Spatial distribution of top soil water content in an experimental catchment of Southeast Brazil

Soil water content is essential to understand the hydrological cycle. It controls the surface runoff generation, water infiltration, soil evaporation and plant transpiration. This work aims to analyze the spatial distribution of top soil water content and to characterize the spatial mean and standard deviation of top soil water content over time in an experimental catchment located in the Mantiqueira Range region, state of Minas Gerais, Brazil. Measurements of top soil water content were carried out every 15 days, between May/2007 and May/2008. Using time-domain reflectometry (TDR) equipment, 69 points were sampled in the top 0.2 m of the soil profile. Geostatistical procedures were applied in all steps of the study. First, the spatial continuity was evaluated, and the experimental semi-variogram was modeled. For the development of top soil water content maps over time a co-kriging procedure was used having the slope as a secondary variable. Rainfall regime controlled the top soil water content during the wet season. Land use was also another fundamental local factor. The spatial standard deviation had low values under dry conditions, and high values under wet conditions. Thus, more variability occurs under wet conditions.

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Using time domain reflectometry in stony forest soil

Canadian Journal of Soil Science ◽

10.4141/s99-004 ◽

2000 ◽

Vol 80 (1) ◽

pp. 3-11 ◽

Cited By ~ 10

Author(s):

D. L. Spittlehouse

Keyword(s):

Standard Deviation ◽

Water Content ◽

Travel Time ◽

Soil Water ◽

Soil Water Content ◽

Time Domain ◽

Soil Bulk Density ◽

Time Domain Reflectometry ◽

Measured Change ◽

A Site

Forest soils often contain many large coarse fragments making it difficult to insert probes to measure soil water content. The ability of time domain reflectometry (TDR) to give reliable measurements of water content in soil with up to 40% coarse fragments was evaluated at a site in the southern interior of British Columbia, Canada. A commercial time domain reflectometer was used with 0.3-, 0.5- and 0.75-m-long probes to measure soil water content of the profile and layers within the profile. A probe had a shorting diode at the surface and two 3-mm-diameter stainless steel rods inserted vertically, 30 mm apart, as the waveguide. Diverging rods or profile discontinuities resulted in erroneous readings that required a review of the recorded signals and recalculation the travel time. Soil physical and hydrologic soil properties were determined and the soil calibrated for TDR. An accuracy of ±0.02 m3m−3 was obtained with measurement of soil bulk density and minimizing probe and travel time errors. Variation in water content between probes reflected the variability in coarse fragment content; however, the ranking of the probes stayed constant with time and rates of change were similar between probes. One standard deviation on the measured change in the volume of water between measurement days for the 0 to 0.5 m depth was ±6 mm (n = 20), equivalent to 0.012 m3m−3. Measurements of water content of the layers had one standard deviation of 0.02 m3m−3. Key words: Time domain reflectometry, forest hydrology, soil water content, water balance

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Measuring Soil Water Content With Time Domain Reflectometry

Soil Science ◽

10.1097/ss.0b013e3181f55aa3 ◽

2010 ◽

Vol 175 (10) ◽

pp. 469-473 ◽

Cited By ~ 8

Author(s):

Zhaoqiang Ju ◽

Xiaona Liu ◽

Tusheng Ren ◽

Chunsheng Hu

Keyword(s):

Water Content ◽

Soil Water ◽

Soil Water Content ◽

Time Domain ◽

Time Domain Reflectometry

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Effects of textural layering on water regimes in sandy soils in a desert-oasis ecotone, Northwestern China

10.5194/egusphere-egu21-9324 ◽

2021 ◽

Author(s):

Chengpeng Sun ◽

Wenzhi Zhao ◽

Hu Liu ◽

Yongyong Zhang ◽

Hong Zhou

Keyword(s):

Water Content ◽

Soil Water ◽

Soil Water Content ◽

Water Infiltration ◽

Northwestern China ◽

Soil Profiles ◽

Burial Depth ◽

Layered Soils ◽

Water Regimes ◽

Desert Oasis

Textural layering of soil plays an important role in distributing and regulating resources for plants in many semiarid and arid landscapes. However, the spatial patterns of textural layering and the potential effects on soil hydrology and water regimes are poorly understood, especially in arid sandy soil environments like the desert-oasis ecotones in northwestern China. This work aims to determine the distribution of textural layered soils, analyze the effects of different soil-textural configurations on water regimes, and evaluate which factors affect soil water infiltration and retention characteristics in such a desert-oasis ecotone. We measured soil water content and mineral composition in 87 soil profiles distributed along 3 transects in the study area. Constant-head infiltration experiments were conducted at 9 of the soil profiles with different texture configurations. The results showed that textural layered soils were patchily but extensively distributed throughout the study area (with a combined surface area percentage of about 84%). Soil water content in the profiles ranged from 0.002 to 0.27 g/cm3 during the investigation period, and significantly and positively correlated with the thickness of a medium-textured (silt or silt loam) layer (P < 0.001). The occurrence of a medium-textured layer increased field capacity (FC) and wilting point (WP), and decreased available water-holding capacity in soil profiles. Burial depth of the medium-textured layer had no clear effects on water retention properties, but the layer thickness tended to. In textural layered soils, smaller water infiltration rate and cumulative infiltration, and shallower depths of wetting fronts were detected, compared with homogeneous sand profiles. The thickness and burial depth of medium-textured layers had obvious effects on infiltration, but the magnitude of the effects depended on soil texture configuration. The revealed patterns of soil textural layering and the potential effects on water regimes may provide new insight into the sustainable management of rainfed vegetation in the desert-oasis ecotones of arid northwestern China and other regions with similar environments around the world.

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