Determining storm sampling requirements for improving precision of annual load estimates of nutrients from a small forested watershed

Jun'Ichiro Ide, Masaaki Chiwa, Naoko Higashi, Ryoko Maruno, Yasushi Mori, Kyoichi Otsuki

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

T'his study sought to determine the lowest number of storm events required for adequate estimation of annual nutrient loads from a forested watershed using the regression equation between cumulative load (ΣL) and cumulative stream discharge (ΣQ). Hydrological surveys were conducted for 4 years, and stream water was sampled sequentially at 15-60-min intervals during 24 h in 20 events, as well as weekly in a small forested watershed. The bootstrap sampling technique was used to determine the regression (ΣL-ΣQ) equations of dissolved nitrogen (DN) and phosphorus (DP), particulate nitrogen (PN) and phosphorus (PP), dissolved inorganic nitrogen (DIN), and suspended solid (SS) for each dataset of ΣL and ΣQ. For dissolved nutrients (DN, DP, DIN), the coefficient of variance (CV) in 100 replicates of 4-year average annual load estimates was below 20% with datasets composed of five storm events. For particulate nutrients (PN, PP, SS), the CV exceeded 20%, even with datasets composed of more than ten storm events. The differences in the number of storm events required for precise load estimates between dissolved and particulate nutrients were attributed to the goodness of fit of the ΣL-ΣQ equations. Bootstrap simulation based on flow-stratified sampling resulted in fewer storm events than the simulation based on random sampling and showed that only three storm events were required to give a CV below 20% for dissolved nutrients. These results indicate that a sampling design considering discharge levels reduces the frequency of laborious chemical analyses of water samples required throughout the year.

Original languageEnglish
Pages (from-to)4747-4762
Number of pages16
JournalEnvironmental Monitoring and Assessment
Volume184
Issue number8
DOIs
Publication statusPublished - Aug 1 2012

Fingerprint

Watersheds
Nutrients
watershed
Sampling
Phosphorus
nutrient
Nitrogen
sampling
phosphorus
dissolved inorganic nitrogen
nitrogen
stratified flow
simulation
Water
water

All Science Journal Classification (ASJC) codes

  • Environmental Science(all)
  • Pollution
  • Management, Monitoring, Policy and Law

Cite this

Determining storm sampling requirements for improving precision of annual load estimates of nutrients from a small forested watershed. / Ide, Jun'Ichiro; Chiwa, Masaaki; Higashi, Naoko; Maruno, Ryoko; Mori, Yasushi; Otsuki, Kyoichi.

In: Environmental Monitoring and Assessment, Vol. 184, No. 8, 01.08.2012, p. 4747-4762.

Research output: Contribution to journalArticle

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