Last Modified: 2025-04-02 12:16:43.284

Software Version

HEC-HMS version 4.13 beta x was used to create this tutorial. You will need to use HEC-HMS version 4.13 beta x, or newer, to open the project files.

Project Files

Download the initial HEC-HMS project files here:

Maricopa_initial.zip

Overview

This tutorial will guide you through the process of using Maricopa County parameter estimation tools to estimate Green-Ampt parameters. The initial Green-Ampt loss tool became available in HEC-HMS version 4.9. It follows methodology in Rawls et al (1983) which is what was used in the 2018 Maricopa County Hydrology Manual. More recently, in version 4.13 beta x, a revised Green-Ampt parameter estimation tool was added that follows methodology in Saxton and Rawls (2006) and is in alignment with the revised 2023 Maricopa County Hydrology Manual. The Maricopa tools were designed specifically to accompany a standard work flow followed by Maricopa County water professionals.

Data

The Maricopa Green-Ampt wizard tool will require several geo-spatial files and tabular CSV files as inputs. These include existing subbasin, soils, and land use shapefiles, as well as landuse and soils tables in CSV format. These files are included in the zipped initial project files located above.

Applying the Maricopa Green-Ampt Parameter Estimation Tool (2023 Method)

Download the "Maricopa_initial.zip" file to your C drive and extract it.
Open HEC-HMS version 4.13 beta x, or newer.
Click File | Open and navigate to the "Maricopa.hms" file within the extracted Maricopa folder to open the project.
Navigate to the Maricopa Green-Ampt parameter estimation tool by clicking Tools | Data | Maricopa | Loss | Green-Ampt...
A popup will appear where you can select the original 2018 methodology based on Rawls et al (1983), or the revised 2023 methodology based on Saxton and Rawls (2006). Select the recommended 2023 Method button to launch a wizard.
The first step of the Maricopa Green-Ampt Wizard requires a basin model to be selected. Select the Maricopa 2023 basin model and click Next.
The second step of the wizard requires a landuse shapefile, landuse lookup table, soils shapefile, and soils lookup table to be selected. All the necessary files are located in the "...data/maricopa_data/green_ampt/2023 Methodology" folder. Select the necessary inputs and click Next.
The third step of the wizard involves defining the fields that will be used to join the landuse shapefile and landuse lookup table, as well as the soils shapefile and the soils lookup table. Specify the join fields and click Next.
The fourth and final step of the wizard involves matching various input parameters to their field names in the two lookup tables (landuse and soils). Match the parameters to their field names in the lookup tables as seen below. If the header names in each of the two input tables follows the normal Maricopa convention, the dropdown menus should default to the correct selections. Click Next.
Once the calculations are complete, the Green and Ampt loss global editor will automatically be populated with Initial Type, Initial Deficit, Suction, Conductivity, and Percent Impervious parameters. The user may choose to edit any of the calculated parameters in the global editor, or accept them as they are. Select Apply to save the loss parameters.
Select Close to exit the Green and Ampt global editor. The Simple Canopy global editor should now be visible with calculated estimates for Max Storage. The user may choose to edit any of the calculated parameters in the global editor, or accept them as they are. Select Apply to save the canopy parameters.
Select Close to exit the Simple Canopy global editor. Save the project.
Additionally, HEC-HMS will output intermediate calculations as notes in the message console.