Fish are an important food source for the people of Inle Lake. With reference to Figure 4(b), identify two other local sources of food.

Using evidence from Figures 4(a) and 4(b), explain why the people of Inle Lake have lived sustainably until recently.

With reference to Figures 4 and 5, identify three environmental impacts that may occur as a consequence of human activities on and around Inle Lake.

From the information in the resource booklet and your own studies, identify two inputs and two outputs of water associated with Inle Lake by labelling the boxes in the diagram below.

With reference to (b)(i), state what will be the natural income of this water resource available for domestic supply.

With reference to Figures 4 and 5, complete the following table.

Identify one possible pollution management strategy for Inle Lake in each of the categories in the table below.

Explain how the use of fertilizers in agriculture may lead to hypoxic water in the areas shown in Figure 7.

Evaluate the possible use of grass carp in controlling the growth of water hyacinth in Inle Lake.

Any two of: tomatoes/cauliflowers/rice/vegetables/fruits/lotus plants/bamboo shoots

Note for examiners: no mark for "inle carp" (as it is a fish), "wood" & "weeds" (are used for construction)

[1 max]

Allow no marks if only evidence is given.
Allow one mark for each piece of evidence with explanation up to [2 max]
Accept reasonable arguments based on Figure 4.
Do not allow explanations on current unsustainable use.

[2 max]

Any three of:
deforestation due to rice planting/collection of building materials;
depletion of fish stocks due to fishing/toxic waste/eutrophication;
reduced light entering lake due to floating gardens/stilt-houses/ water hyacinth;
pollution due to domestic waste/industrial waste/coal mine and power plants;
eutrophication due to fertilisers/domestic waste;
bioaccumulation due to agrochemicals;
increased turbidity due to run-off/sedimentation/deforestation/algal growth;
sedimentation/infilling/reduced water depth due to floating gardens/run-off from hillsides/deforestation;
biodiversity loss due to increased competition from non-native species /increased levels of pollution;
soil degradation and erosion due to deforestation around the lake;

accept answers that give positive environmental impacts such as the examples below:
sustainable farming and harvesting practices (e.g., use of agrochemicals and organic fertilizers) result in protection of the lake/bamboo ecosystem;
floating gardens control flooding;
floating gardens create land to use for farming or home building;

The answer must have impact + link to Inle human activity to gain a mark.
Accept any other reasonable suggestion.

[3 max]

This question requires “Resource Booklet - May 2015 SL paper 2”, available under the "your tests" tab > supplemental materials.

inputs – any two of:
runoff/overland flow;
river (inflow)/Nyaung Shwe river;
precipitation/rain/monsoon /;
throughflow/groundwater flow;
power plant discharge water;    [1 max]

outputs – any two of:
river (outflow);
seepage;
extraction (by power plant/for domestic use);
evaporation;
transpiration/evapotranspiration;
surface runoff after flooding;
plant absorption/animals drinking; [1 max]

Award 1 mark if one correct input and one correct output are shown.

[2 max]

This question requires “Resource Booklet - May 2015 SL paper 2”, available under the "your tests" tab > supplemental materials.

water inputs minus water outputs/natural inputs minus natural outputs / the difference between the natural inputs and natural outputs;

Credit the use of specific examples of water in/outputs. The outputs should NOT include any domestic use of water, as this is the natural income asked for.
Do not accept any resource unless it is water.

[1]

Award [1] for each type.

*could be considered as point source if house can be identified or non-point source if all houses are being considered. Do not credit the same point twice unless specific distinctions are made.
Simple statements of one word are acceptable; many students will write more detail.

[2 max]

This question requires “Resource Booklet - May 2015 SL paper 2”, available under the "your tests" tab > supplemental materials.

All answers should link to pollution in the lake, not, for example overfishing.

[2 max]

fertilizers used on land/floating gardens runs off into the sea/seas around coasts;
excess nutrients lead to rapid algal growth/blooms/eutrophication;
this limits light/photosynthesis of other plants thus reducing O2 levels;
low O2 causes plants/animals/fish/algae die;
increased deaths & decomposition leads to further decrease in O2;
low O2/increased deaths increasing decomposition/O2 reduction is positive feedback;
most areas affected are in MEDCs which can afford to use fertilizers;
hypoxic waters may run off into sea from lakes which have excess nutrients/algal growth/eutrophication;

Note to examiners: NO marks awarded for references to eutrophication caused by urban or industrial waste

[4 max]

This question requires “Resource Booklet - May 2015 SL paper 2”, available under the "your tests" tab > supplemental materials.

Strengths:
grass carp is good for control because it naturally feeds on hyacinth;
grass carp and hyacinth may become a self-regulating/negative feedback system / increased grass carp leads to decreased hyacinth (or vice versa);
better than chemicals/herbicides as no pollution of the water;
better than mechanical removal of hyacinth which is very labour-intensive;
population once introduced will reproduce so only need to do it once;
inexpensive;
the grass carp may become a food source for the local populations;
grass carp may become a part of the natural food web;  [3 max]

Limitations:
is a non-native species so may eat other/desired plants/organisms too;
may out-compete the local carp/other fish species;
grass carp may overpopulate the lake and become a problem themselves;
may bring diseases to the endemic fish species;
risky thing to do as cannot foresee the effect of the grass carp on the ecosystem;
the local population may use the water hyacinth as a resource, which may now become limited;  [3 max]

[4 max]

Only a very small minority gave an incorrect answer here. Most candidates mentioned 2 food sources, rice and vegetables being the common answers.

Most candidates described sustainability rather than explained. This meant many candidates gained zero or one mark only.

The majority gained the marks here. The ones who did not only stated impacts rather than identified them, meaning their answers were too vague.

Many candidates did not read the stem correctly and mentioned inputs and outputs that were not linked to water associated with Inle Lake. Those that did use water usually gained both the marks.

Very few candidates gained a mark for this question. As only one mark was available a simple water inputs minus water outputs was all that was required.

The candidates generally had no problems completing the table. A few gave the answers the wrong way round.

This was generally well answered for the altering the activity part, slightly fewer candidates identified a clean-up and restoration strategy.

The candidates mainly mentioned the process of eutrophication and how that leads to hypoxia. Only the stronger candidates used the map to indicate where in the world this occurs and why. There were some incorrect statements indicating the algae used up the oxygen.

The majority of candidates did look at both the positives and negatives of having grass carp in the lake. Only a handful of candidates left this blank. The weaker candidates usually gave the water hyacinth being eaten by the grass carp as their only answer.