Between the head of the ditch, or perhaps the pump, and where the water is actually used for irrigation, is the ditch itself. Ditch losses are a fact of physics and everyone has to deal with it and try to reduce it. The issue of Reasonable and Beneficial Use also comes up – a ditch loss of 10% or 20% for a mile-long ditch is pretty good, or at least acceptable, but is 80% loss reasonable? Few people would think so.
An unmaintained ditch full of grass and tules will lose more than otherwise due to plant growth. A ditch full of grass and will have lower velocity due to obstructions, and perhaps the ditch won’t convey the full right because the full flow cannot get into the ditch.
Livestock will walk across and in the ditch, which breaks down the ditch banks. This makes more water infiltrate, or soak into the ground.
Ditches get worse gradually, so that nobody notices from day to day. Some maintenance needs are obvious, some not so obvious. What are the problems that come up, and how are they fixed?
Grass and tules in the ditch – backhoe or shovel work to clean out.
- Maintaining slopes – keep the ditch depth using a backhoe to take out accumulation.
- Ditches get walked in, or wear through impermeable layers – the sealing has to be redone.
- The head of the ditch may drop – the ditch banks have to be kept high enough to maintain head for flow.
- The measurement device may wear – it has to be maintained or replaced so you know you are getting your full water right.
Maintenance alone may not be enough. Sometimes ditches have to be improved to make sure the same or more water makes it to the end of the ditch. More water can mean more acres irrigated, or more livestock, or pasture or hay making it to October instead of only to late August. How are ditches upgraded?
- Fencing along the ditch banks is fairly low cost, and keeps livestock out so the ditch banks and bottom don’t get chewed up.
- A liner of plastic or bentonite clay is still on the less expensive side, and can make a ditch nearly leak-proof.
- A half-pipe of PVC or gunnite (sprayed-in concrete) is medium cost, is leak-proof.
- A full pipe is high in cost, but there is no loss, and water can’t accidentally be “mis-diverted” by some other party.
If money were no object, or hay or livestock prices were high enough to make it worth it, then giant water guns (pivots) might water in giant circles, or wheel-lines like the one shown here would make irrigation more efficient, and make water go further, for years to come.