Infiltration in layered loessial deposits: Revised numerical simulations and recharge assessment

Abstract

s u m m a r yThe objective of this study is to assess recharge rates and their timing under layered loessial deposits at the edge of arid zones. Particularly, this study is focused on the case of the coastal plain of Israel and Gaza. First, results of a large-scale field infiltration test were used to calibrate the van Genuchten parameters of hydraulic properties of the loessial sediments using HYDRUS (2D/3D). Second, optimized soil hydraulic parameters were used by HYDRUS-1D to simulate the water balance of the sandy-loess sediments during a 25-year period for three environmental conditions: bare soil, and soil with both sparse and dense natural vegetation.The best inverse parameter optimization run fitted the infiltration test data with the RMSE of 0.27 d (with respect to a moisture front arrival) and R 2 of 96%. The calibrated model indicates that hydraulic conductivities of the two soil horizons, namely sandy loam and sandy clay loam, are 81 cm/d and 17.5 cm/d, respectively. These values are significantly lower than those previously reported, based on numerical simulations, for the same site. HYDRUS-1D simulation of natural recharge under bare soil resulted in recharge estimates (to the aquifer) in the range of 21-93 mm/yr, with an average recharge of 63 mm/yr. Annual precipitation in the same period varied between 100 and 300 mm/yr, with an average of 185 mm/yr. For semi-stabilized dunes, with 26% of the soil surface covered by local shrub (Artemisia monosperma), the mean annual recharge was 28 mm. For the stabilized landscape, with as much as 50% vegetation coverage, it was only 2-3 mm/yr. In other words, loessial sediments can either be a source of significant recharge, or of no recharge at all, depending on the degree of vegetative cover. Additionally, the time lag between specific rainy seasons and corresponding recharge events at a depth of 22 m, increased from 2.5 to 5 years, and to about 20 years, respectively, with an increasing vegetative cover. For this reason, and also likely due to a great depth of loessial sediments, no correlation was found between annual recharge and annual precipitations of the same year or subsequent years. Similarly, no differences were found between summer and winter recharge fluxes. Instead, numerical simulations indicated continuous year-round recharge of the aquifer. We conclude that the layered subsurface acts as a short-term (annual) and long-term (multi-annual) buffer to smooth sudden precipitation/infiltration events. Vegetation conditions can help in predicting long-term recharge rates (as percentage of annual precipitation), which in turn need to be considered when assigning recharge characteristics in regional assessments and models.

Transient potential groundwater recharge under surface irrigation in semiarid environment: An experimental and numerical study

“…The correlation coefficient was also strong for R1 when the threshold value was included. It was consistent with the results of the previous study by Dafny and Šimůnek (), in different situations, that potential recharge may occur only after a threshold value of precipitation events. In other words, groundwater potential recharge would occur only when the hydraulic potential at the wetting front exceeded the suction pressure of the smallest pore scales.…”

Recent Developments and Applications of the HYDRUS Computer Software Packages

“…Historically, one of the most common applications (∼40 papers) of the HYDRUS models have been to estimate subsurface water fluxes and groundwater recharge and how these processes are affected by soil surface and root zone conditions such as precipitation, evaporation, and the presence or absence of plants (e.g., Scanlon et al, 2002, 2003; Garcia et al, 2011; Kurtzman and Scanlon, 2011; Kodešová et al, 2014; Fan et al, 2015; Turkeltaub et al, 2014; Dafny and Šimůnek, 2016; Neto et al, 2016). For example, Dafny and Šimůnek (2016) showed that for the coastal plain of Israel, groundwater recharge dramatically decreases as a percentage of precipitation from ∼30% to ∼10 and 1% for conditions with bare sandy loess and sandy loess with vegetative covers of 26 and 50%, respectively.…”

Effect of initial soil water content and bulk density on the infiltration and desalination of melting saline ice water in coastal saline soil

“…It is important to note that the soil column experiment in the present study was performed on homogeneous soil and melting temperatures, whereas soil spatial heterogeneity is usual for chemical and physical properties, including water, salt and soil pores, which influence hydraulic conductivity and the rate of infiltration of melting saline ice (Assouline, ; Carvalho, Eduardo, Almeida, Santos, & Sobrinho, ; Dafny & Šimůnek, ). The above factors all further influence the salt leaching effect in saline soil (Chaganti et al, ).…”

“…usual for chemical and physical properties, including water, salt and soil pores, which influence hydraulic conductivity and the rate of infiltration of melting saline ice (Assouline, 2013;Carvalho, Eduardo, Almeida, Santos, & Sobrinho, 2015;Dafny & Šimůnek, 2016). The above factors all further influence the salt leaching effect in saline soil (Chaganti et al, 2015).…”