Prerequisites for Accurate Monitoring of River Discharge Based on Fixed-Location Velocity Measurements

K. Kästner (Corresponding Author), A.J.F. Hoitink, P.J.J.F. Torfs, Bart Vermeulen, Nining S. Ningsih, M. Pramulya

Research output: Contribution to journalArticleAcademicpeer-review

13 Citations (Scopus)
63 Downloads (Pure)

Abstract

River discharge has to be monitored reliably for effective water management. As river discharge cannot be measured directly, it is usually inferred from the water level. This practice is unreliable at places where the relation between water level and flow velocity is ambiguous. In such a case the continuous measurement of the flow velocity can improve the discharge prediction. The emergence of horizontal acoustic Doppler current profilers (HADCPs) has made it possible to continuously measure the flow velocity. However, the profiling range of HADCPs is limited, so that a single instrument can only partially cover a wide cross-section. The total discharge still has to be determined with a model. While the limitations of rating curves are well understood, there is not yet a comprehensive theory to assess the accuracy of discharge predicted from velocity measurements. Such a theory is necessary to discriminate which factors influence the measurements, and to improve instrument deployment as well as discharge prediction. This paper presents a generic method to assess the uncertainty of discharge predicted from range-limited velocity profiles. The theory shows that a major source of error is the variation of the ratio between the local and cross-section averaged velocity. This variation is large near the banks, where HADCPs are usually deployed, and can limit the advantage gained from the velocity measurement. We apply our theory at two gauging stations situated in the Kapuas River, Indonesia. We find that at one of the two stations the index-velocity does not outperform a simple rating curve.
Original languageEnglish
Pages (from-to)1058-1076
Number of pages19
JournalWater resources research
Volume54
Issue number2
Early online date30 Jan 2018
DOIs
Publication statusPublished - Feb 2018

Keywords

  • UT-Hybrid-D
  • index velocity
  • velocity profile
  • rating curve
  • Indonesia
  • Kapuas River
  • discharge

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