Water In what ways have you used water today? How much water is used to make a 1KG burger?

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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 DefinedWater Earth

Hydrogeology Defined Water EarthInteractions go both ways GeologyGroundwater

Geology controls flow and availability of groundwater because

Groundwater flows through the pore spaces and/or fractures

Groundwater geologic processes.

Interactions

Hydrogeology Defined WaterEarth InteractionsGeology controls groundwater flow

Permeable pathways are controlled by distributions of geological materials.

ShaleSandstone

Groundwater availability is controlled by geology.

Groundwater availability is controlled by geology. Subsurface contaminant transport is controlled by geology.

Hydrogeology Defined WaterEarth 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 WaterEarth InteractionsGroundwater 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%

Porosity and Permeability

Permeability: Ease with which water will flow through a porous material Sediment: Proportional to

sediment size GravelExcellent SandGood SiltModerate ClayPoor

Rock: Proportional to fracture size and number. Can be good to excellent

Excellent

Porosity and Permeability Permeability is not

proportional to porosity.

Table 11.1

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

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

GainingStream

Pumping well

Low well

Cone of Depression

Water TableDrawdown

Dry Spring

Dry river

Dry well

LosingStream

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

Water In what ways have you used water today? How much water is used to make a 1KG burger?

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