Quantifying the Hydrologic Response of a Regional Basin in Northwest Mexico through High-Resolution Hydrologic Simulations

Northwest Mexico is a semiarid region with a complex hydrologic regime characterized by a nine-month dry period centered in the winter and a dramatic shift during the North American monsoon from June to September, when most of the annual rainfall is received (~60%) and the vegetation vigorously greens. Quantifying the spatiotemporal variability of hydrologic fluxes and states in this water-limited region has been challenging due to lack of long-term hydrometeorological data. In this study, we attempt to address this issue by focusing on the Rio San Miguel, a regional basin of ~3800 km² in northwest Mexico that provides water for domestic and agricultural uses. For this goal, we conduct high-resolution hydrologic simulations with a physically-based model, known as TIN-based Real-Time Integrated Basin Simulator (tRIBS). The model was calibrated and validated using soil moisture (SM) and meteorological observations of a network installed under a combined effort of US and Mexican institutions, and remote sensing images of SM and land surface temperature. Simulations were conducted over a seven year period from 2004 to 2010 on a computer cluster at ASU, with forcings provided by the North American Land Data Assimilation system and time-varying vegetation parameters derived from remote sensing. Results indicate the following: (i) The basin hydrologic response has marked inter-annual variability. (ii) spatial patterns of SM and evapotranspiration (ET) are mainly dominated by soil texture, with an increasing influence on summer ET of ecosystem distributions, (iii) elevation plays also a role, with higher SM and lower ET in areas at mid-elevation, likely due to lateral transfer of SM from areas at higher elevation, and lower SM and higher ET at lower altitude due to higher evaporative demand, and (iv) monthly evaporation efficiency (ratio between ET and precipitation, P) depends mostly on dynamics of ecosystem greening, while the runoff efficiency (ratio between local runoff and P) is mainly associated with the distribution of P and soil texture. Results of this work are important to support water management and infrastructure planning in the basin.