The USDA-ARS experimental watershed network - evolution, lessons learned, and moving forward.
The USDA-Agricultural Research Service's Experimental Watershed Network grew from Dust Bowl era efforts of the Soil Conservation Service in the mid 1930's with the establishment of watersheds in three States; one of which is still in operation. In the mid-50's five centers with intensively instrumented watersheds at the scale of 100 to 700 km2 were established. Primary network research objectives were to quantify the field-scale and downstream effects of conservation practices and develop rainfall-runoff relationships for design of water conservation structures. USDA-ARS has operated over 600 watersheds in its history and continues to operate roughly 120 watersheds, many of which consist of gauged subwatersheds nested within larger gauged watersheds to enable investigation of scaling. With passage of the Clean Water Act in 1972, research objectives have evolved to add a variety of observations relevant to the water quality issues in their respective regions resulting in a more diverse, but less homogeneous network. The core instrumentation and related long record of high-quality observations have led to initiation of a series of multi-location projects to examine trends and directions of these observations across the network. As a result of their long history, intensive monitoring, and well described processes, the USDA-ARS watersheds have been used extensively in the development and validation of numerous watershed models. In addition, they served, and continue to serve as validation sites for aircraft and satellite based remotely sensed instruments. Many of the USDA-ARS Experimental Watersheds have now joined the Long-Term Agro-ecosystem Research Network (LTAR) (Maddox, 2013). This presentation will review major activities and advances derived from the network in addition to discussing some lessons learned in the long-term operation of a national scale network through its evolution from analog to digital instrumentation and internet accessibility.