Translation (from Portuguese) of talk given at XII Symposium of Water Resources of the [Brazilian] Northeast, November 2014. Conference paper available (in Portuguese) at: http://www.abrh.org.br/xiisrhn/anais/papers/PAP018359.pdf

1. Considering the Reliability of Rainwater Harvesting in the
Brazilian Semi-Arid
J. Doss-Gollin1 F.A. Souza Filho2 F.O.E. da Silva2
1Undergraduate
Yale University
2Environmental and Hydraulic Engineering Department
Universidade Federal do Ceará
November 2014
Doss-Gollin et al. (Yale & UFC) XII Simpósio de RH do NE November 2014 1 / 10

2. Outline
1 Context
2 Methods
3 Results
Doss-Gollin et al. (Yale & UFC) XII Simpósio de RH do NE November 2014 2 / 10

3. Context
The Challenge
Figure: Sítio Situação, Senador Pompeu-CE
Highly variable climate
Doss-Gollin et al. (Yale & UFC) XII Simpósio de RH do NE November 2014 3 / 10

4. Context
The Challenge
Figure: Sítio Situação, Senador Pompeu-CE
Highly variable climate
No economies of scale
Doss-Gollin et al. (Yale & UFC) XII Simpósio de RH do NE November 2014 3 / 10

5. Context
The Challenge
Figure: Sítio Situação, Senador Pompeu-CE
Highly variable climate
No economies of scale
Lack of public infrastructure
Doss-Gollin et al. (Yale & UFC) XII Simpósio de RH do NE November 2014 3 / 10

6. Context
P1MC: A Viable Solution?
>500.000 cisterns built
Figure: Cisterns
Doss-Gollin et al. (Yale & UFC) XII Simpósio de RH do NE November 2014 4 / 10

7. Context
P1MC: A Viable Solution?
>500.000 cisterns built
Ceará state: nearly all rural communities beneted
Figure: Cisterns
Doss-Gollin et al. (Yale UFC) XII Simpósio de RH do NE November 2014 4 / 10

8. Context
P1MC: A Viable Solution?
500.000 cisterns built
Ceará state: nearly all rural communities beneted
Use: water for drinking (cooking?)
Figure: Cisterns
Doss-Gollin et al. (Yale UFC) XII Simpósio de RH do NE November 2014 4 / 10

9. Context
P1MC: A Viable Solution?
500.000 cisterns built
Ceará state: nearly all rural communities beneted
Use: water for drinking (cooking?)
Have we met the needs of rural communities?
Figure: Cisterns
Doss-Gollin et al. (Yale UFC) XII Simpósio de RH do NE November 2014 4 / 10

10. Methods
Volume Balance
Vi = Vi−1 +Qi −Ci |0 Vi VC
Vi volume of water in cistern, day i
Vi−1 volume of water in cistern, previous day
VC total volume of tank = 16.000L
Qi volume of water captured, day i
Ci volume of water consumed, day i
Doss-Gollin et al. (Yale UFC) XII Simpósio de RH do NE November 2014 5 / 10

11. Methods
Water Consumed and Captured
Qi = α1(Pi −α2)AT
Ci =
16.000L
165 days dry season
0 rainy season
α1 runo coecient= 0.85
α2 rst-ush discard = 1mm
Pi observed precipitation (mm)
AT roof size (distribution given in article)
Doss-Gollin et al. (Yale UFC) XII Simpósio de RH do NE November 2014 6 / 10

12. Results
Reliability Depends on Geography
Garantia de Água por Post, Telhado de 24.5m2
1
0.98
0.96
0.94
0.92
0.9
0.88
0.86
0.84
0.82
0.8
Garantia de Água por Post, Telhado de 24.5m2
0.8
0.82
0.84
0.86
0.88
0.9
0.92
0.94
0.96
0.98
1
Garantia de Água por Post, Telhado de 45m
2
1
0.98
0.96
0.94
0.92
0.9
0.88
0.86
0.84
0.82
0.8
Figure: Spacial Variation of Reliability
Doss-Gollin et al. (Yale UFC) XII Simpósio de RH do NE November 2014 7 / 10

13. Results
Smaller Roof Means More Vulnerability
10 20 30 40 50 60 70 80 90 100
0
5
10
15
20
25
30
35
40
45
Distribuição de Garantia de Água por Post, Telhado de 24.5m2
Garantia (%)
NúmerodePostes
30 40 50 60 70 80 90 100
0
10
20
30
40
50
60
70
80
Distribuição de Garantia de Água por Post, Telhado de 36m
2
Garantia (%)
NúmerodePostes
55 60 65 70 75 80 85 90 95 100
0
10
20
30
40
50
60
70
80
Distribuição de Garantia de Água por Post, Telhado de 45m2
Garantia (%)
NúmerodePostes
75 80 85 90 95 100
0
20
40
60
80
100
120
Distribuição de Garantia de Água por Post, Telhado de 76.5m
2
Garantia (%)
NúmerodePostes
Figure: Spacial Variation of Reliability
Doss-Gollin et al. (Yale UFC) XII Simpósio de RH do NE November 2014 8 / 10

14. Results
Cisterns Don't Support Increased Consumption
Roof Size
(m2)
Mean Calculated Reliability
CC = 0 CC = 10 CC = 20 CC = 40 CC = 60
24,5 61,9 36,2 29,1 18,1 7,9
36 84,8 65,0 58,0 44,5 23,8
45 90,6 76,4 70,7 59,2 39,9
56 93,5 82,5 78,5 69,7 52,7
76,5 95,6 86,8 84,3 78,6 65,7
110 96,5 89,0 87,2 83,4 74,4
Table: Eect of Adding Dry Season Consumption CC (L/day)
Doss-Gollin et al. (Yale UFC) XII Simpósio de RH do NE November 2014 9 / 10

15. Conclusions
Conclusions
1 Water scarcity in rural communities presents unique challenges.
2 The P1MC does not oer sucient water for multiple uses.
3 The most vulnerable users are those in the most drought-prone regions
and with the smallest roof areas.
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