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How does DSM2-Hydro calculate channel volume?

  • Hydro creates virtual cross-sections by interpolating cross-section input (see Tutorial 1: Channels) to create virtual cross-sections. Virtual cross-sections are created and used internally in Hydro by interpolating cross-section input.
  • Virtual cross-sections are usually not seen by the user. If the variable printlevel >= 5 in the SCALAR input section, virtual cross-sections will be written to output .hof file.
  • The 2012 Annual Report describes a change in the way volume is calculated: it used to use only the area of the cross-section in the middle of a computational reach, but now it uses all 3 of the cross-sections in a computational reach. Also, it describes an important change to the longitudinal interpolation used to create virtual cross-sections.
  • The 2016 Annual Report, section 3.4.2 indicates that the volume of a channel is calculated by multiplying the average of two cross-sectional areas by the distance between them. This process would then be repeated twice for each computational reach to find the volume.
  • Hydro will not converge well if cross-sectional area is not interpolated correctly. Previously, area at a given elevation between cross-section layers was calculated by interpolating area linearly between two layers. It has been changed to a = a1+(.5*(w1+w2))*h, where
    • a1 = area at lower elevation
    • w1 = width at lower elevation
    • w2 = width at higher elevation
    • h = distance from lower elevation to given elevation

References

Annual reports can be found here.

Ferreira I. and Sandhu, N. 2016 "Chapter 3: DSM2 Extension: A GIS-Based Approach."  In: Methodology for Flow and Salinity Estimates in the Sacramento-San Joaquin Delta and Suisun Marsh. 37th Annual Progress Report to the State Water Resources Control Board. California Department of Water Resources.

Liu L., Ateljevich E., and Sandhu P. 2012. “Chapter 2: Improved Geometry Interpolation in DSM2-Hydro.” In: Methodology for Flow and Salinity Estimates in the Sacramento-San Joaquin Delta and Suisun Marsh. 33rd Annual Progress Report to the State Water Resources Control Board. California Department of Water Resources.

Tom B. 1998. “Chapter 6: Cross-Section Development Program.” In: Methodology for Flow and Salinity Estimates in the Sacramento-San Joaquin Delta and Suisun Marsh. 19th Annual Progress Report to the State Water Resources Control Board. California Department of Water Resources.