Writing prompt Grade 9 Science
How Draining Cawthorne Marsh Changed Drumlane's Water
A grade 9 science explanatory prompt where students use a fictional monitoring table to explain how draining a marsh changed floods, summer flow, and temperature.
Objectives
- Students will explain how removing wetland storage changes storm peaks and summer flow.
- Students will connect lower summer flow to higher water temperature in a stream.
- Students will organize a written explanation around evidence from a monitoring table.
Vocabulary
- Baseflow
- Baseflow is the water that keeps a stream flowing even when it has not rained for a while. It comes from groundwater slowly seeping into the streambed.
Also: wetland storage, peak flow, subsidence, drainage ditch, feedback
Teacher overview
Wetlands hold water and then release it slowly, so removing one changes how a stream behaves in storms and in dry weather alike, because water that once left over weeks now leaves in hours. This prompt gives students a fictional marsh drained a century ago, a monitoring table showing what changed, and a public audience to explain it to. The writing task is explanatory rather than persuasive, so the work is in building accurate cause-and-effect chains and choosing which numbers actually carry each point.
Prompt
Background. Cawthorne Marsh is a fictional wetland just upstream of the fictional town of Drumlane. In the 1920s, farmers cut a network of ditches through the marsh and laid drainage tile under the fields to dry the ground for crops. About 600 acres of marsh became farmland. Cawthorne Creek, which used to spread out and wander through the marsh, was straightened into a single deep ditch that carries water quickly to the Drumlane bridge.
A wetland slows water down. Rain that lands on the marsh does not run straight to the creek; it spreads across the surface, soaks into the peat soil, and moves slowly, so water leaves over days and weeks rather than hours. Drainage ditches and tile remove that delay, because they give the water a fast, direct path to the channel.
The marsh soil itself changed too. Peat forms underwater, where there is not enough oxygen for it to rot. Once the ground was drained, air reached the peat and it began to break down. As it broke down, the ground surface sank.
The fictional Drumlane Watershed District has now proposed plugging the main ditches so that part of the marsh floods again. Here is the monitoring record the district published, comparing conditions before drainage with a recent ten-year average.
| Measurement at or near the Drumlane bridge | Before drainage | Recent ten-year average |
|---|---|---|
| Wetland area upstream | 600 acres | 40 acres |
| Peak flow after a two-inch storm | 210 cfs | 460 cfs |
| Hours from the end of a storm to peak flow | 26 | 7 |
| Days each summer with flow below 2 cfs | 4 | 31 |
| Average August water temperature | 63 degrees Fahrenheit | 74 degrees Fahrenheit |
| Marsh ground surface, compared with 1920 | baseline | 3.5 feet lower |
Your task. Write an explanatory article of five to seven paragraphs for the fictional Drumlane town newsletter. Your readers are adults who know the creek but have never studied hydrology. Explain how draining Cawthorne Marsh changed the way water moves through this watershed, and what the district's proposal would change. Use at least four rows of the table, and explain what each number you cite shows. Do not argue for or against the proposal. Your job is to make the process clear.
Planning Organizer
Complete every row before drafting. The rows match the rubric your teacher will use.
| Section of your article | What to write here | My notes |
|---|---|---|
| Opening | One or two sentences naming the marsh, the drainage, and the question your article answers. | |
| How the marsh used to work | The path water took before drainage, in your own words. | |
| What changed during storms | The rows of the table that show storm behavior, and what each one means. | |
| What changed in dry weather | The rows that show summer conditions, and the connection between low flow and temperature. | |
| What changed in the ground | The row on ground surface, and the reason peat breaks down once it is drained. | |
| What restoration would change | Which measurements you would expect to move, and in which direction. | |
| Closing | One sentence summarizing the main cause and effect for a reader in a hurry. |
From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.
Exemplar & Rubric
Exemplar response
A century ago, Cawthorne Marsh covered about 600 acres upstream of Drumlane. Today about 40 acres remain. The Drumlane Watershed District has proposed plugging the old ditches to bring part of the marsh back. To understand what that would do, it helps to understand what the marsh used to do.
Before drainage, rain that fell on the marsh had no fast route to the creek. It spread across the surface, soaked into the peat, and worked its way slowly downstream. The marsh acted as storage. It held water during storms and let it go over the following weeks. The ditches and drainage tile that farmers installed in the 1920s removed that storage by giving water a direct path to a straight channel.
The storm numbers show the result. Before drainage, a two-inch storm produced a peak flow of about 210 cfs at the bridge, and the peak arrived about 26 hours after the rain stopped. Today the same storm produces about 460 cfs, and the peak arrives in about 7 hours. The water is not new; it is the same rain, arriving all at once instead of spread out, because nothing upstream slows it down anymore.
Dry weather shows the other half of the change. Water stored in a marsh does not disappear when the rain stops. It seeps out slowly and keeps the creek running through July and August. With the storage gone, the creek now has far less to draw on. Before drainage, flow at the bridge dropped below 2 cfs on about 4 days each summer. Now it happens on about 31 days.
Lower flow also means warmer water. A creek running at a trickle is shallow and slow, so the sun heats it easily and there is less water to spread that heat through. The August average at the bridge has risen from about 63 degrees Fahrenheit to about 74. That is a change in the creek's habitat, not only in its temperature reading, because warm water holds less dissolved oxygen than cold water.
The ground itself has changed as well. Peat forms underwater, where a lack of oxygen keeps plant material from rotting. Once the ditches drained the marsh, air reached the peat and it began to break down, and the surface settled about 3.5 feet below where it stood in 1920. That sinking is not reversible on any human timescale, which is one reason restoration would return the wetland's function rather than its original ground level.
If the district plugs the ditches, the measurements most likely to move are the storm and summer rows. Restored storage would lower peak flows at the bridge and delay them, and it would add water to the creek during dry weeks, which should also pull the August temperature down. The main cause and effect is that drainage removed the marsh's storage, so the same rainfall now arrives at the bridge quickly and leaves far less behind for the dry weeks that follow.
Rubric
| Criterion | Emerging | Developing | Proficient | Advanced |
|---|---|---|---|---|
| Explanation of the process | Describes the marsh without explaining how water moved | States that storage matters but not why | Explains storage clearly and links it to both storm peaks and summer flow | Explains storage, timing, and the reason the same rainfall produces a different hydrograph |
| Use of the table | Cites no data, or misreads it | Cites one or two rows without interpretation | Cites at least four rows and explains what each shows | Cites four or more rows, interprets each, and connects rows to one another |
| Connected reasoning | States changes as a list with no causes | Names a cause and effect but skips a step | Builds accurate chains from drainage to flow to temperature | Builds chains in both directions, including the peat and subsidence, and predicts restoration effects with reasons |
| Organization and audience | Hard to follow; jargon left undefined | Some structure; technical terms uneven | Clear paragraphs, terms defined for a general reader | Purposeful order, terms defined naturally, and a closing sentence a hurried reader could use |
Differentiation
Support
Give these students the table with the two storm rows and the two dry-weather rows already circled, and a three-paragraph structure instead of five. Provide a completed opening paragraph as a model, and allow a labeled diagram of the marsh before and after drainage to stand in for the paragraph on how the marsh used to work.
Extension
Ask these students to add a paragraph predicting what the monitoring table would look like ten years after restoration, giving a direction and a rough size for each of the six rows and a reason for each prediction. They can also explain why one row on the table would be expected to change very little.
ELL supports
Pre-teach "storage," "peak flow," "baseflow," "peat," and "subsidence" with a labeled cross-section drawing of the marsh in 1915 and today. Provide sentence frames: "Before drainage, water ___ , which meant ___." and "The table shows that ___ changed from ___ to ___, because ___."
Extensions
Have students turn one paragraph of their article into a labeled diagram with arrows showing the path water takes before and after drainage, then trade diagrams and check whether a classmate can retell the process from the drawing alone. Post the strongest pair of diagrams beside the written articles for a short gallery walk.