Attempting to drain heavily saturated agricultural soils in Western Oregon.
The southern portion of the Willamette Valley in Oregon has a high percentage of land that is quite high in clay. The majority of precipitation occurs from fall through late spring and normal rainfall is about 40 inches. High rainfall combined with poorly draining clay soils limits crops that can be grown. Grass seed crops are the main crops grown on these soils as they will tolerate saturated soils for months at a time. Other crops can bring better returns and add rotations if drainage can be improved. Tile drains can be installed in the soil to improve drainage if outlets can be reached. Unfortunately much of the land is quite flat with 0-3 percent slopes so suitably deep natural outlets can be hard to find. Often electric power to run pumps to lift water to the surface cannot be utilized as power lines may not be sufficiently close or are prohibitively expensive to bring to pumping sites.
To be able to install a good working tile drainage system can therefore be quite hard. We decided to see if wind power could be harnessed to run a pump to lift water from a site that had no natural outlet. We approached several windmill manufacturers with all but one telling us that while windmills could pump water it wasn't feasible to pump more than a few hundred gallons per hour. The field we wished to tile was 67 acres and if we receive 1 inch of water on the field it amounts to 1.8 million gallons. Our average rainfall is 6-7 inches per month in the months from Nov to Feb. Pumping a 1000 gallons per hour would mean it would take 11 weeks to get 1 inch off the field. That would be futile. One manufacturer, Tom Conlon of Iron Man Windmills, said he could help us and could provide us with a pump that could meet our needs of pumping the 6-7 inches per month of normal precipitation. 7 inches per month times the 1.8 million gallons then divided by 31 days of 24 hours meant we needed to pump 17000 gallons each hour or 282 gallons each minute to remove normal monthly rainfall.
Crop Production Services, a nationwide crop protection company has had a number of weather stations throughout the Willamette Valley for several years. We were able to use data from a nearby site to determine average wind speeds over the previous couple of winters. Winds appeared to average about 7 mph over the critical winter months. With that info we felt that we had enough wind to get the necessary water movement that we needed. Tom asked us how high we needed to lift the water from the cistern to get it to where we could let it free flow into a ditch that would lead the water flow away from the field. The elevation from the tile line outlet to ground level is 5 feet and about one foot higher to the center of the pump outlet. Tom designed a pump that could be driven with a 16 ft Iron Man windmill that would meet our requirements. It would move 40 gallons per stroke so we would need to average 7 strokes each minute.
The windmill motor is a conventional 702 design mounted on a 53 ft tower with a specially designed pump rod and pump rod guide system. Tom designed a pump to go with the 702 unit that would work with the light to medium wind speeds that are common in western Oregon.
The drainage system was installed late in the late summer of 2010. A pad and cistern were installed in the field at that time so that when the equipment arrived the project could be completed. The pump, tower, and motor arrived just before Christmas. We assembled the tower in our farm shop and then towed it to the field site. The water table was to the surface at the site so moving it across the field to the pad and getting it upright was a real challenge. A sixteen foot windmill has a sixteen inch stroke so for the mill to lift water to the surface plus 4 or so inches to allow gravity to let the water run away from the pump it must lift water 64 inches from inlet to outlet. That means the mill is lifting 160 gallons of water once the pump is full with each stroke for a total weight of over 1300 pounds. The mill will start working at slightly over 5 mph and once working will keep working down to just under 4 mph. It reaches a maximum stroke count of 16-17 strokes per minute before the mill starts to self-regulate itself at just under 20 mph wind speed.
In the first 3 months after installation the mill has averaged about 7 mph so it has met our desired pumping goal. We have installed monitors on the tower to record wind speed, depth of water in the cistern, strokes per minute, and water flow rate. This info is available on the web so we and others can monitor the performance of the project and can be seen at: http://precisionagrilab.com/data/oakpark/
The stroke count is updated every ten minutes so the number you see needs to be divided by ten to get stroke count per minute. Water depth is in meters and wind speed is in kilometers. Pictures of the assembly and placement of the mill, tower, and pump are also available online to be viewed at: http://www.ironmanwindmill.com/library/oak-park-farms.
This project has proven to us that the movement of large quantities of water is practical and feasible at a reasonable cost where getting electricity to the desired outlet is not practical. We plan to add a second smaller mill this fall to improve an old system that has a very undersized mainline. We will install a cistern at the spot where the drainage system comes together to meet the mainline. We will continue to let water run into the mainline but we will lift the additional water and let it run into a ditch which will then flow away from the field.
In the future we will continue to tile additional fields. Where we have natural outlets that allow free flow of water we will do that. Where we need drainage but have either poor or no natural outlet we will use additional windmills.
Oak Park Farms, Shedd, Oregon