scholarly journals Assessing the value of Cl− and δ18O data in modelling the hydrological behaviour of a small upland catchment in northeast Scotland

2008 ◽  
Vol 39 (5-6) ◽  
pp. 337-358 ◽  
Author(s):  
Sarah M. Dunn ◽  
Jeffrey R. Bacon
Keyword(s):  
Model Simulation ◽  
Shallow Groundwater ◽  
Mixed System ◽  
Residence Times ◽  
Catchment Scale ◽  
Infiltration Excess ◽  
Field Experimentation ◽  
Groundwater Source ◽  
The Uk ◽  
Stream Waters

Model simulation of Cl− and δ18O in stream waters has been investigated as a means of improving interpretation of catchment-scale hydrological processes. The procedure has been evaluated for a small upland catchment which is one of the UK Environmental Change Network sites. Precipitation and stream samples have been analysed for hydrochemical determinands since the mid 1990s and, since November 2004, measurement of δ18O has also been undertaken. A conceptual hydrological model STREAM (STorage REsidence times And Mixing) was applied to the catchment to simulate the hydrology and responses of Cl− and δ18O. Results from model simulations confirmed that the catchment generally behaves as a well-mixed system. The feasibility of flow contributions from a deep groundwater source and infiltration excess runoff was examined, in addition to the apparently dominant shallow groundwater response. The ability to estimate mean residence times and draw strong conclusions about catchment processes was limited by the range of uncertainties in the experimental data and modelling. Integration of the tracer data in the model was found to be of value for probing model sensitivities and developing hypotheses that inform the design of further field experimentation. In this way, the modelling provides key feedback within a catchment learning framework.

scholarly journals Using stable isotope tracers to assess hydrological flow paths, residence times and landscape influences in a nested mesoscale catchment

2005 ◽  
Vol 9 (3) ◽  
pp. 139-155 ◽  
Author(s):  
P. Rodgers ◽  
C. Soulsby ◽  
S. Waldron ◽  
D. Tetzlaff
Keyword(s):  
Stream Water ◽  
Spatial Scales ◽  
Isotopic Signature ◽  
Residence Times ◽  
Catchment Scale ◽  
Valley Bottom ◽  
Flow Paths ◽  
Isotope Tracers ◽  
Periodic Regression ◽  
Stream Waters

Abstract. δ18O measurements in precipitation and stream waters were used to investigate hydrological flow paths and residence times at nested spatial scales in the mesoscale (233 km2) River Feugh catchment in the northeast of Scotland over the 2001-2002 hydrological year. Precipitation δ18O exhibited strong seasonal variation, which although significantly damped within the catchment, was reflected in stream water at six sampling sites. This allowed δ18O variations to be used to infer the relative influence of soil-derived storm flows with a seasonally variable isotopic signature, and groundwater of apparently more constant isotopic composition. Periodic regression analysis was then used to examine the sub-catchment difference using an exponential flow model to provide indicative estimates of mean stream water residence times, which varied between approximately 3 and 14 months. This showed that the effects of increasing scale on estimated mean stream water residence time was minimal beyond that of the smallest (ca. 1 km2) headwater catchment scale. Instead, the interaction of catchment soil cover and topography appeared to be the dominant controlling influence. Where sub-catchments had extensive peat coverage, responsive hydrological pathways produced seasonally variable δ18O signatures in runoff with short mean residence times (ca. 3 months). In contrast, areas dominated by steeper slopes, more freely draining soils and larger groundwater storage in shallow valley-bottom aquifers, deeper flow paths allow for more effective mixing and damping of δ18O indicating longer residence times (>12 months). These insights from δ18O measurements extend the hydrological understanding of the Feugh catchment gained from previous geochemical tracer studies, and demonstrate the utility of isotope tracers in investigating the interaction of hydrological processes and catchment characteristics at larger spatial scales.

scholarly journals Using stable isotope tracers to identify hydrological flow paths, residence times and landscape controls in a mesoscale catchment

2005 ◽  
Vol 2 (1) ◽  
pp. 1-35 ◽  
Author(s):  
P. Rodgers ◽  
C. Soulsby ◽  
S. Waldron ◽  
D. Tetzlaff
Keyword(s):  
Stream Water ◽  
Spatial Scales ◽  
Isotopic Signature ◽  
Residence Times ◽  
Catchment Scale ◽  
Mixing Processes ◽  
Flow Paths ◽  
Isotope Tracers ◽  
Periodic Regression ◽  
Stream Waters

Abstract. δ18O tracer measurements of precipitation and stream waters were used to investigate hydrological flow paths and residence times at nested spatial scales in the mesoscale (233 km2 River Feugh catchment in the northeast of Scotland over the 2001-2002 hydrological year. Precipitation δ18O exhibited strong seasonal variation, which although significantly damped by catchment mixing processes, was reflected in stream water outputs at six sampling sites. This allowed δ18O variations to be used to infer the relative influence of soil-derived storm flows with a seasonally variable isotopic signature, and groundwater of more constant isotopic composition. Periodic regression analysis was then used to examine the sub-catchment differences in the mixing of these two main hydrological sources processes more quantitatively, using an exponential flow model to provide preliminary estimates of mean stream water residence times, which varied between 0.4-2.9 years. This showed that the effects of increasing scale on estimated mean stream water residence time was minimal beyond the smallest (ca. 1 km2 headwater catchment scale. Instead, the interaction of catchment soil cover and topography acted as the dominant influence. Responsive hydrological pathways, associated with peat soils in the headwater sub-catchments, produced seasonally variable δ18O signatures in runoff with short mean residence times (0.4-0.8 years). In contrast, areas dominated by more freely draining soils and larger groundwater storage in shallow aquifers appear to provide effective mixing and damping of variable precipitation inputs implying longer residence times (1.4-2.9 years). These insights from δ18O measurements extend the hydrological understanding of the Feugh catchment gained from previous geochemical tracer studies, and demonstrate the utility of isotope tracers in investigating the interaction of hydrological processes and catchment characteristics at the mesoscale.

scholarly journals Use of Dynamic Analysis to Investigate the Behaviour of Short Neutral Sections in the Overhead Line Electrification

2021 ◽  
Vol 6 (5) ◽  
pp. 62
Author(s):  
John Morris ◽  
Mark Robinson ◽  
Roberto Palacin
Keyword(s):  
Dynamic Analysis ◽  
Dynamic Simulation ◽  
Model Simulation ◽  
Analysis Tool ◽  
Overhead Line ◽  
Element Analysis ◽  
Novel Approach ◽  
Section Model ◽  
The Uk ◽  
Neutral Section

The ‘short’ neutral section is a feature of alternating current (AC) railway overhead line electrification that is often unreliable and a source of train delays. However hardly any dynamic analysis of its behaviour has been undertaken. This paper briefly describes the work undertaken investigating the possibility of modelling the behaviour using a novel approach. The potential for thus improving the performance of short neutral sections is evaluated, with particular reference to the UK situation. The analysis fundamentally used dynamic simulation of the pantograph and overhead contact line (OCL) interface, implemented using a proprietary finite element analysis tool. The neutral section model was constructed using physical characteristics and laboratory tests data, and was included in a validated pantograph/OCL simulation model. Simulation output of the neutral section behaviour has been validated satisfactorily against real line test data. Using this method the sensitivity of the neutral section performance in relation to particular parameters of its construction was examined. A limited number of parameter adjustments were studied, seeking potential improvements. One such improvement identified involved the additional inclusion of a lever arm at the trailing end of the neutral section. A novel application of pantograph/OCL dynamic simulation to modelling neutral section behaviour has been shown to be useful in assessing the modification of neutral section parameters.

scholarly journals The impact of conifer harvesting on stream water quality: the Afon Hafren, mid-Wales

2004 ◽  
Vol 8 (3) ◽  
pp. 503-520 ◽  
Author(s):  
C. Neal ◽  
B. Reynolds ◽  
M. Neal ◽  
H. Wickham ◽  
L. Hill ◽  
...  
Keyword(s):  
Water Quality ◽  
Stream Water ◽  
Strong Support ◽  
Shallow Groundwater ◽  
Water Quality Monitoring ◽  
Quality Data ◽  
Stream Water Quality ◽  
Catchment Scale ◽  
Water Quality Data ◽  
The Impact

Abstract. Results for long term water quality monitoring are described for the headwaters of the principal headwater stream of the River Severn, the Afon Hafren. The results are linked to within-catchment information to describe the influence of conifer harvesting on stream and shallow groundwater quality. A 19-year record of water quality data for the Hafren (a partially spruce forested catchment with podzolic soil) shows the classic patterns of hydrochemical change in relation to concentration and flow responses for upland forested systems. Progressive felling of almost two-thirds of the forest over the period of study resulted in little impact from harvesting and replanting in relation to stream water quality. However, at the local scale, a six years’ study of felling indicated significant release of nitrate into both surface and groundwater; this persisted for two or three years before declining. The study has shown two important features. Firstly, phased felling has led to minimal impacts on stream water. This contrasts with the results of an experimental clear fell for the adjacent catchment of the Afon Hore where a distinct water quality deterioration was observed for a few years. Secondly, there are localised zones with varying hydrology that link to groundwater sources with fracture flow properties. This variability makes extrapolation to the catchment scale difficult without very extensive monitoring. The implications of these findings are discussed in relation to strong support for the use of phased felling-based management of catchments and the complexities of within catchment processes. Keywords: deforestation, water quality, acidification, pH, nitrate, alkalinity, ANC, aluminium, dissolved organic carbon, Plynlimon, forest, spruce, Afon Hafren, podzol

Bigdata-based investigation of heterogeneous migration and population distribution

2021 ◽  
Author(s):  
Zhiwei Fan ◽  
L. Xiong ◽  
Bo Zheng
Keyword(s):  
Census Data ◽  
Population Distribution ◽  
Model Simulation ◽  
Human Mobility ◽  
Economic Systems ◽  
Migration Patterns ◽  
Demographic Trend ◽  
Education Levels ◽  
The Uk ◽  
Migration Probability

Abstract Human mobility is very important in understanding complex social and economic systems. With massive empirical datasets from the China Household Finance Survey and the National Statistics in the UK, we construct a migration probability matrix, and analyze the heterogeneous migration patterns. We then develop a random walk model to dynamically simulate the population distribution. In the stationary state, the resulting population distribution is in good agreement with the real statistical data. For comparison, simulations with an optimized gravity model and other datasets such as the census data in China are also performed. Further, the model simulation is applied to predict the demographic trend with different education levels. Our method could be generally extended to other real communities and internet worlds.

Study on the Influence of Shallow Groundwater Source Heat Pumps on Groundwater Quality in Weifang, China

2014 ◽  
Vol 641-642 ◽  
pp. 97-100
Author(s):  
Qiang Huang ◽  
Wei Ping Wang ◽  
Hai Yan Deng
Keyword(s):  
Groundwater Quality ◽  
Heat Pump ◽  
Shallow Groundwater ◽  
Heat Pumps ◽  
Total Hardness ◽  
Project Area ◽  
Research Objects ◽  
Groundwater Source ◽  
Change Curve

Selecting 4 shallow groundwater source heat pump (GSHP) projects as research objects in Weifang city of Shandong province, China, the groundwater quality in the project area was, observed and analyzed by sampling continuously. The results show that the concentrations of chloride and the total hardness are relatively stable, and there are no apparent changes; In the change curve of TDS in different kind of shallow GSHPs, the worse the sealing condition of the project, the more obvious the rising trend of TDS; The concentration of nitrate is generally on the rise, and the concentration of ammonia appears in the trend of first increased then decreased. Therefore, in the region, the shallow GSHPs are not completely free from contamination in the current technology conditions and the application should be controlled and managed strictly. The observation of shallow GSHPs still need be conducted in a long term.

Catchment microbial dynamics: the emergence of a research agenda

2007 ◽  
Vol 31 (1) ◽  
pp. 59-76 ◽  
Author(s):  
D. Kay ◽  
A. C. Edwards ◽  
R. C. Ferrier ◽  
C. Francis ◽  
C. Kay ◽  
...  
Keyword(s):  
Land Surface ◽  
Evidence Base ◽  
Quantitative Information ◽  
Flux Analysis ◽  
Catchment Scale ◽  
Soil Systems ◽  
The Usa ◽  
Groundwater Streams ◽  
The Uk ◽  
Policy Communities

Parallel policy developments driven in the USA by the Clean Water Act and in Europe by the Water Framework Directive have focused attention on the need for quantitative information on the fluxes of faecal indicator bacteria in catchment systems. Data are required on point and diffuse source loadings, fate and transport of these non-conservative parameters, on the land surface, within soil systems, in groundwater, streams, impoundments and nearshore waters. This new information is needed by regulators to inform Total Maximum Daily Load estimates in the USA and Programmes of Measures in Europe both designed to prevent impairment of water quality at locations where compliance is assessed against health-based standards for drinking, bathing or shellfish harvesting. In the UK, the majority of catchment-scale activity in this field has been undertaken by physical geographers although microbial flux analysis and modelling has received much less attention from the research and policy communities than, for example, the nutrient parameters. This paper charts the policy drivers now operative and assesses the evidence base to support current policy questions. Finally, gaps and priority research questions are identified.

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