The Importance of Long-term Observations for Understanding Dryland
The Southwest Watershed Research Center (SWRC) of the United States
Department of Agriculture-Agricultural Research Service has been
conducting arid and semiarid (dryland) watershed research since 1953.
This included establishment and continuous operation of the Walnut Gulch
Experimental Watershed (WGEW) in southeast Arizona. The 149
km2 ephemeral watershed is one of the most densely
instrumented dryland research catchments in the world with a drainage
area greater than 10 km2. This instrumentation
captures many aspects of the hydrological cycle including how
precipitation is partitioned into soil moisture, runoff and
evapotranspiration and its subsequent effects on sediment transport,
vegetation productivity, carbon sequestration, and groundwater recharge.
The long-term, high-resolution record of observations on the WGEW
enables understanding of the mean and variability of the hydrological
processes, not well characterized with shorter term records, that fail
to capture the large variability common to dryland regions. This
presentation will highlight trends in temperature, precipitation, and
runoff over the WGEW observation period. Additional research findings
made by the SWRC and collaborators on erosion; plant productivity and
carbon sequestration; the facilitation of soil water redistribution by
plant roots; and groundwater recharge will also be presented.