I think that clay will hold more water because it has less space between particles. Gravel will have the most permeability because there is more space between particles.I think that clay will hold more water because it has less space between particles. Gravel will have the most permeability because there is more space between particles.

Porosity is the proportion of empty space in a sediment. Permeability is a measure of the ease with which liquids and gases can pass through a sediment. All sediments have pore space and fractures, the greater the percentage of pores or fractures, the greater the porosity. Porosity refers to the sediments ability to hold a fluid, whereas permeability is the sediment’s ability to resist or allow the flow of a fluid through it.

It’s not enough to have pore space, the pores must also be connected so the liquid/gas can flow. Clay, shale, slate, have pores that aren’t connected, so it’s difficult for water to enter or leave these rocks. For groundwater to be able to get into a rock with good porosity, it must also have good permeability. An ‘aquifer’ is a type of body that has sufficient permeability to allow water to flow through it. Unconsolidated materials like gravel, sand, and even silt make relatively good aquifers. On the other hand, an ‘aquitard’ is a body that does not allow transmission of a significant amount of water, such as a clay, a till, or a poorly fractured igneous or metamorphic rock. 

Aquifers allows us to recover groundwater by pumping quickly and easily. Wells can be drilled into the aquifers and water can be pumped out. However, for the water to be drilled out the sediment should have high porosity so that it can hold large amount of water and high permeability so the water can be pumped easily. Hence, understanding porosity and permeability of sediments is crucial to find groundwater resources. This concept also applies to finding oil resources.

VARIABLES IN POROSITY EXPERIMENT

VARIABLES IN PERMEABILITY EXPERIMENT

PROCEDURE FOR POROSITY TEST

Materials - 3 clear cups,1 measuring cup, 200 ml of water, 200nml of dry gravel, sand, and clay.

1. Gather all materials.
2. Measure 200 ml of gravel into a glass cup and gently shake the cup so that the surface of gravel is flat.
3. Take 200 ml of water in a glass.
4. Pour water over the gravel little by little until the water level reaches the surface of the gravel. As it takes some time for water to go to the bottom of the cup, make sure to pour a bit of water at a time and then wait before pouring some more.
5. Record the volume of water you poured into gravel. This is called pore space.
6. Calculate porosity using the formula, Porosity = Pore Space/Total Volume x 100%.
7. Repeat experiment 2 more times for accuracy
8. Repeat procedure using sand & clay.

PROCEDURE FOR PERMEABILITY TEST

Materials - 1 funnel, 3 filter papers, 100 ml of dry gravel, sand, and clay,1 measuring cup, 100 ml of water, 1 stopwatch, 3 clear cups, 1 marker

1. Gather all materials.
2. Place a filter paper inside a funnel and then place the funnel over a clear glass cup.
3. Using a marker, mark the glass cup to indicate 20 ml, 40 ml, 60 ml, 80 ml and 100 ml.
4. Fill the funnel with 100 ml of gravel.
5. Tap the funnel lightly to make the surface of the gravel flat.
6. Take 100 ml of water in a cup.
7. Start the stopwatch as you pour all the water over the gravel.
8. At regular intervals, record the time & volume of water that poured down into the cup.
9. Repeat the experiment 2 more times for accuracy.
10. Repeat the procedure using sand & clay.

Clay has the highest porosity, followed by sand and then gravel.

Entire amount of water was able to pass through gravel in approx. 20 secs. Sand allowed only 80 ml of water to pass through in approx. 24 mins. However, clay allowed the least amount of water to pass through, only 60 ml passed in approx. 18 mins. 

GRAVEL

• It has large particles which creates larger pore spaces. However, due to large particle size it is unable to hold water. The porosity range is normally between 25% to 40%
• Due to large pore spaces, water easily flows through it making it highly permeable.

SAND

• Particle size is smaller than gravel, so pore spaces are smaller, but there are still enough voids to hold water. Porosity is between 30% to 45%.
• Pores are large enough for water to flow through easily but the rate is slower than gravel, so sand has moderate permeability.

CLAY

• It has very fine particles and the pores are extremely small. While it holds lots of water, the water doesn't drain easily due to small size of pore spaces. The porosity is between 40% to 60%.
• T he permeablity is low as it has very fine particles that create small pores restricting water flow.

All rocks/sediments have pore spaces and fractures. For the water to be able to flow between sediments/rocks it is not enough to have more pore spaces, the pore spaces must also be connected. Clay has pores that are not interconnected and therefore it is difficult for the water to flow through. However, in gravel all of the pores are well connected to one another allowing water to flow through easily.

Hence, clay is the most porous sediment but very low permeability. Clay usually acts as an aquitard, impeding the flow of water. Gravel and sand are both porous and permeable, making them good aquifer materials. Gravel has the highest permeability.  

This experiment can be used to determine water or oil reserves in a region. Scientists conduct many different tests to find such reserves. One of the tests is determining porosity and permeability of the sediments in that region. To locate groundwater, scientists will looks for sediments that have high porosity and also high permeability.

1. Each sediment can have furrther different types, like gravel comes in many different varieties like pea gravel, marble, crushed bluestone etc. So the porosity and permeability results for each sediment variety may differ. 
2. If the sample sediment is wet, it may impact the results. To avoid this error, in each trial a dry sample was used.
3. Making sure the weighing machine is accurate.

• http://deq.louisiana.gov

• http://courses.lumenlearning.com

• https://sitesmedia.s3.amazonaws.com/creekconnections/files/2014/03/PorosityPermeability-activity.pdf

I'd like to acknowledge my teacher, Mrs. Parhar for all the advice she has given. I would also like to acknow ledge my parents for the support and advice they gave me all they way.