Base Flow Regime Research Articles

Estimating Manning’s coefficient n for sheet flow during rainstorms

Many hydrological and soil erosion models employ Manning’s coefficient (n) to calculate the velocity of sheet flow (SF). However, Manning’s coefficient of SF cannot be estimated accurately due to the strong influences of rainfall, slope gradient, ground surface roughness, sediment size, etc. The effects of rainfall, especially rainstorms, on Manning’s n are usually ignored. In this study, flume tests were conducted with rainfall intensities ranging from 40 to 120 mm h−1, unit width inflow discharges ranging from 0.02 to 0.06 m2 min−1, bed surface roughness values ranging from 0.009 to 0.25 mm, and slope gradients ranging from 3° to 7°. Manning’s n and the correction (Δnr) induced by raindrops were calculated. The results indicated that Manning’s n without rainfall increased with increasing surface roughness and decreasing unit width inflow discharge. In rainstorms, Manning’s n increased with increasing rainfall intensity and surface roughness and decreasing unit width inflow discharge. Δnr increased with increasing rainfall intensity and surface roughness and decreased slightly with increasing unit width inflow discharge. Manning’s n significantly decreased with increasing Froude number (Fr) according to a power function, while Δnr significantly decreased logarithmically with increasing Fr. The Δnr values of this study were greater than 0 when Fr was less than approximately 2.15. For slope gradients of 3°, 5° and 7°, the rainfall increased n by 1.47–49.33 %, 0.44–21.81 % and 0.43–23.94 % for the cases of Fr < 2.15, respectively. This result indicates that the effects of rainfall on Manning’s n of SF cannot be ignored for laminar flows and low Reynolds numbers (<900). Additionally, two empirical equations for predicting Manning’s n and Δnr under rainfall conditions were devised. The correction Δnr due to raindrop impact was affected by the inflow or base flow regimes. This study experimentally provides basic insights into the effects of rainfall on Manning’s coefficient.

Investigating the rocket base flow characteristics and thermal environment of different nozzle configurations considering afterburning

During launch vehicle ascent, the base flow regimes of multi-nozzle rockets become increasingly complex owing to plume interactions. We developed a numerical method using the hybrid RANS/LES approach and the discrete ordinate method to accurately estimate the base thermal environment. Moreover, the finite-rate chemical kinetics are employed to calculate afterburning reactions. The validity of the numerical method is established by achieving a good agreement between the numerical results and wind tunnel data. Subsequently, the reacting and non-reacting flows of the three types of nozzle configurations were simulated at six different altitudes. The numerical results reveal that the plume interactions become stronger with the increase in flight height and total number of nozzles, and the maximum Cp of the four-nozzle rocket was 34.75% and 56.52% higher than that for three- and two-nozzle rocket at 40 km, respectively. After considering the afterburning effect, the maximum temperatures of the two-, three-, and four-nozzle rockets increased by 10.16%, 7.69%, and 5.43%, respectively, owing to the difference in plume collisions. With increasing altitude, the rocket base heating rate distribution changed significantly. The peak heat flux of the rocket base initially increases before decreasing with the maximum value of 147.32 kW/m2, 872.75 kW/m2, and 1395.80 kW/m2 for two-, three-, and four-nozzle rockets, respectively.

Double Diffusive Convection of Power Law Fluids Through Taylor–Couette Flow

The proposed study focuses on the effect of double diffusive convection on the flow structures of power-law fluids between two coaxial cylinders of finite aspect ratios with end caps. We adopted a D2Q9 axisymmetric lattice Boltzmann model to predict the power-law fluid flow and D2Q4 (Lattice Boltzman method) model for azimuthal velocity, concentration, and the temperature. For ( is the solutal and thermal buoyancy forces ratio), fixed Taylor number with increasing Rayleigh number , the thermal base flow regime is more pronounced for the pseudoplastic fluid compared to the dilatant fluid. In addition, the thermal base flow in the annulus is delayed when increases. Thus, the increase of the behavior index has a stabilizing effect on the flow structure. On the other hand, when , the solute buoyancy forces in the annulus prevail over the centrifugal and thermal buoyancy forces, and the flow becomes ultimately a solute base flow for . For , the flow becomes a thermal base flow for . Thus, the mass transfer with negative values has a greater stabilizing effect on the flow structures than with positive .

Review on Thermal Analysis of Automobile Radiator

Radiators are used to transfer thermal energy from one medium to another for the purpose of cooling. Low efficiency heat exchangers used in automotive as radiator may cause to serious dangers for the engine. Hence, thermal scientists and engineers always pursuit modern methods to enhance the heat removal of the engine. It seems nanofluids implementation in automotive cooling system promises to achieve high efficiency radiators. This paper reviews almost all performed studies in this area that are available in the literature. Author collects details about nanoparticles materials and size, base fluid, volume, concentration, flow regime and Reynolds number used in studies. Usually, maximum heat transfer enhancement and maximum need of pumping power that occurs at the highest volumetric concentration of nanoparticles, simultaneously. On the other hand, using nanofluids, due to the enhanced heat carrying capacity of the nanofluids; the pumping power required will also be reduced.

Streamflow Recession Analysis Using Water Height

AbstractRecession analysis is widely used for characterizing aquifer and basin properties based on the falling limb of the hydrograph. However, recession analysis using streamflow discharge requires a relationship (the rating curve) between simultaneous measurements of water height, h, and discharge, Q, across a wide range of flows, which is expensive to obtain, and changes in time. We leverage the relationship between h and Q (typical power law) to perform recession analysis using h directly, thus permitting identification of transient flow regimes, where only h is available. Recession analysis evaluates the rate of change in discharge, −dQ/dt, as a function of discharge, Q, in a bilogarithmic plot where the slope, b, contains information about aquifer characteristics. While values of b are not conserved when replacing Q with h, we find that the variability in values of b within and between events is captured in recession analysis for both Q and h. For example, when considering individual recessions from a large number of watersheds, a change from a smaller b at high discharge/stage to a larger b at lower discharge/stage occurs in most watersheds and suggests a transition to a more long‐lasting, and less drought‐sensitive, baseflow regime. With the advent of low‐cost reliable pressure loggers, as well as satellites that provide global reporting of river stage, recession analysis using water height expands the number of river systems where recession analysis can be conducted and provides the potential for insights into the variability of watershed drainage characteristics without the need for a discharge record.

Impact of dam flushing operations on sediment dynamics and quality in the upper Rhône River, France

The Rhône River (France) has been used for energy production for decades and 21 dams have been built. To avoid problems due to sediment storage, dam flushing operations are periodically organized. The impacts of such operations on suspended particulate matter (SPM) dynamics (resuspension and fluxes) and quality (physico-chemical characteristics and contamination), were investigated during a flushing operation performed in June 2012 on 3 major dams from the Upper Rhône River. The concentrations of major hydrophobic organic contaminants (polychlorinated biphenyls, polycyclic aromatic hydrocarbons - PAHs, bis(2-ethylhexyl)phthalate [DEHP] and 4-n-nonylphenol), trace metal elements, particulate organic carbon (POC) and particle size distribution were measured on SPM samples collected during this event as well as on those obtained from 2011 to 2016 at a permanent monitoring station (150 km downstream). This allows to compare the SPM and contaminant concentrations and fluxes during the 2012 dam flushing operations with those during flood events and baseflow regime. At equal water discharge, mean SPM concentrations during flushing were on average 6–8 times higher than during flood events recorded from 2011 to 2016. While of short duration (19 days), the flushing operations led to the resuspension of SPM and contributed to a third of the mean annual SPM flux. The SPM contamination was generally lower during flushing than during baseflow or flood, probably due to the fact that flushing transports SPM only issued from resuspended sediment, with no autochtonous particles nor eroded soil. The only exception are PAHs and DEHP with higher concentrations during flushing, which must be issued from the resuspension of legacy-contaminated sediments stored behind the dams before the implementation of emission regulations. During flushing, the variations of POC and contaminant concentrations are also mostly driven by particle size. Finally, we propose a list of recommendations for the design of an adequate monitoring network to evaluate the impact of dam flushing operations on large river systems.

Streamflow prediction under extreme data scarcity: a step toward hydrologic process understanding within severely data-limited regions

ABSTRACTStreamflow prediction in ungauged basins is necessary to support water resources management decisions. Herein we refine and evaluate the Streamflow Prediction under Extreme Data-scarcity (SPED) model, a framework designed for streamflow prediction within regions of sparse hydrometeorological observation. With the SPED framework, inclusion of soft data directs optimization to balance runoff efficiency with the selection of hydrologically representative parameters. Here SPED is tested in catchments around the world, including four well-gauged catchments, by mimicking data-scarcity and comparing against data-intensive approaches. By differentiating equifinal models, SPED succeeds where traditional approaches are likely to fail: partially dissimilar reference/target catchments. For instance, in a pair of reference/target catchments with different base flow regimes, SPED outperforms a model calibrated only to maximize efficiency (NSE of 0.54 versus 0.08). SPED performs consistently (NSE range: 0.54–0.74) across the diverse climatological and physiographic settings tested and proves comparable to state-of-the-science methods that use robust data networks.

Groundwater-flow characterization in a multilayered karst aquifer on the edge of a sedimentary basin in western France

On the edge of sedimentary basins, burial of geological layers can involve the formation of confined karst aquifers. In some cases, relationships between confined and unconfined karst aquifers can exist and imply an increased difficulty in delineating contributive areas of karst system outlets with accuracy. This work aims to develop a multi-disciplinary approach to highlight groundwater exchanges between multilayered karst aquifers feeding a single spring.Toulon Springs, located in western France, provides the opportunity to study relationships between two multilayered karst aquifers. Hydrograph and chemograph analysis coupled with principal component analysis (PCA) are used to evaluate groundwater-flow origins on the northern edge of a sedimentary basin. Natural hydrodynamic responses (baseflow recession analysis, auto-cross correlation function) show an important volume of water located in a saturated zone of the Toulon karst system. Significant contrasts in water quality as a function of the hydrological regime (flood, recession, and baseflow regime) and comparison with shallow and deep water show the participation of a deep aquifer supporting the flow of Toulon Springs.

Simulation of dynamic stall using direct-forcing immersed boundary method at low Reynolds number

PurposeThe purpose of this study is simulation of dynamic stall behavior around the Eppler 387 airfoil in the low Reynolds number flow with a direct-forcing immersed boundary (DFIB) numerical model.Design/methodology/approachA ray-casting method is used to define the airfoil geometry. The governing continuity and Navier–Stokes momentum equations and boundary conditions are solved using the DFIB method.FindingsThe purposed method is validated against numerical results from alternative schemes and experimental data on static and oscillating airfoil. A base flow regime and different vortices patterns are observed, in accordance with other previously published investigations. Also, the effects of the reduced frequency, the pitch oscillation amplitude and the Reynolds number are studied. The results show that the reduced frequency has a major effect on the flow field and the force coefficients of the airfoil. On the other hand, the Reynolds number of the flow has a little effect on the dynamic stall characteristics of the airfoil at least in the laminar range.Practical implicationsIt is demonstrated that the DFIB model provides an accurate representation of dynamic stall phenomenon.Originality/valueThe results show that the dynamic stall behavior around the Eppler 387 is different than the general dynamic stall behavior understanding in the shedding phase.

Legacy of contaminant N sources to the NO3\u2212 signature in rivers: a combined isotopic (\u03b415N-NO3\u2212, \u03b418O-NO3\u2212, \u03b411B) and microbiological investigation

Nitrate content of surface waters results from complex mixing of multiple sources, whose signatures can be modified through N reactions occurring within the different compartments of the whole catchment. Despite this complexity, the determination of nitrate origin is the first and crucial step for water resource preservation. Here, for the first time, we combined at the catchment scale stable isotopic tracers (δ15N and δ18O of nitrate and δ11B) and fecal indicators to trace nitrate sources and pathways to the stream. We tested this approach on two rivers in an agricultural region of SW France. Boron isotopic ratios evidenced inflow from anthropogenic waters, microbiological markers revealed organic contaminations from both human and animal wastes. Nitrate δ15N and δ18O traced inputs from the surface leaching during high flow events and from the subsurface drainage in base flow regime. They also showed that denitrification occurred within the soils before reaching the rivers. Furthermore, this study highlighted the determinant role of the soil compartment in nitrate formation and recycling with important spatial heterogeneity and temporal variability.

Urban base flow with low impact development

AbstractA novel form of urbanization, low impact development (LID), aims to engineer systems that replicate natural hydrologic functioning, in part by infiltrating stormwater close to the impervious surfaces that generate it. We sought to statistically evaluate changes in a base flow regime because of urbanization with LID, specifically changes in base flow magnitude, seasonality, and rate of change. We used a case study watershed in Clarksburg, Maryland, in which streamflow was monitored during whole‐watershed urbanization from forest and agricultural to suburban residential development using LID. The 1.11‐km2 watershed contains 73 infiltration‐focused stormwater facilities, including bioretention facilities, dry wells, and dry swales. We examined annual and monthly flow during and after urbanization (2004–2014) and compared alterations to nearby forested and urban control watersheds. We show that total streamflow and base flow increased in the LID watershed during urbanization as compared with control watersheds. The LID watershed had more gradual storm recessions after urbanization and attenuated seasonality in base flow. These flow regime changes may be because of a reduction in evapotranspiration because of the overall decrease in vegetative cover with urbanization and the increase in point sources of recharge. Precipitation that may once have infiltrated soil, been stored in soil moisture to be eventually transpired in a forested landscape, may now be recharged and become base flow. The transfer of evapotranspiration to base flow is an unintended consequence to the water balance of LID. © 2016 The Authors Hydrological Processes Published by John Wiley &amp; Sons Ltd.

Which baseflow metrics should be used in assessing flow regimes of urban streams?

AbstractDetermining the impact of urbanisation on baseflow is complex because of the multiplicity of factors that govern subsurface flows. Although many metrics are available to quantify the baseflow regime, the lack of consensus on which metrics need to be used for baseflow characterisation limit their practical application for stormwater management. We performed principal component and correlation analyses on a set of 32 baseflow metrics to identify a subset of non‐redundant metrics for baseflow characterisation. We compared the results for streamflow time series from natural and urban catchments. We found that a subset of five metrics, including at least one metric from each of the four ecologically significant flow characteristic groups (i.e. magnitude, duration, frequency, and timing), explained most of the variability in baseflow regime for both natural and urban catchments. In addition, we analysed the relationship between this set of metrics and some low flow percentiles obtained from flow duration curves. Flow percentiles were only highly correlated to the magnitude and duration metrics, confirming that flow duration curves could be satisfactorily used for baseflow characterisation, but in combination with metrics representing frequency and timing. Metrics based on integration of the flow duration curve, however, cannot simply substitute the consideration of a suite of metrics. We discuss the practicality of our results with a regional regression study; the analyses show how the metrics can be used to quantify the alterations to baseflow caused by urbanisation, and to determine baseflow restoration objectives for urbanised catchments based on pre‐development baseflow regime. Copyright © 2015 John Wiley &amp; Sons, Ltd.

The impact of stormwater source-control strategies on the (low) flow regime of urban catchments

Stormwater management strategies increasingly recognise the need to emulate the pre-development flow regime, in addition to reducing pollutant concentrations and loads. However, it is unclear whether current design approaches for stormwater source-control techniques are effective in restoring the whole flow regime, and in particular low flows, towards their pre-development levels. We therefore modelled and compared a range of source-control stormwater management strategies, including some specifically tailored towards enhancing baseflow processes. The strategies were assessed based on the total streamflow volume and three low flow metrics. Strategies based on harvesting tanks showed much greater volume reduction than those based on raingardens. Strategies based on a low flow rate release, aimed at mimicking natural baseflow, failed to completely restore the baseflow regime. We also found that the sensitivity of the low flow metrics to the proportion of catchment treated varied amongst metrics, illustrating the importance of metrics selection in the assessment of stormwater strategies. In practice, our results suggest that realistic scenarios using low flow release from source-control techniques may not be able to fully restore the low flow regime, at least for perennial streams. However, a combination of feasibly-sized tanks and raingardens is likely to restore the baseflow regime to a great extent, while also benefitting water quality through the retention and filtration processes.

Impact of Land Use Change and Land Management on Irrigation Water Supply in Northern Java Coast

Impact of Land Use Change and Land Management on Irrigation Water Supply in Northern Java Coast

Using hydrogeochemical signatures of stream water to assess pathways for rainfall events: towards a predictive model

AbstractThanks to its simple division into agricultural and forestry land use, the Corbeira catchment (Galicia, Spain) is used as a case study to build a predictive model using hydrogeochemical signatures. Stream data acquired under recessional flow conditions over a one year period were obtained from a sampling station near the downstream end of the catchment, and using principal component analysis, it is shown that some of the analytical parameters are covariant, and some are negatively correlated. These findings support inferences about the pathways of rainfall in the catchment. Specific signatures may be associated with the dominant hydrological source, either surface runoff or subsurface waters: additionally, the dominant land use in that part of the catchment, where the flow originated, can also be predicted. The dominant runoff shows a strong covariance between suspended solids (SS) and particulate phosphorus (PP), with a clear negative correlation with pH. Dissolved organic carbon (DOC) data are associated with this covariant set when these compounds are available in the soils in question. Dissolved phosphorus, total organic nitrogen and dissolved nitrates are also associated with the same covariant set when the runoff flows through areas of extensive agricultural use. The SS − PP covariance is less significant at lower flows. Typical base flow regimes show a significant covariance between salinity and pH, with a marked negative correlation with SS − PP set, confirming the dominance of subsurface waters in the baseflow, as expected. Seasonally divergent DOC − SS behaviour proves to be a useful tracer for rainfall regimes. The DOC trend shows a sinusoidal annual variation in amplitude, determined by the rainfall regime. As a result, flow from the catchment is dominated by surface water whenever there is synchronicity between the peaks of DOC and SS. Copyright © 2013 John Wiley &amp; Sons, Ltd.

An investigation of monitorability issues for groundwater in the Zachs Knob syncline area, Northeast Tennessee, USA

A dye trace was conducted in 2007 to verify a site conceptual model for groundwater monitorability near an orphan landfill in Sullivan County, Tennessee. The old landfill is in the Valley and Ridge physiographic province. Multiple tracing efforts in this area dating back to 1980 were either unsuccessful or yielded ambiguous results, causing the site to be deemed un-monitorable. Available geologic information, water chemistry data, and subsurface investigation results were compiled to produce a site conceptual model for about 120 ha of land, including the old landfill area. Eosine dye was used as a mimic for potential contamination effects in order to document the monitorability of the local aquifer as part of a hydrogeologic report for a new disposal facility permit. The site exhibits characteristics of a youthful karst setting at the surface. Overflow conduits left behind from a geologically older hydrologic system were found after detailed investigation. These remnant karst features were adjusted to a higher baseflow regime and act as a constraint to the maximum water table elevations in the present hydrologic system. Eosine dye was chosen as the best surrogate leachate after background water and bench scale leachate/dye interaction tests were done. The eosine injection was conducted in a variety of ways across the site to mimic potential leachate release scenarios from the proposed liner system for a new solid waste disposal facility. Eosine was visually detected in local springs and positively detected in some domestic supply and monitoring wells. Subsurface drainage patterns indicated two main groundwater basins in the area of study. Follow-up dye traces with simultaneous injections of pyranine and sulforhodamine B were conducted in 2009 to comply with the request of State regulators. The inferred drainage patterns were confirmed with dye detections at proposed monitoring points for each of the two main groundwater basins.

A three-dimensional PSME model for rotating flows in an annular cavity

A pseudospectral matrix-element (PSME) numerical model is described for the simulation of rotating flows in a three-dimensional annular cavity. Temporal discretisation is implemented using a second-order semi-implicit scheme. Modified compressibility is invoked to handle the coupling between velocity and pressure while maintaining the incompressibility constraint. The governing continuity and Navier–Stokes momentum equations and boundary conditions are discretised using Chebyshev and Fourier collocation formulae. The model is validated against numerical results from alternative schemes and experimental data on rotating flows in an annular cavity. A base flow regime and instability patterns are observed, in accordance with other previously published investigations. It is demonstrated that the PSME model provides an accurate representation of rotating flows in an annular cavity.

MAGNITUDE, FREQUENCY AND DURATION OF INSTREAM FLOWS TO STIMULATE AND FACILITATE CATADROMOUS FISH MIGRATIONS: AUSTRALIAN BASS (MACQUARIA NOVEMACULEATA PERCIFORMES, PERCICHTHYIDAE)

ABSTRACTThe migratory response and behaviour of catadromous Australian bass with regard to hourly mean river flows and water temperatures was assessed over 15 months. Fish movement was assessed using a 75‐km passive acoustic telemetry array in the regulated Shoalhaven River below Tallowa Dam, NSW, Australia. The majority (62%) of downstream pre‐spawning migrations from freshwater to estuarine habitats were stimulated by a series of flow pulses from April to September, but a proportion of fish (38%) commenced downstream migrations under regulated baseflow conditions after a sustained decrease in water temperature to below 15°C in late autumn. Equal numbers of fish undertook post‐spawning upstream return migrations during flow pulses and during regulated baseflow conditions, with regulated baseflow migrants exhibiting a preference for dusk–dawn passage through freshwater pool–riffle sequences. The median magnitude of flow pulses at the time of commencement of downstream and upstream freshwater migrations by Australian bass was not large, equivalent to natural (in the absence of river regulation) flows equalled or exceeded for 56% and 48% of time, respectively. There was no evidence for increased numbers of migrants with increasing flow pulse magnitude, with individual fish ignoring some flow pulses but responding to subsequent events. In regulated rivers, the release of more frequent flow pulses with peak magnitudes approximating the natural 50th flow duration percentile may be more effective in stimulating greater numbers of Australian bass to undertake pre‐spawning and post‐spawning migrations between freshwater and estuarine habitats than the release of a single, larger event. The propensity of Australian bass to also undertake spawning migrations under regulated baseflow conditions emphasizes the need for provision of baseflow regimes in regulated rivers that can facilitate migrations by large bodied fishes. Copyright © 2011 John Wiley &amp; Sons, Ltd.

CAA Simulation and Intensity Based Evaluation of a Model Experiment for Indirect Combustion Noise

The efficient prediction of combustion noise by a zonal approach is discussed. For the so called propagation zone an optimized finite difference method adopted from fan tone noise propagation is applied together with a linear perturbation approach based on the Euler equations. Special attention is payed to the indirect noise generation in the propagation zone, where initially quiet perturbations of the fluid state radiate noise when accelerated or decelerated in a varying base flow regime. A non-isentropic mathematical model is chosen. The approach is compared with a previously published experiment for the assessment of indirect combustion noise. The numerical results show the strong influence of reflections from the inflow boundary of the plenum on the resulting pressure response in the outlet duct. By assuming reasonable reflections from the plenum, the observed time signal of the pressure reaches a reasonable agreement between numerical simulation and experiment. Furthermore, the acoustic intensity is used to show the good quality of the numerical solution. Finally, the intensity based source location identifies the nozzle as a dominant source of sound, with large magnitudes of generation and annihilation of acoustic energy. The source power found in the heated volume is more than two orders of magnitude smaller than in the nozzle. This result again underlines the importance of indirect combustion noise.

Mercury contaminations from historic mining to water, soil and vegetation in Lanmuchang, Guizhou, southwestern China

Concentrations of total mercury and methylmercury (MeHg) were measured in soil and vegetation samples collected from a small area with a long history of Hg-mining. Hg distributions were determined in stream-waters during two sampling periods. Total Hg concentrations in soil and vegetation samples were highly elevated ranging from 0.41 to 610 mg kg − 1 and from 0.02 to 55 mg kg − 1 , respectively. MeHg concentrations varied from 0.41 to 8.8 μg kg − 1 in soil samples and from 0.65 to 5.5 μg kg − 1 in vegetations. The concentrations of total Hg in stream waters varied from 55.0 to 7020 ng L − 1 in the flood-flow regime and from 24.8 to 679 ng L − 1 in the base-flow regime, respectively. Average dissolved Hg concentration was 15.7 ng L − 1 in the wet season and 21.0 ng L − 1 in the dry season. However, particulate Hg was typically > 70% of total Hg in the flood-flow regime. Higher concentrations of particulate Hg primarily originated from summer floods were the major pathway of Hg transportation, which were evidenced by the positive correlation between particulate Hg and total suspended solids (TSS). The contaminated soils and distribution patterns of Hg in the stream-waters may serve as an important source of Hg to the local environment in the study area.