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2.3 Summary of current analysis of use
2.3.1 How water is used
This report examines four main water uses: abstraction, impoundment, discharge and engineering.
The main abstracting sectors are energy (using water for cooling) and water supply for domestic use and as partof a production process.
The same two sectors are also major impounders although for different purposes; energy is generated through hydropower and water is stored in reservoirs (other impoundments include flood defence and canals).
Over 90% of clean water used by households is discharged to mains sewers and many other water uses are non-consumptive with water being returned in an altered state and used to dilute pollution or to dissipate heat. Behind sewage and refuse disposal the next most significant sector for point source pollution is fish farming, along with manufacturing. Harbours, canals, flood defence, river straightening and alteration through towns etc. are all good examples of engineering activity.
2.3.2 How water use is valued
Due to the complexity of many industrial processes, placing a value on their usage of water is not straightforward. The most appropriate methods are discussed in the Water Use report 13 but, unfortunately, there is not sufficient data on the water use and non-water costs of businesses to be able to apply this model to Scotland (let alone to the Solway Tweed RBD). Therefore, it has been necessary to partly rely on estimates originally derived for Canadian industry and transfer the values to Scotland. No similar analysis has been undertaken in England but the value of this work will be considered in later phases of the economic analysis.
The results are given in Table 2 and Figure 3. Inflation factors and exchange rates are applied to transfer the values to 2004 UK pounds.
Table 2 Industrial value of water use (p/m3) *
| Manufacturing industry |
1991
($Can) |
2004 values
($Can) |
2004 values
(£UK) |
| Food |
0.017 |
0.30 |
0.125 |
| Beverage |
0.038 |
0.50 |
0.21 |
| Rubber products |
0.006 |
0.10 |
0.04 |
| Plastic products |
0.032 |
0.40 |
0.16 |
| Textile products |
0.005 |
0.10 |
0.04 |
| Wood |
0.020 |
0.30 |
0.125 |
| Paper and allied products |
0.031 |
0.40 |
0.16 |
| Primary metal |
0.107 |
0.13 |
0.055 |
| Fabricated metal products |
0.048 |
0.60 |
0.25 |
| Transport equipment |
0.025 |
0.30 |
0.125 |
| Non-metallic mineral products |
0.023 |
0.30 |
0.125 |
| Refined petroleum and coal products |
0.288 |
0.36 |
0.15 |
| Chemical and chemical products |
0.072 |
0.90 |
0.375 |
The information available and the needs of the research meant that the focus was on particular methods and users. Table 3 summarises the values calculated. However, it should be noted that the values were calculated using different methods and based on different assumptions, and therefore the results for sectors are not directly comparable.
Table 3 Summary of the valuation techniques and results for sectors considered
| Sector |
Valuation technique |
Key assumptions |
Value |
| Households |
Gibbons’ willingness to pay formula |
Assumes all consumers pay volumetric charges levied to metered customers in England, Wales and Scotland |
0.102 - 0.244 |
| |
|
Includes value of both clean and dirty water |
p/m3 |
| |
Benefits transfer from stated preference study |
Only considers value of supply of clean water |
0.067 p/m3 |
| Agricultural irrigation |
Net-back analysis |
Assumes that the West Pfeffer catchment is representative of other areas where potatoes are irrigated |
£5128/ha |
| |
|
Value includes both naturally available water and water applied through irrigation |
|
| |
Transfer of net-back analysis |
Data from England and Scotland combined despite different agricultural support arrangements and climate |
23-138 p/m3 |
| Aquaculture |
Net-back analysis |
Uses average value for farmed trout |
0.67 p/m3 |
| |
Avoided cost |
Considers value of water for waste disposal but not as medium for growth |
1.86-13.89 p/m3 |
| Salmon angling |
Benefits transfer of travel cost method study |
Assumes salmon anglers in Donegal are representative of others throughout Scotland and Northern Ireland |
£175/day |
| Industry |
Benefits transfer from marginal productivity approach study |
Industrial water use in Scotland and Northern Ireland assumed to be the same as for Canada |
4-37.5 p/m3 |
| |
|
Assumes no improvements in water efficiency since 1991 |
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| Power generation |
Avoided cost |
Assumes generation from hydropower is comparable to generation from nuclear fuels, as this study does not consider environmental effects |
0.03 p/m3 |
Results are based on the information available and the techniques developed at the time. However, there are a number of areas in which understanding can and should be improved. In particular, the understanding of the volume of water supplied to and discharged from different sectors could be improved. In turn, this could help to identify issues of water use at a more precise geographic level in order to facilitate assessment of the Solway Tweed river basin district.
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