kWh selama tahun 2018. Dapat disimpulkan curah hujan tidak berpengaruh langsung terhadap produktivitas energi listrik yang dihasilkan sedangkan debit air berpengaruh terhadap produktivitas energi listrik.

Exemples de mélange de magmas en contexte plutonique: les enclaves des tonalites–granodiorites du massif de Bono (Sardaigne septentrionale)

1989 ◽  
Vol 26 (6) ◽  
pp. 1264-1281 ◽  
Author(s):  
C. Cocirta ◽  
J. B. Orsini ◽  
C. Coulon
Keyword(s):  
Geochemical Data ◽  
Mixing Process ◽  
Calc Alkaline ◽  
Specific Group ◽  
Mineralogical Analysis ◽  
Magmatic Origin ◽  
Interaction Mechanisms ◽  
Compositional Variations ◽  
End Members ◽  
Host Rocks

In calc-alkaline orogenic plutons, the dark xenoliths and their host rocks must be considered the expression of partial mixing of magma.Three associations of this type have been investigated and are illustrated by the Bono pluton (northern Sardinia)— a composite pluton including three intrusives of different nature (tonalitic to granodioritic) and containing a very large number of basaltic xenoliths of magmatic origin. Detailed mineralogical analysis of the two end members in each association, coupled with geochemical data, has determined the major petrogenetic mechanisms intervening in the mixing process in a plutonic setting: temperature equilibration, mechanical exchanges of crystals, chemical exchanges, etc. The most important result of this article, however, is to show that each intrusion is related to a specific group of xenoliths that is characterized by constant FeOt/MgO. The latter reflects the different composition of basaltic components, and it is concluded that each intrusive event is associated with a unique mixing episode. As in volcanic settings, the mixing process may have initiated the intrusion.The extreme compositional variations in the magmatic xenoliths, recognized in several series of orogenic plutons, is explained here by different initial basaltic end members and by variation in the intensity of the interaction mechanisms. [Journal Translation]

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>

scholarly journals Quantifying the differential contributions of deep groundwater to streamflow in nested basins, using both water quality characteristics and water balance

2013 ◽  
Vol 45 (2) ◽  
pp. 200-212 ◽  
Author(s):  
M. C. Ockenden ◽  
N. A. Chappell ◽  
C. Neal
Keyword(s):  
Water Budget ◽  
Quality Characteristics ◽  
Mixing Model ◽  
Rainfall Runoff ◽  
Bicarbonate Concentration ◽  
Deep Groundwater ◽  
Two Component ◽  
End Members ◽  
Chemical Mixing ◽  
High Storage

This paper describes use of a hydro-chemical mixing model and a water budget to investigate the presence of deep runoff pathways in two small, nested sub-catchments of the Eden basin, UK (8.8 km2 Blind Beck and 1.0 km2 Low Hall stream). A linear relationship between bicarbonate concentration and electrical conductivity was used in a two-component mixing model. End-members were identified as a high-solute, deep groundwater and a low-solute, soil-water. The mixing model indicated 69% ± 10% deep groundwater in Low Hall for September–December 2008 and 46% ± 8% in Blind Beck for the same period. The water budget also indicated more deep groundwater in Low Hall stream. These results were consistent with the findings of rainfall–runoff models which also indicated the presence of high storage, deeper pathways.

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.

Geochemistry and time-series analyses of orbitally forced Upper Cretaceous marl–limestone rhythmites (Lehrte West Syncline, northern Germany)

2005 ◽  
Vol 142 (1) ◽  
pp. 31-55 ◽  
Author(s):  
BIRGIT NIEBUHR
Keyword(s):  
Clay Minerals ◽  
Low Frequency ◽  
Geochemical Data ◽  
Carbonate Content ◽  
Element Geochemistry ◽  
Low Magnesium ◽  
Magnesium Calcite ◽  
High Carbonate ◽  
Time Series Analyses ◽  
End Members

A cyclic marl–limestone succession of Middle–Late Campanian age has been investigated with respect to a Milankovitch-controlled origin of geochemical data. In general, the major element geochemistry of the marl–limestone rhythmites can be explained by a simple two-component mixing model with the end-members calcium carbonate and ‘average shale’-like material. Carbonate content varies from 55 to 90%. Non-carbonate components are clay minerals (illite, smectite) and biogenic silica from sponge spicules, as well as authigenically formed zeolites (strontian heulandite) and quartz. The redox potential suggests oxidizing conditions throughout the section. Trace element and stable isotopic data as well as SEM investigations show that the carbonate mud is mostly composed of low-magnesium calcitic tests of planktic coccolithophorids and calcareous dinoflagellate cysts (calcispheres). Diagenetic overprint results in a decrease of 2% δ18O and an increase in Mn of up to 250 ppm. However, the sediment seems to preserve most of its high Sr content compared to the primary low-magnesium calcite of co-occurring belemnite rostra. The periodicity of geochemical cycles is dominated by 413 ka and weak signals between 51 and 22.5 ka, attributable to orbital forcing. Accumulation rates within these cycles vary between 40 and 50 m/Ma. The resulting cyclic sedimentary sequence is the product of (a) changes in primary production of low-magnesium calcitic biogenic material in surface waters within the long eccentricity and the precession, demonstrated by the CaCO3 content and the Mg/Al, Mn/Al and Sr/Al ratios, and (b) fluctuations in climate and continental weathering, which changed the quality of supplied clay minerals (the illite/smectite ratio), demonstrated by the K/Al ratio. High carbonate productivity correlates with smectite-favouring weathering (semi-arid conditions, conspicuously dry and moist seasonal changes in warmer climates). Ti as the proxy indicator for the detrital terrigenous influx, as well as Rb, Si, Zr and Na, shows only low frequency signals, indicating nearly constant rates of supply throughout the more or less pure pelagic carbonate deposition of the long-lasting third-order Middle–Upper Campanian sedimentary cycle.

Occasional floods on the Russian Plain: types, frequency and conditions for the origin in the face of changing climate

2020 ◽  
Author(s):  
Maria Kireeva ◽  
Ekaterina Rets ◽  
Frolova Natalia ◽  
Gorbarenko Artem
Keyword(s):  
Discharge Rate ◽  
Geographic Location ◽  
Low Flow ◽  
Russian Plain ◽  
Amur River Basin ◽  
Russian Science ◽  
Unit Discharge ◽  
Flood Peak ◽  
Natural Zones ◽  
Flood Peaks

<p>In the last decade, floods on the rivers of Russia have become one of the most terrifying natural disasters. Among the catastrophic events, historical flood in Krymsk (2012), Amur River basin (2013), Veliky Ustyug (2016), floods in the Voronezh and Volgograd Region (2018) and Irkutsk and Novgorod Region (2019) can be called.</p><p>Floods on the rivers of the Russian Plain are divided into three main genetic types: rain, snowmelt and mixed. There is also a classification by seasons in which they can be observed. The seasonality of the flood peaks passage depends on the geographic location of the catchment and it’s local features. For most of the rivers of Central Russia, it was traditionally believed that occasional floods are mainly observed in the summer-autumn low flow period. In the summer, they are most often associated with intensive rainfall, and in the fall, with prolonged and drizzling rains. The influence of climate change on the processes of runoff formation has led to a transformation of the conditions for the occurrence of flood peaks and the need to rethink traditional ideas.</p><p>In this work, we analyzed the daily discharge time-series and highlighted flood peaks at 60 hydrological stations located in different natural zones of the European territory of Russia. Occasional flood peaks were divided into 5 classes, taking into account the time of their formation and genesis: a) thaw peaks during the winter low flow period, b) mixed peaks during the winter low flow period, c) mixed peaks during the rise of the main seasonal (snowmelt) wave, d) rain peaks during the decline of the main seasonal (snowmelt) wave, e) rain peaks during the summer-autumn low flow period.</p><p>The total number of peaks, the maximum peak discharge and its unit discharge rate, the beginning, end and duration of the flood peak, the total runoff volume of the flood, the relative stability of the low-flow period were estimated.</p><p>On average, the number of flood peaks in the rivers of the study area varies from 1 to 8 events per year. The greatest number of flood peaks is characteristic of the foothills of the Caucasus and the rivers of the Kola Peninsula, as well as the most western regions - the upper reaches of the Seversky Donets, Dnieper, and Western Dvina. The maximum unit discharges of rain floods on average is from 5 to 50 and more and thaw from 2 to 20 l/s*km<sup>2</sup>. The spatial pattern shows that higher unit discharges are typical for the windward western slopes of the hills, and relatively low ones are observed on the leeward, eastern slopes. In general, unit discharge rats increase from southwest to east, northeast.</p><p>In recent decades, the seasonality of flood peaks has changed significantly, they began to be observed in almost any period of the year, the number of events in the pre-flood period increased, as well as in the autumn period, at the time of transition to negative air temperatures.</p><p>The study was supported by the Russian Science Foundation grant No.19-77-10032</p>

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