scholarly journals Water storage change estimation from in situ shrinkage measurements of clay soils

2012 ◽  
Vol 9 (11) ◽  
pp. 13117-13154 ◽  
Author(s):  
B. te Brake ◽  
M. J. van der Ploeg ◽  
G. H. de Rooij
Keyword(s):  
Soil Water ◽  
Water Storage ◽  
Soil Surface ◽  
Surface Elevation ◽  
Measurement Scale ◽  
Soil Water Storage ◽  
Soil Layers ◽  
Shrinkage Curve ◽  
Elevation Changes ◽  
Storage Change

Abstract. Water storage in the unsaturated zone is a major determinant of the hydrological behaviour of the soil, but methods to quantify soil water storage are limited. The objective of this study is to assess the applicability of clay soil surface elevation change measurements to estimate soil water storage changes. We measured moisture contents in soil aggregates by EC-5 sensors, and in volumes comprising multiple aggregates and intra-aggregates spaces by CS616 sensors. In a prolonged drying period, aggregate-scale storage change measurements revealed normal shrinkage for layers ≥ 30 cm depth, indicating volume loss equalled water loss. Shrinkage in a soil volume including multiple aggregates and voids was slightly less than normal, due to soil moisture variations in the profile and delayed drying of deeper soil layers upon lowering of the groundwater level. This resulted in shrinkage curve slopes of 0.89, 0.90 and 0.79 for the layers 0–60, 0–100 and 0–150 cm. Under a dynamic drying and wetting regime, shrinkage curve slopes ranged from 0.29 to 0.69 (EC-5) and 0.27 to 0.51 (CS616). Alternation of shrinkage and incomplete swelling resulted in an underestimation of volume change relatively to water storage change, due to hysteresis between swelling and shrinkage. Since the slope of the shrinkage relation depends on the drying regime, measurement scale and combined effect of different soil layers, shrinkage curves from laboratory tests on clay aggregates require suitable modifications for application to soil profiles. Then, the linear portion of the curve can help soil water storage estimation from soil surface elevation changes. These elevation changes might be measurable over larger extents by remote sensing.

scholarly journals Water storage change estimation from in situ shrinkage measurements of clay soils

2013 ◽  
Vol 17 (5) ◽  
pp. 1933-1949 ◽  
Author(s):  
B. te Brake ◽  
M. J. van der Ploeg ◽  
G. H. de Rooij
Keyword(s):  
Soil Water ◽  
Volume Change ◽  
Water Loss ◽  
Water Storage ◽  
Bulk Soil ◽  
Soil Water Storage ◽  
Dry Period ◽  
Soil Layers ◽  
Storage Change

Abstract. The objective of this study is to assess the applicability of clay soil elevation change measurements to estimate soil water storage changes, using a simplified approach. We measured moisture contents in aggregates by EC-5 sensors, and in multiple aggregate and inter-aggregate spaces (bulk soil) by CS616 sensors. In a long dry period, the assumption of constant isotropic shrinkage proved invalid and a soil moisture dependant geometry factor was applied. The relative overestimation made by assuming constant isotropic shrinkage in the linear (basic) shrinkage phase was 26.4% (17.5 mm) for the actively shrinking layer between 0 and 60 cm. Aggregate-scale water storage and volume change revealed a linear relation for layers ≥ 30 cm depth. The range of basic shrinkage in the bulk soil was limited by delayed drying of deep soil layers, and maximum water loss in the structural shrinkage phase was 40% of total water loss in the 0–60 cm layer, and over 60% in deeper layers. In the dry period, fitted slopes of the ΔV–ΔW relationship ranged from 0.41 to 0.56 (EC-5) and 0.42 to 0.55 (CS616). Under a dynamic drying and wetting regime, slopes ranged from 0.21 to 0.38 (EC-5) and 0.22 to 0.36 (CS616). Alternating shrinkage and incomplete swelling resulted in limited volume change relative to water storage change. The slope of the ΔV–ΔW relationship depended on the drying regime, measurement scale and combined effect of different soil layers. Therefore, solely relying on surface level elevation changes to infer soil water storage changes will lead to large underestimations. Recent and future developments might provide a basis for application of shrinkage relations to field situations, but in situ observations will be required to do so.

scholarly journals Spatial variability and temporal stability of water storage in a cultivated tropical soil

Bragantia ◽  
2010 ◽  
Vol 69 (suppl) ◽  
pp. 153-162 ◽  
Author(s):  
Antonio Carlos Andrade Gonçalves ◽  
Marcos Antonio Trintinalha ◽  
Marcos Vinicius Folegatti ◽  
Roberto Rezende ◽  
Cássio Antonio Tormena
Keyword(s):  
Water Content ◽  
Soil Water ◽  
High Efficiency ◽  
Temporal Stability ◽  
Water Storage ◽  
Soil Surface ◽  
Soil Water Storage ◽  
Soil Conditions ◽  
Content Uniformity ◽  
Water Application

Irrigated agricultural fields usually show variable crop water demand. If water application is done to match this spatially variable demand, the water use efficiency can be substantially improved. Soil water management by irrigation has been one of the most important factors to increase crop yield. To look for the economic viability of the process, the use of several inputs, particularly water, should be done with high efficiency levels. Historically, irrigation uniformity has been evaluated above the soil surface, in which applied water was the only factor to be taken into account. However, the crop will respond to soil water content uniformity, which can differ from the uniformity of water application. To evaluate temporal stability of spatial pattern of soil water storage (SWS), this work was done on a Brazilian clayed soil. Volumetric water content from soil surface to 0,30m depth, was measured by TDR in 80 points regularly spaced (3 x 3 m) on an experimental area cultivated with bean crop, irrigated by conventional sprinkling. The evaluations were done immediately before and after a water application by irrigation. Experimental semivariograms made from values obtained in the field showed that SWS distribution was spatially structured and strongly stable in time, being regulated mainly by intrinsic factors of the soil. In addition, obtained results showed that water application uniformity did not influence the spatial distribution pattern of SWS in these soil conditions.

Accuracy of the neutron probe for measuring changes in soil water storage under potatoes

2002 ◽  
Vol 138 (2) ◽  
pp. 135-152 ◽  
Author(s):  
S. R. GAZE ◽  
M. A. STALHAM ◽  
E. J. ALLEN
Keyword(s):  
Field Experiment ◽  
Soil Water ◽  
Water Storage ◽  
Surface Profile ◽  
Soil Surface ◽  
Bare Soil ◽  
Irrigation Scheduling ◽  
Soil Water Storage ◽  
Neutron Probe ◽  
Areal Sampling

The neutron probe (NP) is used widely to measure changes in soil water storage in research and more recently to aid irrigation scheduling. Its accuracy is rarely questioned and most of the relationships between soil water changes and productivity are based on its use. A field experiment was conducted at Cambridge University Farm in 1999 to address whether the NP could accurately measure changes in soil water content (SWC) under irrigation or substantial rain (>10 mm). The experiment was a replicated split-plot design with four irrigation treatments allocated to the main plots, and surface profile (ridge, flat) and crop (potato cv. Saturna, bare soil) treatments allocated to the subplots. The mean results from four NP access tubes per plot installed to measure soil moisture deficit (SMD) across the row-width were analysed. The NP was inconsistent in measuring known irrigation or rainfall input. In relatively dry soil (SMD>40 mm), the NP generally measured 93 to 110% of 18 mm of irrigation within 4 h of irrigation. The NP recorded much less water applied as irrigation in wetter soil, and often only 40 to 70% of the applied irrigation (18 or 36 mm) was measured. There were occasions when the NP did not measure all the water input even when the SMDs before irrigation were greater than the water subsequently applied. Some of the ‘missing’ water might be attributed to drainage, however, results from an additional experiment using an open-topped tank of soil showed that the NP was unable to detect all the water added to the soil, particularly where the water was largely confined close to the soil surface. Replicated measurements of the change in SMD in the field experiment were precise for a given event and treatment (mean S.E. = 1·3 mm) but were not accurate when compared against the input measured in rain gauges. It was concluded, that the NP could not be used reliably to measure changes in soil water storage after irrigation or substantial rain. For periods when there were minimal inputs of water, there was a closer correlation between changes in SMD measured by the NP and those predicted by a modified Penman–Monteith equation than after substantial inputs of water. However, for predicted changes in SMD of c. 20 mm, there was a range of c. ±5 mm in the changes in SMD measured by the neutron probe.The value of the NP for monitoring SMDs where there is irrigation, or substantial rain, must be seriously doubted. Consequently, its limitations for scheduling irrigation, testing models or quantifying the effects of treatments on crop water use in potatoes must be appreciated, especially where the areal sampling limitations of single access tubes positioned only in the ridge centre have not been addressed.

scholarly journals New interpretation of the role of water balance in an extended Budyko hypothesis in arid regions

2015 ◽  
Vol 12 (10) ◽  
pp. 11013-11052 ◽  
Author(s):  
C. Du ◽  
F. Sun ◽  
J. Yu ◽  
X. Liu ◽  
Y. Chen
Keyword(s):  
Steady State ◽  
Water Balance ◽  
Soil Water ◽  
Arid Regions ◽  
Water Storage ◽  
Soil Water Storage ◽  
Unsteady State ◽  
Monthly Water Balance ◽  
Storage Change

Abstract. The Budyko hypothesis (BH) is an effective approach to investigating long-term water balance at large basin scale under steady state. The assumption of steady state prevents applications of the BH to basins, which is unclosed, or with significant variations in soil water storage, i.e., under unsteady state, such as in extremely arid regions. In this study, we choose the Heihe River Basin (HRB) in China, an extremely arid inland basin, as the study area. We firstly use a calibrated and then validated monthly water balance model, i.e., the abcd model to quantitatively determine annual and monthly variations of water balance for the sub-basins and the whole catchment of the HRB and find that the role of soil water storage change and that of inflow from upper sub-basins in monthly water balance are significant. With the recognition of the inflow water from other regions and the soil water storage change as additional possible water sources to evapotranspiration in unclosed basins, we further define the equivalent precipitation (Pe) to include local precipitation, inflow water and soil water storage change as the water supply in the Budyko framework. With the newly defined water supply, the Budyko curve can successfully describe the relationship between the evapotranspiration ratio and the aridity index at both annual and monthly timescales, whilst it fails when only the local precipitation being considered. Adding to that, we develop a new Fu-type Budyko equation with two non-dimensional parameters (ω and λ) based on the deviation of Fu's equation. Over the annual time scale, the new Fu-type Budyko equation developed here has more or less identical performance to Fu's original equation for the sub-basins and the whole catchment. However, over the monthly time scale, due to large seasonality of soil water storage and inflow, the new Fu-type Budyko equation generally performs better than Fu's original equation. The new Fu-type Budyko equation (ω and λ) developed here enables one to apply the BH to interpret regional water balance over extremely dry environments under unsteady state (e.g., unclosed basins or sub-annual timescales).

scholarly journals Calibration of a non-invasive cosmic-ray probe for wide area snow water equivalent measurement

2016 ◽  
Author(s):  
M. J. P. Sigouin ◽  
B. C. Si
Keyword(s):  
Remote Sensing ◽  
Linear Regression ◽  
Soil Water ◽  
Snow Water Equivalent ◽  
Water Storage ◽  
Cosmic Ray ◽  
Measurement Scale ◽  
Soil Water Storage ◽  
Neutron Intensity ◽  
Snow Water

Abstract. Measuring snow water equivalent (SWE) is important for many hydrological purposes such as modeling and flood forecasting. Measurements of SWE are also crucial for agricultural production in areas where snowmelt runoff dominates spring soil water recharge. Typical methods for measuring SWE include point measurements (snow tubes) and large-scale measurements (remote sensing). We explored the potential of using the cosmic-ray soil moisture probe (CRP) to measure average SWE at a measurement scale between those provided by snow tubes and remote sensing. The CRP measures above ground moderated neutron intensity within a radius of approximately 300 m. Using snow tubes, surveys were performed over two winters (2013/2014 and 2014/2015) in an area surrounding a CRP in an agricultural field in Saskatoon, Saskatchewan, CAN. The raw moderated neutron intensity counts were corrected for atmospheric pressure, water vapor, and temporal variability of incoming cosmic ray flux. The mean SWE from manually measured snow surveys was adjusted for differences in soil water storage before snowfall between both winters because the CRP reading appeared to be affected by soil water below the snowpack. The SWE from the snow surveys was negatively correlated with the CRP-measured moderated neutron intensity, giving Pearson correlation coefficients of −0.92 (2013/2014) and −0.94 (2014/2015). A linear regression performed on the manually measured SWE and moderated neutron intensity counts for 2013/2014 yielded an r2 of 0.84. Linear regression lines from the 2013/2014 and 2014/2015 manually measured SWE and moderated neutron counts were very similar, thus differences in antecedent soil water storage did not appear to affect the slope of the SWE vs. neutron relationship. The regression equation obtained from 2013/2014 was used to model SWE using the moderated neutron intensity data for 2014/2015. The CRP-estimated SWE for 2014/2015 was similar to that of the snow survey, with a RMSE of 7.7 mm. The CRP-estimated SWE also compared well to estimates made using snow depths at meteorological sites near (< 10 km) the CRP. Overall, the empirical equation presented provides acceptable estimates of average SWE using moderated neutron intensity measurements. Using a CRP to monitor SWE is attractive because it delivers a continuous reading, can be installed in remote locations, requires minimal labour, and provides a landscape-scale measurement footprint.

Soil water storage in a semi-arid Eucalyptus populnea woodland invaded by woody shrubs, and the effects of shrub clearing and tree ringbarking.

1984 ◽  
Vol 6 (2) ◽  
pp. 75 ◽  
Author(s):  
GG Johns
Keyword(s):  
Soil Water ◽  
Water Storage ◽  
Soil Surface ◽  
Bare Soil ◽  
Arid Environment ◽  
Soil Water Storage ◽  
Water Response ◽  
Shrub Clearing ◽  
Eucalyptus Populnea ◽  
Semi Arid

Soil water was monitored over a six year period in an intact shrub invaded semi-arid Elrcalyptlts popztlrlea woodland (control) and on areas which had been treated by either shrub-clearing, or by ringbarking of trees and shrub-clearing. Measurements were made under both the shrubby thicket areas near the eucalypt, and the sparsely shrubbed interthicket areas more distant from the trees. Average soil water storage over the six years for all treatments was only 26 nun. Much of this water was stored in the upper 500 Inm of the profile and hence was susceptible to direct evaporation from the usually bare soil surface. In the intact n.oodland and following wet weather, significantly more soil water was stored under thickets than under the interthicket areas. With the return of dry weather this cxtra soil water was rapidly depleted, and thicket soils would often become drier than interthicket soils. After pro- longed dry weather, soil matric potentials of - 10 to -1 2 MPa were recorded at a depth of 500 mm. Matric potentials by this time were least negative under thickets. Shrub clearing without rinpbarking increased thicket and interthicket soil water storage by 17% and 2396 respectively. The ring- barking and shrub clearing treatment increased thicket profile storage more than that of the interthicket (81% and 64% respectively). The effect of ringbarkinp lvas often pronounced at a distance of 25 rn from the tree. The contrasting soil water response to the two treatments indicated that in this semi-arid environment only a relatively srnaU change in soil water balance may accrue from incomplete clearing. The ren~oval of both shrubs and trees is probably necessary to make a large difference to soil water storage.

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