1 Introduction
2 Methodology for Data Collection
3 Results and Discussion
3.1 Household Characteristics
Household characteristics | Unit | Mean | Median | Standard deviation | Minimum | Maximum | Skewness | Kurtosis | Confidence interval (95 %) |
---|---|---|---|---|---|---|---|---|---|
Household size (occupancy) | No./hh | 7.04 | 7.00 | 2.35 | 2 | 13 | 0.24 | −0.55 | 0.23 |
Number of children (<15 years) | 2.22 | 2.00 | 1.74 | 0 | 7 | 0.53 | −0.35 | 0.17 | |
Number of adult males members (15–65 years) | 2.27 | 2.00 | 1.07 | 0 | 5 | −0.13 | 0.24 | 0.10 | |
Number of adult females members (15–65 years) | 2.33 | 2.00 | 1.01 | 1 | 5 | 0.45 | −0.72 | 0.09 | |
Number of elders (>65 years) | 0.22 | 0.00 | 0.49 | 0 | 2 | 2.12 | 3.77 | 0.05 | |
Household type | % | Houses (91.9 %) | Apartments (8.1 %) | ||||||
Total built-up area of all floors | m2/hh | 314.6 | 325.0 | 114.5 | 100. | 500. | −0.10 | −1.03 | 11.2 |
Garden area per household | 29.56 | 30.00 | 24.38 | 0.00 | 100. | 1.26 | 1.81 | 2.38 | |
Number of rooms in the household | No. | 4.19 | 4.00 | 1.18 | 2 | 6 | −0.16 | −0.82 | 0.11 |
Number of floors in the household | No. | 1.48 | 1.00 | 0.61 | 1 | 3 | 0.89 | −0.21 | 0.06 |
Monthly family income/household | 1000 ID/month | 1857 | 1570 | 1105 | 258 | 4470 | 0.5 | −0.9 | 108 |
3.1.1 The Influence of Household Characteristics on the Total Average Water Consumption (l/hh/day)
3.1.2 The Influence of Household Characteristics on the Average Per Capita Water Consumption (l/p/d)
3.1.3 Influence of Per Capita Income on the Average Per Capita Water Consumption (l/p/d)
Income group | Income range in Iraqi Dinar (ID) | |
---|---|---|
Per household | Per capita | |
Low | <1 × 106
| <15 × 104
|
Medium | 1 × 106 − 2 × 106
| 15 × 104 − 30 × 104
|
High | >2 × 106
| >30 × 104
|
Income group | Low | Medium | High |
---|---|---|---|
Number of households | 92 | 176 | 139 |
3.2 Average Per Capita Water Use for Different End-Uses (Micro-Components)
3.3 The Influence of Per Capita Income on Water End-Uses
End-use | Parameter/variable | Unit | Full sample | Low income | Medium income | High income | Comparison with past studies |
---|---|---|---|---|---|---|---|
Bath | Frequency of taking bath per capita per day | frequency/day | 0.004 | 0.00 | 0.00 | 0.01 | 0.044 (Blokker et al. 2010) |
Volume of water use in each bath | liter/bath | 132.00 | 0.00 | 0.00 | 132.00 | 100 in France (Estrela et al. 2001) | |
Shower | Frequency of showering per capita per day | frequency/day | 0.49 | 0.34 | 0.47 | 0.61 | 0.73 (Athuraliya et al. 2012) |
Duration of each shower | min/shower | 8.64 | 8.87 | 8.72 | 8.38 | 7.55 (Gato 2006) | |
Flow rate | liter/min | 9.02 | 9.48 | 9.27 | 8.39 | 16 in France (OFWAT 1997) | |
Hand wash basin | Frequency of using taps per capita per day | frequency/day | 10.46 | 9.96 | 10.31 | 10.98 | 4.1 (Blokker et al. 2010) |
Duration of tap use | seconds/use | 60.81 | 58.31 | 61.02 | 62.20 | 21.3 (Gato 2006) | |
Flow rate | liter/min | 8.14 | 8.13 | 8.24 | 8.02 | 2.6 (Athuraliya et al. 2012) | |
Toilet | Frequency of toilet use per capita per day | frequency/day | 4.65 | 5.39 | 4.66 | 4.14 | 4.2 (Roberts 2005) |
Water use in each flush (L) | liter/flush | 5.51 | 6.01 | 5.36 | 5.38 | 9.5 in the UK (OFWAT 1997) | |
Dish washing | Frequency of washing dishes per day | frequency/day | 3.00 | 3.00 | 3.00 | 3.00 | 2.1 (Jacobs and Haarhoff 2004) |
Duration of running water in each wash | min/capita | 1.47 | 1.16 | 1.50 | 1.64 | ||
Flow rate | liter/min | 8.36 | 9.54 | 8.39 | 7.54 | 5.4 (Marinoski et al. 2014) | |
Laundry | Frequency of laundry per day | frequency/day | 1.48 | 0.83 | 1.46 | 1.93 | 0.69 (Athuraliya et al. 2012) |
Volume of water/washing load | liter/load | 167.32 | 190.02 | 161.01 | 160.28 | 80 in the UK (Estrela et al. 2001) | |
House washing | Frequency of house washing per day | frequency/day | 0.69 | 0.51 | 0.69 | 0.80 | |
Duration of each wash | min/capita | 2.13 | 1.79 | 2.1 | 2.38 | ||
Flow rate | liter/min | 9.80 | 12.20 | 9.88 | 8.12 | ||
Vehicle washing | Frequency of vehicles washing per day | washes/day | 0.07 | 0.06 | 0.10 | 0.04 | |
Duration of each wash | min/capita | 1.39 | 1.81 | 1.34 | 1.1 | ||
Flow rate | liter/min | 12.82 | 12.79 | 12.75 | 13.08 | 10.2 (Marinoski et al. 2014) | |
Swimming pool | Frequency of filling swimming pool per day | frequency/day | 0.001 | 0.00 | 0.00 | 0.002 | |
Volume of water provided to fill the swimming pool | m3
| 36.00 | 0.00 | 0.00 | 36.00 | ||
Garden watering | Frequency of garden watering per day | frequency/day | 0.13 | 0.07 | 0.14 | 0.14 | 0.4 (Roberts 2005) |
Duration of each watering | min/capita | 13.01 | 13.11 | 11.88 | 14.49 | 20 (Athuraliya et al. 2012) | |
Flow rate | liter/min | 11.67 | 11.64 | 11.94 | 11.34 | 10.2 (Marinoski et al. 2014) | |
Cooking | Volume of water consumed in cooking | l/p/d | 13.66 | 11.20 | 12.85 | 16.33 | 10–20 (Gleick and Iwra 1996) |
Total water consumption | l/p/d | 271.39 | 241.22 | 272.18 | 290.36 | 180 in urban residential areas (Stephenson 2003) |
3.3.1 Shower and Bath
3.3.2 Hand Wash Basin (taps)
3.3.3 Toilet Use
3.3.4 Dishwashing
3.3.5 Laundry
3.3.6 House Washing
3.3.7 Cooking
3.3.8 Garden Watering
3.3.9 Vehicle Washing
3.4 Modelled Daily Per Capita Usage with Household Characteristics
-
Demographic characteristics: number of children, elders, adult males and adult females.
-
Physical characteristics: total household built-up area, garden area, number of rooms, number of floors and per capita income.
3.4.1 Models Based on Multiple Linear Regression (STEPWISE)
Correlation coefficient value (R) | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
Demographic characteristics | Physical characteristics | ||||||||||
No. of children | No. of adult females | No. of adult males | No. of elders | No. of rooms | No. of floors | Total built-up area | Garden area | Income | |||
Per capita water consumption (l/p/d) | All investigated households | −0.560 | 0.467 | −0.474 | −0.204 | −0.028 | −0.064 | 0.008 | 0.013 | 0.602 | |
Low income households | −0.745 | −0.279 | −0.263 | −0.408 | −0.773 | 0.000 | −0.664 | −0.361 | 0.777 | ||
Medium income households | −0.808 | 0.467 | −0.766 | −0.270 | −0.859 | −0.638 | −0.699 | −0.330 | 0.844 | ||
High income households | −0.501 | 0.196 | −0.807 | −0.254 | −0.766 | −0.532 | −0.678 | −0.443 | 0.803 |
-
The ANOVA (F-test) to examine the significance of the regression model. The model is statically significant when p < 0.05, which means the overall regression model is a good fit for the independent variables entered in the model (Yasar et al. 2012).
-
The t-test to examine the significance of the regression coefficients. The regression coefficients are statistically significant (i.e. different to zero) if p < 0.05 (Yasar et al. 2012).
3.4.2 Models Based on Evolutionary Polynomial Regression (EPR)
-
The minimization of the number of terms, and
-
Maximization of the accuracy of the model to calibration set (i.e. minimization of the summation of square errors) (Giustolisi and Savic 2009).
3.4.3 Comparison of Models
Per capita water consumption modelled with household demographic characteristics | Per capita water consumption modelled with household physical characteristics | Per capita water consumption modelled with demographic and physical characteristics | ||||
---|---|---|---|---|---|---|
STEPWISE | EPR | STEPWISE | EPR | STEPWISE | EPR | |
All investigated households | 0.54 | 0.63 | 0.74 | 0.85 | 0.87 | 0.92 |
Low income households | 0.88 | 0.90 | 0.82 | 0.85 | 0.95 | 0.97 |
Medium income households | 0.92 | 0.96 | 0.86 | 0.89 | 0.96 | 0.98 |
High income households | 0.84 | 0.86 | 0.76 | 0.79 | 0.90 | 0.91 |
3.4.4 Sensitivity
4 Model Application
4.1 Scenarios Definition
4.2 Implication of Future Scenarios on Water Demand
GSG scenarios | Period | Average annual growth rate of indicators (%) | ||
---|---|---|---|---|
Population | Income | Built-up area | ||
Market forces (KF) | 1995–2025 | 2.2 | 1.8 | 2.3 |
2025–2050 | 1.1 | 1.6 | 1.5 | |
Fortress world (FW) | 1995–2025 | 2.4 | 1.7 | 2.5 |
2025–2050 | 1.5 | 0.7 | 1.7 | |
Great transition (GT) | 1995–2025 | 2.0 | 2.3 | 1.8 |
2025–2050 | 0.8 | 1.8 | 0.5 | |
Policy reform (PR) | 1995–2025 | 2.1 | 1.9 | 2.0 |
2025–2050 | 1 | 1.7 | 0.9 |
5 Conclusion
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The per capita water consumption increases with the rise in household income and decreases with the increase in the household occupancy.
-
Frequency of all water end-uses increases with the increase in per capita income except for toilet usage. Toilet use frequency in low income households is higher than that in medium and high income groups.
-
The duration of hand wash basin tap in Duhok is much higher than typical values in the developed world. This indicates an additional water use activities (e.g. ablution) via the hand wash basin tap.
-
Flow rate from different water end-uses decreases with increase in the per capita income, suggesting that households in high income group are relatively new and fitted with water efficient appliances.
-
Per capita consumption decreases with the increase in male adults, elders and children but increases with the increase in number of adult females in a household. Additionally, the change in the number of elders and children has identical effect on per capita consumption.
-
Using the collected data, it is possible to predict per capita water consumption. The quality of prediction improves when the full data was disaggregated into low, medium and high income group households.
-
The models based on EPR offer a marginal improvement in the predictions quality.
-
The demographic characteristics provide more accurate predictions of per capita water consumption than the predictions resulting from the use of physical characteristics of the investigated households.
-
Of the investigated scenarios, domestic water demand is expected to be highest in the fortress world scenario. This is because of the expected growth rate of population and built-up area is high in this scenario.