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United States Department of Agriculture

Agricultural Research Service

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Precipitation in August on the Walnut Gulch Experiment Watershed

Hydrologic Processes and Global Climate Change
are studied at the Southwest Watershed Research Center to:

  • Investigate hydrologic processes and related variability with special emphasis on modeling, scaling and global change issues to understand water supply, water quality, energy and CO2 fluxes from managed and natural semi-arid watersheds
  • Integrate interdisciplinary field experiments, simulation models, remote sensing and geographic information systems (GIS) to improve our databases and our understanding of the impacts of global change on semiarid watersheds

Runoff Modeling

Runoff models are being developed, calibrated, validated, and applied for use in estimating the hydrologic responses to changes in rangeland management practices and/or climatic fluctuations.

An example is the KINEROS model.

 Flow front

A wave front traveling down a normally dry, alluvial channel on the Walnut Gulch Experimental Watershed.

 Runoff vs. Area Infiltration losses account for the runoff vs. area relationship seen in the graph at the right.

Climate Change
Carbon dioxide and moisture flux on rangelands

Atmospheric carbon dioxide (CO2) levels have doubled since the last Ice Age (from 175 ppm) and increased 25 to 30% during the last 150 years (from 275 to 355 ppm). CO2 levels are expected to double again over the next century.

Carbon dioxide and soil moisture flux measurements are being made at the Walnut Gulch Experimental Watershed.

The role of grasslands in mitigating human impacts on the global carbon balance and moisture fluxes is being evaluated to determine how carbon source/sink relationships and moisture fluxes change along large-scale natural environmental gradients.

 Tucson grassland

Last Modified: 11/1/2005