Urbanization alters dramatically watershed ecosystem processes. Land-use change and anthropogenic activities contribute to increased inputs of nutrients and other materials, while changes to land cover alter hydrology and the corresponding movement of materials. These changes have ramifications for both watershed processes and downstream systems. The impacts of urbanization on aquatic systems are well-studied, and frequently encapsulated in the ‘urban stream syndrome’ (Walsh et al. 2005) that describes, among others, increased nutrient loading and stream flashiness. However, there is some evidence that aridland cities behave differently (Grimm et al. 2004, 2005), and the complex dynamics among catchment characteristics, storm attributes, and runoff in highly urbanized settings of the arid Southwest remains poorly understood.
To enhance our understanding of stormwater dynamics and watershed functioning in aridland, urban environments, the Central Arizona–Phoenix Long-Term Ecological Research (CAP LTER) program began monitoring stormwater runoff at the outflow of the Indian Bend Wash (IBW) in 2008. The IBW is a tributary to the Salt River in central Arizona, and is a major drainage within the greater Phoenix metropolitan area, encompassing much of the City of Scottsdale. A model of soft engineering, the IBW as it runs through much of the City of Scottsdale is comprised largely of a series of artificial lakes, parks, paths, golf courses, ball fields, and other non-structural elements designed with the dual roles of providing outdoor amenities to the City residents while serving as an effective flood water conveyance feature. A unique biogeochemistry of this novel system is detailed by Roach et al. (2008), and Roach and Grimm (2011).
Stormwater sampling is conducted at numerous locations. The longest running sampling location is near the outflow of the IBW ~0.6 km above its confluence with the Salt River. The sampling location coincides with a permanent USGS gauging station (USGS 09512162 INDIAN BEND WASH AT CURRY ROAD, TEMPE, AZ) that provides corresponding discharge data. Additional sampling sites in the Indian Bend Wash catchment include at the Silverado Golf Course (SGC) and Lake Marguerite (LM), both in Scottsdale, Arizona. These sites were part of a separate stormwater study (Stormwater Nitrogen in Arizona (SNAZ)), and additional data, such as rainfall chemistry, at those sites are available in a data package specific to the SNAZ project. Sampling at both SGC and LM are colocated with Maricopa County Flood Control District monitoring stations, which are a source of discharge data at those locations. The CAP LTER also monitors discharge at several locations along the Salt River in central Arizona. At all sites, automated stormwater sampling equipment (ISCO® 6700 automated pump sampler) is used to collect discrete stormwater samples throughout the hydrograph of most runoff-generating storms.
Grimm N.B., Arrowsmith J.R., Eisinger C., Heffernan J., MacLeod A., Lewis D.B., et al. (2004) Effects of urbanization on nutrient biogeochemistry of aridland streams. In: Geophysical Monograph Series. (Eds R.S. DeFries, G.P. Asner and R.A. Houghton), pp. 129–146. American Geophysical Union, Washington, D. C.
Grimm N.B., Sheibley R.W., Crenshaw C.L., Dahm C.N., Roach W.J. and Zeglin L.H. (2005) N retention and transformation in urban streams. Journal of the North American Benthological Society 24, 626–642.
Hale R.L., Turnbull L., Earl S., Grimm N., Riha K., Michalski G., et al. (2014a) Sources and Transport of Nitrogen in Arid Urban Watersheds. Environmental Science & Technology 48, 6211–6219.
Hale R.L., Turnbull L., Earl S.R., Childers D.L. and Grimm N.B. (2014b) Stormwater Infrastructure Controls Runoff and Dissolved Material Export from Arid Urban Watersheds. Ecosystems 18, 62–75.
Roach W.J. and Grimm N.B. (2011) Denitrification mitigates N flux through the stream–floodplain complex of a desert city. Ecological Applications 21, 2618–2636.
Roach W.J., Heffernan J.B., Grimm N.B., Arrowsmith J.R., Eisinger C. and Rychener T. (2008) Unintended consequences of urbanization for aquatic ecosystems: a case study from the arizona desert. BioScience 58, 715–727.
Walsh C.J., Roy A.H., Feminella J.W., Cottingham P.D., Groffman P.M. and Morgan II R.P. (2005) The urban stream syndrome: current knowledge and the search for a cure. Journal of the North American Benthological Society 24, 706–723.
