PSC 121 Prince George's Community College Hydrology Movement of Water Underground USGS

PSC 121 Prince George's Community College Groundwater Any water that is below the surface Any water that is below the surface May be in soils or porous rocks May be in soils or porous rocks Can be tapped for wells or supply artesian springs Can be tapped for wells or supply artesian springs Click on image to view a groundwater animation

PSC 121 Prince George's Community College 256 cm Boulder 64 cmCobble 2 mm Pebble Gravel mmSand mmSilt Mud Clay Clay Sediment Size Classifications

PSC 121 Prince George's Community College Physical Properties of Sediments and Water Flow – Pore Space Unoccupied or void space between sediment particles Unoccupied or void space between sediment particles Can be filled with air or water Can be filled with air or water Measured by packing solid in a container to measure the total volume; water is added just to the surface filling the empty space Measured by packing solid in a container to measure the total volume; water is added just to the surface filling the empty space added water = pore space

PSC 121 Prince George's Community College Physical Properties of Sediments and Water Flow – Pore Space If particles are round and the same size they will pack a certain way leaving a regular pore space. If particles are round and the same size they will pack a certain way leaving a regular pore space. If this is the case, the pore space does not depend on the particle size. The larger the particles, the larger but fewer the spaces. For smaller particles, there are more but smaller spaces. If this is the case, the pore space does not depend on the particle size. The larger the particles, the larger but fewer the spaces. For smaller particles, there are more but smaller spaces.

PSC 121 Prince George's Community College Physical Properties of Sediments and Water Flow – Pore Space More but smaller spaces Larger but fewer spaces Mixed – less empty space

PSC 121 Prince George's Community College Physical Properties of Sediments and Water Flow – Pore Space Larger but fewer spaces Mixed – less empty space Most sediments are not regular in shape and pack more tightly. This reduces the pore space even more and reduces the connectivity of the space.

PSC 121 Prince George's Community College Physical Properties of Sediments and Water Flow – Water Retention Amount of water that is retained as water flows through sediments Amount of water that is retained as water flows through sediments Water is retained on the surface so the greater the surface area, the higher the water retention Water is retained on the surface so the greater the surface area, the higher the water retention Which will have more retention for the same volume - gravel or sand? Which will have more retention for the same volume - gravel or sand?

PSC 121 Prince George's Community College Physical Properties of Sediments and Water Flow – Water Retention For the same volume, smaller particles will have more surface area, and therefore, greater water retention. Sand will have higher water retention.

PSC 121 Prince George's Community College Physical Properties of Sediments and Water Flow- Permeability Measure of the flow of water through ground material Measure of the flow of water through ground material Depends on the size of sediment particles because it is controlled by the connectivity of pore space and surface area Depends on the size of sediment particles because it is controlled by the connectivity of pore space and surface area Comparison animation

PSC 121 Prince George's Community College Physical Properties of Sediments and Water Flow- Permeability To determine permeability you can measure : To determine permeability you can measure : flow time:time for a set amount of water to flow through the sediment (minutes/100 mL) or flow rate: volume of water that flows through a given amount of sediment in a set amount of time (mL/minute)

PSC 121 Prince George's Community College Physical Properties of Sediments and Water Flow- Permeability Measurement Measurement Value Flow Time (min/100 mL) Flow Rate (mL/min) High Low P High P Medium Medium P Low High P Low P P = relative permeability

PSC 121 Prince George's Community College Groundwater Animation for Kids This site has a cute animation about the importance of groundwater. It runs about 4 minutes and requires Macromedia Flash 5 (or newer version). Click on image to view a groundwater animation