Colloid Facilitated Transport of Radioactive Cations in the Vadose Zone: Field Experiments Oak Ridge

Planning MAR Schemes Using Physical Models: Comparison of Laboratory and Field Experiments

Applied Sciences ◽

10.3390/app9183652 ◽

2019 ◽

Vol 9 (18) ◽

pp. 3652

Author(s):

Jana Sallwey ◽

Felix Barquero ◽

Thomas Fichtner ◽

Catalin Stefan

Keyword(s):

Vadose Zone ◽

Laboratory Experiments ◽

Field Experiments ◽

Managed Aquifer Recharge ◽

Physical Models ◽

Aquifer Recharge ◽

Operational Parameters ◽

Flow Processes ◽

Models Comparison ◽

Other Regarding

Infiltration experiments in the context of managed aquifer recharge (MAR) are often conducted to assess the processes influencing the operation of full-scale MAR schemes. For this, physical models such as laboratory experiments and, less often, field experiments are used to determine process specifics or operational parameters. Due to several assumptions, scale-related limitations, and differing boundary conditions, the upscaling of results from the physical models is not straightforward. Investigations often lead to over- or underestimations of flow processes that constrain the translation of results to field-like conditions. To understand the restrictions and potential of different physical models for MAR assessment, surface infiltration experiments in different scales and dimensions, which maintained the same operational parameters, were conducted. The results from the different setups were compared against each other regarding the reproduction water flow in the vadose zone and the influence of parameters such as soil type and climate. Results show that mostly qualitative statements can be made, whereas quantitative analysis through laboratory experiments is limited.

Download Full-text

Estimation of overland flow metrics at semiarid condition: Patagonian Monte

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-9-5837-2012 ◽

2012 ◽

Vol 9 (5) ◽

pp. 5837-5869

Author(s):

M. J. Rossi ◽

J. O. Ares

Keyword(s):

Vadose Zone ◽

Field Experiments ◽

Overland Flow ◽

Statistical Modelling ◽

Life Forms ◽

Water Infiltration ◽

Plant Life Forms ◽

Distributed Modelling ◽

Physically Based ◽

Water Mass Balance

Abstract. Water infiltration and overland flow (WIOF) processes are relevant in considering water partition among plant life forms, the sustainability of vegetation and the design of sustainable hydrological management. WIOF processes in arid and semiarid regions present regional characteristic trends imposed by the prevailing physical conditions of the upper soil as evolved under water-limited climate. A set of plot-scale field experiments at the semi-arid Patagonian Monte (Argentina) was performed in order to estimate infiltration-overland descriptive flow parameters. The micro-relief of undisturbed field plots at z-scale <1 mm was characterized through close-range stereo-photogrammetry and geo-statistical modelling. The overland flow areas produced by experimental runoff events were video-recorded and the runoff speed was measured with ortho-image processing software. Antecedent and post-inflow moisture were measured, and texture, bulk density and physical properties of the soil at the upper vadose zone were estimated. Field data were used to calibrate a physically-based, time explicit model of water balance in the upper soil and overland flows with a modified Green-Ampt (infiltration) and Chezy's (overland flow) algorithms. Modelling results satisfy validation criteria based on the observed overland flow areas, runoff-speed, water mass balance of the upper vadose zone, infiltration depth, slope along runoff-plume direction, and depression storage intensity. The experimental procedure presented supplies plot-scale estimates of overland flow and infiltration intensities at various intensities of water input which can be incorporated in larger-scale hydrological grid-models of arid regions. Findings were: (1) Overland flow velocities as well as infiltration-overland flow mass balances are consistently modelled by considering variable infiltration rates corresponding to depression storage and/or non-ponded areas. (2) The statistical relations presented allow the estimation of theoretical hydrodynamic parameters (Chezy's frictional C, average overland flow depth d*) through measurable characteristics of the surface soil and overland flow kinetics. (3) A protocol of field experiments and coupled time-distributed modelling to 1–2 above is described. The methodology and results obtained in this study are probably relevant to similar arid-semiarid areas of the world.

Download Full-text

Colloid-Facilitated Transport of Radionuclides Through the Vadose Zone

10.2172/836445 ◽

2003 ◽

Author(s):

Markus Flury

Keyword(s):

Vadose Zone ◽

Facilitated Transport

Download Full-text

Colloid-Facilitated Transport of Cesium in Vadose-Zone Sediments: The Importance of Flow Transients

Environmental Science & Technology ◽

10.1021/es100391j ◽

2010 ◽

Vol 44 (19) ◽

pp. 7443-7449 ◽

Cited By ~ 37

Author(s):

Tao Cheng ◽

James E. Saiers

Keyword(s):

Vadose Zone ◽

Facilitated Transport ◽

Flow Transients

Download Full-text

Intercomparison of In Situ Sensors for Ground-Based Land Surface Temperature Measurements

Sensors ◽

10.3390/s20185268 ◽

2020 ◽

Vol 20 (18) ◽

pp. 5268

Author(s):

Praveena Krishnan ◽

Tilden P. Meyers ◽

Simon J. Hook ◽

Mark Heuer ◽

David Senn ◽

...

Keyword(s):

Surface Temperature ◽

Land Surface Temperature ◽

Land Surface ◽

Field Experiments ◽

Prediction Models ◽

Weather Prediction ◽

Surface Air Temperature ◽

Near Surface ◽

Oak Ridge

Land surface temperature (LST) is a key variable in the determination of land surface energy exchange processes from local to global scales. Accurate ground measurements of LST are necessary for a number of applications including validation of satellite LST products or improvement of both climate and numerical weather prediction models. With the objective of assessing the quality of in situ measurements of LST and to evaluate the quantitative uncertainties in the ground-based LST measurements, intensive field experiments were conducted at NOAA’s Air Resources Laboratory (ARL)’s Atmospheric Turbulence and Diffusion Division (ATDD) in Oak Ridge, Tennessee, USA, from October 2015 to January 2016. The results of the comparison of LSTs retrieved by three narrow angle broadband infrared temperature sensors (IRT), hemispherical longwave radiation (LWR) measurements by pyrgeometers, forward looking infrared camera with direct LSTs by multiple thermocouples (TC), and near surface air temperature (AT) are presented here. The brightness temperature (BT) measurements by the IRTs agreed well with a bias of <0.23 °C, and root mean square error (RMSE) of <0.36 °C. The daytime LST(TC) and LST(IRT) showed better agreement (bias = 0.26 °C and RMSE = 0.67 °C) than with LST(LWR) (bias > 1.1 and RMSE > 1.46 °C). In contrast, the difference between nighttime LSTs by IRTs, TCs, and LWR were <0.47 °C, whereas nighttime AT explained >81% of the variance in LST(IRT) with a bias of 2.64 °C and RMSE of 3.6 °C. To evaluate the annual and seasonal differences in LST(IRT), LST(LWR) and AT, the analysis was extended to four grassland sites in the USA. For the annual dataset of LST, the bias between LST (IRT) and LST (LWR) was <0.7 °C, except at the semiarid grassland (1.5 °C), whereas the absolute bias between AT and LST at the four sites were <2 °C. The monthly difference between LST (IRT) and LST (LWR) (or AT) reached up to 2 °C (5 °C), whereas half-hourly differences between LSTs and AT were several degrees in magnitude depending on the site characteristics, time of the day and the season.

Download Full-text