DOI: 10.6073/pasta/1bdaf5e8a2fa47ca47852943a36cb256
title: Long-term monitoring of stormwater runoff and water quality in urbanized watersheds of the greater Phoenix metropolitan area, ongoing since 2008

description: Urbanization dramatically alters 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 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 major drainage in the greater Phoenix
  metropolitan area, draining much of the City of Scottsdale, and a
  tributary to the Salt River. A model of soft engineering, the IBW as
  it runs through 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 and as a floodplain.
  A unique biogeochemistry of this novel system is detailed by Roach et
  al. (2008), and Roach and Grimm (2011).

      
  Stormwater sampling is conducted 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. Automated stormwater sampling equipment (ISCO® 6700
  automated pump sampler) is used to collect discrete stormwater samples
  throughout the hydrograph of most runoff-generating storms.

      
  Data and expertise garnered by the stormwater monitoring near the
  outflow of the IBW helped pave the way for a more expansive stormwater
  research effort facilitated by a leveraged grant from the National
  Science Foundation (DEB-0918457, NSF Ecosystems, 2009-13). Through the
  Stormwater Nitrogen in Arizona (SNAZ) project, ten hierarchically
  nested urban stormwater catchments in Scottsdale and Tempe, AZ were
  instrumented with automated stormwater samplers (ISCO® 6700 automated
  pump samplers). A subset of those 11 locations were fitted with
  bubbler modules (ISCO® 720 bubbler modules) for quantifying water
  height (and subsequently discharge), and tipping-bucket rain gauges
  (ISCO® 674). The ten study catchments differed in type of stormwater
  infrastructure, spanning a continuum from highly engineered stormwater
  infrastructure in older residential areas to non-engineered washes in
  the desert, but not in land-use type (land use in all study catchments
  is predominantly residential). As per sampling near the outflow of the
  IBW, discrete stormwater samples were collected from most
  runoff-generating storms at the outflow of the 10 study catchments
  from the fall of 2010 through the summer 2012. Rainfall samples were
  collected at a subset of the locations during several storms to
  provide data that would contribute to an assessment of sources of
  materials in runoff. Results of this study are detailed by Hale et al.
  (2014a, 2014b). Sampling at most locations ceased at the end of the
  SNAZ award period, but the CAP LTER continues its long-term monitoring
  of runoff near the outflow of the IBW. Four new sites that drain into
  the Salt River were added in the winter of 2016. Three of the new
  sites are located near downtown Phoenix in the Rio Salado habitat
  restoration area, and the fourth catching runoff from numerous
  freeways and entering the Salt River channel above the Tempe Town
  Lake.

      
  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.