Water Supply Management Flashcards
(43 cards)
What is the UN definition of ‘water security’?
the capacity of a population to safeguard sustainable access to adequate quantities of acceptable quality water for sustaining livelihoods, human well-being, and socio-economic development, for ensuring protection against water-bourne pollution and water-related disasters, and for preserving ecosystems in a climate of peace and political stability.
What is virtual water?
Virtual water is water embedded in commodities
What is the waterfootprint?
The water footprint is the total volume of freshwater that is used to produce the foods and services consumed by an individual, business or nation
What three things can water infrastructure help with?
1) Protection against floods
2) Improving water quality
3) Ensuring water supply
Three points about the limits to infrastructure expansion
- Infrastructure expansion for water supply is constrained (‘peak water limit’)
- Marginal benefit of new infrastructures decreases with cumulative investment
- It has substantial (often unanticipated) socio-economic-environmental costs
There’s a shift from ‘hard-path’ to ‘soft-path’ solutions through a….
growing emphasis on improving the productivity of existing infrastructure by making water management more efficient
5 main purposes of reservoirs?
- Irrigation
- Hydropower
- Water supply (domestic and industry)
- Flood control
- Multiple purposes
Negative impacts of reservoirs?
- Resettlement of inhabitants
- River fragmentation, dams may affect the passage of migratory fish, can be partially overcome by constructing bypasses of fish ladders
- Alteration of downstream flow regime
- Sediment trapping, the dam blocks downstream transport of sediment, sediment accumulates in the reservoir (reservoir capacity diminishes in time), sediment supply to downstream areas is reduced (erosion of downstream river beds and banks)
Long term negative effects
- Supply demand cycle
- Reservoir effects
What are water resources management plans?
They show how a water company propose to manage the supply-demand balance over a planning period of 25-years
They are produced every 5 years by the water company and need to be approved by the EA
3 aspects covered in water resources management plans?
1) The demand expected in a water resource zone (WRZ) across the 25-years planning period
2) The supply from each WRZ, incorporating the effects of changes in licences and climate change
3) The measures that will be implemented where forecast demand will exceed supply (e.g. leakage reduction, metering, water transfers, new reservoirs)
What are water resource system models?
- Water resource system models are used to support the quantitative assessment underpinning the WRMP (supply side)
- WRS models can simulate the movement of water through a water supply and distribution system, including reservoirs, pipes, treatment plans etc.
4 components of a reservoir
1) Dam
2) outlet from ‘outlet tower’
3) bottom outlet
4) spillways
7 different water fluxes
1) precipitation
2) seepage losses
3) inflow
4) evaporation
5) release (from outlets)
6) outflow (flow spillways)
7) outflow (from bottom spillways)
Where do inflows come from in a) reservoirs dammed in valley sides b) bank-side reservoirs
a) inflows come from upstream rivers and drainage catchment
b) inflows come from river abstraction
What is the evaporation equation?
E = e*S
where e = evaporation for squared meters (depends on local climate)
S = reservoir surface area
What is the surface area of the reservoir linked to?
SA is linked to the reservoir storage level and both are linked to the storage
The relationships between these variables depend on the geometry of the reservoir
Two methods of obtaining the stage-storage-area relationships
1) end area method
2) surface area method
Explain the end area method in 3 steps
1) Valley cross sections are surveyed at various points
2) The end area of each cross section can be computed at selected values of water elevation (h)
3) The end area is multiplied by the horizontal distance between cross sections to obtain the storage (s) at each selected elevation
Explain the surface area method in 3 steps
1) From a topographic map of the reservoir, estimate the reservoir surface area (S) at selected values of water elevation (h)
2) for each pair (h,S) compute the storage (s)
3) Interpolate the data pairs (h,s) and (h,S) to obtain the stage-storage curve and the stage-area curve
When do spills take place?
Spills take place when the water level exceeds a threshold on the level, or equivalently a storage threshold (i.e. the reservoir (active) capacity)
What is release?
This is a ‘controlled output’, in fact it depends on the operator’s decision (how much water one wants to take out of the reservoir). The simplest decision model is the Standard Operating Policy
What is the Deployable Output (DO)?
The Deployable Output (or firm yield) is the maximum rate at which a system can supply water continuously through a dry period with a known or assumed severity
Advantages of using historical drought to define the DO
1) Easier to communicate to the public, water companies aim to supply water through the worst drought in ‘living memory’
2) Allows for using simplified approaches to hydrological modelling for assessing the DO (or computing other performance indicators) whenever long flow records are available
