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Feasibility of Rainwater Harvesting in Arid Environments

By Brianda Hernandez Rosales and NWAL

2023

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PART 6

Run-Through Example

Peach Springs, AZ

Hualapai Reservation

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Outline of Videos – Six Part Series

  • Part 1: Introduction
  • Part 2: Rainwater Harvesting Equation
  • Part 3: AquaCrop Model
  • Part 4: Cultivable Area
  • Part 5: Cost and Maintenance
  • Part 6: Run-through Example – Northwestern Arizona

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  • Headquarters and homelands of the Hualapai Tribe
  • Elevation: 1,457 m (4,780 ft)
  • Area: 20.5 km² (8 mi2)
  • Population: 1,500
  • Climate: Mild and Arid

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Service Layer Credits: National Geographic, Esri, Garmin, HERE, UNEP-WCMC, USGS, NASA, ESA, METI, NRCAN, GEBCO, NOAA, increment P Corp.

Peach Springs, Arizona – Hualapai Reservation

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Rainfall Depth for Peach Springs, AZ

  • Timeframe: 1992 – 2022
  • Long-term Average Rainfall Depths: 9.0 inches
  • Count 1992-2022
    • Dry years: 8
    • Normal years: 16
    • Wet years: 7

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Rainfall Depth for Peach Springs, AZ

Month

Dry Year�Average ppt (in)

Normal Year�Average ppt (in)

Wet Year�Average ppt (in)

January

0.47

0.57

1.53

February

0.66

1.05

1.96

March

0.51

0.84

0.50

April

0.22

0.43

0.49

May

0.03

0.28

0.20

June

0.17

0.11

0.20

July

0.95

1.19

1.44

August

1.18

1.43

1.53

September

0.53

1.11

0.62

October

0.42

0.41

1.31

November

0.18

0.62

0.80

December

0.39

1.00

2.06

Average Total

5.72

9.03

12.63

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Rainfall Depth for Peach Springs, AZ

Month

Dry Year�Average ppt (in)

Normal Year�Average ppt (in)

Wet Year�Average ppt (in)

January

0.47

0.57

1.53

February

0.66

1.05

1.96

March

0.51

0.84

0.50

April

0.22

0.43

0.49

May

0.03

0.28

0.20

June

0.17

0.11

0.20

July

0.95

1.19

1.44

August

1.18

1.43

1.53

September

0.53

1.11

0.62

October

0.42

0.41

1.31

November

0.18

0.62

0.80

December

0.39

1.00

2.06

Average Total

5.72

9.03

12.63

Growing Season

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RAINWATER HARVESTING

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V = Volume of Collected Rainwater (ft3)

Rd = Rainfall Depth (ft)

Ar = Area of Rooftop (ft2)

Rc = Runoff Coefficient (unitless)

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Rainwater Harvesting Equation

The 4H Building on the Hualapai Reservation (one of the buildings considered for rainwater harvesting)

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RAINWATER HARVESTING

8

 

V = Volume of Collected Rainwater (ft3)

Rd = Rainfall Depth (ft)

Ar = Area of Rooftop (ft2)

Rc = Runoff Coefficient (unitless)

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Rainwater Harvesting Equation

The 4H Building on the Hualapai Reservation (one of the buildings considered for rainwater harvesting)

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Area: 2,290 ft2

Runoff Coefficient: 0.90 Galvanized Metal

2,290 ft2

Area considered for garden

Gutter System

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RAINWATER HARVESTING

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V = Volume of Collected Rainwater (ft3)

Rd = Rainfall Depth (ft)

Ar = Area of Rooftop (ft2)

Rc = Runoff Coefficient (unitless)

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Rainwater Harvesting Equation

2,290 ft2

Area considered for garden

Gutter System

Normal Year

 

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RAINWATER HARVESTING

10

 

V = Volume of Collected Rainwater (ft3)

Rd = Rainfall Depth (ft)

Ar = Area of Rooftop (ft2)

Rc = Runoff Coefficient (unitless)

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Rainwater Harvesting Equation

2,290 ft2

Area considered for garden

Gutter System

Dry Year

 

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RAINWATER HARVESTING

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V = Volume of Collected Rainwater (ft3)

Rd = Rainfall Depth (ft)

Ar = Area of Rooftop (ft2)

Rc = Runoff Coefficient (unitless)

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Rainwater Harvesting Equation

2,290 ft2

Area considered for garden

Gutter System

Wet Year

 

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Rainfall Depth for Peach Springs, AZ

Month

Dry Year�Average ppt (in)

Normal Year�Average ppt (in)

Wet Year�Average ppt (in)

January

0.47

0.57

1.53

February

0.66

1.05

1.96

March

0.51

0.84

0.50

April

0.22

0.43

0.49

May

0.03

0.28

0.20

June

0.17

0.11

0.20

July

0.95

1.19

1.44

August

1.18

1.43

1.53

September

0.53

1.11

0.62

October

0.42

0.41

1.31

November

0.18

0.62

0.80

December

0.39

1.00

2.06

GS Total

3.08

4.56

4.48

Growing Season

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Net Irrigation using the AquaCrop Model

Net Irrigation is the required amount of water (irrigation) a crop needs to yield healthy, harvestable crops – Maize in our case. The Net Irrigation was simulated using the AquaCrop Model for the three classified precipitation years with their respective rainfall depths and temperatures.

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Consider:

    • Precipitation
    • Temperature

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Less irrigation is needed if the growing season temperatures are cooler due to lower evapotranspiration.

1.10 feet

Normal Year

1.06 feet

1.04 feet

Wet Year

Dry Year

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Area that can be cultivated

 

Normal Year

741 ft2

Dry Year

479 ft2

Wet Year

742 ft2

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What is the dry yield of maize?

Normal Year

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196 lbs. of Maize

Dry Year

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126 lbs. of Maize

Wet Year

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196 lbs. of Maize

 

Simulated from AquaCrop

Unit Conversion

Cultivable Area

Remember – this is only for the growing season, April through September

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Cost and Maintenance for a RWH System in Peach Springs, AZ

4H Building in Peach Springs, AZ

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  • Gutters: installed

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  • Cistern(s): Capacity of at least 5,857 gallons to optimize the rainwater harvesting during a normal precipitation year.

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  • Distribution System: drip line, hydraulic pump, piping.

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  • Low and simple maintenance

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Remember – this is only for the growing season, April through September

Gutter System

Cisterns

Piping

Hydraulic Pump

Figure created on BioRender

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Conclusion of the Rainwater Harvesting Video Series

  • Rainwater harvesting can help alleviate some of the stresses associated with water security for food production.
  • Simple information can calculate the average rainwater that can be collected and how much of an area can be cultivated.
  • Rainwater harvesting is scalable to any environment, even with arid and semi-arid climates.
    • An average 3,850 gallons of rainwater can be harvested with only 3 inches of rain on a 2,290 ft2 roof.

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Photo borrowed from Dendgarden.com

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THANK YOU FOR WATCHING!