Abstract
In this research, we examined temporal variations in soil water content (θ), infiltration patterns, and potential recharge at three sites with different mountain block positions in a semiarid Mediterranean climate in Baja California, Mexico: two located on opposing aspects (south- (SFS) and north-facing slopes (NFS)) and one located in a flat valley. At each site, we measured daily θ between 0.1 and 1 m depths from May 2014 to September 2016 in four hydrological seasons: wet season (winter), dry season (summer) and two transition seasons. The temporal evolution of θ and soil water storage (SWS) shows a strong variability that is associated mainly with high precipitation (P) pulses and soil profile depth at hillslope sites. Results shows that during high-intensity P events sites with opposing aspects reveal an increase of θ at the soil–bedrock interface suggesting lateral subsurface fluxes, while vertical soil infiltration decreases noticeably, signifying the production of surface runoff. We found that the dry soil conditions are reset annually at hillslope sites, and water is not available until the next wet season. Potential recharge occurred only in the winter season with P events greater than 50 mm/month at the SFS site and greater than 120 mm/month at the NFS site, indicating that soil depth and lack of vegetation cover play a critical role in the transport water towards the soil–bedrock interface. We also calculate that, on average, around 9.5% (~34.5 mm) of the accumulated precipitation may contribute to the recharge of the aquifer at the hillslope sites. Information about θ in a mountain block is essential for describing the dynamics and movement of water into the thin soil profile and its relation to potential groundwater recharge.
Highlights
Understanding the dynamics and transport of soil water content (θ) in thin mountain soils is essential for describing infiltration in superficial and deeper soil layers
We found the fraction of infiltration that passed to underlying soil layers required precipitation events greater than ~10.5 mm for infiltration fronts to pass below the shallow soil layer precipitation events greater than ~10.5 mm for infiltration fronts to pass below the shallow soil layer
This study presents a comparison of soil water content measurements, soil water storage, infiltration and potential recharge at three sites representing different topographic positions in a mountain block within a semiarid Mediterranean climate ecosystem
Summary
Understanding the dynamics and transport of soil water content (θ) in thin mountain soils is essential for describing infiltration in superficial and deeper soil layers. Plant distributions in mid-latitude regions exhibit changes between pole-facing slopes and equator-facing slopes (in the northern hemisphere, north (NFS) and south (SFS) facing slopes), and it is recognized as a global phenomenon [25,26,27,28] This aspect of control is derived from increased exposure to solar radiation on the equator-facing slope and the consequences on the soil water content through evaporation and transpiration [26,29,30,31,32]. Spatial patterns in vegetation have consequences on the spatiotemporal distributions of θ [25,26] that might affect the potential for recharge in mountain systems on slopes with opposing aspects and soil water storage (SWS). We analyzed the spatiotemporal variation of θ at different depths to answer the following questions: how do soil depth, aspect, and precipitation magnitude control soil water content and infiltration in semiarid Mediterranean mountain systems? The comparison across sites was intended to yield information on potential recharge, which is important for quantifying available water resources in downstream valley areas
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