Water In what ways have you used water today?

How much water is used to make a 1KG burger?

4000 Litres of Water

How much water is used to make a pair of leather shoes?

16, 000 Litres of Water

Where does the water we use come from?

11: Groundwater Water resources Geologic Agent

Earth materials Rock Sediment (Soil) Fluids (Water) Geologic processes Form, Transform and Distribute (redistribute) Earth materials  Water is a primary agent of many (all?) geologic processes Hydrogeology Defined WaterEarth

Hydrogeology Defined Water Earth Interactions go both ways  Geology  Groundwater  Geology controls flow and availability of groundwater because  Groundwater flows through the pore spaces and/or fractures  Groundwater  geologic processes.  Interactions

Hydrogeology Defined Water  Earth Interactions Geology controls groundwater flow Permeable pathways are controlled by distributions of geological materials. Shale Sandstone

Hydrogeology Defined Water  Earth Interactions Geology controls groundwater flow Permeable pathways are controlled by distributions of geological materials. Groundwater availability is controlled by geology.

Hydrogeology Defined Water  Earth Interactions Geology controls groundwater flow Permeable pathways are controlled by distributions of geological materials. Groundwater availability is controlled by geology. Subsurface contaminant transport is controlled by geology. Geology controls groundwater flow Permeable pathways are controlled by distributions of geological materials. Groundwater availability is controlled by geology. Subsurface contaminant transport is controlled by geology.

Hydrogeology Defined Water  Earth Interactions Groundwater controls geologic processes Igneous Rocks: Groundwater controls water content of magmas. Metamorphic Rocks: Metasomatism (change in composition) is controlled by superheated pore fluids. Volcanism: Geysers are an example of volcanic activity interacting with groundwater.

Hydrogeology Defined Water  Earth Interactions Groundwater controls geologic processes Landforms: Valley development and karst topography are examples of groundwater geomorphology. Landslides: Groundwater controls slope failure. Earthquakes: Fluids control fracturing, fault movement, lubrication and pressures.

Ground Water Zones Degree of saturation defines different soil water zones

Ground water and the Water cycle Infiltration Infiltration capacity Overland flow Ground water recharge GW flow GW discharge

Porosity and Permeability Porosity: Percent of volume that is void space. Sediment: Determined by how tightly packed and how clean (silt and clay), (usually between 20 and 40%) Rock: Determined by size and number of fractures (most often very low, <5%) 1% 5% 30%

Porosity and Permeability Permeability: Ease with which water will flow through a porous material Sediment: Proportional to sediment size Gravel  Excellent Sand  Good Silt  Moderate Clay  Poor Rock: Proportional to fracture size and number. Can be good to excellent Excellent Poor

Porosity and Permeability Permeability is not proportional to porosity. Table % 5% 30%

Water table: the surface separating the aerated zone from the saturated zone. Measured using the water level in a well The Water Table Fig. 11.1

Precipitation Infiltration Ground-water recharge Ground-water flow Ground-water discharge to Springs Streams and Wells Ground-Water Flow

Velocity (speed) is proportional to Permeability Slope of the water table Ground-Water Flow Fast (e.g., cm per day) Slow (e.g., mm per day)

Infiltration Recharges ground water Raises water table Provides water to springs, streams and wells Natural Water Table Fluctuations

Reduction of infiltration causes water table to drop Wells go dry Springs go dry Discharge of rivers drops Artificial causes Pavement Drainage Natural Water Table Fluctuations

Pumping wells Accelerates flow near well May reverse ground-water flow Causes water table drawdown Forms a cone of depression Effects of Pumping Wells

Pumping wells Accelerate flow Reverse flow Cause water table drawdown Form cones of depression Low river Gaining Stream Gaining Stream Pumping well Low well Cone of Depression Water Table Drawdown Dry Spring Effects of Pumping Wells

Dry river Dry well Effects of Pumping Wells Dry well Losing Stream Continued water- table drawdown May dry up springs and wells May reverse flow of rivers (and may contaminate aquifers) May dry up rivers and wetlands

Ground-Water/ Surface-Water Interactions Gaining streams Humid regions Wet season Loosing streams Humid regions, smaller streams, dry season Arid regions Dry stream bed

Confined Aquifers & Artesian Wells Hydraulic Head Cap Rock Impermeable Layer

Confined Aquifers

Ground-Water Contamination Dissolved contamination travels with ground water flow Contamination can be transported to water supply through an aquifer’s down flow Pumping will draw contamination into water supply

Ground-Water Contamination Leaking Gasoline Floats on water table Dissolves in ground water Transported by ground water Contaminates shallow aquifers

Ground-Water Contamination Dense solvents E.g., dry cleaning fluid (TCE) Sinks past water table Flows down the slope of an impermeable layer Contaminates deeper portions of aquifers

Ground-Water Contamination Effects of pumping Accelerates ground water flow toward well Captures contamination within cone of depression May reverse ground water flow Can draw contamination up hill Can cause saltwater intrusion

Ground Water Action Ground water chemically weathers bedrock E.g., slightly acidic ground water dissolves limestone Caves are formed Permeability is increased Caves drain Speleothems form

Ground Water Action Karst Topography Caves (Speleothem) Sink holes Karst valleys Disappearing streams Giant springs