The diagram shows a storm hydrograph for a river.
State how many hours the discharge was over 40 cumecs.
From the graph, the discharge was over 40 cumecs for 6 hours.
Note
State the lag time for the storm event shown on the hydrograph.
The lag time is the time between the peak rainfall intensity and the peak discharge on the hydrograph.
Lag time = Time of peak discharge - Time of peak rainfall intensity
Note
Outline why the rising limb on this hydrograph is steeper than the falling limb.
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The rising limb is steeper as it is responding to the precipitation falling in the drainage basin/rapid increase of rainwater reaching the river/rapid run-off;
1 mark , -
whereas the falling limb still has rain reaching the river slowly/by throughflow / groundwater flow
1 mark .
Explain the formation of two landforms on a river floodplain.
Landform 1: Meanders
Meanders are sinuous bends in the river channel that form due to the erosional and depositional processes of the river.
On the outer bend, the river flows faster, causing lateral erosion and undercutting of the river bank, forming a river cliff.
On the inner bend, the river flows slower, causing deposition of eroded material, forming a slip-off slope or point bar.
Over time, the meanders migrate downstream, and the neck of the meander becomes narrower until it is cut off, forming an oxbow lake.
Landform 2: Levees
Levees are raised embankments of sediment that form along the banks of a river during flooding events.
When the river overflows its banks during a flood, the water spreads out, and its velocity decreases, causing the deposition of coarse sediment along the banks, forming levees.
The levees are higher closer to the river channel and slope away from the river, creating a natural embankment.
Note
Discuss the environmental consequences of eutrophication and the pollution of aquifers.
Groundwater pollution and eutrophication may be caused by farming, fertilizer and waste run-off. Eutrophication occurs in a surface water store, causing algal blooms and reduced levels of oxygen in the water, whereas aquifer pollution results in the declining quality and quantity of water.
Other environmental consequences could include adverse impacts on habitats, flora and fauna, or creation of dead zones.
| Marks | Overall Description |
|---|---|
| 0 | The work does not reach a standard described by the descriptors below. |
| 1-2 | • Response is too brief, lists unconnected information, not focused on question and lacks structure • Very brief or descriptive, listing unconnected comments or irrelevant information • Very general knowledge with large gaps or errors • Examples/case studies absent or only listed • No evidence of analysis • Terminology missing, undefined, irrelevant or incorrect • No evaluation or conclusion expected • Information not grouped logically • Maps/graphs/diagrams absent, irrelevant or unclear |
| 3-4 | • Response is too general, lacks detail, not focused on question and largely unstructured • Very general response • Outlines relevant and irrelevant examples, statistics, facts • Links to question merely listed • Analysis not relevant • Basic terminology used with errors or inconsistently • Irrelevant conclusion • No critical evaluation of evidence • Information not logically grouped • Maps/graphs lack detail or incorrectly interpreted |
| 5-6 | • Response partially addresses question, with narrow argument, unsubstantiated conclusion, and limited evaluation • Describes relevant supporting evidence • Outlines appropriate links to question • Partially addresses question or repeats one point • Relevant terminology used with minor errors • General conclusions, misaligned with evidence • Other perspectives/strengths/weaknesses listed • Some logical grouping but inconsistent • Maps/graphs don't follow conventions |
| 7-8 | • Response addresses whole question, evaluated analysis and relevant but unbalanced conclusion • Describes correct relevant evidence covering all main points • Describes appropriate links • Clear but one-sided analysis • Complex terminology correct but inconsistent • Relevant but unbalanced conclusion • Other perspectives described • Consistent logical grouping • Maps/graphs support analysis |
| 9-10 | • Response is in-depth and question-specific; justified analysis and conclusion through well-developed evaluation • Explains integrated examples, statistics, details • Explains appropriate links • Balanced analysis discussing complexity • Complex terminology used correctly throughout • Balanced conclusion aligned with evidence • Systematic evaluation of perspectives • Discusses strengths/weaknesses • Logically structured • Maps/graphs properly annotated and support argument |
