Spatial and temporal variability of pore‐water pressures in residual soil slopes in a tropical climate

Abstract

It is critical to understand and quantify the temporal and spatial variability in hillslope hydrological data in order to advance hillslope hydrological studies, evaluate distributed parameter hydrological models, analyse variability in hydrological response of slopes and design efficient field data sampling networks. The spatial and temporal variability of field-measured pore-water pressures in three residual soil slopes in Singapore was investigated using geostatistical methods. Parameters of the semivariograms, namely the range, sill and nugget effect, revealed interesting insights into the spatial structure of the temporal situation of pore-water pressures in the slopes. While informative, mean estimates have been shown to be inadequate for modelling purposes, indicator semivariograms together with mean prediction by kriging provide a better form of model input. Results also indicate that significant temporal and spatial variability in porewater pressures exists in the slope profile and thereby induces variability in hydrological response of the slope. Spatial and temporal variability in pore-water pressure decreases with increasing soil depth. The variability decreases during wet conditions as the slope approaches near saturation and the variability increases with high matric suction development following rainfall periods. Variability in pore-water pressures is greatest at shallow depths and near the slope crest and is strongly influenced by the combined action of microclimate, vegetation and soil properties.

Constraining dynamic TOPMODEL responses for imprecise water table information using fuzzy rule based performance measures

“…1c and d along with their cup depth below the soil surface. Notwithstanding, the tensiometer responses are consistent with similar responses on steep wet hillslopes published more recently on comparable slopes in Oregon (Torres et al, 1998), Japan (Uchida et al, 2001) and Singapore (Rezaur et al, 2002).…”

Bank erosion of legacy sediment at the transition from vertical to lateral stream incision

“…Soil pore pressure becomes less negative as soil saturation increases. Spatiotemporal variability is greatest in soils between rain events and decreases as the soil approaches saturation (Rezaur et al, 2002). To observe pore pressure variability as the subsurface approaches saturation, soil pore pressure was measured with six sets of tensiometers where each set included a tensiometer with a length of 25 (T25), 55 (T55), and 85 cm (T85).…”

Spatiotemporal Patterns of Soil Matric Potential in the Shale Hills Critical Zone Observatory

“…Compared with abundant research on soil moisture content (either gravimetric water content w or volumetric water content θ), limited research has been done to understand the spatiotemporal variability or pattern of soil matric potential (ψ), which exhibits a nonlinear relationship with w or θ. However, the energy status of soil water, as represented by ψ , is often more critical to processes such as water flow and solute transport (Hayashi et al, 2009), slope instability and erosion (Rezaur et al, 2002), tree xylem sap flow (Meinzer et al, 2013), greenhouse gas emission (Castellano et al, 2010), and soil water availability to plants (Pan et al, 2013). A total of 12 studies on ψ spatiotemporal variability are summarized in Table 1, from which four knowledge gaps were identified:…”