| Sumario: |
The economic activities of the Sonora strongly depend on groundwater extraction, which is generally of recent
meteoric origin. Understanding the hydrological functioning in this semi-arid region, located in northwestern
Mexico, is crucial for integrated water management in a changing climate. This study presents a spatio-temporal
analysis of the isotopic composition (δ18O, δ2
H, d-excess) during the 2018 rainy season in the Sonora River Basin
(SRB), a region influenced by the characteristic weather conditions of the North American Monsoon (NAM). The
basin is located in the central region of Sonora and covers an area of approximately 27,000 km2
. Precipitation
was collected using six passive totalizers, distributed spatially from the coast of the Gulf of California up to 1,425
m asl inland. The rainfall isotopic composition is comparable with the Global Meteoric Water Line (GMWL) and
with the records of the Global Isotope Network in Precipitation (GNIP) in Chihuahua, Mexico, between 1962 and
1988, and Tucson, Arizona (2018). The temporal variability of rainfall isotope ratios was Δ18O = 7.4‰ and Δ2
H
= 49.8‰, with a clear depletion pattern (low δ18O) as the monsoon rainy season progressed. The isotopic lapse
rate was found to be − 1.0‰ in δ18O per km of elevation as a result of the topography relief and rainout effects
within the basin. The influence of tropical cyclones such as Hurricane Sergio (October 2018) provided the opportunity to isolate the effects of a tropical storm with respect to the deep convective precipitation, typical of the
NAM systems over northwest Mexico
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