Get Updates on Upcoming Courses


Get Updates on Upcoming Courses

How often would you like to receive emails?

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


This course is the second installment in our four-part HSPF Hydrology Webinar Series—others include Introduction to HSPF Continuous Simulation; HSPF Calibration and Validation; and Solving Stormwater Problems with HSPF Modeling. Save 20% and earn 4 PDH / 0.4 CEU with our full-series bundle!

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.

Train Your Team
Get the whole team trained! We offer additional savings if you register as a group. For group pricing information, contact us at

* Presentations are scheduled for approximately one hour with a 15-20 minute question and answer session to follow. Presentations may exceed scheduled time. * Each state and certification agency have different requirements; it is your responsibility to know what they are. Note that 1 PDH = 0.1 CEU. * Purchase of this course allows you access to the presentation(s) for 6 months from the order date.

On-Demand Webcast
Each Session: 1 H 30 M
Lectures: 1
Credits: 1 PDH / 0.1 CEU

On-Demand Webcast > Stormwater ($79.00)


Special Group Pricing Available


Your Purchase Order Request has been submitted successfully