scholarly journals Discovery of a large subsoil nitrate reservoir in an arroyo floodplain and associated aquifer contamination

Geology ◽  
2021 ◽  
Author(s):  
Benjamin S. Linhoff ◽  
John J. Lunzer
Keyword(s):  
Vadose Zone ◽  
Chihuahuan Desert ◽  
Monsoon Season ◽  
Zone Model ◽  
Desert Plant ◽  
Lateral Movement ◽  
Chloride Mass Balance ◽  
Aquifer Contamination ◽  
Large Reservoir ◽  
One Dimensional

In an area of elevated nitrate (NO3) groundwater concentrations in the northern Chihuahuan Desert in central New Mexico (United States), a large reservoir of nitrate was found in the subsoil of an arroyo floodplain. Nitrate inventories in the floodplain subsoils ranged from 10,000 to 38,000 kg NO3-N/ha—over twice as high as any previously measured arid region. The floodplain subsoil NO3 reservoir was over 100 times higher than the adjacent desert (59–95 kg NO3-N/ha). Chloride mass balance calculations of subsoils indicate arroyo floodplain subsoils have undergone negative recharge since 2600–8600 yr ago, while the surrounding desert has had negative recharge since 13,000–17,000 yr ago. Compared to the adjacent desert, plant communities are larger and more abundant in the floodplain, though subsoil NO3 is apparently not utilized. We demonstrate that NO3 accumulates in the subsoil of the floodplain through evaporation of monsoon season precipitation funneled into the arroyo. Through a one-dimensional vadose zone model, we show that the NO3 inventories in the arroyo floodplain could be acquired 8 to 75 times faster than through atmospheric deposition through the lateral movement

scholarly journals Effect of hysteresis on water flow in the vadose zone under natural boundary conditions, Siloam Village case study, South Africa

2017 ◽  
Vol 20 (1) ◽  
pp. 88-99 ◽  
Author(s):  
I. A. Arrey ◽  
J. O. Odiyo ◽  
R. Makungo ◽  
M. O. Kataka
Keyword(s):  
Boundary Conditions ◽  
Vadose Zone ◽  
Zone Model ◽  
Natural Boundary ◽  
One Dimensional ◽  
Equation Analysis ◽  
Richard's Equation ◽  
1D Model ◽  
Natural Boundary Conditions ◽  
Hydrus 1D

Abstract A one-dimensional vadose zone model was used to simulate flow under natural boundary conditions. The effects of hysteresis and temporal variability of meteorological conditions were evaluated. Simulations were performed in HYDRUS-1D code for the period April 2013–January 2014 (6601 hours) at three different locations in a delineated portion of the sub-quaternary catchment A80A of Nzhelele with different soil textures. Soil hydraulic characteristics were estimated in a Rosetta library dynamically linked to the HYDRUS-1D model which is based on the numerical solution of a one-dimensional Richard's equation. Analysis of the simulation results suggests that ignoring hysteresis for soils of similar textural class does not lead to any significant deviation of the model predicted soil moisture, unlike for soils with different textural classes.

scholarly journals Supplemental Material: Discovery of a large subsoil nitrate reservoir in an arroyo floodplain and associated aquifer contamination

2021 ◽  
Author(s):  
Benjamin Linhoff ◽  
John Lunzer
Keyword(s):  
Mass Balance ◽  
Vadose Zone ◽  
Sampling Methods ◽  
Chloride Mass Balance ◽  
Aquifer Contamination ◽  
Additional Information ◽  
Zone Modeling

Additional information on site background, sampling methods, chloride mass balance calculations, and vadose zone modeling.<br>

scholarly journals Supplemental Material: Discovery of a large subsoil nitrate reservoir in an arroyo floodplain and associated aquifer contamination

2021 ◽  
Author(s):  
Benjamin Linhoff ◽  
John Lunzer
Keyword(s):  
Mass Balance ◽  
Vadose Zone ◽  
Sampling Methods ◽  
Chloride Mass Balance ◽  
Aquifer Contamination ◽  
Additional Information ◽  
Zone Modeling

Additional information on site background, sampling methods, chloride mass balance calculations, and vadose zone modeling.<br>

Analysis of a Transient Asymmetrically Heated/Cooled Open Thermosyphon

1993 ◽  
Vol 115 (3) ◽  
pp. 621-630 ◽  
Author(s):  
G. F. Jones ◽  
J. Cai
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Vertical Plate ◽  
Numerical Study ◽  
Vertical Wall ◽  
Constant Heat Flux ◽  
Closed Form Expression ◽  
Transient Temperature ◽  
Large Reservoir ◽  
One Dimensional

We present a numerical study of transient natural convection in a rectangular open thermosyphon having asymmetric thermal boundary conditions. One vertical wall of the thermosyphon is either heated by constant heat flux (“warmup”) or cooled by convection to the surroundings (“cooldown”). The top of the thermosyphon is open to a large reservoir of fluid at constant temperature. The vorticity, energy, and stream-function equations are solved by finite differences on graded mesh. The ADI method and iteration with overrelaxation are used. We find that the thermosyphon performs quite differently during cooldown compared with warmup. In cooldown, flows are mainly confined to the thermosyphon with little momentum and heat exchange with the reservoir. For warmup, the circulation resembles that for a symmetrically heated thermosyphon where there is a large exchange with the reservoir. The difference is explained by the temperature distributions. For cooldown, the fluid becomes stratified and the resulting stability reduces motion. In contrast, the transient temperature for warmup does not become stratified but generally exhibits the behavior of a uniformly heated vertical plate. For cooldown and Ra > 104, time-dependent heat transfer is predicted by a closed-form expression for one-dimensional conduction, which shows that Nu → Bi1/2/A in the steady-state limit. For warmup, transient heat transfer behaves as one-dimensional conduction for early times and at steady state and for Ra* ≥ 105, can be approximated as that for a uniformly heated vertical plate.

scholarly journals A case study of field-scale maize irrigation patterns in western Nebraska: implications for water managers and recommendations for hyper-resolution land surface modeling

2017 ◽  
Vol 21 (2) ◽  
pp. 1051-1062 ◽  
Author(s):  
Justin Gibson ◽  
Trenton E. Franz ◽  
Tiejun Wang ◽  
John Gates ◽  
Patricio Grassini ◽  
...  
Keyword(s):  
Vadose Zone ◽  
Land Surface ◽  
Spatial Scales ◽  
Crop Model ◽  
Zone Model ◽  
Field Scale ◽  
Maize Production ◽  
Operational Forecasts ◽  
Local Water ◽  
Model Benchmark

Abstract. In many agricultural regions, the human use of water for irrigation is often ignored or poorly represented in land surface models (LSMs) and operational forecasts. Because irrigation increases soil moisture, feedback on the surface energy balance, rainfall recycling, and atmospheric dynamics is not represented and may lead to reduced model skill. In this work, we describe four plausible and relatively simple irrigation routines that can be coupled to the next generation of hyper-resolution LSMs operating at scales of 1 km or less. The irrigation output from the four routines (crop model, precipitation delayed, evapotranspiration replacement, and vadose zone model) is compared against a historical field-scale irrigation database (2008–2014) from a 35 km2 study area under maize production and center pivot irrigation in western Nebraska (USA). We find that the most yield-conservative irrigation routine (crop model) produces seasonal totals of irrigation that compare well against the observed irrigation amounts across a range of wet and dry years but with a low bias of 80 mm yr−1. The most aggressive irrigation saving routine (vadose zone model) indicates a potential irrigation savings of 120 mm yr−1 and yield losses of less than 3 % against the crop model benchmark and historical averages. The results of the various irrigation routines and associated yield penalties will be valuable for future consideration by local water managers to be informed about the potential value of irrigation saving technologies and irrigation practices. Moreover, the routines offer the hyper-resolution LSM community a range of irrigation routines to better constrain irrigation decision-making at critical temporal (daily) and spatial scales (< 1 km).

scholarly journals Vadose zone infiltration and its implication for groundwater contamination risk assessment in Siloam village, Limpopo province, South Africa

2019 ◽  
Vol 11 (2) ◽  
Author(s):  
Ivo Arrey ◽  
John O. Odiyo ◽  
Rachel Makungo ◽  
Milton Kataka
Keyword(s):  
South Africa ◽  
Risk Assessment ◽  
Vadose Zone ◽  
Root Zone ◽  
Risk Identification ◽  
Groundwater Table ◽  
Limpopo Province ◽  
Zone Model ◽  
Organic Additives ◽  
Moisture Fluxes

Risk assessment methods and approaches are useful for environmental planning and decision-making when dealing with risk identification and reduction in a changing global context. This is particularly true for arid and semi-arid regions, such as Siloam village, Limpopo province, South Africa, where it is a common practice to apply fertilisers to the soil during planting season for increasing crop yield. Estimates of vadose zone soil moisture fluxes were used to determine the likelihood of applied agricultural fertilisers to reach the groundwater table. This study combines field observations in the study area and a one-dimensional numerical model to explore the moisture fluxes and their implications for contaminant transport in the vadose zone. Model simulations revealed a lag time of 117 days at topsoil and 913 days beyond the root zone for deep percolation of soluble non-reactive inorganic and organic additives to reach the groundwater table. Preliminary results of this study suggest that the vadose zone is permeable and the groundwater is vulnerable to contamination within the evaluated time scale. Given that disaster risks are inevitable, reasonable methods for control and mitigation of agricultural impacts at this site are highly recommended.

Vadose Zone Model-Data Fusion: State of the Art and Future Challenges

2012 ◽  
Vol 11 (4) ◽  
pp. vzj2012.0140 ◽  
Author(s):  
Johan A. Huisman ◽  
Jasper A. Vrugt ◽  
Ty P.A. Ferre
Keyword(s):  
Data Fusion ◽  
Vadose Zone ◽  
State Of The Art ◽  
Zone Model ◽  
Model Data ◽  
Future Challenges
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