Unit 7.1: Model My Watershed

Introduction

Humans are agents of change in the Critical Zone. This unit focuses on the land/water connection and on how human-induced land use change affects local hydrology. This unit draws on the previous module relating data to predict the characteristics regarding water moving through the built environment. In this unit, you will use a powerful tool, Model My Watershed^TM, to:

• Describe what a watershed is and delineate a watershed on a map;
• Identify the key factors in a watershed that impact runoff and sediment yield, describe how increased storm-water runoff affects landscapes (e.g., erosion, channel incision, sedimentation) and describe how those factors are impacted by human development;
• Evaluate the impact of human alterations to the landscape and investigate how best-management practices can lessen those impacts;
• Compare social and economic impacts from both runoff changes and from mitigation measures;
• Analyze how neighborhood redevelopment can affect local communities, to their benefit and/or to their detriment.

A water cycle budget tells us that precipitation is partitioned between runoff, infiltration or evapotranspiration. Often times, we assume that the annual change in soil moisture storage is zero but this certainly is not the case in times of drought! Soils, or lack thereof -ie. impermeable surfaces, are a key player and urban land and water managers are paying closer attention to how to better manage runoff, both in terms of quantity and quality. This unit allows you to explore both causative factors of extreme urban runoff and best management strategies for dealing with these flows.

Unit 7.1: Model My Watershed

Part 1 - Watershed Modeling

Model my Watershed Background

• The class should:
• Review the Water balance Equation: Ppt = ET + Runoff + Infiltration;
• Review function of Daily Water Budget using:
• Micro Site Model
• Review Watershed Delineation
• Watershed Delineation Animation - Simple
• Watershed Visualization - Verde River
• Discuss what to do for the assignment and discuss tips for running the model.
• Preview the material found at Model My Watershed - about.
• Play around with the Micro Site Model to get a feeling for the effect of Land cover and Soil on the Water Budget.

• You will complete one of the following two activities as detailed by your instructor. Pay particular attention to the limitations of this model and how you might validate its results.

Option A - Model My Watershed

Activity - Use "Model My Watershed" to investigate the water budget and water quality of your site

• Launch the Model My Watershed App (either login as a User or a Guest).
• Zoom into some area of interest;
• For rural watershed-scale areas, turn on HUC-12 Watershed boundaries using "Select by Boundaries".
• For smaller urban areas, use "Draw Area" to define your area of interest.
• Analyze Tab contains:
• Land Tab - Bar chart of % Landcover
• Soil Tab - Bar chart of % Soil infiltration capacity
• Animals Tab - Farm census for your area
• Point Sources (if any) from EPA NPDES (National Pollutant Discharge Elimination System)
• Water Quality - Delaware River Basin only
• Model Tab (Site Storm Model (with precipitation controlled by slider) or Watershed Multi-year (annual) Model
• Runoff/Hydrology Tab - Water Budget components: Graphs (above), Table (below)
• Water Quality Tab - Water Quality component Tables: Landcover source zone (above), TMDL (below)
• Do these make sense based on what you know about the area?
• How does amount of precipitation affect the water balance? (site storm model)
• Which seasons contribute the most sediment to the stream? Why? (multi-year model)

Option B - Stormwater Management - Best Management Practices (BMP)

Use this Stormwater Management Activity to answer the question - What are the water-related issues on your campus or in your area?

• Identify potential issues on your campus that relate to storm-water runoff. For example, are there areas where water pools in a storm, or gullies or rills that develop because water is not infiltrated? Take photos of them and annotate them to describe what is happening.
• Using what you have learned from the Generic Model, describe what combinations of storm intensities, land cover types and soil textures are most common on your campus.
• How do local conditions (impervious surfaces, fine soils, etc.) influence the fate of the rainwater in your area? Are there places on the campus where you often see puddles, erosion, deposition or other results of storm runoff?

Activity - Research different types of BMPs.

• Research different types of best management practices (BMPs).

Each individual or group should select one of the BMPs below or develop one of their own, with the approval of the instructor. Each group should describe how the BMP is designed, built and maintained to address your local conditions. They should also discuss how, if at all, this BMP is modified to reflect the environment in which it is built (urban, rural, temperate, arid). In addition, they should provide information on the cost/sq. ft. of the BMP; the average reduction of runoff that it provides; where this BMP is best implemented (large scale development, single home, campus, etc.) and, finally, recommend where, if at all, this BMP should be integrated on or near their campus. Below is a list of typical BMPs. Also see references below.

• Green/vegetated roofs
• Permeable pavement
• Bio-retention cells
• Vegetated infiltration basins
• Rain gardens
• Grassed swales
• Rain barrels and cisterns
• Riparian buffers

Part 2 - Watershed Modeling (Continued)

In-class

Class Discussion

• Be prepared to discuss any questions about the model or the results that you obtained from the previous class period's activities.
• Continue working on the same option you chose in Part 1 or as directed by your instructor:

Option A (cont) - Model My Watershed or Stormwater Management Activity

• Activity - Use "Model My Watershed" to investigate the impact of Conservation practices on your watershed

• Launch the Model My Watershed App (either login as a User or a Guest)
• Zoom into some area of interest;
• For rural watershed-scale areas, turn on HUC-12 Watershed boundaries using "Select by Boundaries".
• For smaller urban areas, use "Draw Area" to define your area of interest. (Best choice for scenario analysis)
• Enter the Model Tab and select the "Site Storm Model"
• Start a new scenario by using the "+ Conservation Practice" tab in the upper left.
• Define one or more areas having a "new" conservation practice and compare how the area's water budget changes using the "Compare" icon in the upper right. Return to the previous page using the "Navigate Scenarios" link at the bottom left of the page.
• A turning ring icon is displayed under the "Runoff and Water Quality" icons to indicate when the model is recalculating values.
• Investigate at least 2 scenarios under the Model/Runoff Tab and write a short summary of the conditions and related water balance.
• Investigate at least 2 scenarios under the Model/Water Quality Tab and write a short summary of the conditions and related water quality.
• Fill out the following worksheet to document ways you have reduced storm runoff
• Worksheet: Student Worksheet (Microsoft Word 2007 (.docx) 18kB Feb19 17)

Option B (cont) - Investigate Stormwater Management BMP's to answer the question:

Focus Question: How can you modify your campus in a way that is acceptable to the community and improves the hydrology?

Using a Google Earth image of your campus, each group should indicate areas where you would recommend BMPs to reduce runoff. What BMPs would you recommend at each site? Why that BMP? You will find that BMPs are basically the same throughout different environments. However, they will use different vegetation that reflects local climate. These projects should be presented to the class.

Presentations (3-4 min each)

• Each presenter/group should develop a map with recommended changes to the existing conditions and a summary to provide an overview for classmates of what they recommend, what challenges they anticipate and how they addressed them.

Class Discussion

• Once all of you and your peers have provided the class with their scenario overviews, you should discuss similarities and differences in treatments and what challenges they had improving the hydrology while reducing impacts on their community. You should also discuss whether there are any areas near where they live that have similar problems and how one could address those problems.

Homework

• Please complete this online assessment prior to the next class period. Assessment: Model My Watershed Pre / Post Test (Acrobat (PDF) 250kB Feb12 17).

Additional Resources

Model My Watershed Instruction Sheets are available from WikiWatershed, an initiative of Stroud™ Water Research Center

• Finding Your Watershed
• Using Model my Watershed
• Using the Micro Site Storm Model

Best Management Practices

• EPA - National Menu of BMP's for Stormwater link
• USDA/NRCS - Unlock the Secrets of Soil - Soil Health
• USFS - National Best Management Practices (BMP) - Watershed scale
• UIext - Stormwater BMP - Start at home
• VA WRRC - Stormwater BMP Clearinghouse

Other Related resources

• TR-55 Model
• Using Curve Numbers (link unavailable0
• Mill Creek Article
• Related SERC activity: Watershed Delineation Unit
• Kid's Activity: Watershed World Activity (Acrobat (PDF) 189kB Aug2 13)