WR Flashcards
Rainfall measurement methods
- Bucket
- Weather radar
- Satellites
Adv. Disadv. Bucket
Advantages:
1. High Precision
2. Cheap to install
3. Low maintenance
4. Existing long records
Disadvantages:
1. Only specific location
Adv. Disadv. Weather radar
Advantages:
1. High space and time resolution
Disadvantages:
1. Indirect
2. Expensive
3. Sensitive to topography, climate
Adv. Disadv. Satellites
Advantages:
1. Global coverage
Disadvantages:
1. Very indirect
2. Sensitive to clouds
3. Low space and time resolution
4. High initial cost
Measuring soil moisture (TDR, neutron probe)
Advantages:
1. High quality
2. High frequency
Disadvantages:
1. Prone to damage
2. Point scale measurement
Measuring soil moisture (satellite)
Advantages:
1. Global coverage
Disadvantages:
1. Low accuracy
2. Dependent on vegetation
3. Poor space and time resolution
Measuring GW
Advantages:
1. High quality
Disadvantages:
1. High cost of installation (drilling)
2. Low spatial coverage
Measuring Streamflow
Advantages:
1. High quality
2. Easy and cheap to install and maintain
3. High spatial coverage
Disadvantages:
1. Need to construct rating curves
2. Weirs can cause ecological problems by obstructing/altering flows.
Measuring ET
- Lysimeter (scale)
- Eddy Covariance Systems (vapour and wind)
Main legislation goals for GW
- Protect aquatic status
- Sustainable abstraction
- Reduce pollution
- Prevent deterioration
- Mitigate flood and draught impacts
What is the control of nitrate?
limit is 11.3 mgN/L
What are the main stages of development of GW?
- Exploration
- Evaluation
- Exploitation/management
Well yield
Maximum pumping rate which can be applied without lowering well water level below pump intake level.
Aquifer yield
Maximum pumping rate without causing unacceptable decline in the hydraulic head.
Catchment yield
Maximum pumping rate sustained by the complete hydrogeological system (no unacceptable heads or changes in the cycle) without causing unacceptable declines in hydraulic head or any other unacceptable changes.
Sustainable yield
- Does not exceed annual recharge
- Does not lower the water table to permit intrusion of water of undesirable quality.
Sustainable yield Qws
Qws = R + dR - Dr (natural recharge plus additional recharge due to pumping minus residual discharge imposed.)
Groundwater footprint
GF = Aa(Qw/(R-E)) E-contribution to streamflow
Specific capacity
Pumping rate per unit drawdown
Drawdown
Sw = AQ + BQ^n
AQ
Formation loss
BQ^n
Well loss
Deployable output depends on
- Physical properties of aquifer and borehole
- License
- Environment
- Quality
- Source works
Limitation of current GW methodology
- Data availability and quality
- Subjectivity (drought curve)
- Sources considered in isolation
- Reliance on historic data
- Climate change impacts?
What are the GW levels of protection
- Exclusion or total removal
- Control and modify
- Do nothing, rely on natural processes
Steps of modelling source protection zones:
- Conceptual model
- Equations to represent the model
- Collect field data
- Test model against data
- Calibrate
- Sensitivity analysis
- Simulate/predict
Nelder - Mead procedure
- Guess initial simplex
- Omit the worst point
- Reflect the simplex
- Expand or contract in direction of best point
- Shrink simplex towards best point
Advantage/Disadvantage of Newtons’ Method
Advantage:
- Less steps to converge than gradient descent
Disadvantage:
- More calculations per step
What is the main need for water storage
Availability and demand fluctuate
Main sources of contamination
- Sewage pathogens
- Nitrates from fertilizers
- Heavy metals
- Chlorinated discharges from waste disposal
Self-sufficiency indicator
(ER+I)/O
ER - effective rainfall
I - recycling
O - total use
Catchment stress indicator
[(A+B)-(H+I) / ER]
A - GW abstraction
B - SW abstraction
H - leakage volume
I - recycling
ER - effective rainfall
Main issues for water resource management
- Predicting demand
- Predicting supply
- Reducing demand
- Increasing supply
Why is predicting demand difficult?
- growth of population
- industrial growth
- future agricultural requirements
- range of non hydrological expertise
Five strands of water demand management
- Internal and external re-use
- Consumption technology
- Land use planning
- Educational initiatives
- Water pricing
Internal and external reuse for water demand management
e.g. reusing shower water for flushing the toilet