Ground Water 2

Question 1

well efficiency

Answer 1

ratio of theoretical specific capacity to the measured one

Question 2

well loss

Answer 2

energy dissipation from turbulent flow in the vicinity of the well

forms due to the convergence of streamlines, leads to increased velocity

significant for large Q

Question 3

deployable output
- definition
- factors

Answer 3

well water levels during drought period, should allow supply and demand balance

depends on
- licences
- environment
- water quality
- physical aquifer/well characteristics

Question 4

drought curve
- use
- cons

Answer 4

used to determine deployable yield, at the intersection of the curve and DAPWL
- curve defined such that all observed data is to the right
-DAPWL = deepest advisable pumped water level

cons
- curve is subjective
- doesnt consider well interactions
-lack of data

Question 5

baseflow separation
- aim
- techniques

Answer 5

Aim: measuring GW discharge into rivers

Techniques
- channel water budget
- seepage water, point measurement
- tracers
- numerical modelling

Question 6

measuring GW recharge
- techniques

Answer 6

chloride mass balance
- for arid/semi-arid climates
- assumes a SS thus chloride flux at surface same as at root zone due to insignificant plant capture

modelling: Penman Grindley
- based on root constant = max soil moisture deficit without an effect on ET
- above leads to decreased with AE -> P as SMD -> FC

Question 7

rapid recharge

Answer 7

high rainfall leads to fracture flow in unsaturated zone, can cause flow into boreholes

Question 8

measuring hydraulic head

Answer 8

deep jacking tensionometer

Question 9

GW protection approaches
- approach selection

Answer 9

• do nothing
• control/modify hazard
• remove hazard

selected based on: risk = hazard * vulnerability
- no pathway means no risk
- hazard is the prob of event, assumed 1
- vulnerability = damage

Question 10

aquifer vulnerability factors

Answer 10

• geological (major aquifer?)
• overlying soil ( leaching ability ?)
• depth of water table (deep ?)

Question 11

DRASTIC
- use
- weighting

Answer 11

for aquifer vulnerability, all sored 1-10 with 10 being highest polluting potential

Depth of GW - 5
Recharge - 4
Aquifer media - 3
Soil media - 2
Topology - 1
Impact of unsaturated zone - 5
Conductivity (hydraulic) - 3

Question 12

well zone of contribution

Answer 12

are with pathways to the well
- Time related capture zone (area branded by isochrone, below is UK)
— zone 1, t = 50 days for biological contamination
—- zone 2, t = 400 days for slow degrading pollutants
— zone 3 = well catchment

• well catchment, t= Inf
• source protection zone, has a specific level of protection determined by models

Question 13

source protection zone model steps

Answer 13

• conceptual model
• data collection
• mathematical model
• test against observations
• sensitivity analysis = find parameters most likely to control models behaviour
• perform simulation