irrigation scheduling and saving

I case studY

By: Abdulaziz Youssef Kharouf

ICON - Intelligent Consult Consultant Engineers®

irrigation scheduling and saVing

introduction

Innovative irrigation practices are becoming more essential considering the rapid technological advancements and environmental resources strains elevating the necessity of breeding innovation to enhance water use efficiency, gain an economic advantage and reduce environmental burdens. Innovative measures can often be as simple as applying or re-applying the basic principles effectively. In this case study, we will explore the irrigation water saving achieved by merely re-visiting/re-scheduling the existing irrigation controller schedules of an automatic irrigation system serving a large private plot’s landscape in Abu Dhabi, United Arab Emirates without any other modifications on the existing irrigation network/system (zero cost intervention). According to the results, irrigation water saving of around 20% was achieved by only adjusting and optimizing the irrigation schedules.

implementation

A study worth mentioning in this context by Cooley et al. (2009) compiled a list of currently available options for “improving the efficiency of water use in California agriculture”, and pointed out that all solutions fall under one of three categories: efficient irrigation technologies, improved irrigation scheduling, or regulated deficit irrigation, where the category with the largest potential for water savings is improving irrigation scheduling.

In this case study’s project, a survey was conducted on the existing irrigation and landscape assets to identify existing system’s condition and problems with the irrigation system that reduces performance and overall irrigation efficiency. All the existing irrigation assets were surveyed and assessed including the supply source, tanks, pumps, lines, valves, controllers, irrigation devices, meters and soil condition. A full report was produced with the assessment and recommendation of simple cost-effective interventions that can be applied to improve the efficiency of the system element. As a first step, it was decided to only implement improvements on the irrigation schedule to assess the achievable water saving from that intervention alone.

Regarding the existing irrigation schedules, it was found that they were a mix of multiple timings and were not consistent. Manual irrigation instances were

also applied randomly and relatively intensely. Also, the applied irrigation demand rates were not following the local municipality irrigation demand rates (which are carefully selected irrigation rates based on studies and experience to select optimal values that match with the actual plantations water requirements) and were indicating over-irrigation.

Firstly, the plot’s operations/maintenance team were reeducated on the correct practices in regards to applying manual irrigation only when necessary. A Foreman was assigned to monitor and ensure that no unnecessary manual irrigation was applied during the study period.

Secondly, the current irrigation demand rates applied needed to be adjusted to the local municipality guidelines’ demand rates, as the municipality demand rates are optimal and consider seasonal adjustments. However, this adjustment requires comprehensive interventions on the overall system and existing irrigation devices. For the sake of this study; only intervention on the irrigation scheduling was done.

Finally, new irrigation schedules were formulated for the 3 existing pump sets. Valves for the same irrigation device (bubbler, drip, sprayer) were clustered in cycles in a way to ensure that cycle flow does not exceed respective pump’s capacity. Also, the operation time for valves under the same irrigation device were unified, where the operation time was selected to optimize achieving the required irrigation water demand for the specific plant type based on the irrigation device application rate (volume unit over time unit).

Results & discussion

The implementations above resulted in considerable water saving by; monitoring/controlling manual irrigation to apply it only when required for operation and maintenance activities (education/awareness sessions for labors and operators) and rescheduling the irrigation operation to:

• Apply automatic irrigation schedule respecting clustering of plantations which are irrigated with the same irrigation device

• Cluster valves under the same irrigation device type in cycles of very close cycle flows that fully utilize but do not exceed pump capacity.

• Run time for the hydro-zones have been selected carefully verifying the irrigation application for each plant according to the local municipality requirements taking into consideration the seasonal adjustment, which ensures higher efficiency of the system and delivers the different plants water requirements without over or under irrigating.

More interventions were explored such as installing flow sensors downstream the pumps to read flows outside the automatic irrigation cycles, solar syncs for each controller (semi weather stations) that can update seasonal adjustments factors and other interventions. However, for the sake of this study stage it was decided to only apply enhancements on the existing irrigation schedule to assess the strong ramifications a poorly studied irrigation scheduling could have on the overall irrigation network.

conclusion & Recommendations

Improving the irrigation scheduling for this subject existing automatic irrigation system helped achieve water saving of around 20% with zero cost required for the intervention. The existing irrigation schedules were re-assessed and basic principles were applied to enhance efficiency. With the currently available and rapidly developing irrigation technologies; it is vital to periodically revisit existing irrigation systems to reassess their efficiency and study potential interventions that would help with water saving, gain an economic advantage and reduce environmental burdens.

References

H. Cooley, J. Christian-Smith and P.H. Gleick. 2009. Sustaining California Agriculture in an Uncertain Future. Pacific Institute, Oakland, CA. Available online at: http://www.pacinst.org/reports/california_agriculture/ (verified 29 Jan. 2021).