A comprehensive sixth-grade earth and environmental science investigation into watershed topography, ridgeline divides, and runoff dynamics across the Merrimack River basin. Students analyze contour maps, model point and nonpoint nutrient transport, and simulate surface runoff from headwaters to the Atlantic estuary.
Trace ridgelines in brown. Mark farm fertilizers in green marker, and suburban parking runoff in red.
Mark high & mid zones
STEP 3
Simulate Rainstorm
Mist 5-8 pumps of rain over high ridges. Watch water channels merge and transport dissolved markers downstream.
Track nutrient flow paths
Experimental Setup Slide 5 of 7
Environmental Science Impact
Point vs. Nonpoint Source Nutrients
Point Source
Pollution discharged from a single, identifiable pipe or location.
• Factory drainage pipes
• Sewage treatment plant outfall
Easy to trace and regulate
Nonpoint Source
Pollution carried from broad land areas by rainfall and runoff.
• Fertilizer runoff from farms & lawns
• Oil, rubber & salt from highway networks
Difficult to trace; cumulative damage
Water Quality Dynamics Slide 6 of 7
Detective Mission Synthesis
Case Debrief & Solution
Can You Crack the Case?
On your topographic worksheet, you will use elevation contours to trace the exact journey of nutrient runoff from Hawk Ridge Dairy down the Merrimack River to the coast.
Key Scientific Evidence
Identify which side of the ridgeline divide the fertilizer fell upon.
Watershed Protection Action
Design a vegetative riparian buffer zone to filter runoff before it enters streams.
Mission Complete Slide 7 of 7
Precipitation Event
Water Movement
Nutrient Migration (Green/Red Marker)
Final Collection Point
Trial 1: Mist
(3 light pumps)
Trial 2: Shower
(6-8 pumps)
Trial 3: Downpour
(12+ pumps)
Hydrological Analysis & Claims
1. Ridgeline Boundary Effect: Did water or dissolved nutrients cross over the brown ridgeline divide? Explain how high terrain controls the path of surface runoff.
2. Stream Confluence: What happened when runoff from two separate valleys met at the bottom of the slope? How does this model how tributaries combine into the Merrimack River?
3. Environmental Application: Based on your observations, why are coastal estuaries (like Newburyport at the Merrimack's mouth) especially vulnerable to fertilizer used by farms far upstream?
Watershed Detectives Lab Guide Page 2 of 2
CLAIM: (Identify the specific contaminant source for Station M2)
EVIDENCE: (Contour elevations, slope direction, stream connections, station data)
REASONING: (Explain how gravity and drainage divides dictate runoff transport)
Ecological Action Plan: What physical land management practice (e.g. forested riparian buffer, retention pond) should be installed at the offending site to protect the Merrimack River?
Watershed Detectives Worksheet • Merrimack Topography Page 2 of 2
