Diagnosis Shall Precede Prescriptions

System Assessments



Conducting a field assessment of an irrigation system is usually the very first step in improving on-farm irrigation efficiency. The system design and construction documents depict and define what the system distribution uniformity should be found to be in this assessment. But those plans are only plans.  What then is constructed must be tested and measured, usually requiring sampling strategic points across the system for pressure and flow rate. With certain latitude, we follow the drip/micro irrigation system evaluation protocol developed by Cal Poly Irrigation Training and Research Center (ITRC). We will prepare a scope of work and plan of work with your stated objectives to bound the work and ensure your intention's are achieved.

Of all the factors to evaluate an irrigation system, none surpasses the term DU, which stands for Distribution Uniformity. Karmeli & Keller (1974) considered two components of non-uniformity in the design of a drip/micro system: manufacturing variation and pressure differences. It should be noted that this formula was intended for the design, not evaluation, of an irrigation system. Their recommendation for a new DU equation was:




where cvm is the manufacturing coefficient of variation (standard deviation divided by the mean) of emitter flow rates, qmin Iq / qavg is the ratio of "minimum" to average flow rates due to pressure differences. 

In "Drip and Micro Irrigation Design and Management - for Trees, Vines, and Plants (Practice plus Theroy), 4th Edition - 2011", Burt and Styles expertly guide us....the hungry planet, in precision irrigation design and system management.  Here, all of the sources of non-uniform distribution are assessed. We have adopted their "teasing apart" of Karmeli & Keller's work.

 During the Discovery Phase, we listen, comment, and make requests for historical records, drawings, and your preferences.


   Simply enough, we prescribe reasonable modifications which suit your budget and return those investments in the time-frame you set.

   In "Rapid field evaluation of drip and microspray distribution uniformity", C.M. Burt (2003) Director of California's Irrigation Training and Research Center provides field-proven, technician oriented concepts for system assessment.

Most urban systems in fair to good condition take at least three days to evaluate and generate the technical report. On-farm Conservation Activity Plans (CAP 118 AZ-NRCS) which involve cost-sharing have more requirements and take significantly longer to prepare. But if cost-sharing is not your cup of tea, some elements could be deleted, like water analysis.  Sampling methods can geared to match your business objectives, and confidence intervals may be narrowed, at your discretion.

System's which have not be maintained would require the minimum types and numbers of fixes before it would make any sense to perform the performance evaluation.