By Wyatt Hatch, PE

Am I getting enough water? This may be the most frequent question agricultural water users ask during irrigation season.

Irrigators depend on efficient systems to provide water when it’s needed, not to mention making sure their water rights are fulfilled.

Agricultural irrigation systems are typically supplied from surface water that is often times delivered through an open channel ditch. Using open channel flow measurement is an effective way to understand whether you’re getting enough water.

If you have the right equipment, open channel flow measurement is straightforward, effective, and needs little time and effort to perform. After a series of flow measurements have been collected at varying stages, a simple staff gauge reading can be used to determine the flow at any discharge stage and allow you to determine if you are getting enough water during irrigation season.

The following three steps will allow you to determine your irrigation ditch flow:

Step 1: Select Your Site

Select a site that best represents the overall channel. A good site will have most of the following characteristics:

  • Straight and uniform section (approximately 300 feet upstream and downstream).
  • Desirable measurement sections (i.e. rectangular, parabolic, trapezoidal).
  • Clean section of the ditch that is free from debris (i.e. boulders, weeds, etc.).
  • Consistent water velocity throughout section confined in one channel (greater than 0.5 ft/s).
  • Low turbulence.
  • Wadable.
  • Location far enough removed from a stream confluence so backwater effects are not present.