- Title
- Investigating long-term temporal variability of soil moisture and differences in dynamics in wet and dry periods
- Creator
- Duzzo Grohs, Rita
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2022
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Soil moisture represents a reservoir of water in the soil, that is crucial to the hydrologic cycle and land-atmosphere interactions. Soil moisture allows vegetation to grow, affects evapotranspiration, water distribution, and food production. Because of its high spatial and temporal variability, and uncertainties on its future availability, studies on long-term soil moisture trend are important to manage and allocate water, and to help to develop strategies for water security (McDonough et al., 2020). The main attributes (e.g., topography, soil properties) that drive the spatial organization of soil moisture change according to the wetness period (e.g., dry or wet), and are also dependent on the climate in which the catchment is inserted. Previous work analysed soil moisture spatial and temporal variability in dry and wet conditions in a temperate climate (Grayson et al., 1997; Western et al., 1999) and in a humid-subtropical climate (Famiglietti et al., 1998) and found that soil properties (e.g., porosity and hydraulic conductivity) governed soil moisture temporal variability in wet conditions, while elevation, aspect, and clay content dictated governed soil moisture variability in dry conditions (Famiglietti et al., 1998). This work investigates soil moisture temporal and spatial variability in conditions that are wetter and drier than average, in two Australian catchments located in a semiarid subhumid climate, through the comparison of physical drivers of soil moisture using in-situ dataset in clay and sandy soils. Preferential flow is known to contribute for spatial soil moisture variability. It allows water and solutes to move faster along the soil profile than they would with uniform infiltration (Hendrickx & Flury, 2001; Hardie et al., 2013). Macropore flow is one form of preferential flow, characterised for the flow in fissures or cracks (Gerke, 2006). Our study area encompasses a region characterised by Vertisols, that is, soils rich in expansive clay and the presence of cracks in the soil mentioned in other studies (Rüdiger, 2006; Martinez, 2010). An investigation on macropore preferential flow was never carried in the site, thus, this study aims to apply a dual-porosity model to assess how a model that accounts for preferential paths perform in the site. Along with soil moisture temporal and spatial variability, climate change adds uncertainty to climate and consequently to soil moisture modelling. Soil moisture has an important role in land-atmosphere feedback mechanisms (Koster et al., 2004; Zhang et al., 2008; Seneviratne et al., 2010; Whan et al., 2015; Lo et al., 2021) and it represents an important influence in climate-change projections (Seneviratne et al., 2010). Long periods of soil moisture data (e.g., greater than 10-15 years) are necessary to investigate temporal anomalies and to be able to evaluate the impact of those anomalies within a hydrological context (Brocca et al., 2014; Brocca et al., 2017). Studies on long-term soil moisture trends are predominantly carried on a global scale, with a coarse spatial resolution dataset (25 to 100 km pixel) (Sheffield & Wood, 2008a; Dorigo et al., 2012; Albergel et al., 2013; Deng et al., 2020) that mask local and regional trends. The global scale studies on soil moisture trends usually analyse surface soil moisture (~7 cm) trends (Sheffield & Wood, 2008a; Dorigo et al., 2012; Feng & Zhang, 2015; Deng et al., 2020), and not the profile layer (~100 cm). Surface and profile soil layers impact differently the soil moisture processes, i.e., the surface layer is where the flux of mass and energy with the atmosphere occurs (Brocca et al., 2009), while the profile soil moisture is a better representation of vegetation (Wigneron et al., 1999; Santos et al., 2014). This study investigates the long-term variability of soil moisture in New South Wales, Australia, both in the surface (0-10 cm) and the profile layers of soil (0-100 cm), in a finer spatial resolution (5×5 km pixel).
- Subject
- soil moisture; spatial variability; dry and wet periods; HYDRUS; long-term variability; dual-porosity; preferential flow; SASMAS
- Identifier
- http://hdl.handle.net/1959.13/1500644
- Identifier
- uon:54978
- Rights
- Copyright 2022 Rita Duzzo Grohs
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
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| View Details Download | ATTACHMENT01 | Thesis | 13 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 236 KB | Adobe Acrobat PDF | View Details Download |