Infiltration, Soil Moisture, and Unsaturated Flow

1991 ◽  
pp. 137-151 ◽  
Author(s):  
Keith Beven
Keyword(s):  
Soil Moisture ◽  
Unsaturated Flow

scholarly journals Hydrological Analysis of Basin Behaviour from Soil Moisture Data

1988 ◽  
Vol 19 (1) ◽  
pp. 1-18 ◽  
Author(s):  
Lotta Andersson
Keyword(s):  
Soil Moisture ◽  
Root Distribution ◽  
Unsaturated Flow ◽  
Drainage Basin ◽  
Main Tool ◽  
Probe Field ◽  
Soil Moisture Dynamics ◽  
Soil Moisture Accounting ◽  
Forest Sites ◽  
Moisture Dynamics

Soil moisture dynamics in the Velen drainage basin (Sweden) were analyzed in order to assess the degree of and the reasons for spatial variation in basin behaviour. The main tool was a modified version of the soil moisture accounting routine in the conceptual runoff model HBV, optimized against neutron probe field data. Simulated soil moisture dynamics, interception and percolation rates agreed well with measurements and other calculations. Integration of simulated evapotranspiration from sites with different characteristics agreed well with water balance computations for the area. It was shown that unsaturated flow through macropores probably occurred after heavy rainstorms. During spring, evapotranspiration was limited to values below the potential (Penmans equation) even at times when no soil moisture deficit existed. Soil moisture differences between forest and grassland (including a deforested site) were, during summer, mainly attributed to differences in the root distribution with depth. The effect of interception on the total evapotranspiration rates was only significant during periods when transpiration demands were low. Soil moisture differences between forest sites were mainly attributed to topography but variations in soil characteristics and root distribution had to be considered, especially during dry periods.

The importance of preferential flow in controlling groundwater recharge in tropical Africa and implications for modelling the impact of climate change on groundwater resources

2010 ◽  
Vol 1 (4) ◽  
pp. 234-245 ◽  
Author(s):  
M. O. Cuthbert ◽  
C. Tindimugaya
Keyword(s):  
Soil Moisture ◽  
Preferential Flow ◽  
Unsaturated Flow ◽  
Uniform Flow ◽  
Richards Equation ◽  
Tropical Africa ◽  
Lateritic Soils ◽  
Flow Models ◽  
Spatial Coverage ◽  
The Impact

An improved water table fluctuation technique for estimating recharge is applied to a sustained (10-year) groundwater level monitoring record in Uganda, a rare dataset for tropical Africa, and compared against results from soil moisture balance models (SMBMs) and unsaturated flow models. The results show that recharge is directly proportional to rainfall (long-term average rainfall is around 1200 mm/a), even during times when high soil moisture deficits are anticipated. This indicates that preferential and/or localized flow mechanisms dominate the recharge behaviour. SMBMs and unsaturated flow models, based on uniform flow governed by the Richards equation, are shown to be inappropriate for estimating recharge in this location underlain by lateritic soils. Given the large spatial coverage of lateritic soils both globally and in tropical Africa, and despite the convenience of physically based uniform flow models and, in particular, SMBMs, concern is raised over the use of such models for recharge estimation, and thus for exploring future trends due to climate or land use change, unless backed up by sufficient hydraulic data to enable the recharge processes to be confirmed. More research is needed to assess how widespread preferential flow may be within other major soil groups and climate zones.

Hydrogeologic Investigation of a Radioactive Waste Management Site in Southern Alberta

1975 ◽  
Vol 12 (3) ◽  
pp. 349-361 ◽  
Author(s):  
Franklin W. Schwartz
Keyword(s):  
Soil Moisture ◽  
Radioactive Waste ◽  
Waste Management ◽  
Unsaturated Flow ◽  
Water Level Fluctuations ◽  
Laboratory Studies ◽  
Radioactive Waste Management ◽  
Block Data ◽  
Defence Research ◽  
Observation Wells

For the past 2 years, detailed field and laboratory studies have focused on the hydrogeologic investigation of a proposed, subsurface, radioactive waste management site in Alberta at the Defence Research Establishment Suffield. The basic approach has involved test drilling and sampling augmented by down-hole geophysical techniques to establish stratigraphic sequences. In addition, piezometers and soil moisture – temperature blocks have been emplaced to define the saturated–unsaturated flow regime. Laboratory studies of drift and bedrock samples have characterized variations in mineralogy, texture, and sorptive properties.Piezometric data indicate that the site is predominantly a recharge area with median values of permeability ranging from 2.8 × 10−2 to 2.8 × 10−4 ft/day (1 × 10−5 to 1 × 10−7 cm/s). To reach the zone of saturation, recharge water must pass downward through a maximum of 120 ft (36.3 m) of unsaturated, glacial drift with cation exchange capacities ranging from 25 to 105 mequiv per 100 g. The absence of water level fluctuations in observation wells and the soil moisture block data indicate that the quantity of water moving downward through the waste management site is small.

Soil Moisture Analyses to Locate Shallow Ground Water: A Solution to a Vexing Problem

2001 ◽  
Author(s):  
Lloyd E. Deuel ◽  
George H. Holliday
Keyword(s):  
Soil Moisture ◽  
Water Table ◽  
Unsaturated Flow ◽  
Particle Density ◽  
Field Capacity ◽  
Degree Of Saturation ◽  
Monitoring Wells ◽  
Perched Water ◽  
Perched Water Table ◽  
Potential Contaminant

Abstract EPA and most States require a hydrogeologic assessment of contaminated sites to identify and characterize the upper most aquifer and potential pathways for contamination. The advancement of soil borings, followed by the completion of monitoring wells in boreholes is often the first step in direct site characterization. These monitoring wells have the potential to contaminate deeper ground waters; if the site has a contaminated seasonal perched water table from which water is allowed to enter the borehole before the well is cased. This condition is particularly troublesome when a temporary monitoring well is used for assessment purposes and contaminate concentrations are compared to maximum concentration limits (MCLs) for drinking water. A seasonal or permanent perched water table may be contaminated, but separated and protected from deeper useable groundwater by the unsaturated ‘vadose’ zone. The lack of saturation in the vadose naturally restricts the movement of water due to unsaturated flow dynamics and the corresponding flux of soluble constituents irrespective of attenuating reactions with soil. This paper presents a method of distinguishing saturated zones from unsaturated zones by comparative analysis of existing soil moisture and the field capacity or 33.3 kPa (1/3 bar) moisture equivalent. Moisture measurements are made for core samples collected in continuous fashion to a selected depth and sample interval determined by the use and sensitivity required in the interpretation of the data. Soil moisture profiles in conjunction with geophysical measurements of bulk density and particle density allow determination of volume wetness and degree of saturation. Additionally, these data are used to assess the movement of water in the soil profile and potential contaminant migration to useable groundwater. The authors have used this technique to differentiate vadose zones sandwiched between seasonal perched water and even thin continuous saturated zones from useable groundwater. Actual field data are presented to demonstrate the ease with which false positive results are generated that portends an adverse impact to groundwater and the need for costly risk reduction analysis or remediation.

Conditions for lateral downslope unsaturated flow and effects of slope angle on soil moisture movement

2013 ◽  
Vol 486 ◽  
pp. 321-333 ◽  
Author(s):  
Meixia Lv ◽  
Zhenchun Hao ◽  
Zhen Liu ◽  
Zhongbo Yu
Keyword(s):  
Soil Moisture ◽  
Unsaturated Flow ◽  
Slope Angle ◽  
Moisture Movement

scholarly journals Geostatistic Interpolation of Soil Moisture

1997 ◽  
Vol 28 (4-5) ◽  
pp. 307-328 ◽  
Author(s):  
Nils-Otto Kitterød ◽  
E. Langsholt ◽  
W. K. Wong ◽  
L. Gottschalk
Keyword(s):  
Soil Moisture ◽  
Unsaturated Zone ◽  
Preferential Flow ◽  
Unsaturated Flow ◽  
Three Dimensional ◽  
Indicator Kriging ◽  
Flow Paths ◽  
Flow Models ◽  
Semivariogram Analysis ◽  
Preferential Flow Paths

The spatial distribution of soil moisture defines preferential flow paths in the unsaturated zone. Hence, three dimensional (3D) estimates of soil moisture are of great importance to understand transport of contaminants as well as remediation processes in the unsaturated zone. In this study 3D estimates conditioned on spatially frequent observations of soil moisture, have been obtained by kriging. The observations were divided into subdomains consistent with the local stratigraphy and directional semivariogram analysis was applied. It was found difficult to clearly identify a 3D semivariogram function in this case, but from a georadar survey two semivariogram functions were derived, describing two different sedimentological units. By conditioning the estimates of soil moisture on the sedimentological architecture computed by indicator kriging, more accurate estimates were achieved. These improvements were quantified by a ‘jackknife’ cross validation procedure. Besides the practical aspects of finding the most important flow paths estimates of soil moisture are valuable when validating unsaturated flow models.

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