Flowing artesian wells are a fascinating piece of Mother Nature in action. “Artesian” means that the water level rises above the depth of completion. The sand aquifer is confined by clay layers and pressure builds up. If the water level in the well is above the completion zone but below the ground, it is a non-flowing artesian well. If the pressure level (head) is above ground, it is a flowing artesian well.
In the diagram, the aquifer (sand or gravel, or in the Winnipeg area fractured limestone) comes to the surface for recharge at an elevation higher than the well, resulting in water flow.
The diagram shows the situation that leads to the salt water discharge at the northern end of Lake Winnipegosis. The geologic formation takes its head all the way back to South Dakota, where it outcrops.
But, in much of the Canadian Prairies the explanation is much different.
The flowing well in the photo is on the University of Saskatchewan Goodale farm, just southeast of Saskatoon. We installed it in the Forestry Farm aquifer at a depth of 112 feet as part of some soil salinity studies in 1986.
The aquifer sand is at 112 feet at that location but that sand does not come to surface anywhere. That formation extends east and underlies the Strawberry Hills upland. Sloughs in the hills are a primary source of the water inflow that charges up the pressure in the aquifer. The aquifer ends abruptly approximately 200 metres south of this well location.
- From the Alberta Farmer Express: Don’t cut corners on irrigation savings
North of Saskatoon that same aquifer extends right to the river and drains as springs to the river. Consequently the pressure does not build up as high and no flowing conditions are encountered.
But, back to the flowing well on the Goodale Farm. When it was installed in 1986 the water level was 11 feet above ground. In the dry periods of the 1990s to 2001/2002 the head fell to eight feet above ground. After the recent big snow winters and wet summers the head is 14 feet above ground.
We put in 10 feet of six-inch screen so we could lay some water on the ground for demonstration purposes and to do “backflush” experiments on the adjacent saline soils. It does 20 gallons per minute all by itself. Students get a kick out of cranking open the gate valve and seeing Mother Nature do her thing.
Henry’s Handbook of Soil and Water includes many tales of flowing wells and describes the “backflush” work we did on the saline soils. It also explains how a flowing well or hole can be plugged.
At first flush you may think a flowing well is great — water on tap with no pump required. But, flowing wells can be a problem. If uncontrolled they can spill water where it is not wanted.
Most of our saline soils are caused by artesian discharge from situations just like Goodale farm. If you see a farm advertised with flowing wells in place, investigate it carefully before jumping in.
Pliny the Elder (AD 23 to AD 79) said: “Tales sunt aquae, qualis terra per quam fluunt.” Waters take their nature from the strata through which they flow.
Good farming for 2014.