# Watershed area and discharge relationships

#### Summary

Students use USGS WaterData website to find data on area, average annual discharge and response to high-precip events in small watersheds in southern New England. Data for the class are compiled to generate graphs showing the regional relationships between (1) area and discharge, and (2) area and time-lag between precip and maximum discharge.

terms: discharge, watershed, flood

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## Context

#### Audience

undergraduate elective course in environmental geology

#### Skills and concepts that students must have mastered

retrieving data from a website
retrieving data from a graph
basic map skills (finding a location)
unit conversion/dimensional analysis

#### How the activity is situated in the course

This exercise is a stand-alone exercise that provides part of our discussion of the water cycle and local river systems.

## Goals

#### Content/concepts goals for this activity

The main goal of this exercise is to understand the regional relationship between watershed area and river discharge. The secondary goal is to understand that the time/duration of high discharge events also scales with watershed size.

#### Higher order thinking skills goals for this activity

As the class's data are compiled, student can see first hand how well the data support their hypotheses. Outliers are examined in greater detail, to see if those watersheds differ (in land use, water management) from the main population.

## Description and Teaching Materials

In this activity, students are supplied a worksheet that walks through accessing and retrieving streamflow data from the USGS WaterData website. Students record their data on the worksheet. Students are asked to convert discharge from cfs to metric units, and to scale up average discharge in volume/second to annual discharge. Students bring their worksheets to class to supply specific data: watershed area, annual discharge, maximum discharge following a precip event, and time lag between min and maximum discharge in response to a precip event. In class, we compile these data, and generate three graphs that show watershed area (x-axis) against (a) annual discharge, (b) max discharge following a storm, and (c) time in hours for a storm to be expressed in high discharge.

Student Worksheet for Watershed Area/Discharge Assignment (Microsoft Word 2007 (.docx) 127kB Apr15 13)

## Teaching Notes and Tips

This exercise can be ended following question #12. This limits the hypotheses to the first one: correlation between watershed area and discharge. If there has been a large precipitation event in the days/weeks before this exercise is assigned, students should continue with the entire worksheet to explore the 2nd and 3rd hypotheses.

## Assessment

If the students come to class prepared to share the required data, and the data are in appropriate units and on reasonable scale, then they have successfully completed the exercise. This exercise could be completed as a lab section or in a computer lab, if instructor supervision is needed.