State the relationship between the discharge and the flood recurrence interval shown on the graph.

Suggest why a logarithmic graph was used to show these data.

Estimate the flood recurrence interval for a discharge of 10 000 cumecs.

Suggest how changes over time in the amount of water stored as ice in the hydrological cycle could lead to increased river flows.

Suggest how changes over time in the amount of water stored as ice in the hydrological cycle could affect the size of one or more other stores in the hydrological cycle.

Examine the environmental impacts of agriculture on water quality.

The relationship is positive [1].
OR
As discharge increases, the flood recurrence interval increases [1].

This allows a wide range of values to be shown [1] because the data set includes a minimum of 1.2 years to a maximum of 60 years for recurrence interval [1].
OR
The slope of the line indicates the rate of change between the two variables [1] and allows comparison between different drainage basins [1].

Accept other possibilities that indicate that the graph makes the relationship clearer [1].

45 (years) (allow 43–47) [1] Do not penalize incorrect units.

Award [1] for each suggested effect due to changes in ice storage and up to [2] for development/exemplification.

For example: The melting of ice could lead to an increase in river flow [1] and this happens seasonally in cold parts of the world [1] and in the future climate change could increase melting and river flow even further [1].

Award [1] for each suggested change in size and up to [2] for development/exemplification.

For example: Melting of ice could lead to an increase in the water stored in the oceans [1], which could increase ocean storage above 97 % [1].

Another change might be runoff from melting ice increasing lake storage [1].

Responses should show an understanding of any of the following: salinization, agro-chemical runoff, groundwater pollution, eutrophication of watercourses. Credit other valid positive impacts.

As agriculture becomes more intensive, there are greater inputs of chemical fertilizer and irrigation and greater outputs of waste, eg manure and chemical fertilizer. These can lead to a variety of types of environmental impacts in different areas.

Good answers may include a structured discussion of the relative importance of a variety of agricultural impacts on water quality. An alternative approach would be to question who or what (land, incomes, ecosystems, local businesses) is impacted, and recognize that some parts of the world may be more seriously affected than others.

At band D, answers are likely to be mainly descriptive and/or look only at one impact.

At band E, expect either a more detailed explanation of a range of impacts or an examination of how some places are affected by different impacts more than others.

At band F expect both.

Marks should be allocated according to the Paper 2 markbands (available under the "Your tests" tab > supplemental materials).