4th UF Water Institute Symposium Abstract

Submitter's Name Stacia Davis
Session Name Poster Session: Impact of changing drivers on water resources
Poster Number 41
Author(s) Stacia Davis,  University of Florida (Presenting Author)
  Michael Dukes,  University of Florida
  Rafael Munoz-Carpena, University of Florida
  Improving the model for evaluating the efficacy of weather-based irrigation controllers
  Smart controllers are evaluated for irrigation scheduling efficacy using the Smart Water Application Technologies (SWAT) testing protocol. The SWAT test is considered the industry standard by the Irrigation Association and the government standard by the EPA WaterSense program. The SWAT test was designed as a daily soil water balance with many simplifications to a complex system that rarely reflect dynamic soil water responses. However, government agencies and water purveyors require SWAT results for rebate programs in attempts to increase water conservation efforts. The objective of this research was to evaluate models that can determine efficacy of weather-based irrigation controllers while more accurately representing the real system. In this study, the real system consisted of a bahiagrass pasture located in Citra, FL where time domain reflectometry (TDR) sensors measured soil moisture at various depths across a 94 cm root zone. Volumetric water content was collected at fifteen-minute intervals from 1 January 2004 to 22 June 2004 totaling 173 days. Rainfall and irrigation were measured using a tipping bucket rain gauge. Soil moisture was predicted using three models: A) the original SWAT test, B) hourly soil water balance, and C) modified Green-Ampt with Redistribution (MGAR) model. In addition to the timestep change from daily to hourly in the hourly soil water balance model, restrictions to soil water level at maximum allowable depletion and field capacity were updated to permanent wilting point and saturation, respectively. Additionally, drainage was estimated using a decreasing exponential function. The MGAR model was updated to incorporate irrigation and evapotranspiration in addition to rainfall. It is expected that both the hourly soil water balance and MGAR resulted in better representation of the measured soil moisture while increasing the likelihood of translating from SWAT test performance to real world performance.