Soil and Ground Water

Question 1

what’s the difference between ground water and soil water

Answer 1

Ground water - exists below the water table in the saturated zone in rocks, drift and soil

Soil water - above the water table in soils

soil and ground water zones act as buffers between catchment inputs and run off

Question 2

what are the hydro logically important characteristics of soils? Explain them

DSCPP

Answer 2

Depth - amount of storage/ buffering

Structure - voids will aid through flow and percolation; layers impede percolation

Composition - affects structure (% clay)

Porosity - fraction of soil volume that is occupied by pores

Permeability - capacity for water through put

Question 3

Explain capillary forces

• Surface tension
• Adsorption

Answer 3

surface tension - attractive forces (hydrogen bonds) between liquid molecules that are greater than attraction to air

Adsorption - electrostatic forces bind water molecules strongly onto solid particles

strength of the force = soil suction → dependent o the amount of water present and pore size distribution within soil

Question 4

What’s the difference between

• the saturated zone and
• the unsaturated zone

Answer 4

Saturated zone =
ground water beneath the water table, water movement is mostly lateral

Unsaturated zone = soil water above the water table, water movement is mostly vertical

Question 5

Define the following terms

• Infiltration
• Perched Water Table
• Saturation
• Soil Moisture Deficit

Answer 5

• Infiltration = the prices by which water enters the soil surface, it is limited by soil structure and saturation
• Perched Water Table = May exist when setting of the soil below the surface is slow
• Saturation = occurs when all pore spaces are filled
• Soil moisture deficit = exists once evaporation and/ or prolonged drainage have begun

Question 6

Define these terms

• Aquifer
• Aquitard
• Aquiclude

Answer 6

Aquifer = water bearing permeable rock

Aquitard = A zone that restricts the movement of groundwater from one aquifer to another

Aquiclude = an impermeable Aquitard

Question 7

What are 3 types of aquifer composition

Answer 7

• Shallow drift materials like GLACIAL GRAVELS
• Permeable rock materials like CHALK
• Fractured rock materials like LIMESTONE

Like soil water, each is driven by capillary forced and regulated by permeability

Question 8

Distinguish between a confined and unconfined aquifer

Answer 8

Confined aquifer has a flow boundary above and below it, flow is constructed vertically but not horizontally
The water is under pressure and if intersected by a borehole will rise higher than the boundary forming an artesian well

An unconfined aquifer has no boundary above it so the water table is free to rise and fall dependent on the volume of water contained
The lower boundary (water table) is unconfined and May intersect the surface

Question 9

What is Darcy’s law

Answer 9

Rate of flow of water through a porous medium was proportional to the hydraulic gradient

Question 10

How much of gross precipitation is intercepted and evaporated?

Answer 10

20-50%

Question 11

How does snow and ice impact the hydrology of rivers

Answer 11

Gradually releases water

Amount of intercepted snowfall is much higher than rainfall

It is available for evaporation through sublimation or release through snowmelt