Chapter 11: Groundwater Lab (porosity and Permeability) Lab write up instructions Grab Your Lab notebooks So we can get started!

Where does our Groundwater Infiltrate?

Purpose The purpose of this lab is to give students the skills to: Measure porosity and flow rate of different sediments typically found in the Temescal Wash Explain how flow rate and groundwater travel are related and are both dependent on porosity and connectivity of pore spaces.

Materials (No Need to Copy) Part 1 (Porosity Lab 1 set per group) 1. 500 mL beakers or plastic cups with 150 mL line 2. 150 mL each Dry fine sand (or silt if available), coarse sand, small gravel 3. Graduated cylinder & access to container of water (or sink) Part 2 ( Flow Rate Lab 1 Set Per Group) 1. 250 mL beakers or graduated cylinders 2. 150 mL each Dry fine sand (or silt if available), coarse sand, small gravel 3. 3 plastic cups with holes in bottom (or funnels) with 150 mL line 4. 3 filter papers or cloth mesh for bottom of plastic cups 5. 1 Stopwatch 6. 3 containers, beaker, or nearby sink to collect water

Part 1:Porosity

Procedures Part 1 (Porosity Lab) Preparation: 1. Mark Sediment Fill Line 2. For each lab station, fill three plastic cups with 150 mL of water. Mark this volume with a line on the outside of the cup. This line will be used as the fill line for sediments. To calculate porosity of each type of sediment: 1. Fill each cup with sediment to the fill line (representing a sediment volume of 150 mL). 2. Measure out 100 mL of water in a graduate cylinder and pour just enough water into sediment cup to slightly cover top of sediment. 3. Make sure the sediment is completely wet (all pores are filled with water). 4. Record amount of water poured into sediment; this volume represents volume of pore space in between grains of the sediment. 5. Calculate porosity (in %): [(Volume of Water) / (Volume of Sediment)] x 100

Part 2: Flow Rate

Procedures Part 2 (Flow Rate) Compare flow rate of each type of sediment: 1. Calculate the area of the cup bottom: Measuring diameter (d) of bottom, divide by 2 to obtain radius (r), and then calculate Area (A = π*r^2 2. Fill each cup with sediment to the fill line (representing a sediment volume of 150 mL). 3. Measure out 250 mL of water in a graduate cylinder or beaker and slowly pour water into sediment cup held above another cup to collect water flowing through. Try to keep the water level just at the sediment surface. 4. Record time from start of pouring to time when water stops dripping from bottom of sediment cup (less than 1 drop/second).

Procedures Part 2 (Flow Rate) (Cont.) 5. Record amount of water poured through sediment; this represents the flow volume. 6. Repeat this for the last two sediments 7. Calculate flow rate (mL/s = cm^3/s):(Volume of Water) / (Time of Flow Through) 8. Convert the flow rate (cm^3/s) to flux (cm/s):(Flow rate, cm^3/s) / (Bottom area, cm^2)

Remember! ML=CM^3

Observations: Part 1

Observation: Part 2

Discussion: Part 1 1. Which sediment had the greatest porosity? Why? Did this match your prediction? 2. Which sediment would allow for more groundwater storage? 3. How do you think mixing gravel and silt would impact the porosity?

Discussion: Part 2 1. Which sediment had the greatest flow rate? Why? Did this match your prediction? 2. Why might it be important for hydrogeologists to be able to determine the permeability of different sediments?

Lab Obtained FroM: http://groundwaterconnections.weebly.com/uploads/9/6/5/0/9650096/gcl ess2_2013-01-31.pdf