Numerical solutions to the nonlinear Boussinesq equation, applied to a steeply sloping aquifer and assuming uniform hydraulic conductivity, indicate that late-time recession discharge decreases nearly linearly in time. When recession discharge is characterized by -dQ/dt=aQ[superscript b], this is equivalent to constant dQ/dt or b=0. This result suggests that a previously...
Multiplicative random cascades (MRCs) can parsimoniously generate highly intermittent patterns similar to those in rainfall. The elemental MRC model parameter is the cascade weight, which determines how rainfall at one scale is partitioned at the next smallest scale in the cascade. While it is known that the probability density of...
In lentic water bodies, such as lakes, the water temperature near the surface typically increases during the day, and decreases during the night as a consequence of the diurnal radiative forcing (solar and infrared radiation). These temperature variations penetrate vertically into the water, transported mainly by heat conduction enhanced by...
Based on a literature overview, this paper summarizes the impact and legacy of the contributions of Wilfried Brutsaert and Jean-Yves Parlange (Cornell University) with respect to the current state-of-the-art understanding in hydraulic groundwater theory. Forming the basis of many applications in catchment hydrology, ranging from drought flow analysis to surface...
Prediction of colloid transport in the subsurface is relevant to researchers in a variety of fields such as contaminant transport, wastewater treatment, and bioremediation. Investigations have traditionally relied on column studies whereby mechanistic inferences must be drawn on the basis of colloid behavior at the outlet. Over the past decade,...
Accurate methods are needed to measure changing soil water content from meter to kilometer scales. Laboratory results demonstrate the feasibility of the heat pulse method implemented with fiber optic temperature sensing to obtain accurate distributed measurements of soil water content. A fiber optic cable with an electrically conductive armoring was...
The movement of air in natural porous media is complex and challenging to measure. Yet gas transport has important implications, for instance, for the evolution of the seasonal snow cover and for water vapor transport in soil. A novel in situ multi-sensor measurement system providing high-resolution observation of gas transport...
To explain the dynamic behavior of the matric potential at the wetting front of gravity
driven fingers, we take into account the pressure across the interface that is not continuous
and depends on the radius of the meniscus, which is a function of pore size and the dynamic
contact angle...
Full Text:
measurements of saturation overshoot
on infiltration, Water Resour. Res., 40, W04215, doi:10.1029/
2003WR002670
We propose a novel, accurate quantification of precipitation and evaporation, as needed to understand fundamental hydrologic processes. Our system uses a collection vessel placed on top of a slender rod that is securely fixed at its base. As the vessel is deflected, either by manual perturbation or ambient forcing (for...
The Actively Heated Fiber Optic (AHFO) method is shown to be capable of measuring soil water
content several times per hour at 0.25 m spacing along cables of multiple kilometers in length. AHFO is
based on distributed temperature sensing (DTS) observation of the heating and cooling of a buried fiber-optic...
Full Text:
probe
measurements: Geometry and dispersion effects, Water Resour. Res., 38(1), 1–14, doi:10.1029
A new apparatus is presented that is capable of applying a constant fluid pressure at inflow and outflow boundaries. The apparatus can be refilled during operation and does not rely on an overflow mechanism. The device is constructed of two vessels, one that contains the delivered fluid and the other...
The heat pulse probe method can be implemented with actively heated fiber optics (AHFO) to obtain distributed measurements of soil water content (θ) by using reported soil thermal responses measured by Distributed Temperature Sensing (DTS) and with a soil-specific calibration relationship. However, most reported applications have been calibrated to homogeneous...
Surface tensions of high-salinity solutions are significantly different from those of pure water. Our objective was to develop and test a methodology to determine whether these surface tension effects predictably alter imbibition into dry and moist porous media. Static and dynamic experiments were performed using four grades of quartz sand...
The method of recession analysis proposed by Brutsaert and Nieber (1977) remains one of the few analytical tools for estimating aquifer hydraulic parameters at the field scale and beyond. In the method, the recession hydrograph is examined as −dQ/dt = f(Q), where Q is aquifer discharge and f is an...
Hydrologic research is a very demanding application of fiber-optic distributed temperature sensing (DTS) in terms of precision, accuracy and calibration. The physics behind the most frequently used DTS instruments are considered as they apply to four calibration methods for single-ended DTS installations. The new methods presented are more accurate than...
We present a novel approach based on fibre-optic distributed temperature sensing (DTS) to measure the two-dimensional thermal structure of the surface layer at high resolution (0.25 m, ≈ 0.5 Hz). Air temperature observations obtained from a vertically oriented fibre optics array of approximate dimensions 8 m x 8 m and...
Snowpack base temperatures vary during accumulation and diurnally. Their measurement
provides insight into physical, biological and chemical processes occurring at the snow/soil interface.
Recent advances in Raman-spectra instruments, which use the scattered light in a standard
telecommunications fiber-optic cable to infer absolute temperature along the entire length of the fiber,...
Raman spectra distributed temperature sensing (DTS) by fiber-optic cables has
recently shown considerable promise for the measuring and monitoring of surface and
near-surface hydrologic processes such as groundwater–surface water interaction,
borehole circulation, snow hydrology, soil moisture studies, and land surface energy
exchanges. DTS systems uniquely provide the opportunity to monitor...
Solutions to the Boussinesq equation describing drainage into a fully penetrating channel have been used for aquifer characterization. Two analytical solutions exist for early- and late-time drainage from a saturated, homogeneous, and horizontal aquifer following instantaneous drawdown. The solutions for discharge Q can be expressed as dQ/dt = −aQ [superscript...
Water vapor transport in the vicinity of imbibing saline solutions was investigated in two-dimensional (2-D) chambers using a light transmission technique. Concentrated NaNO3 solutions (brines) were applied as point sources to the surface of homogenous packs of prewetted silica sand for four different sand grades. The same solutions were applied...
Shrinkage cracks in soil function as a dominant control on the partitioning and distribution of moisture fluxes in the vadose zone. Their dynamics influence moisture balance and control water availability for runoff, deep infiltration, and near-surface storage. We present a new low-cost field instrument to monitor the temporal change in...
Quality concerns drive many water studies and practices, but obtaining samples from water bodies over time and space for quality determination is often difficult and expensive. We present a low-cost approach that allows integration of water samples over timescales of days to months to allow more widely distributed acquisition of...
Instruments for distributed fiber-optic measurement of temperature are now available with temperature resolution of 0.01°C and spatial resolution of 1 m with temporal resolution of fractions of a minute along standard fiber-optic cables used for communication with lengths of up to 30,000 m. We discuss the spectrum of fiber-optic tools...
Irrigation experiments on 12 instrumented field plots were used to assess the impact of dynamic soil crack networks on
infiltration and run-off. During applications of intensity similar to a heavy rainstorm, water was seen being preferentially
delivered within the soil profile. However, run-off was not observed until soil water content...
Though many arid and contaminated sites have high salinity, prediction of effects of salinity on water movement in soils has been based on dilute solution approximations. Here a sensitivity analysis compares predicted liquid and vapor pressure in variably saturated porous media found using both the dilute approximations and a more...
Natural hydraulic barriers exist at Yucca Mountain, Nevada, a potential high-level nuclear waste repository, that have been identified as possible lateral diversions for reducing deep percolation through the waste storage area. Historical development of the conceptual model of lateral diversion has been limited by available field data, but numerical investigations...
A soil’s capillarity, associated with the parameter sorptivity, is a dominant control on
infiltration, particularly at the onset of rainfall or irrigation. Many mathematical models
used to estimate sorptivity are only valid for dry soils. This paper examines how sorptivity
and its capillary component (as wetting front potential) change with...
Liquid saturation and gas-liquid interfacial area are important parameters for evaluating the transport and fate of contaminants in unsaturated subsurface environments. Recent findings indicate that interfacial surface area controls the relative degree of transmitted light in laboratory systems containing translucent porous media. Equations are derived to estimate the specific gas-liquid...