The effect of irrigation schedules on water table depth and root zone soil moisture

H. T. Nguyen, J. P. Walker

Research output: Chapter in Book/Report/Conference proceedingConference PaperOther

1 Citation (Scopus)

Abstract

Indiscriminate use of irrigation water, particularly in existing areas of shallow water table, can result in further water table rise leading to water logging and secondary salinity problems. Hence, it is essential that irrigators have a clear understanding of how their often ad-hoc irrigation scheduling practices impact on both the local water table level and on-farm soil moisture content, which influences crop yield, a primary motivator of irrigators. We have studied the impact of irrigation scheduling on both water table rise and root zone soil moisture content in a desk-top study. A Richards' equation based soil moisture model has been used to study the effect of flood irrigation frequency and duration of inundation on the water table depth and root zone soil moisture content. While the study was not intended to represent a specific study site, the results should be applicable to typical flood irrigation regions in semi arid regions having a shallow water table depth, such as that in south-eastern Australia. Using a series of simulations, we explored the effect of altering time between flood irrigation events from 5 to 20 days, and duration of flood irrigation events from 1 to 6 hours. The initial water table level, soil type and climatic data used for the simulations are typical of semi-arid southeastern Australia. Therefore, the results should provide at least a qualitative indication of relative effects of different irrigation scenarios on water table depth and root zone soil moisture. This study shows that the time interval between flood irrigation events has a more significant impact on the depth to water table than the duration of inundation. In order to control or limit future water table rise, the interval between irrigation events should be sufficiently far apart; at least 14 days in our situation. This is almost a 50% increase in the time between irrigation events as compared to typical practice being 4 hours every 10 days. Moreover, an inundation period of 2 hours was found to be sufficient to mitigate any undue water stress on the crops. This is a further water saving with a 50% decrease in the inundation duration. Hence a 2 hour flood irrigation event once every 14 days during the irrigation season was found to be more sustainable than the current practice. This study indicates that in addition to improved irrigation techniques, the key to avoiding water table rise is improved efficiency in scheduling irrigation to meet as precisely as possible the water needs of the crop, rather than applying irrigation water in a more ad-hoc approach.

Original languageEnglish
Title of host publicationMODSIM05 - International Congress on Modelling and Simulation
Subtitle of host publicationAdvances and Applications for Management and Decision Making, Proceedings
Pages1286-1292
Number of pages7
Publication statusPublished - 1 Dec 2005
EventInternational Congress on Modelling and Simulation 2005: Advances and Applications for Management and Decision Making - Melbourne, Australia
Duration: 12 Dec 200515 Dec 2005

Publication series

NameMODSIM05 - International Congress on Modelling and Simulation: Advances and Applications for Management and Decision Making, Proceedings

Conference

ConferenceInternational Congress on Modelling and Simulation 2005
Abbreviated titleMODSIM 2005
CountryAustralia
CityMelbourne
Period12/12/0515/12/05

Keywords

  • Irrigation schedules
  • Root zone
  • Soil moisture
  • Water table depth

Cite this

Nguyen, H. T., & Walker, J. P. (2005). The effect of irrigation schedules on water table depth and root zone soil moisture. In MODSIM05 - International Congress on Modelling and Simulation: Advances and Applications for Management and Decision Making, Proceedings (pp. 1286-1292). (MODSIM05 - International Congress on Modelling and Simulation: Advances and Applications for Management and Decision Making, Proceedings).