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Soil waters are a central component of the terrestrial water cycle. Their δ2H, δ18O, and d‐excess values contain rich information about hydroclimate, including the source of moisture and its evaporative history. Paleoclimate workers seek to investigate ancient hydroclimates via triple oxygen isotope geochemistry, termed Δ′17O, which is analogous to d‐excess but can be measured in oxygen‐bearing minerals in paleosols. Observations of Δ′17O in soil water across climates, seasons, and depths are needed to establish a framework for applying Δ′17O to paleohydrology. We measured the δ18O, δ2H, and Δ′17O values in soil waters (0–1 m) and precipitation in the Mojave, Great Basin, and Chihuahuan Deserts and in a temperate forest in Michigan. Evaporation drives covariation in Δ′17O and d‐excess in soil waters. The range of Δ′17O values in soil waters (−148 to 44 per meg) spans the heretofore observed range of Δ′17O in the water cycle. The uppermost 20 cm of the soil profiles experience the greatest isotopic variation as soil water is subject to infiltration and evaporation. Each environment displays a distinct pattern in δ18O, d‐excess, and Δ′17O of soil water. Soil water at the forested site has isotope values that closely adhere to meteoric waters. In contrast, at the dryland sites, evaporation causes soil waters to deviate from meteoric waters along site‐specific trajectories. The Δ′17O patterns in soil waters adhere to expectations based on d‐excess, strongly affirming the utility of Δ′17O in fossilized soil sediments and in modern soil waters to investigate the water cycle.

Relatively little is currently known about the spatiotemporal variability of land surface conditions during the North American monsoon, in particular for regions of complex topography. As a result, the role played by land–atmosphere interactions in generating convective rainfall over steep terrain and sustaining monsoon conditions is still poorly understood. In this study, the variation of hydrometeorological conditions along a large-scale topographic transect in northwestern Mexico is described. The transect field experiment consisted of daily sampling at 30 sites selected to represent variations in elevation and ecosystem distribution. Simultaneous soil and atmospheric variables were measured during a 2-week period in early August 2004. Transect observations were supplemented by a network of continuous sampling sites used to analyze the regional hydrometeorological conditions prior to and during the field experiment. Results reveal the strong control exerted by topography on the spatial and temporal variability in soil moisture, with distinct landscape regions experiencing different hydrologic regimes. Reduced variations at the plot and transect scale during a drydown period indicate that homogenization of hydrologic conditions occurred over the landscape. Furthermore, atmospheric variables are clearly linked to surface conditions, indicating that heating and moistening of the boundary layer closely follow spatial and temporal changes in hydrologic properties. Land–atmosphere interactions at the basin scale (~100 km²), obtained via a technique accounting for topographic variability, further reveal the role played by the land surface in sustaining high atmospheric moisture conditions, with implications toward rainfall generation during the North American monsoon.

This study describes the physical and biophysical characteristics of watersheds near Chihuahua City, Mexico. Natural resource assessments in which water resources play a major role are being addressed by official agencies within the Mexican government. These natural resources assessments are critical in arid regions where surface water resources are scarce and groundwater is the main source of the vital liquid. The water supply of the city of Chihuahua, Mexico is directly dependent on the quality and quantity of water in surrounding aquifers. However, the water resources of the area adjacent to the city are insufficient in volume and time to supply the demand of the agriculture, urban, industrial, ecological and treaty needs in the region. In addition, changes in land cover associated with extended drought conditions and social and economic factors may have affected the biophysical (land and vegetation cover) conditions of the watersheds feeding the aquifers, negatively altering the recharge of the aquifers. In order to quantify the factors impacting recharge of Chihuahua City's aquifers, a descriptive study of the physical and biophysical characteristics of the watersheds around Chihuahua City was made using a GIS (geographic information system) and remote sensing images. The major watersheds' sub-basins around Chihuahua City are characterized using digital elevation models (DEMs), Landsat Thematic Mapper scenes and digital thematic maps. An effort to describe the ecologic-hydrologic status of these sub-basins will be made using standard procedures published by INE-SEMARNAT and other previous work. The study is aimed to help in land use planning and the prospecting for and characterization of water resources in the area.