scholarly journals Identifying, characterizing and predicting spatial patterns of lacustrine groundwater discharge

2016 ◽  
Author(s):  
Christina Tecklenburg ◽  
Theresa Blume
Keyword(s):  
Flow Field ◽  
Groundwater Flow ◽  
Spatial Patterns ◽  
Lake Water ◽  
Large Scale ◽  
Groundwater Discharge ◽  
Small Scale ◽  
Lake Water Quality ◽  
Near Shore ◽  
Groundwater Flow Field

Abstract. Lacustrine groundwater discharge (LGD) can play an important role for lake water balances and lake water quality. However, quantifying LGD and their spatial patterns is challenging as pronounced spatial variability is paired with a large spatial extent of the aquifer–lake interface and factors controlling LGD patterns are not well understood. We used intensive field measurements including 520 vertical temperature profiles in the near shore area, sediment temperature measurements with a fibre-optic cable along 6 transects from shoreline to shoreline and radon measurements of lake water samples to identify LGD patterns at a lake in north eastern Germany. Sediment characteristics, topographic indices and gradients of the groundwater flow field were considered as potential controls of small scale and large scale LGD patterns. The results revealed that LGD was concentrated in the near shore area with stronger rates and higher variability in the northern part of the lake. LGD generally decreased with distance to shore and offshore LGD was insignificant except for some local hotspots of LGD on steep steps towards the lake bottom. Large scale groundwater inflow patterns were correlated with topography and the groundwater flow field whereas small scale patterns correlated with grainsize distributions of the lake sediment. Regression models using external controls as explanatory variables had limited power to predict LGD rates, but results encourage the use of topographic indices and sediment heterogeneities as an aid for targeted experimental designs.

scholarly journals Identifying, characterizing and predicting spatial patterns of lacustrine groundwater discharge

2017 ◽  
Vol 21 (10) ◽  
pp. 5043-5063 ◽  
Author(s):  
Christina Tecklenburg ◽  
Theresa Blume
Keyword(s):  
Flow Field ◽  
Spatial Variability ◽  
Groundwater Flow ◽  
Spatial Patterns ◽  
Lake Water ◽  
Large Scale ◽  
Groundwater Discharge ◽  
Temperature Profiles ◽  
Near Shore ◽  
Groundwater Flow Field

Abstract. Lacustrine groundwater discharge (LGD) can significantly affect lake water balances and lake water quality. However, quantifying LGD and its spatial patterns is challenging because of the large spatial extent of the aquifer–lake interface and pronounced spatial variability. This is the first experimental study to specifically study these larger-scale patterns with sufficient spatial resolution to systematically investigate how landscape and local characteristics affect the spatial variability in LGD. We measured vertical temperature profiles around a 0.49 km2 lake in northeastern Germany with a needle thermistor, which has the advantage of allowing for rapid (manual) measurements and thus, when used in a survey, high spatial coverage and resolution. Groundwater inflow rates were then estimated using the heat transport equation. These near-shore temperature profiles were complemented with sediment temperature measurements with a fibre-optic cable along six transects from shoreline to shoreline and radon measurements of lake water samples to qualitatively identify LGD patterns in the offshore part of the lake. As the hydrogeology of the catchment is sufficiently homogeneous (sandy sediments of a glacial outwash plain; no bedrock control) to avoid patterns being dominated by geological discontinuities, we were able to test the common assumptions that spatial patterns of LGD are mainly controlled by sediment characteristics and the groundwater flow field. We also tested the assumption that topographic gradients can be used as a proxy for gradients of the groundwater flow field. Thanks to the extensive data set, these tests could be carried out in a nested design, considering both small- and large-scale variability in LGD. We found that LGD was concentrated in the near-shore area, but alongshore variability was high, with specific regions of higher rates and higher spatial variability. Median inflow rates were 44 L m−2 d−1 with maximum rates in certain locations going up to 169 L m−2 d−1. Offshore LGD was negligible except for two local hotspots on steep steps in the lake bed topography. Large-scale groundwater inflow patterns were correlated with topography and the groundwater flow field, whereas small-scale patterns correlated with grain size distributions of the lake sediment. These findings confirm results and assumptions of theoretical and modelling studies more systematically than was previously possible with coarser sampling designs. However, we also found that a significant fraction of the variance in LGD could not be explained by these controls alone and that additional processes need to be considered. While regression models using these controls as explanatory variables had limited power to predict LGD rates, the results nevertheless encourage the use of topographic indices and sediment heterogeneity as an aid for targeted campaigns in future studies of groundwater discharge to lakes.

scholarly journals Harnessing Paleohydrologic Modeling to Solve a Prehistoric Mystery

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Yehuda Levy ◽  
Nigel A. Goring-Morris ◽  
Yoseph Yechieli ◽  
Avihu Burg ◽  
Haim Gvirtzman
Keyword(s):  
Water Resources ◽  
Flow Field ◽  
Groundwater Flow ◽  
Human Evolution ◽  
Hydrological Model ◽  
Groundwater Discharge ◽  
Jordan Valley ◽  
The Past ◽  
Groundwater Flow Field ◽  
The Last Glacial

Abstract A riddle arises at the Epipaleolithic and Neolithic sites that dot the lower Jordan Valley. The area has no water resources yet it has long been a focus of inquiry into the transition from mobile hunter-gatherer to sedentary agriculture-based cultures. How then is there such clear evidence of life here, and particularly at such a critical moment in human evolution? Keen to unravel this conundrum, a numerical hydrological model was devised to simulate the groundwater flow field within the Eastern Aquifer of the Judea and Samaria Mountains during the transition from the last glacial to the current interglacial. The model exhibits a range of groundwater flow regimes that prevailed in the past, demonstrating that there was once much larger groundwater discharge at these sites.

Groundwater flow simulation and its application in GaoSong ore field, China

2018 ◽  
Vol 10 (2) ◽  
pp. 276-284 ◽  
Author(s):  
Gang Chen ◽  
Shiguang Xu ◽  
Chunxue Liu ◽  
Lei Lu ◽  
Liang Guo
Keyword(s):  
Numerical Model ◽  
Flow Field ◽  
Groundwater Flow ◽  
Mine Water ◽  
Permeability Coefficient ◽  
Water Inrush ◽  
Seepage Field ◽  
Groundwater Seepage ◽  
Calculation Results ◽  
Groundwater Flow Field

Abstract Mine water inrush is one of the important factors threatening safe production in mines. The accurate understanding of the mine groundwater flow field can effectively reduce the hazards of mine water inrush. Numerical simulation is an important method to study the groundwater flow field. This paper numerically simulates the groundwater seepage field in the GaoSong ore field. In order to ensure the accuracy of the numerical model, the research team completed 3,724 field fissure measurements in the study area. The fracture measurement results were analyzed using the GEOFRAC method and the whole-area fracture network data were generated. On this basis, the rock mass permeability coefficient tensor of the aquifer in the study area was calculated. The tensor calculation results are used in the numerical model of groundwater flow. After calculation, the obtained numerical model can better represent the groundwater seepage field in the study area. In addition, we designed three different numerical models for calculation, mainly to explore the influence of the tensor assignment of permeability coefficient on the calculation results of water yield of the mine. The results showed that irrational fathom tensor assignment would cause a significant deviation in calculation results.

scholarly journals A Study on the Instantaneous Turbulent Flow Field in a 90-Degree Elbow Pipe with Circular Section

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Shiming Wang ◽  
Cheng Ren ◽  
Yangfei Sun ◽  
Xingtuan Yang ◽  
Jiyuan Tu
Keyword(s):  
Flow Field ◽  
Turbulent Flow ◽  
Flow Separation ◽  
Large Scale ◽  
Small Scale ◽  
Eddy Simulation ◽  
Dean Vortex ◽  
Instantaneous Flow Field ◽  
Instantaneous Pressure ◽  
Turbulent Flow Field

Based on the special application of 90-degree elbow pipe in the HTR-PM, the large eddy simulation was selected to calculate the instantaneous flow field in the 90-degree elbow pipe combining with the experimental results. The characteristics of the instantaneous turbulent flow field under the influence of flow separation and secondary flow were studied by analyzing the instantaneous pressure information at specific monitoring points and the instantaneous velocity field on the cross section of the elbow. The pattern and the intensity of the Dean vortex and the small scale eddies change over time and induce the asymmetry of the flow field. The turbulent disturbance upstream and the flow separation near the intrados couple with the vortexes of various scales. Energy is transferred from large scale eddies to small scale eddies and dissipated by the viscous stress in the end.

Spatial and Temporal Assessment of Titiwangsa Lake Water Quality Using Chemometrics Analysis

2018 ◽  
Vol 7 (3.14) ◽  
pp. 20
Author(s):  
Hafizan Juahir ◽  
Adiana Ghazali ◽  
Azimah Ismail ◽  
Mahadzirah Mohamad ◽  
Firdaus Mohamad Hamzah ◽  
...  
Keyword(s):  
Water Quality ◽  
Lake Water ◽  
Monitoring Program ◽  
Water Quality Monitoring ◽  
Quality Monitoring ◽  
Current Status ◽  
Small Scale ◽  
Lake Water Quality ◽  
Night Time ◽  
Time Period

Titiwangsa Lake is a renowned recreational lake in Kuala Lumpur, Malaysia. The present study was purposely to define the current status of Titiwangsa Lake water quality and propose a water quality monitoring program to conserve and sustain the health of this lake. Samples were collected in January 2017 during the day and night-time periods. Spatial classification using hierarchical agglomerative cluster analysis (HACA) has clustered the sampling stations into low, medium and high contaminated areas. Temporal classification of discriminant analysis (DA) forward stepwise mode has highlighted DO, chlorophyll-a and E-coli are the significant variables. They showed a lower range of data during the day-time period compared to night-time period. DA backward stepwise model showed  significant variables of total suspended solid (TSS) and total phosphate (TP) were higher in concentration during the day-time period as compared to night-time period. The significant of varimax factors (VFs) in the principal component analysis (PCA) might contribute by the landscaping, small-scale domestic wastewater, urban stormwater and land erosion. In a nutshell, based on HACA classification, samples can be collected at only three stations represent each cluster during the next water quality monitoring activities as this could reduce the time and cost of sampling and sample analysis. 

scholarly journals A study of the flow-field evolution and mixing in a planar turbulent jet using direct numerical simulation

2002 ◽  
Vol 450 ◽  
pp. 377-407 ◽  
Author(s):  
S. A. STANLEY ◽  
S. SARKAR ◽  
J. P. MELLADO
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Direct Numerical Simulation ◽  
Large Scale ◽  
Computational Study ◽  
Practical Interest ◽  
Small Scale ◽  
Mixing Process ◽  
Mean Velocity ◽  
Small Scales

Turbulent plane jets are prototypical free shear flows of practical interest in propulsion, combustion and environmental flows. While considerable experimental research has been performed on planar jets, very few computational studies exist. To the authors' knowledge, this is the first computational study of spatially evolving three-dimensional planar turbulent jets utilizing direct numerical simulation. Jet growth rates as well as the mean velocity, mean scalar and Reynolds stress profiles compare well with experimental data. Coherency spectra, vorticity visualization and autospectra are obtained to identify inferred structures. The development of the initial shear layer instability, as well as the evolution into the jet column mode downstream is captured well.The large- and small-scale anisotropies in the jet are discussed in detail. It is shown that, while the large scales in the flow field adjust slowly to variations in the local mean velocity gradients, the small scales adjust rapidly. Near the centreline of the jet, the small scales of turbulence are more isotropic. The mixing process is studied through analysis of the probability density functions of a passive scalar. Immediately after the rollup of vortical structures in the shear layers, the mixing process is dominated by large-scale engulfing of fluid. However, small-scale mixing dominates further downstream in the turbulent core of the self-similar region of the jet and a change from non-marching to marching PDFs is observed. Near the jet edges, the effects of large-scale engulfing of coflow fluid continue to influence the PDFs and non-marching type behaviour is observed.

scholarly journals Grazing Altered the Pattern of Woody Plants and Shrub Encroachment in a Temperate Savanna Ecosystem

2019 ◽  
Vol 16 (3) ◽  
pp. 330 ◽  
Author(s):  
Zhiyong Zhang ◽  
Bo Zhang ◽  
Xiao Zhang ◽  
Xiaohui Yang ◽  
Zhongjie Shi ◽  
...  
Keyword(s):  
Spatial Patterns ◽  
Woody Plants ◽  
Large Scale ◽  
Population Decline ◽  
Grazing Pressure ◽  
Shrub Encroachment ◽  
Small Scale ◽  
Adult Trees ◽  
Aggregated Distribution ◽  
Grazing Pressures

Ulmus pumila-dominated temperate savanna is an important tree-grass complex ecosystem in the Otindag sand land, northern China. To date, few investigations have been undertaken on the spatial patterns and structure of this ecosystem and its driving factors under different grazing pressures. The objective of our study therefore is to explore whether grazing has affected the population structure/pattern of woody plants and shrub encroachment in a temperate savanna ecosystem. Results indicate that species richness and seedlings decreased with increasing grazing pressure. An increase in grazing pressure did not significantly affect adult-tree density, but it hindered the normal regeneration of U. pumila seedlings, further inducing population decline. U. pumila seedlings had a more significant aggregated distribution than juvenile or adult trees. The adult and juvenile trees had an aggregated distribution at the small scale and a random distribution at the large scale. Shrubs also showed a significant aggregated distribution. No clear effect on the spatial patterns of adult trees was observed; however, there was a noticeable effect for juveniles and seedlings under different grazing pressures. U. pumila seedlings had a positive association with their juveniles and Spiraea aquilegifolia, but a negative association with Caragana microphylla. Shrub encroachment occurred with decreasing grazing pressures. In conclusion, overgrazing led to the decline of U. pumila population, but the decrease in grazing pressure increased shrub encroachment in the temperate savanna ecosystem. Moderate grazing management may be a better way to enhance the stability of U. pumila population and reduce shrub encroachment.

Environmental footprint of small-scale, historical mining and metallurgy in the Swedish boreal forest landscape: The Moshyttan blast furnace as microcosm

The Holocene ◽  
2019 ◽  
Vol 29 (4) ◽  
pp. 578-591 ◽  
Author(s):  
Erik Myrstener ◽  
Harald Biester ◽  
Christian Bigler ◽  
William Lidberg ◽  
Carsten Meyer-Jacob ◽  
...  
Keyword(s):  
Blast Furnace ◽  
Lake Water ◽  
Near Infrared ◽  
The Other ◽  
Small Scale ◽  
Charcoal Production ◽  
Lake Water Quality ◽  
The Past ◽  
Stable Conditions ◽  
Iron Blast Furnace

The history of mining and smelting and the associated pollution have been documented using lake sediments for decades, but the broader ecological implications are not well studied. We analyzed sediment profiles covering the past ~10,000 years from three lakes associated with an iron blast furnace in central Sweden, as an example of the many small-scale furnaces with historical roots in the medieval period. With a focus on long-term lake-water quality, we analyzed multiple proxies including geochemistry, pollen and charcoal, diatom composition and inferred pH, biogenic silica (bSi), visible near-infrared spectroscopy (VNIRS)-inferred lake-water total organic carbon (LW-TOC), and VNIRS-inferred sediment chlorophyll (sed-Chl). All three lakes had stable conditions during the middle Holocene (~5000 BCE to 1110 CE) typical of oligo-dystrophic lakes: pH 5.4–5.6, LW-TOC 15–18 mg L−1. The most important diatom taxa include, for example, Aulacoseira scalaris, Brachysira neoexilis, and Frustulia saxonica. From ~1150 CE, decreases in LW-TOC, bSi, and sed-Chl in all three lakes coincide with a suite of proxies indicating disturbance associated with local, small-scale agriculture, and the more widespread use of the landscape in the past (e.g. forest grazing, charcoal production). Most important was a decline in LW-TOC by 30–50% in the three lakes prior to the 20th century. In addition, the one lake (Fickeln) downstream of the smelter and main areas of cultivation experienced a shift in diatom composition (mainly increasing Asterionella formosa) and a 0.6 pH increase coinciding with increasing cereal pollen and signs of blast furnace activity. The pH did not change in the other two lakes in response to disturbance; however, these lakes show a slight increase (0.3–0.5 pH units) because of modern liming. LW-TOC has returned to background levels in the downstream lake and remains lower in the other two.

Analysis of Crank Angle-Resolved Vortex Characteristics Under High Swirl Condition in a Spark-Ignition Direct-Injection Engine

2017 ◽  
Author(s):  
Fengnian Zhao ◽  
Penghui Ge ◽  
Hanyang Zhuang ◽  
David L. S. Hung
Keyword(s):  
Flow Field ◽  
Flow Structure ◽  
High Speed ◽  
Large Scale ◽  
Early Stage ◽  
Direct Injection ◽  
Spark Ignition ◽  
Small Scale ◽  
Vortex Center ◽  
Intake Stroke

In-cylinder air flow structure makes significant impacts on fuel spray dispersion, fuel mixture formation, and flame propagation in spark ignition direct injection (SIDI) engines. While flow vortices can be observed during the early stage of intake stroke, it is very difficult to clearly identify their transient characteristics because these vortices are of multiple length scales with very different swirl motion strength. In this study, a high-speed time-resolved 2D particle image velocimetry (PIV) is applied to record the flow structure of in-cylinder flow field along a swirl plane at 30 mm below the injector tip. First, a discretized method using flow field velocity vectors is presented to identify the location, strength, and rotating direction of vortices at different crank angles. The transients of vortex formation and dissipation processes are revealed by tracing the location and motion of the vortex center during the intake and compression strokes. In addition, an analysis method known as the wind-rose diagram, which is implemented for meteorological application, has been adopted to show the velocity direction distributions of 100 consecutive cycles. Results show that there exists more than one vortex center during early intake stroke and their fluctuations between each cycle can be clearly visualized. In summary, this approach provides an effective way to identify the vortex structure and to track the motion of vortex center for both large-scale and small-scale vortices.

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