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Feasibility of Rainwater Harvesting in Arid Environments

By Brianda Hernandez Rosales and Native Waters on Arid Lands

2023

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PART 2

Rainwater Harvesting Equation

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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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Rainwater Harvesting Equation

  • Where, V is the volume of rainwater that can be collected
  • Rd is the annual average rainfall depth
  • Ar is the area of the catchment
  • Rc is the runoff coefficient of the catchment material.

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Rainfall Depth (Rd )

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Rainfall Depth (Rd )

  • PRISM Climate Group
    • https://prism.oregonstate.edu/
  • 30 Year Normals
    • 1990-2020
  • Monthly Precipitation Data
    • At least 20-30 years to get an average
  • Water Year
    • October 1st to September 30th

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Rainfall Dataset

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Characterizing the Climate

  • Normal, Wet and Dry Precipitation Years
  • At least 30-years of data
  • Indian Meteorological Department’s classification
    • Dry year is < 20% of long-term average
    • Normal year is ± 20% of the long-term average
    • Wet year is > 20% of the long-term average

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Rainfall Depths for Peach Springs, AZ

Long-term average: 245 mm

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Catchment Area (Ar)

Texas A&M – Agrilife Extension

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Runoff Coefficient (Rc)

  • Based on the material properties of the catchment area (e.g., imperviousness, infiltration capacity, etc.)
  • Most common roofing material:
    • Galvanized metal
    • Sheet roof
    • Tiled roof
    • Concrete roof

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Potential Volume of water that can collected during the month of August in Northwestern Arizona, on the Hualapai Reservation

Rainwater Harvesting Equation: Example

Potential rainwater that can be collected during the month of August in Peach Springs, Arizona is an average of 1,842 gallons!

V = 0.1183 ft x 2,290 ft2 x 0.90

V = 243.8 ft3 x (7.45 gals/ft3)

V = 1,842 gallons

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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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Questions about this project?�� Please Contact:

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