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Using Flux Measurements to Determine Sprinkler Irrigation Efficiency at Biosphere 2

Using Flux Measurements to Determine Sprinkler Irrigation Efficiency at Biosphere 2. H.D. Adams 1,2 , L.M. Benton 2 , M.L. Cavanaugh 2 , J.R. Martin 2 , A.L. Neal 3 , S. Rajagopal 3 , R. Rosolem 3 , A.P. Tyler 1 , J.C. Villegas 2

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Using Flux Measurements to Determine Sprinkler Irrigation Efficiency at Biosphere 2

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  1. Using Flux Measurements to Determine Sprinkler Irrigation Efficiency at Biosphere 2 H.D. Adams1,2, L.M. Benton2, M.L. Cavanaugh2, J.R. Martin2, A.L. Neal3, S. Rajagopal3, R. Rosolem3, A.P. Tyler1, J.C. Villegas2 1Dept. of Ecology and Evolutionary Biology, 2School of Natural Resources, 3Dept. of Hydrology and Water Resources The University of Arizona, Tucson, AZ

  2. Introduction • Lawns, golf courses, sport fields and other areas planted in turfgrass are common, important components of urban systems • Effective and efficient irrigation management is: • important economically and ecologically • required for turfgrass function, particularly in water-limited areas

  3. Introduction • Arizona: ~18,200 hectares of golf courses (Schmidt 2006) • Many, many more hectares of turfgrass in urban areas being irrigated • Are these facilities and residences making an effort to maximize water use efficiency of their lawns? turfgrass.unl.edu

  4. Introduction • Why Bermudagrass? • Grass of choice in southern US • Tolerates high sunlight and high air temperatures • Able to grow in shallow soil conditions and withstand trampling • Can tolerate salty water, salty soil conditions • Needs little water once established www.answers.com

  5. Introduction • Bermudagrass requires: • 508 mm of precipitation inputs needed for survival • 762 mm for acceptable color • 1016 mm for adequate color and growth • Oracle, AZ received less than 500 mm, so irrigation is necessary www.lawnsprinklers.us

  6. Objectives • To establish the pre-response conditions of turfgrass under early-season, pre-watering conditions • To measure and consider influence of environmental variables on turfgrass phenology, including measurements of: • carbon, water and energy flux via eddy covariance • distributed soil moisture and soil salinity • the distribution of applied water from the sprinkler irrigation system on-site • Provide suggestions for efficient irrigation management at Biosphere 2

  7. Why Care? • Better irrigation efficiency at Biosphere 2 lawn makes sense economically and environmentally • Reduces chance of high soil salinity from over-watering • Potential to guide irrigation regimes in other turfgrass areas of similar climate • Brides like nice grass (Biosphere weddings!) www.redflagdeals.com

  8. Jeffrey, isn’t it lovely to have efficiently irrigated grass at our Biosphere wedding? Doesn’t she mean Biodome?

  9. Field Site • Biosphere 2, Oracle, AZ • ~56.3 km North of Tucson • Elevation: 1378 m • Average Annual Temperature • Maximum: 23.55oC • Minimum: 9.94oC • February to April - Max: 18.83oC, Min: 4.94oC • Average Annual Precipitation: 492.8mm • February to April: 109.2mm • Soil: loam and fill www.pbase.com Be sure to visit the Chalet Village

  10. Field Site • Located on north side of Biosphere 2 • Lawn area ~1.24 acres • Surrounded: • South and East sides by buildings • North and west sides by large berm

  11. Field Site South Tower Daytime predominant wind direction

  12. Field Site Sprinklers x North Tower x South Tower

  13. Methods • Tower Instrumentation and Variables Measured • 3-D sonic anemometer (wind direction and speed) • Infrared gas analyzer (fCO2, fH2O) • Net radiometer (Rnet) • CR5000 Datalogger collected data

  14. Methods • Other Site Instrumentation – Automated • Ground heat flux plates (G) • TDR soil water content probes (automated θ) • Tipping bucket (P) • Point Measurements • Rain gauges placed at equal intervals across field • Spatial irrigation inputs measured every 2 weeks • EM38 (relative soil salinity) • Measured at each grid point every 2 weeks • Hydrosense (manual θ) • Measured at each grid point every 2 weeks

  15. Methods – Tower Comparison Carbon Flux Latent Heat SensibleHeat

  16. Methods – Energy Balance Closure Daily Half Hourly

  17. Methods – 2D Schmid Footprint P=0.5 source area for westerly winds (+/- 30°) Full source area 4/17/08 Rule of thumb (1:100) would need 175 m in direction of mean wind (total source area). Gash (1986) model says 240 m in direction of mean wind. We have 80-100m of lawn, large berm, desert flora.

  18. Results – Soil Moisture Initial Dry Down – Irrigation Period – Intense (2 hours / station) Irrigation Period

  19. Results – Diurnal Energy Net Radiation Ground Heat Flux Sensible Heat Latent Heat Pre-Irrigation Data looks reasonable, Wide range of “morning” LE

  20. Results – Diurnal Energy Ground Heat Flux Net Radiation Sensible Heat Latent Heat Irrigation results in higher LE – driven by water or available energy?

  21. Results – Diurnal CO2 mg/m2s CO2 flux doesn’t change much – perhaps increase in LE is just E at this point.

  22. Results - Grid Soil Moisture Eddy Tower Soil moisture for day 1, before irrigation

  23. Results – ET time series ET near ETcrop during initial watering, above ETcrop (near ETo) during intensive watering

  24. Results - Salinity Found out where the Tubing is! No real salty spots!

  25. Results - Sprinkler Irrigation Units Check! Irrigation as measured by precipitation gage grid

  26. Results - Grid Soil Moisture Soil moisture for day 3, after irrigation

  27. Results - Grid Soil Moisture Irregularity in soil moisture due to irregular sprinkler irrigation

  28. Discussion Point – Irrigation Efficiency Index • Two Indices were developed • IUE 0 • IUE > 0, overwatering • IUErel1 • IUErel >1, overwatering

  29. Show plot here Discussion Point – Irrigation Efficiency Index

  30. Discussion Point – Positioning is important. Wet spot Wet spot Wet spots based on grid data are at “30, 25”, are we catching this at the south tower?? Maybe if we just used north tower…

  31. Towers can be used on lawn at Biosphere 2 Salinity effect many not be evident due to use of well water Irrigation efficiency can be improved Early irrigation schedule is near ideal Late schedule (double-watering) is overwatering Spatial coverage of sprinklers is poor Highly variable soil moisture across lawn Poor drainage in some locations near edge of lawn Sprinkler operation may be defective! Conclusions

  32. Proposed Future of Towers • Look for green-up in CO2 signal • Plants may not be fully active during irrigation study • Soil respiration may offset signal in early spring • Comparison of records between towers • Error analysis using co-located measurements • Distribution of soil moisture, footprints • Irrigation during summer months • Will the towers be there?

  33. Recommendations • Irrigate during nighttime • Reduce ET losses • Promote increase in soil moisture • Irrigate with less water • Consider timing of operation of each sprinkler head • Spatial distribution of water and resultant soil moisture • Improve drainage • Prevent water-logging • Consider use of reclaimed water • What about salinity associated with this?

  34. Acknowledgments We would like to thank: • Shirley Kurc, Jim Shuttleworth, and Travis Huxman for their guidance on this project • John Adams, and the many Biosphere 2 staff members who assisted us throughout the semester • Greg Barron-Gafford at the University of Arizona for his help in providing instruments • James B. Callegary at the USGS for use of his EM38 • Dave Breshears at the University of Arizona for use of his soil moisture and eddy covariance equipment

  35. Juan Henry QUESTIONS?

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