PERLNDs, IMPLNDs, and RCHRESs—Oh My! – 2021

What in the world are PERLNDs, IMPLNDs, and RCHRESs???

PERLND, IMPLND, and RCHRES are the three major modules in Hydrological Simulation Program – Fortran (HSPF) that work together to simulate streamflow. While PERLNDs represent hydrologic processes on pervious land areas, IMPLNDs simulate impervious areas. RCHRESs, on the other hand, route the PERLND- and IMPLND-generated runoff to a downstream point of interest.

Join prolific speaker Doug Beyerlein (P.E., P.H., D.WRE) for this live, educational webinar examining the PERLND, IMPLND, and RCHRES modules used to simulate streamflow; the differences in PERLND and IMPLND algorithms, input parameters, and appropriate parameter values; and how to route streamflow through a conveyance system using RCHRES.

We’ll begin by taking a look at the PERLND module. The heart of HSPF, this module includes 17 parameters that require user input to compute surface runoff, interflow, and groundwater, in addition to soil moisture and evapotranspiration. We’ll then move on to the IMPLND module. While the algorithms, input parameters, and appropriate parameter values are simple in comparison to the PERLNDs, we’ll learn how the IMPLND module still has an important role in calculating total runoff, particularly in generating peak flows. We’ll then jump into the RCHRES module, which routes the PERLND and IMPLND-generated runoff through a conveyance system (either natural or human-made) to simulate streamflow. We’ll wrap up by examining the equations, assumptions, and limitations of the RCHRES module.

Learning Objectives 
Attendees can expect the discussion and education of the following learning objectives.

  • Define a PERLND, IMPLND, and RCHRES.
  • Learn the 17 PERLND parameter values, how they interact to compute runoff, and appropriate parameter values for each.
  • Analyze how IMPLND parameters and algorithms generate surface runoff.
  • Understand the relationship and interaction between PERLNDs, IMPLNDs, and RCHRESs and how they work together to simulate streamflow.
  • Learn how to route streamflow through a conveyance system.
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Course Includes

  • 1 Lesson
  • Course Certificate