Identifying riparian sinks for watershed nitrate using soil surveys

J Environ Qual. 2001 Sep-Oct;30(5):1596-604. doi: 10.2134/jeq2001.3051596x.

Abstract

The capacity of riparian zones to serve as critical control locations for watershed nitrogen flux varies with site characteristics. Without a means to stratify riparian zones into different levels of ground water nitrate removal capacity, this variability will confound spatially explicit source-sink models of watershed nitrate flux and limit efforts to target riparian restoration and management. We examined the capability of SSURGO (1:15 840 Soil Survey Geographic database) map classifications (slope class, geomorphology, and/or hydric soil designation) to identify riparian sites with high capacity for ground water nitrate removal. The study focused on 100 randomly selected riparian locations in a variety of forested and glaciated settings within Rhode Island. Geomorphic settings included till, outwash, and organic/alluvial deposits. We defined riparian zones with "high ground water nitrate removal capacity" as field sites possessing both >10 m of hydric soil width and an absence of ground water surface seeps. SSURGO classification based on a combination of geomorphology and hydric soil status created two functionally distinct sets of riparian sites. More than 75% of riparian sites classified by SSURGO as organic/alluviumhydric or as outwash-hydric had field attributes that suggest a high capacity for ground water nitrate removal. In contrast, >85% of all till sites and nonhydric outwash sites had field characteristics that minimize the capacity for ground water nitrate removal. Comparing the STATSGO and SSURGO databases for a 64000-ha watershed, STATSGO grossly under-represented critical riparian features. We conclude that the SSURGO database can provide modelers and managers with important insights into riparian zone nitrogen removal potential.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Data Collection
  • Ecosystem
  • Environmental Monitoring*
  • Models, Theoretical
  • Nitrates / analysis*
  • Nitrogen / analysis*
  • Rain
  • Soil Pollutants
  • Trees*
  • Water Movements*
  • Water Pollutants

Substances

  • Nitrates
  • Soil Pollutants
  • Water Pollutants
  • Nitrogen