In IB Geography, what’s the best way to explain “altered drainage basin systems” in one sentence?

Say that human activities change the balance between stores and flows, which alters how quickly water moves to the channel and therefore changes discharge patterns. That sentence works because it signals “system thinking,” which IB Geography rewards. Then add one specific flow (like infiltration) and one hydrograph effect (like higher peak discharge). Examiners are looking for linked cause and effect, not a list. Finish by naming the outcome: flood risk, erosion, or reduced baseflow.

How do I link human activities to a storm hydrograph without drawing one?

Use three terms: lag time, peak discharge, and rising limb. For urbanisation, you can state that impermeable surfaces increase surface runoff, creating a steeper rising limb, shorter lag time, and higher peak discharge. For deforestation, add reduced interception and increased erosion to extend your chain of reasoning. For dams, explain increased storage and regulated discharge, but mention altered sediment transport for evaluation. This is classic IB Geography method writing: process first, graph effect second.

What mistakes cost marks on drainage basin questions?

A common mistake is describing the activity but not naming the store or flow that changes. Another is claiming “dams always reduce flooding” without adding that outcomes depend on reservoir capacity, management, and event magnitude. Students also forget sediment, which is often the bridge between land-use change and channel capacity. Finally, many answers miss evaluation language like “locally,” “downstream,” and “risk transfer,” which are gold in IB Geography. Use RevisionDojo’s Essay-focused tools and practice sets to make these links automatic.