Nitrate loss from a restored floodplain in the Lower Cosumnes River, California

Sheibley, R. W., et al., 2006. Hydrobiologia

Original research (primary data)
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Floodplain restoration has been advocated as a means to restore several ecological services associated with floodplains: water quality improvement, fish rearing habitat, wildlife habitat, flood control, and groundwater recharge. A history of agricultural encroachment on the lower Cosumnes River has resulted in extensive channelization and levee construction. In fall 1998, an experimental floodplain was established by breaching a levee in order to restore the connection between the main channel and its historic floodplain. In this study, we examined how effective this newly restored floodplain was at processing nitrate (NO3-) before reentering the main channel downstream. Two methods were used to examine nitrate loss. In December 2001, we determined denitrification potentials of the floodplain soils before seasonal flooding inundated the floodplain. Next, we conducted a series of field soil column (mesocosm) experiments from March to June 2002 to study NO3–N loss from the overlying water in both sandy and clayey soils and at three levels of NO3–N (ambient, +1 mg N l(-1), +5 mg N l(-1)). In addition, we examined NO3–N loss from mesocosms with water only to determine if loss was related primarily to soil or water column processes. Denitrification potentials were highly variable ranging from 1.6 to 769 ng N2O-N cm(-3) h(-1). In addition, the denitrification potential was highly correlated with the amount of bioavailable carbon indicating that carbon was a limiting factor for denitrification. Nitrate-N loss rates from mesocosms ranged from 2.9 to 21.0 mu g N l(-1) h(-1) over all treatments and all 3 months examined. Significant loss of NO3–N (60-93%) from the water only treatment only occurred in June when warmer temperatures and solar radiation most likely increased NO3–N uptake by phytoplankton. When scaled up, potential NO3–N loss from the restored floodplain represented 0.6-4.4% of the annual N load from the Lower Cosumnes River during a typical wet year and similar to 24% during a dry year. During dry water years, the effectiveness of the floodplain for reducing nitrate is limited by the amount of N supplied to the floodplain. Results from this study suggest that restored floodplains can be an effective NO3- sink.

Case studies

Basic information

  • Case ID: INT-140-1
  • Intervention type: Restoration
  • Intervention description:

    In 1997, four breaches were cut into the east and south levee in order to reconnect the riparian floodplain with the adjacent Cosumnes River. Subsequent storms carried large woody debris, sand, water and associated nutrients onto the floodplain. On the lower Cosumnes River, levees are now being intentionally breached in an effort to restore river-floodplain connectivity. These intentional levee breaches allow water from the channel to spill into retired farmland during storm events, thus simulating natural flooding events. The development of floodplain topography from sediment deposition during floods on the lower Cosumnes River has led to the establishment of riparian vegetation and recruitment of large woody debris

  • Landscape/sea scape ecosystem management: Yes
  • Climate change impacts Effect of Nbs on CCI Effect measures
    Reduced water quality  Positive Nitrate-N loss rates
  • Approach implemented in the field: Yes
  • Specific location:

    The study site was located within the confines of the Cosumnes River Preserve, a restored flood- plain habitat located 34 km south of Sacramento, CA.

  • Country: United States of America
  • Habitat/Biome type: Other ecosystem type |
  • Issue specific term: Not applicable


  • Notes on intervention effectivness: The study looked at the extent to which the restored floodplain was able to reduce nitrate concentrations (impact water quality). There was no control per se but it is saying what the floodplain is capable of and anything it does will be additional (effective) to the situation without the intervention (even though this was not tested) because initially there was just no floodplain at all, only a channeled river.
  • Is the assessment original?: Yes
  • Broadtype of intervention considered: Not applicable
  • Compare effectivness?: No
  • Compared to the non-NBS approach: Not applicable
  • Report greenhouse gas mitigation?: No
  • Impacts on GHG: Not applicable
  • Assess outcomes of the intervention on natural ecosystems: No
  • Impacts for the ecosystem: Not reported
  • Ecosystem measures:
  • Assess outcomes of the intervention on people: No
  • Impacts for people: Not reported
  • People measures:
  • Considers economic costs: No
  • Economic appraisal conducted: No
  • Economic appraisal described:
  • Economic costs of alternative considered: No
  • Compared to an alternative: Not reported

Evaluation methodology

  • Type of data: Quantitative
  • Is it experimental: No
  • Experimental evalution done: Not applicable
  • Non-experimental evalution done: Empirical case study
  • Study is systematic: