Photos are of various weirs/diversion dams. They are really the same thing. However in use, in rivers it is a weir if all it does is present a threshold to raise the water, or sometimes to prevent water from eroding faster in some place, and spread out the fall. Diversion is used if the weir directs the flow into another channel — directing or dividing part of the stream.
“Take out 01” is the weir and diversion at beginning of Noble Ditch and Farmers Canal just above Emmett. It is a combination of a weir on one side channel, and a diversion dam on the other channel — both backing the water up so that even in low flow times, then a certain amount is always present for the canals. Fortunately for the residents of New Plymouth and Fruitland these canal’s water rights supercede many others because they came first and thus have priority.
“Take Out 03” shows this “take-out” point with reference to the city.
“Take Out 04 1 Canal” — shows the water from origin going across the entire town as a single canal. The long very straight, north to south single canal splits at bottom of image into two canals — shown in “Take Out 05 Twin Canals” as twin canals hugging the edge of the bluff as they turn and go west. Note how close they are for most of the way along Emmett Valley.
“Take Out 06 Bench & Black Cyn”– the beginnings of both canals at Black Canyon Dam. Note the Black Cyn Canal life begins when the dam was built ~1930 — but took some years to be complete its entire length. Progress was dependent upon the developer’s sale and occupation of the service area. This took over 30 years. The Bench Canal, was a replacement canal. It had originated many years earlier when the Emmett Bench farmers got groups of farmers to donate labor going way up the river, just downstream from Horseshoe Bend, laboriously digging a canal along the river bank. However, this canal was completely obliterated by the dam’s reservoir, and the dam itself. So beginning at the dam, this new canal allowed much more water to go to the bench. The bench had previously been at the mercy of seasonal flows down creeks, and the small amounts their early efforts had brought If you look at all the photos you will seen many more weirs and diversion dams all down the Emmett Valley as the Payette is tapped again and again most often towards the downstream end of the Bench, and the farm land around the mouth of Big Willow.
Note in “Take Out 07 Undr Creek”, that some creeks ran dry early, but were still a hazard to a canal. In this case the canal was put underground, thus a cloud burst or similar upstream, bringing a wall of water and huge amounts of mud and debris could simply go right over the top of the canal with no problem. Other creeks with more lengthy and dependable flow, then they put a collection pond upstream to catch the debris and limit how much water or debris might be allowed into their canal, but still use the additional water. When and if additional water became available then farmers could water acres for which they usually did not have sufficient water. A plus. Creeks like Big Willow have a tremendous headwater area and any irrigation facilities can be overwhelmed by sudden storms and flash floods over such a huge drainage basin. So these creeks make good use of weirs and impound areas.
The lower Payette, through the years became heavily utilized by the use of weirs. However, these weirs took a lot of labor and capital to build. They were not in much use until the dam was built in 1930 because spring ice break up and floods would simply wipe away any hard work done on weirs, or sometimes even re-route the river around them. The most important thing of all was that the dam leveled the playing field — keeping water in reserve for dry spells, and impounding floods. So the leveling out of flow allowed heavy use of weirs, and thus many additional acres could be serviced.
Another factor was the permits and purchase of water rights from the state gov’t. It took knowledgeable people to go thru the bureaucracy to get these. Small farmers or independents had no chance. This is group effort. Bridges as well had to be permitted. As, more and more of the state’s available water is claimed by those with permits and ownership of water, then more and more use of the river becomes more difficult. All that is heavily impacted by federal regs over whole drainage basins. The Payette’s basin is huge, with huge supplies of snow, however it is a contributor to the Snake and then Columbia drainage basins as well. All are additionally encumbered and modified as dams are built downstream or upstream creating still more dependence upon the river flow. It becomes a large management problem.
Note, that luckily indeed, for Idaho farmers they got their dam, canals, weirs, etc., in place early in the game, or they would have been entirely preempted by settlers and downstream usage.
From time to time we hear some environmentalist bemoaning the dams on the Columbia and Snake because of Salmon migration disturbance. They jump up and down with plans and pushing to eliminate these dams. They do not understand that the major push for dams first was for flood control, only second for agriculture, and very last for electricity. Although the priority shifts thru the years. Few today worry about flood control, or even know of it. But this is only because it was handled many years ago. Flood control (including ice jam dams) has allowed population and use of flood plains — totally unthinkable without it. Idaho mountains get extreme weather and rapidly varying ice breakup used to devastate the flood plains — and destroy and carry away anything in the flood plains. There is real evidence in front of ones eyes, if they but look, at flood plains and how dynamic they can be. I have witnessed many floods, and witnessed bridges taken out by ice jams. Rivers can change course, instantly in such floods. River flow can vary by 200-300% over climate cycles. Dams, level out all this. It is a tragedy for salmon to be impacted. However the tragedy would be compounded and multiplied by dozens of times without the dams.
“Take Out 09 Payette Ditch” is the beginning of Payette canal, also a weir or diversion on a branch of Payette around Birding Island. Servicing all of Payette’s farmland. You can follow the canal all along the bluff to the point it dumps in the Weiser River at mouth of the Cove (south edge of Weiser).