CEE 1030 1nd Edition Lecture 17 Groundwater Outline of Last Lecture I Hydrolic cycle II Running water III Divides and drainage networks IV Vocab terms V Stream erosion transport and deposition Outline of Current Lecture I Groundwater II Infiltration of water III Permeability features IV Groundwater movement and storage V Review VI Hydraulic gradient VII Groundwater systems Current Lecture I II Groundwater a Source of drinking water source of irrigation b Most of Earth s freshwater is contained in groundwater and glaciers c Groundwater is found in pore spaces of soil and sediment and fractures in bedrock d Groundwater water that has infiltrated the land s surface Infiltration of water a Soil moisture zone uppermost layer of the regolith from which plant roots extract water b Some water retained as surface film on soil particles c Saturation zone layer of regolith in which all voids in sediment and rock are completely filled with water d Groundwater water in the saturation zone e Upper limit of saturation zone water table f Aeration zone all ground above saturation zone i Some groundwater drawn upward from saturation zone by capillary action ii Lowermost layer of aeration zone capillary fringe These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute III IV V VI g Water table depth is irregular i Water table depth usually a subdued replica of ground s surface topography ii Also associated with variations in rainfall and permeability h Groundwater moves slowly tends to pile up between high areas beneath valleys Permeability features a Aquitard impermeable layer of rock or sediment that hinders or prevents water movement b Aquifer permeable rock or sediment that allows groundwater to move freely Groundwater movement and storage a Rate of groundwater movement and storage potential depends on the composition and nature of the regolith and bedrock b Key factors i Porosity the percentage of total volume of rock or sediment that consists of pore spaces ii Permeability the ability of sediment or rock to transmit fluid c Effects of porosity and permeability i Specific yield portion of groundwater that drains ii Specific retention portion of groundwater retained d Groundwater dissolves rock i Rainwater dissolves CO2 from the air and decaying plants forming carbonic acid ii Carbonic acid reacts with limestone to form calcium carbonate iii Acidic groundwater flows through joints in rock forms caverns iv Cavern features 1 Speleothem general term for dripstone a Stalactites hanging from ceiling b Stalagmites form on floor c Dripstone calcite deposited as dripping water evaporates 2 Karst topography landscape shaped by groundwater that dissolves the bedrock a Sinkholes surface depression produced in a region where soluble rock has been dissolved and removed by groundwater Review a Most of Earth s freshwater is contained in glaciers and groundwater b Most of Earth s water is contained in oceans c Rocks with lots of pore spaces between particles have high porosity d In order to have reliable access to groundwater a well must be drilled below the water table Hydraulic gradient VII a How steep the slope is related to the movement of water b Steeper the slope faster the water flow c Hydraulic conductivity how fast groundwater flows through the ground determined by sediment permeability fluid viscosity d Darcy s Law discharge rate varies with hydraulic gradient hydraulic conductivity and cross sectional area of aquifer Groundwater systems a Water may flow for meters to hundreds of km from recharge to discharge b Localized near surface flow may move in a different direction than deep regional flow c Spring a natural outflow of groundwater that occurs where water table intersects land surface i Hot springs water heated by cooling of igneous rock ii Geysers intermittent hot springs that erupt from the ground with great force d Wells most common way to access groundwater drill hole into the saturation zone i When water is drawn up through the well the water table around the well is lowered e Artesian systems i Where groundwater is under pressure well or spring that pierces aquitard will flow out ii Water towers are artificial artesian systems