geography a level coursework infiltration rates

Processes and pathways of the water cycle

There are a number of distinct processes and pathways of the water cycle that link its main components.

Water Balance

Within a drainage basin, the flows of water are summarised using this equation: P = E + Q +/- S or Precipitation = Evapotranspiration + Streamflow +/- Storage. You can find out more about water balance here .

Flows of water

Evaporation

Evaporation is the process of water changing from liquid to water vapour. It requires a significant amount of energy to do this. This energy does not heat the water but transfers into latent heat (the heat required to convert a solid into a liquid or vapour, or a liquid into a vapour, without change of temperature). This is then released when condensation occurs. Significant amounts of heat energy are carried into the atmosphere from tropical oceans by the Hadley Cell. The warm air moves north and south of the equator where cooling releases latent heat. As the result of this mid and high latitudes receive energy that makes them warmer than they would be without this. Also, evaporation is important in moving water from oceans and seas to land.

Transpiration

Transpiration is the transfer of water vapour from vegetation to the atmosphere.  This occurs mostly via pores in leaves known as stomata. 10% of atmospheric water originates from transpiration. Wind speed, availability of water to the plant and air temperature all affect the rate of transpiration at any one time. Rates of transpiration also vary between seasons.

Condensation

Condensation involves water vapour returning to a liquid state. When water vapour reaches dew-point (temperature when the air becomes saturated) water droplets and clouds appear. Closer to the ground fog, mist and dew are examples of condensation.

Cloud formation

Clouds form when moist air cools. Cooling can occur in a number of ways. The first is by convection. As warm air rises it cools, forming cumulus clouds. Secondly, the air cools when a warm air mass meets a cold air mass. Warm air rises above the cold mass, causing it to cool and form stratus and cirrus clouds. Thirdly, clouds form through advection. This is when a large mass of air moves over a cooler surface, for example, an ocean. The atmosphere is cooled below the dew-point resulting in stratus clouds forming. Finally, orographic uplift also forms clouds. This is when the air is forced to rise over a range of mountains or hills. As the air rises it cools and condensation can occur, forming clouds.

Cloud formation and lapse rates

A lapse rate is a change in temperature with increasing height through the atmosphere. There are three types of lapse rate. These are:

• environmental lapse rates
• dry adiabatic lapse rates
• saturated adiabatic lapse rates

Precipitation

Precipitation is any form of water (rain, sleet, snow) that falls from the atmosphere to the land or oceans. In mountainous locations in high latitudes precipitation usually falls as snow. Over time this can either become compressed, forming ice, or melt and flow through the drainage basin.

The duration of rainfall affects the speed of transfer through the drainage basin. Long periods of rainfall lead to the soil becoming saturated and an increase in surface runoff. Rain over a short period of time is usually absorbed by soil and vegetation.

The intensity of rainfall can also affect the transfer of water through the drainage basin. More intense rainfall typically results in increased surface runoff.

In arid regions, such as the Sahel (the sub-Saharan region in Africa), the climate has a wet and dry season. During the dry season, surface storage dries up. During the wet season, there can be localised flooding.

Interception

Interception is the temporary storage of water on the surface of plants and buildings before it reaches the surface. The rate of interception is determined by the time of year and the type of vegetation. Pine trees intercept more precipitation than oak trees. Buildings are designed to intercept rainfall through roofs. It is then transferred to rivers and streams via guttering and underground pipes.

Infiltration, throughflow, percolation, groundwater flow and runoff

Infiltration is the movement of water into the soil. The type of soil affects the rate of infiltration. Sandy soil has a higher infiltration rate than clay soil.

Water is transferred through the soil as throughflow. Water moves through soil under the force of gravity towards rivers and streams. Some water enters rocks below the soil through percolation. Some rocks are impervious an do not let water enter e.g. granite. Permeable rocks can be porous (e.g. chalk and sandstone) in that they allow water to enter their pores. Other permeable rocks are pervious (e.g. limestone) and water flows along joints (verticle cracks) and bedding planes (layers).

Where water reaches impermeable bedrock below ground it flows over the surface of the rock. This is known as groundwater flow.

When the soil is saturated surface runoff occurs. Also, surface runoff can happen in semi-arid areas where the soil is baked hard. Rainfall is so intense that the soil does not have the capacity to absorb it.

Ablation is the loss of water stored as ice or snow through melting, runoff, evaporation, sublimation, calving of icebergs or the removal of loose snow by wind.

A giant piece of Ice breaks off the Perito Moreno Glacier in Patagonia, Argentina

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WATER EQ1 Lesson 4 Infiltration rates experiment and write-up Edexcel A Level Geography

Subject: Geography

Age range: 5-7

Resource type: Lesson (complete)

Last updated

2 September 2018

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The fourth lesson in Enquiry Question 1 in the water unit for Year 2 of Edexcel A Level Geography - Paper 1. This lesson looks at infiltration rates and gets the students to conduct their own experiments around the school grounds. There is also a follow-up homework task (IST).

This lesson is also available as part of Enquiry Question 1 Bundle and a Water Bundle. Thank you for looking.

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Water Enquiry Question 1 Edexcel A Level Geography

All 8 lessons which comprise the first Enquiry Question for the water topic of Edexcel A Level Geography. You will find all lessons and resources, with notes under the slides to help show how the lessons flows, as well as homeworks and exam questions too. Please look out for other water resources and carbon resources too (being uploaded through June 2018). Thanks for looking.

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Make your own fieldwork equipment: Infiltration

What you need

Section of drainpipe

Water container

What you do

Place the drainpipe on the surface of the soil or land. Insert the ruler into the drainpipe so that it is standing on the soil surface. Pour a predetermined amount of water into the drainpipe. Time how long it takes for the water to infiltrate, or measure how much water remains in the drainpipe after a given length of time.

When you use it

Compare infiltration rates between different land uses: soils, grassland, woodland, agricultural land, footpaths, tarmac. Use in a study of footpath erosion or trampling (the water will not infiltrate into saturated ground) or in an investigation into the role of man made surfaces in increasing the risk of flooding in urban areas.

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Factors effecting infiltration rates

                      Investigating how factors affect infiltration rates

The purpose of this investigation was to help me gain a clearer understanding of infiltration and the effects that the various factors have on it. These factors include the environment, gradients, vegetation and the antecedent conditions.  This will help me develop my understanding of its role in the hydrologic cycle.

The rate of infiltration is the amount of water absorbed into the soil from the ground surface; we measure this in centimetres per minute. Infiltration levels are affected by a number of different factors. Low infiltration can be caused by clay soil, intense rainfall, icy ground, compressed soil, saturated ground, hard baked ground and steep slopes.  Factors that increase infiltration rates are high infiltration are fertile land, flat surfaces, vegetation, soft soil, sand, and weather conditions.

Surface runoff is created when there is a gradient in the land, or when the surface is unable to infiltrate into the land. Depending on the weather the amount of surface runoff may increase or decrease. If there was heavy rain then there would be an increase of surface runoff and the opposite when it’s hot or the rate of rainfall is small. This therefore shows me that the gradient will affect the infiltration rates. If the land was on a large gradient then the rainfall or water will find it increasingly harder to penetrate into the soil, this is due to surface runoff. If the land was at a small gradient or on a flat surface, then the water will be infiltrated at a much quicker pace. As it’s focused on that one point of soil and it’s not moving at a quick rate like you would get if there was surface runoff.

The amount of vegetation will decrease the levels of interception in the soil. This is because the plants and grass is intercepting the water and delaying or stopping the water being infiltrated into the soil. Interception refers to  that does not reach the soil, but is instead intercepted by the vegetation and plants. If the area had no vegetation then the infiltration rates will increase, unlike if the land was full of vegetation because less will be collected due to interception.

This is a preview of the whole essay

Antecedent conditions will affect the infiltration rates depending on the weather before we took are experiment. If it had been a hot day and the soil was had baked then the water absorbed would be a lot less and possibly create surface run off. But also the water absorb may even increase as the soil is dry and needing water. If it had been raining then and the land was saturated then no more water could be absorbed into the soil. If it had been a dry day and there was no rainfall then this would be a good weather condition and the level of infiltration will be steady and possibly conclude in a good collection of results.

                                            The experiment grounds.

This image is an overlooking view of are experiment, the circled grounds is where we took are results and tested the infiltration rates. The arrows pointing to each site is the different area’s, which where sampled grounds.

We chose this area as it provided me with the suitable grounds for my experiment. It also had the variable land sources, for vegetation cover, gradients, no vegetation and tree cover. It was also still in the school grounds which meant we has easy access towards the site.

Site 1- 0 º  slope, under tree, no vegetation

Site 2- 5  º  slope under tree, no vegetation

Site 3- 13 º  slope, 100% grass cover

Site 4- 0  º  slope, 100% grass cover

Site 5- 0  º  slope, 58% grass cover

Site 6- 10.5% slope, 65% grass cover.

Key questions

• Does the infiltration rates get affected if there was more vegetation cover?

• Does the gradient affect infiltration rates?

• Does the antecedent conditions effect infiltration rates?

                          Data Analysis and explanation

We found that the relationship of the infiltration rate and the gradient showed no correlation and was almost unchanged; this is shown in fig 1. The R ² =0.0018 which means there is little correlation towards the data and correlation. The graph shows me that as the gradient increased the level of infiltration stayed the same, therefore this didn’t matched with my hypotheses.  All the points on the graph where scattered some were also anomalies showing me there is no significant results telling me the relationship was negative. Our experiment was contained in a plastic pipe which would of stopped surface run-off and would on concentrated on one particular point in the soil. This therefore meant are results were fixed and not an accurate experiment.

In my hypotheses I correctly predicted in fig 2 that vegetation will affect the infiltration rate. If there was more vegetation then the process of infiltration will be delayed by interception, which captures precipitation and delays the amount of rainfall reaching the surface. Although from fig 2 my graph shows that the rate of infiltration didn’t decrease as much as we expected, because some of the graph points were very scattered as anomalies. Therefore there was no strong correlation with the line of best fit. Not completely proving my hypothesis.

The graph above is called the ‘significance of the spearman’s rank correlation coefficients and degrees of freedom’ technique this will statistically show if my data shows any significant results. I need to know if the relationship between gradients, infiltration and vegetation are significant and occurred by chance. The graph above tells me that 0.2 at 4 gradient- is to low of significance as it’s lower than 5% therefore it is only 95% reliable. To have a more accurate number of results we could have done more experiments. This would eventually come to a pattern and become clearer. This will then show me a more accurate set of results, with a clear pattern and correlation.

In fig 3 the averages of soil were 2.4cm/m, grass was 1.59cm/m, soil and grass was 0.62. This will then show me that the level of infiltration was best with soil showing me that my hypothesis was correct proving my points that interception most affected the infiltration rates. Interception would delay and stop the amount of infiltration into the soil. If the soil was clear this would then therefore allow it to infiltrate without any obstacles or elements.  

Aimee Andrews

Document Details

• Word Count 1081
• Page Count 4
• Subject Geography

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A study of infiltration

This resource focuses on infiltration rates for different surfaces. Students complete an infiltration study, beginning with an initial hypothesis, through the method, to an analysis and evaluation. The resource provides a complete set of step-by-step instructions for carrying out this individal fieldwork study whether at school or for homework. 

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