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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.scales [10] with substantial variations observed with soil depth [11][12][13]. For instance, θ in different soil layers is influenced by the productivity of terrestrial plants with varying rooting depths [14][15][16].Precipitation pulses are a first-order control on the seasonal variation of θ during the hydrological year, in particular for semiarid regions characterized by long periods of no rainfall [9,17,18]. In semiarid Mediterranean climate systems, the seasonality of precipitation (P) leads to high water availability in the winter season when potential evapotranspiration is low [19]. Winter precipitation influences diffuse recharge processes through vertical infiltration occurring in the soil profile (e.g., [20][21][22][23]). In mountain systems within these settings, soil thickness is generally shallow leading to the potential for rapid flow into fractures that underlie the soil [24]. As a result, the shallow monitoring of θ and its spatiotemporal variability in response to P should yield inferences on potential recharge in mountain block systems.Mountain block systems often have spatial variations in vegetation mediated by topographic position. For instance, plant distributions in mid-latitude regions exhibit changes between pole-facing slopes and equator-facing slopes (i...

En este estudio se llevó a cabo la evaluación de los períodos de sequía histórica que han afectado al Valle de Guadalupe en el Estado de Baja California, México, el cual pertenece a la subcuenca que lleva el mismo nombre. En esta región se llevan a cabo actividades agrícolas de gran importancia como el cultivo de olivo, hortalizas, hierbas de olor y uva de mesa, siendo la más representativa la producción de uva para la elaboración de vino. Por ser una zona semiárida el recurso hídrico superficial es limitado, por lo tanto, toda la demanda de agua la provee el Acuífero Guadalupe. Para cumplir con el objetivo de este estudio se utilizó el cálculo del índice de reconocimiento de sequía (IRS) para llevar a cabo la clasificación anual histórica, la severidad, la duración y la frecuencia de la sequía meteorológica. Se encontraron cuáles han sido los periodos más representativos que han afectado a la región (1999 - 2009) y se concluye que los resultados generados pueden relacionarse con el descenso en el volumen de recarga del acuífero.

Evaluating how meteorological drought affects areas covered by natural ecosystems is challenging due to the lack of ground-based climate data, historical records, and weather station observation with limited coverage. This research tests how the surface reflectance–derived indices (SRDI) may solve this problem by assessing the condition and vegetation dynamics. We use long–term, monthly surface reflectance data (26 hydrological years, 1992/93–2017/18) from Landsat 5 TM, 7 ETM+, and 8 OLI/TIRS satellites and calculated the following five SRDI: Normalized Difference Vegetation Index (NDVI), Land Surface Temperature (LST), Vegetation Health Index (VHI), Normalized Difference Water Index (NDWI), and Modified Soil Adjusted Vegetation Index (MSAVI). The SRDI allows us to detect, classify, and quantify the area affected by drought in the Guadalupe Valley Basin (GVB) via correlations with the Reconnaissance Drought Index (RDI) and the Standardized Precipitation Index (SPI) (weather station-based data). For particular SRDI–RDI and SRDI–SPI combinations, we find positive seasonal correlations during April–May (IS2) and for annual (AN) values (MSAVI IS2–RDI AN, R = 0.90; NDWI IS2–SPI AN, R = 0.89; VHI AN–RDI AN, R = 0.86). The drought–affected GVB area accounted for >87% during 2001/02, 2006/07, 2013/14, and 2017/18. MSAVI and NDWI are the best meteorological drought indicators in this region, and their application minimizes the dependence on the availability of climatic data series.