What is TreeWat?
TreeWat is a tool designed to optimize a limited irrigation water supply in orchard crops. It provides an estimation of the relative decline in production of an orchard which receives insufficient irrigation water to meet its maximum crop water requirements (ETc), resulting in a reduction in its consumptive use. Furthermore, TreeWat provides optimal irrigation scheduling under irrigation supply restrictions, based on what is known of the specific tree responses to water deficits at different growth stages. Six different tree crops (almond, citrus, peach, pistachio, plum, olive) are considered in this first model version.
TreeWat computes all the water balance components of the orchard on a daily basis (runoff, deep percolation, change in root zone soil water content, evaporation from the soil, and tree transpiration) and obtains seasonal values for actual transpiration (Ta) and for maximum transpiration (Tp). Using an empirical function that relates seasonal transpiration to seasonal production in relative terms, the model calculates the expected relative yield reduction based on the relative transpiration reduction. These functions reflect the optimal responses observed with deficit irrigation that avoids severe stress at critical periods.
The model outputs are the full irrigation requirements (obtained when water supply is sufficient), the optimal irrigation schedule under water restrictions, and the corresponding decline in production predicted. Furthermore, all the water balance components associated with both, the full and deficit irrigation schedules are reported.
Potential uses
Irrigation restrictions are becoming the norm in many areas and farmers are faced frequently with situations where there is insufficient water for irrigation. If this is known in annual crops at planting time, the farmers can adjust the planted area to match the available irrigation supply. However, what can they do if the crop is a perennial orchard?. Under limited irrigation, yield and income would be reduced, and even the life of the orchard may be threatened. TreeWat attempts to provide an estimate of the relative impact on yield of a limited amount of water available for irrigation.
TreeWat should be used by planners and orchardists to assess the impact that seasonal irrigation restrictions of different magnitude have on orchard yield and to identify optimal irrigation schedules under these scenarios.
Specifically, we recommend its use for:
- Assessing different irrigation strategies varying in water availability
- Distribute a limited amount of water within the irrigation season
- Estimation of the relative yield impact of deficit irrigation programs designed to optimize the use of a limited amount of water
Be aware of
Fruit tree yield is determined by a myriad of processes, including events that take place the previous years, and which are modulated by the environment of the current (and previous) year/s. TreeWat does not take into account many of these processes. Water is a necessary input for the growth and production of the tree but many other factors affect tree productivity, including those introduced by the orchardist in its management program. Nevertheless, research in the last thirty years has investigated the responses of fruit trees to variable water supply, and TreeWat is an attempt to use such information to provide answers to the complex question of how an orchard responds to limited water supply.
- Given the empirical nature of the relations between yield and transpiration implemented in the model, it should not be used for yield prediction as a function of different irrigation strategies or for simulating the impact of a short period of water stress on yield in absolute terms.
- In relation to the method of irrigation, TreeWat has been designed exclusively for localized irrigation (drip or microsprinkler), which is the most common irrigation method used in tree orchards of the semiarid areas.
Development team
Margarita García-Vila
Institute for Suistainable Agriculture-CSIC
Francisco Orgaz
Institute for Suistainable Agriculture-CSIC
Elías Fereres
University of Cordoba and Institute for Suistainable Agriculture-CSIC
José Aranda Pozo
University of Cordoba and Institute for Suistainable Agriculture-CSIC
Samuel Lara Arcos
Institute for Suistainable Agriculture-CSIC
Acknowledgments
TreeWat was supported by the European Commission under the SHui project (Grant Agreement No. 773903) and by the Junta de Andalucía, with European funds, through the PREDISEG project.
