WR Flashcards
(92 cards)
1
Q
Rainfall measurement methods
A
- Bucket
- Weather radar
- Satellites
2
Q
Adv. Disadv. Bucket
A
Advantages:
1. High Precision
2. Cheap to install
3. Low maintenance
4. Existing long records
Disadvantages:
1. Only specific location
3
Q
Adv. Disadv. Weather radar
A
Advantages:
1. High space and time resolution
Disadvantages:
1. Indirect
2. Expensive
3. Sensitive to topography, climate
4
Q
Adv. Disadv. Satellites
A
Advantages:
1. Global coverage
Disadvantages:
1. Very indirect
2. Sensitive to clouds
3. Low space and time resolution
4. High initial cost
5
Q
Measuring soil moisture (TDR, neutron probe)
A
Advantages:
1. High quality
2. High frequency
Disadvantages:
1. Prone to damage
2. Point scale measurement
6
Q
Measuring soil moisture (satellite)
A
Advantages:
1. Global coverage
Disadvantages:
1. Low accuracy
2. Dependent on vegetation
3. Poor space and time resolution
7
Q
Measuring GW
A
Advantages:
1. High quality
Disadvantages:
1. High cost of installation (drilling)
2. Low spatial coverage
8
Q
Measuring Streamflow
A
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.
9
Q
Measuring ET
A
- Lysimeter (scale)
- Eddy Covariance Systems (vapour and wind)
10
Q
Main legislation goals for GW
A
- Protect aquatic status
- Sustainable abstraction
- Reduce pollution
- Prevent deterioration
- Mitigate flood and draught impacts
11
Q
What is the control of nitrate?
A
limit is 11.3 mgN/L
12
Q
What are the main stages of development of GW?
A
- Exploration
- Evaluation
- Exploitation/management
13
Q
Well yield
A
Maximum pumping rate which can be applied without lowering well water level below pump intake level.
14
Q
Aquifer yield
A
Maximum pumping rate without causing unacceptable decline in the hydraulic head.
15
Q
Catchment yield
A
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.
16
Q
Sustainable yield
A
- Does not exceed annual recharge
- Does not lower the water table to permit intrusion of water of undesirable quality.
17
Q
Sustainable yield Qws
A
Qws = R + dR - Dr (natural recharge plus additional recharge due to pumping minus residual discharge imposed.)
18
Q
Groundwater footprint
A
GF = Aa(Qw/(R-E)) E-contribution to streamflow
19
Q
Specific capacity
A
Pumping rate per unit drawdown
20
Q
Drawdown
A
Sw = AQ + BQ^n
21
Q
AQ
A
Formation loss
22
Q
BQ^n
A
Well loss
23
Q
Deployable output depends on
A
- Physical properties of aquifer and borehole
- License
- Environment
- Quality
- Source works
24
Q
Limitation of current GW methodology
A
- Data availability and quality
- Subjectivity (drought curve)
- Sources considered in isolation
- Reliance on historic data
- Climate change impacts?
25
What are the GW levels of protection
1. Exclusion or total removal
2. Control and modify
3. Do nothing, rely on natural processes
26
Steps of modelling source protection zones:
1. Conceptual model
2. Equations to represent the model
3. Collect field data
4. Test model against data
5. Calibrate
6. Sensitivity analysis
7. Simulate/predict
27
Nelder - Mead procedure
1. Guess initial simplex
2. Omit the worst point
3. Reflect the simplex
4. Expand or contract in direction of best point
5. Shrink simplex towards best point
28
Advantage/Disadvantage of Newtons' Method
Advantage:
- Less steps to converge than gradient descent
Disadvantage:
- More calculations per step
29
What is the main need for water storage
Availability and demand fluctuate
30
Main sources of contamination
- Sewage pathogens
- Nitrates from fertilizers
- Heavy metals
- Chlorinated discharges from waste disposal
31
Self-sufficiency indicator
(ER+I)/O
ER - effective rainfall
I - recycling
O - total use
32
Catchment stress indicator
[(A+B)-(H+I) / ER]
A - GW abstraction
B - SW abstraction
H - leakage volume
I - recycling
ER - effective rainfall
33
Main issues for water resource management
1. Predicting demand
2. Predicting supply
3. Reducing demand
4. Increasing supply
34
Why is predicting demand difficult?
- growth of population
- industrial growth
- future agricultural requirements
- range of non hydrological expertise
35
Five strands of water demand management
1. Internal and external re-use
2. Consumption technology
3. Land use planning
4. Educational initiatives
5. Water pricing
36
Internal and external reuse for water demand management
e.g. reusing shower water for flushing the toilet
37
Consumption technology for water demand management
e.g. Redesigning existing systems (such as a washing machine)
38
Land use planning for water demand management
Could restrain urban development where the supply is problematic.
39
Educational initiatives for water demand management
Persuading citizens, farmers, managers to use water wisely.
40
Water pricing for water demand management
Metering of water use
41
Why does nitrate leaching increase in winter?
More rainfall, hence crops do not up the nitrate as much.
42
Ways to meet world demand for food
- Rainfed croplands
- Water harvesting and better use of rainwater
- Promoting agricultural trade to water-scarce areas
- Changing food demand patterns
- Reduce food waste
43
Main advantages of irrigation
- Increased crop yield
- Protection against climate variability
44
Main challenges of irrigation
- Environmental degradation
- Salt/fertilizer runoff contaminating surface water
- Salt/nutrient enrichment compromising groundwater
45
What are the types of irrigation
- Flood or surface
- Sprinkler
- Drop (trickle)
- Railgun
46
Flood (surface) irrigation
Entire field flooded
47
Sprinkler irrigation
Water pumped and sprayed onto crop
48
Drip irrigation
Water drips slowly only wetting the immediate root zone
49
Railgun irrigation
Retracting hose reel drawn across field.
50
Examples of possible technologies to use in agriculture
- GPS
- GIS
- field sensors
- variable rate applicators
- yield monitors for harvesting
- computer systems in cabs
- automated soil sampling and testing
51
Constructed wetlands for water treatment
Artificially constructed water storage basin providing a biofiltration capability.
52
Permeable reactive barrier for water treatment
Reactive porous media to retain pollutants.
53
How can reliability of the system be measured
Number of data in satisfactory state / total number of data
54
How can resilience of the system be measured
Probability of the next state being satisfactory given that you are in a unsatisfactory state
55
How can vulnerability of the system be measured
Extent of differences between the threshold value and the unsatisfactory time series value.
56
Water resources main goals
- Meet global demand
- Ensure future water supply
- Ensure sustainable use
- Achieve high standards of aquatic ecology
57
Pareto front
Set of solutions for which none of the objective functions can be improved without compromising one of the objective function values.
58
Characteristics of constructed wetlands
- Area supporting plants that grow in water
- Continually wet soils
- Rock/gravel substrates that have some water cover
59
Steps of system definition
1. Define geographical limits
2. Map water infrastructure (e.g. reservoirs)
3. Map physical environment (e.g. topography)
4. Map the built environment
5. Map water demanding activities
60
Main principles of system conceptualisation
1. Abstraction (what is important/what can you omit)
2. Classification (unify similar parts into units)
3. Parsimony (simplest model possible)
61
What does the control curve contain?
- the reservoir levels below which restrictions on water use should be introduced
- projections of the reservoir content into the future under different “dry” scenarios based upon past rainfall information: 0, 25% and 50% of average rainfall over the next 12 months;
- estimates of the target flows downstream of the reservoir intake
62
Adv. Disadv. Rippl diagram
Advantages:
- simple and widely used
- takes seasonality into account
Limitations:
- reservoir full at start
- no drought more severe than historical
- constant draft
- no evaporation losses
63
Adv. Disadv. Sequent Peak
Advantages:
- allows seasonally variable draft
- takes seasonality into account
Limitations:
- reservoir full at start
- no drought more severe than historical
- no evaporation losses
64
Reservoir Design methods
Mass curve methods:
- Rippl diagram
- Sequent Peak algorithm
Low-flow period based methods:
- Wait method
- Alexander method
65
Adv. Disadv. Wait Method
Advantages:
- simple
- takes seasonality into account
Limitations:
- reservoir full at start
- no drought more severe than historical
- constant draft
- no evaporation losses
- not widely used
66
Adv. Disadv. Alexander Method
Advantages:
- easy to use
- provides capacity estimate for any probability of failure
Disadvantages:
- reservoir full at time 0, so there are no repeated failures;
- annual flows are independent;
- annual flows are Gamma distributed;
- within-year storage is not estimated;
- draft constant;
- no account of evaporation losses taken.
67
Income elasticity of demand
IED = (Consumption(A) - Consumption(B)) / (Income(A) - Income (B))
for IED < 1, commodity is a necessity of life
68
Best Management Practices
- Measures designed to minimise negative effects of agricultural production
- Farm operations that efficient use of resources, safety, economic viability
69
What are the components of a Decision Support System (DSS)
- A model
- A database
- An interface for decision makers to evaluate model outputs
70
Steps for decision making in Water Resources
1. System Definition
2. System Conceptualisation
3. Model Development
4. Data Collection
5. Model Parametrisation
6. Model Simulation
7. System Optimisation
71
Components of Model Simulation
1. Initial condition (observed state of the system)
2. Environmental Forcing (short/long term)
3. Human Forcing (demands, population growth, etc.)
72
Sources of System Uncertainty
- Epistemic (structural) uncertainties
- Human forcing variability
- Natural (stochastic variability)
- Initial state uncertainties
- Parameter uncertainties
73
Epistemic uncertainties and ways to quantify
Imperfect representation of processes in a model.
Quantified by using information from different models given the same forcing.
74
Human forcing variability and ways to quantify
Incomplete knowledge of future water demands, population growth, etc...
Use of multiple development scenarios to quantify (e.g. climate scenario graph)
75
Natural variability and how to quantify
Natural forcing (weather) is uncertain.
At short scales, numerical weather prediction models can be used.
Quantify by using different weather scenarios from a stochastic weather model.
76
Goals of precision agriculture
1. Describe the spatial distribution of factors affecting crop growth.
2. Apply variate rate treatment of agrochemicals and fertilizers depending on location specific requirements.
3. Maximise profitability
4. Minimise environmental impacts
77
S
S = 1000/CN - 10
78
Initial abstraction
I_a = 0.2 x S
79
Curve Method Runoff
P_e = (P - I_a)^2 / (P - I_a + S)
80
Water limitation equation
ET/P <= 1
81
Energy limitation equation
ET/P <= R_n/λP = Φ
82
Source protection zones travel times
Zone 1: 50 day travel time to the well
Zone 2: 400 day travel time to the well
Zone 3: All catchment
83
What does the drought curve show?
Minimum pumping rate for a given GWL
84
Difference between internal, external re-use and recycling
Internal: re-use by same user
External : re-use by neighbouring user without re-entry to distribution system
Recycling: with re-entry to distribution system
85
Alexander method transform
C = Tau_1 * X_av / alpha
CP = CP1 /alpha
86
Agriculture threats to SW and GW
- Cultivation
- Fertilisation
- Manure spreading
- Pesticide application
- Housed livestock
- Manure storage
- Farmyard runoff
- High density stocking of grazing livestock
- Fuel storage
- Septic tank drain field
- Clear cutting
- Aquaculture
87
Recharge area water balance
P = Q_s + R + E_R
Q_s surface water component of the runoff
E_R evapotranspiration from recharge area
88
Discharge area water balance
Q = Q_s + D - E_D
Q_s surface water component of the runoff
D average annual GW discharge
E_D evapotranspiration from discharge area
89
Ways to measure GW discharge to rivers
- Physical techniques
- Seepage meters (point measurement)
- Tracers
- Modelling
- Chemical balance
90
Strands of aquifer protection
1. Geological vulnerability (major aquifer, minor aquifer, no aquifer)
2. Soil vulnerability (leaching)
3. Depth of water table (shallow, deep)
91
Triangular UH equations
T_R = 1.67 T_P
Q = 0.5 * Q_P (T_P + T_R)
92
SPZ Pumping rate - radius relationship equation
Q_w = pi*W*R^2
