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Potential Evaporation and Irrigation in Manoa Valley

Potential Evaporation and Irrigation in Manoa Valley. Geography 405 Liat Portner, George Bugarin , Alexa Grinpas,Henry Pascher , Nicole Miller, Maeghan Castillo, Joshua Silva, Elise Kama, Keiichiro Yoshida. Purpose. Main Objective: Evaluate the water balance of Manoa Valley

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Potential Evaporation and Irrigation in Manoa Valley

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  1. Potential Evaporationand Irrigation in Manoa Valley Geography 405 Liat Portner, George Bugarin, AlexaGrinpas,HenryPascher, Nicole Miller, Maeghan Castillo, Joshua Silva, Elise Kama, Keiichiro Yoshida

  2. Purpose • Main Objective: Evaluate the water balance of Manoa Valley Our Objective: Estimate the Potential Evaporation and Irrigation for Manoa Valley

  3. PE Modeling Methods • Net Radiation, (Air) Temperature, Wind speed and Relative Humidity measured at the 2 weather stations were used to calculate PE • Interpolated to Grid cells using inverse distance weighting and the Normal Ratio Method • Distance from each grid to each weather station • Mean PE at each grid and both weather stations PE_i=[1/d_l*(PE_l*(N_i/N_l))]+[1/d_m *(PE_m*(N_i/N_m))] 1/d_l +1/d_m

  4. Irrigation Sampling Methods • Based on four main residential streets, spanning entire length of Manoa Valley • Rate, Frequency, Area, Grid Location

  5. Irrigation Modeling • Interpolating to grid: • y = mean daily irrigation • x = mean daily (PE-RF) • Assumptions: • Days with no rainfall- days with irrigation (and the reverse) • All irrigation occurring at 6:00 PM

  6. PE Results (1) • PE peaks during midday • Low PE during night • Driven by Radiation • Cloud Cover

  7. PE Results (2)

  8. Seasonal variation of PE

  9. Irrigation Results (1) Peak mean PE correlates with IRR events

  10. Irrigation Results (2)

  11. Discussion (1) • Inverse relationship between PE and RF • Grids 6,12 and 19 can be accounted for by orientation of valley

  12. Discussion (2) • Direct relationship between PE and IRR • Note: Irrigation not actually occurring in every grid cell

  13. Basin Totals

  14. Potential Evaporation Errors • Weather stations • Interpolating from only two sources • Topography • Crude assignment of mean values

  15. Irrigation Errors • Measuring Irrigation • Imprecise measuring tools • Sample size and randomization • Interpolation Assumption • Everyone irrigating when no rain • Everyone irrigating at 6:00 PM • Irrigation occurring in all grids

  16. Conclusion • PE and IRR lower at back of valley, higher at front • Rainfall decreases as PE increases • Irrigation increases as PE increases • Irrigation increases as rainfall decreases • Making up for increasing demands of water • Less water available because less water and land cover

  17. Questions?

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