Geo Internal Assesment 2005

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Newton College

Investigating the Quebrada Sachavacayoc River, a Tributary of the Tambopata River in Madre de Dios, Peru


Tiziana Gelmi Candusso


2,500 words



Map 1.5 Puerto Maldonado: a small urban area located in Madre de Dios.

       River Madre de Dios

Puerto Maldonado, which has 28000 people in it

River Tambopata


Few main Roads                    

Figure 1.1 Waiting for our Boat to arrive in Puerto Maldonado’s Port




          Fig 1.2 Industries in Puerto Maldonado  

        Extractive industry:

Truck with tree trunks going to the city.

This increases the surface run off, therefore increases the sediment in the rivers.

Map 1.6 Tambopata, a piece of the inner Rainforest of Madre de Dios


Location of the analyzed sites (see map 1.7)

I will refer to the sites as Site A – F, these are the locations of each of these sites:

Site A  site on Quebrada Sachavacayoc River nearer to the Tambopata river

Site B  site on Quebrada Sachavacayoc River a bit further inside from the Tambopata river

Site C  Lake Sachavacayoc (middle of lake)

Site D  Lake Sachavacayoc (inlet)

Site E  Low Bridge of Trail (near platform)

Site F  High bridge of Trail (half way back to lodge)

        Map 1.7 Sketch Map of the location of sites


Map 1.8 Location of Figures in Sketch map of the analyzed sites

Figure 1.3 Precipitation Graph of Tambopata        

The Tambopata Forest has a seasonal rainfall with approx. less than 20 cm/mess a year.

The Graph shows an average of the precipitation in the years 2002, 2003 and what usually falls most of the years.


Figure 1.4 Tambopata Soil seen from the boat        


Aims and hypothesis


  • Aim 1:

To compare the velocity of the river in two different sites of the same river.

  • Hypothesis 1.1:

The velocity of the river further away from the mouth of itself will be steeper

  • Justification 1.2:

Will happen due to the structure of a river, and where it comes from; it should be going down a slope. Further away from the mouth, the river will have a steeper gradient, which means water will have a greater velocity due to Newton’s law of gravity.

  • Aim 2:

To see where the water flows will be faster.

  • Hypothesis 2.1:

The velocity will be faster before a meander

  • Justification 2.2:

Happens because the river water slows down with the curve and the friction caused by it in the outer edge of the river, we can see this in the theory sustaining the water velocities in a meander (see fig 2.1)

Figure 2.1 Velocities of a river in a meander


  • Aim 3:

To see where will the ph be more basic

  • Hypothesis 3.1:

The pH will be higher at the end of the river

  • Justification 3.2:

This will happen because the river will have more sediment due to the turbulent waters lifting all the sediment up and transporting it. More sediment, more basic, this is because the sediment contains Phosphates, nitrates from the soil and other ions which are more basic than water. We see “Soil typically contains about 1–5 ppm of ammonia” ammonia is a Basic substance in soil.


  • Aim 4:

To see which point is the deepest point of the river

  • Hypothesis 4.1:

The deepest zone across the river will be the middle of it

  • Justification 4.2:

“The greater the velocity of the water, the greater the frictional drag” this means that because non of the sites are in a meander, the greater velocity will be in the middle, which means that there will be a greater erosion, therefore the deepest zone will be in the middle.


  • Aim 5:

To compare the discharge between to sites of the river

  • Hypothesis  5.1:

The Discharge will be greater nearer to the Tambopata River

  • Justification 5.2:

This will happen due to more tributaries that should exist and add up water to the Quebrada Sachavacayoc River. We can see this also happens in the Mississippi river “Discharge increases steadily downstream as more tributaries add water to the river”


  • Aim 6:

To see where will the amount of sediment will be higher and the turbidity denser

  • Hypothesis  6.1:

The Turbidity will be higher in fast parts of the river, in slow parts there will be less turbidity

  • Justification 6.2:

This will happen because there is more time for sedimentation, and less lifting of soil molecules. We can see this because “bed load is highly dependent upon water velocity, the rate of transport varying with about the cube of the water velocity”


  • Aim 7:

To see the amount of vegetation near the river and further apart

  • Hypothesis 7.1:

The vegetation will be denser right after the floodplain ends

  • Justification 7.2:

 Will happen like this because the river usually floods as seen in the definition: “A plain bordering a river and subject to flooding“ and therefore little vegetation has adapted to this environment saturated of water.


  • Aim 8:

To see the variation of temp throughout the different places of the river

  • Hypothesis 8.1:

The temperature will be higher in calm waters,

  • Justification 8.2:

I think this because there is time for the water to heat up when it is calmer, because of less movement of molecules therefore heat is energy is absorbed faster by the molecules as seen in chemistry.

  • Aim 9: 

To see where the temperature will be higher, in the lake or in the river

  • Hypothesis 9.1:

The lake will have a higher temperature

  • Justification 9.2:

This will happen because the water is calmer, therefore has more time to heat up and absorb the energy, due to its high thermal capacity (see justification 8.2)




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        On the trip the Tambopata Lodge we did a transportation investigation in which we recorded the types of boats we saw (fig 3.1).

Figure 3.1 Boat seen on trip to the Tambopata lodge        

The main way of transportation between Puerto Maldonado and the inner Rainforest was by boat.

Boat used as transportation in River Tambopata.


We broke down tree sticks into the same sizes and then we chose a throwing place (see fig 3.3). We did this because we tried with orange skin first but they weren’t as visible ...

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