scholarly journals Seasonal logging, process response, and geomorphic work

2014 ◽  
Vol 2 (1) ◽  
pp. 117-125 ◽  
Author(s):  
C. H. Mohr ◽  
A. Zimmermann ◽  
O. Korup ◽  
A. Iroumé ◽  
T. Francke ◽  
...  
Keyword(s):  
Quantile Regression ◽  
Overland Flow ◽  
Timber Harvest ◽  
Dry Season ◽  
Sediment Flux ◽  
Slope Instability ◽  
High Temporal Resolution ◽  
Relative Role ◽  
Concentration Data ◽  
Dimensional Parameter

Abstract. Deforestation is a prominent anthropogenic cause of erosive overland flow and slope instability, boosting rates of soil erosion and concomitant sediment flux. Conventional methods of gauging or estimating post-logging sediment flux often focus on annual timescales but overlook potentially important process response on shorter intervals immediately following timber harvest. We resolve such dynamics with non-parametric quantile regression forests (QRF) based on high-frequency (3 min) discharge measurements and sediment concentration data sampled every 30–60 min in similar-sized (∼0.1 km2) forested Chilean catchments that were logged during either the rainy or the dry season. The method of QRF builds on the random forest algorithm, and combines quantile regression with repeated random sub-sampling of both cases and predictors. The algorithm belongs to the family of decision-tree classifiers, which allow quantifying relevant predictors in high-dimensional parameter space. We find that, where no logging occurred, ∼80% of the total sediment load was transported during extremely variable runoff events during only 5% of the monitoring period. In particular, dry-season logging dampened the relative role of these rare, extreme sediment-transport events by increasing load efficiency during more efficient moderate events. We show that QRFs outperform traditional sediment rating curves (SRCs) in terms of accurately simulating short-term dynamics of sediment flux, and conclude that QRF may reliably support forest management recommendations by providing robust simulations of post-logging response of water and sediment fluxes at high temporal resolution.

scholarly journals Seasonal logging, process response, and geomorphic work

2013 ◽  
Vol 1 (1) ◽  
pp. 311-335 ◽  
Author(s):  
C. H. Mohr ◽  
A. Zimmermann ◽  
O. Korup ◽  
A. Iroumé ◽  
T. Francke ◽  
...  
Keyword(s):  
Quantile Regression ◽  
Overland Flow ◽  
Timber Harvest ◽  
Dry Season ◽  
Sediment Flux ◽  
Slope Instability ◽  
High Temporal Resolution ◽  
Sediment Discharge ◽  
Dimensional Parameter ◽  
Water And Sediment

Abstract. Deforestation is a prominent anthropogenic cause of erosive overland flow and slope instability, boosting rates of soil erosion and concomitant sediment flux. Conventional methods of gauging or estimating post-logging sediment flux focus on annual timescales, but potentially overlook important geomorphic responses on shorter time scales immediately following timber harvest. Sediments fluxes are commonly estimated from linear regression of intermittent measurements of water and sediment discharge using sediment rating curves (SRCs). However, these often unsatisfactorily reproduce non-linear effects such as discharge-load hystereses. We resolve such important dynamics from non-parametric Quantile Regression Forests (QRF) of high-frequency (3 min) measurements of stream discharge and sediment concentrations in similar-sized (~ 0.1 km2) forested Chilean catchments that were logged during either the rainy or the dry season. The method of QRF builds on the Random Forest (RF) algorithm, and combines quantile regression with repeated random sub-sampling of both cases and predictors. The algorithm belongs to the family of decision-tree classifiers, which allow quantifying relevant predictors in high-dimensional parameter space. We find that, where no logging occurred, ~ 80% of the total sediment load was transported during rare but high magnitude runoff events during only 5% of the monitoring period. The variability of sediment flux of these rare events spans four orders of magnitude. In particular dry-season logging dampened the role of these rare, extreme sediment-transport events by increasing load efficiency during more moderate events. We show that QRFs outperforms traditional SRCs in terms of accurately simulating short-term dynamics of sediment flux, and conclude that QRF may reliably support forest management recommendations by providing robust simulations of post-logging response of water and sediment discharge at high temporal resolution.

scholarly journals Efficiency of a constructed wetland for wastewaters treatment

2012 ◽  
Vol 24 (3) ◽  
pp. 255-265 ◽  
Author(s):  
Fernanda Travaini-Lima ◽  
Lúcia Helena Sipaúba-Tavares
Keyword(s):  
Chlorophyll A ◽  
Constructed Wetland ◽  
Rainy Season ◽  
Loading Rate ◽  
Dry Season ◽  
Rate Data ◽  
Inlet Channel ◽  
Concentration Data ◽  
Detention Time ◽  
Removal Efficiencies

AIM: The limnological characteristics of three different inlets water of the constructed wetland were compared in terms of concentration data and loading rate data and evaluated the removal efficiencies of nutrients, solids, BOD5, chlorophyll-a and thermotolerant coliforms (TC) by the treatment system; METHODS: The constructed wetland, measuring 82.8 m² and with detention time of 1 hour and 58 minutes in the rainy season and 2 hours and 42 minutes in the dry one, was provided with four species, Cyperus giganteus Vahl, Typha domingensis Pers., Pontederia cordata L. e Eichhornia crassipes (Mart.) Solms. The sampling sites evaluated in the dry (D) and rainy (R) seasons were: inlet water from aquaculture farm = IA; inlet channel of rainwater runoff = IR; inlet from UASB wastewater = IB; outlet wetland = OUT. The conductivity, pH, temperature, dissolved oxygen, alkalinity, BOD5, total soluble and dissolved solids, nitrogen, phosphorus, chlorophyll-a and TC were analyzed. Multivariate analyses, such as Cluster and Principal Components Analysis (PCA), were carried out to group sampling sites with similar limnological characteristics; RESULTS: In the PCA with the concentration data was retained 90.52% variability of data, correlating the inlet IB with high concentrations of conductivity, alkalinity, pH, TC, nutrients and solids. Regarding loading rate data, the PCA was retained 80.9% of the data's total variability and correlated the sampling sites IA D, IA R and OUT R with higher BOD5, chlorophyll-a, TDS, nitrate, nitrite, total-P, temperature, oxygen and water flow. The highest removal efficiencies rates occurred in the dry season, mainly in concentration, with 78% of ammonia, 95.5% of SRP, 94.9% of TSS and 99.9% of TC; CONCLUSIONS: The wetland was highly efficacious in the removal of nutrients, solids, BOD5, chlorophyll-a and TC, mainly during the dry season. The system restructuring to increase the detention time during the rainy season and a pre-treatment of UASB wastewater, can increase the retention of nutrients and solids by wetland.

scholarly journals Water discharge and sediment flux changes in the Lower Mekong River

2005 ◽  
Vol 2 (6) ◽  
pp. 2287-2325 ◽  
Author(s):  
X. X. Lu ◽  
R. Y. Siew
Keyword(s):  
Water Discharge ◽  
Sediment Concentration ◽  
Dry Season ◽  
Water Levels ◽  
Sediment Flux ◽  
Mekong River ◽  
Water Level Fluctuations ◽  
Main Stream ◽  
Discharge Water ◽  
Ecological Changes

Abstract. The Lower Mekong River has witnessed extremely low water levels over the past few years. There is speculation that the changes are a consequence of the construction and operation of the Chinese cascade dams in the upper part of the Mekong main stream, the Lancang River. Dam construction on upper streams can produce a series of induced effects downstream, particularly in terms of water, sediment, channel and ecological changes. The infilling of the Manwan reservoir in 1992 caused water levels to fall to record lows in various parts of the Mekong River, and sediment concentration values decreased similarly. Analyses of discharge and sediment flux at various gauging stations on the Lower Mekong River have indicated a disruption in water discharge, water fluctuations and sediment transport downstream of the Manwan Dam, after its reservoir was infilled in 1992. Dry season flows showed a declining trend, and water level fluctuations in the dry season increased considerably in the post-dam (1993–2000) period. Monthly suspended sediment concentration (SSC) has also decreased significantly in several gauging stations in the post-dam period. The estimation of sediment flux is challenging since the measurements of SSC were sporadic. Our estimation based on the available data indicated that the areas along the upper-middle and lowermost reaches of the Mekong River have experienced a decline in sediment flux, possibly due to sedimentation in the Manwan Dam. However, the decrease is only statistically significant at Chiang Saen. Areas located in the mid-length of the river show less sensitivity to the operation of the Manwan Dam, as sediment fluxes have remained stable or even increased in the post-dam period.

Transportable Automated HRMS Platform Enables Insights into Water Quality Dynamics in Real Time

2020 ◽  
Author(s):  
Michael Stravs ◽  
Christian Stamm ◽  
Christoph Ort ◽  
Heinz Singer
Keyword(s):  
Real Time ◽  
Illicit Drugs ◽  
High Resolution Mass Spectrometry ◽  
High Temporal Resolution ◽  
Enabling Technology ◽  
Real Time Control ◽  
Concentration Data ◽  
Time Control ◽  
Data Points ◽  
Raw Wastewater

Tracking the occurrence of a plethora of chemicals in the aquatic environment at high temporal resolution over extended periods is a huge challenge. Here, we present a transportable high-resolution mass spectrometry platform including a fully automated workflow for advanced data processing. It measured several thousand concentration data points at 20-min intervals over several weeks, providing unprecedented insights into pollution dynamics, e.g. acute pesticide toxicity peaks in a small creek, intra-day variation of illicit drugs in raw wastewater and identifying contamination clusters of unknowns. This enabling technology has potential for researching and managing chemicals in natural and technical environments beyond current possibilities, e.g. real-time control in process engineering and sewer operation (water management and environmental toxicology), industrial surveillance (law enforcement) and wastewater-based epidemiology (public health).

Impact of tile-drainage on the hydro-sedimentary responses of hydromorphic agricultural soils by tracing water and suspended solids from the field to the catchment scale.

2020 ◽  
Author(s):  
Arthur Gaillot ◽  
Célestine Delbart ◽  
Pierre Vanhooydonck ◽  
Olivier Cerdan ◽  
Sébastien Salvador-Blanes
Keyword(s):  
Soil Water ◽  
Suspended Solids ◽  
Overland Flow ◽  
Agricultural Soils ◽  
Subsurface Drainage ◽  
High Temporal Resolution ◽  
Field Scale ◽  
Catchment Scale ◽  
Surface Drainage ◽  
The Impact

<p>Since the 1960’s, large landscape modifications were carried out to improve agriculture productivity. One of these changes was the ploughing of humid plains together with the installation of subsurface drainage, which currently represents 10 % of arable lands in the world. Studies have shown the impact of subsurface drainage on the water regime, and especially decreases in flow peaks. Drainage increases water and sediment connectivity. Less effort was devoted to investigate the impact on the erosion dynamics and very few studies were designed at the catchment scale. However, the understanding of water and suspended solids dynamics from field to catchment outlet is a key to set efficient conservation measures to reduce erosion up. Here we focus on water and suspended solids dynamics from the soil profile scale to the field scale. We propose to trace both water and suspended solids to determine the relative contributions between surface and subsurface sources. Water tracing gives indication on  pathways while suspended solids trace sources (i.e. soil surface vs. deeper soil). The study site is composed of a 5ha field within a 2500 ha agricultural catchment representative of the French agricultural intensive openfield catchments. The studied field is representative of the catchment. It is a cereal crops openfield. Two drainage methods exist in the field: subsurface drainage with drains 120 cm-deep and surface drainage with artificial channels created after the winter seeding. The soil in this field is a loamy clay soil with clay floor at 45 cm of depth. Quantification of suspended solids and water fluxes (surface and subsurface) are monitored at high temporal resolution both at the field (since January 2019) and catchment (since September 2013) scale. Since November 2019, we trace water flows (rain, soil water subsurface flow and overland flow) using water ions and stable isotopes. Suspended solids are analysed through their mineralogy and primary particle size. At the field scale, the first results show a rapid response of surface drainage to rain inputs - confirmed by ions tracing - and suspended solids are mainly coming from surface drainage. Subsurface drainage reacts with a significant delay. Ions tracing shows that subsurface runoff seems to result from a replacement of older soil water by rain inputs.</p>

scholarly journals Water discharge and sediment flux changes over the past decades in the Lower Mekong River: possible impacts of the Chinese dams

2006 ◽  
Vol 10 (2) ◽  
pp. 181-195 ◽  
Author(s):  
X. X. Lu ◽  
R. Y. Siew
Keyword(s):  
Water Discharge ◽  
Sediment Concentration ◽  
Dry Season ◽  
Water Levels ◽  
Sediment Flux ◽  
Mekong River ◽  
Water Level Fluctuations ◽  
Main Stream ◽  
The Past ◽  
Ecological Changes

Abstract. The Lower Mekong River has witnessed extremely low water levels over the past few years. There is speculation that the changes are a consequence of the construction and operation of the Chinese cascade dams in the upper part of the Mekong main stream, the Lancang River. Dam construction on upper streams can produce a series of induced effects downstream, particularly in terms of water, sediment, channel and ecological changes. Analyses of discharge and sediment flux at various gauging stations on the Lower Mekong River have indicated a disruption in water discharge, water fluctuations and sediment transport downstream of the first Chinese dam among the 8 cascades (i.e. the Manwan Dam), after its reservoir was infilled in 1992. Dry season flows showed a declining trend, and water level fluctuations in the dry season increased considerably in the post-dam (1993–2000) period. Monthly suspended sediment concentration (SSC) has also decreased significantly in several gauging stations in the post-dam period. The estimation of sediment flux is challenging since the measurements of SSC were sporadic. Our estimation based on the available data indicated that the areas along the upper-middle and lowermost reaches of the Mekong River have experienced a decline in sediment flux, possibly due to sedimentation in the Manwan Dam. However, the decrease is only statistically significant at the nearest gauging station below the Dam (i.e. Chiang Saen). Areas located in the mid-length of the river show less sensitivity to the operation of the Manwan Dam, as sediment fluxes have remained stable or even increased in the post-dam period.

scholarly journals Parameter uncertainty and sensitivity analysis in sediment flux calculation

2011 ◽  
Vol 8 (1) ◽  
pp. 1469-1506 ◽  
Author(s):  
B. Cheviron ◽  
M. Delmas ◽  
O. Cerdan ◽  
J.-M. Mouchel
Keyword(s):  
Parameter Uncertainty ◽  
Power Laws ◽  
Sediment Flux ◽  
Mathematical Framework ◽  
Concentration Data ◽  
Sediment Fluxes ◽  
Sediment Budgets ◽  
Source Data ◽  
Order Of Magnitude ◽  
Rating Curves

Abstract. This paper examines uncertainties in the calculation of annual sediment budgets at the outlet of rivers. Emphasis is put on the sensitivity of power-law rating curves to degradations of the available discharge-concentration data. The main purpose is to determine how predictions arising from usual or modified power laws resist to the infrequence of concentration data and to relative uncertainties affecting source data. This study identifies cases in which the error on the estimated sediment fluxes remains of the same order of magnitude or even inferior to these in source data, provided the number of concentration data is high enough. The exposed mathematical framework allows considering all limitations at once in further detailed investigations. It is applied here to bound the error on sediment budgets for the major French rivers to the sea.

scholarly journals Lysimeter based evaporation and condensation dynamics in a Mediterranean ecosystem

2021 ◽  
Author(s):  
Sinikka Paulus ◽  
Tarek S. El-Madany ◽  
René Orth ◽  
Anke Hildebrandt ◽  
Thomas Wutzler ◽  
...  
Keyword(s):  
Terrestrial Ecosystems ◽  
Dry Season ◽  
Mediterranean Ecosystem ◽  
High Temporal Resolution ◽  
Wet Season ◽  
Night Time ◽  
Near Surface ◽  
Seasonally Dry ◽  
Soil Adsorption ◽  
One Year

Abstract. The input of liquid water to terrestrial ecosystems is composed of rain and non-rainfall water input (NRWI). The latter comprises dew, fog, and adsorption of atmospheric vapor on soil particle surfaces. Although NRWIs can be relevant to support ecosystem functioning in seasonally dry ecosystems, they are understudied, being relatively small, and therefore hard to measure. In this study, we test a routine for analyzing lysimeter data specifically to determine NRWI. We apply it on one year of data from large high-precision weighing lysimeters at a semi-arid Mediterranean site and quantify that NRWIs occur for at least 3 h on 297 days (81 % of the year) with a mean diel duration of 6 hours. They reflect a pronounced seasonality as modulated by environmental conditions (i.e., temperature and net radiation). During the wet season, both dew and fog dominate NRWI, while during the dry season it is soil adsorption of atmospheric vapor. Although NRWI contributes only 7.4 % to the annual water input NRWI is the only water input to the ecosystem during 15 weeks, mainly in the dry season. Benefitting from the comprehensive set of measurements at the Majadas instrumental site, we show that our findings are in line with (i) independent model simulations forced with (near-) surface energy and moisture measurements and (ii) eddy covariance-derived latent heat flux estimates. This study shows that NRWI can be reliably quantified through high-resolution weighing lysimeters and a few additional measurements. Their main occurrence during night-time underlines the necessity to consider ecosystem water fluxes at high temporal resolution and with 24-hour coverage.

scholarly journals Wind Tunnel Measurement of Turbulent and Advective Scalar Fluxes: A Case Study on Intersection Ventilation

2012 ◽  
Vol 2012 ◽  
pp. 1-13 ◽  
Author(s):  
Libor Kukačka ◽  
Štĕpán Nosek ◽  
Radka Kellnerová ◽  
Klára Jurčáková ◽  
Zbyněk Jaňour
Keyword(s):  
Wind Tunnel ◽  
Flow Direction ◽  
Quadrant Analysis ◽  
High Temporal Resolution ◽  
Scalar Flux ◽  
Concentration Data ◽  
Measured Velocity ◽  
Scalar Fluxes ◽  
Wind Tunnel Measurement ◽  
Street Intersection

The objective of this study is to determine processes of pollution ventilation in the X-shaped street intersection in an idealized symmetric urban area for the changing approach flow direction. A unique experimental setup for simultaneous wind tunnel measurement of the flow velocity and the tracer gas concentration in a high temporal resolution is assembled. Advective horizontal and vertical scalar fluxes are computed from averaged measured velocity and concentration data within the street intersection. Vertical advective and turbulent scalar fluxes are computed from synchronized velocity and concentration signals measured in the plane above the intersection. All the results are obtained for five approach flow directions. The influence of the approach flow on the advective and turbulent fluxes is determined. The contribution of the advective and turbulent flux to the ventilation is discussed. Wind direction with the best dispersive conditions in the area is found. The quadrant analysis is applied to the synchronized signals of velocity and concentration fluctuation to determine events with the dominant contribution to the momentum flux and turbulent scalar flux.

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