Protect surface waters and grazing with solar pump systems

This is especially true on leased land, where drilling a well can be hard to justify. In some cases, a lack of electrical service may preclude standard watering systems altogether. Thankfully, using solar power to pump water is now a reliable and affordable alternative.

Matt Booher

Crop and Soil Extension Agent / Virginia Cooperative Extension, Rockingham County

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For the past three years, the Augusta County office of Virginia Cooperative Extension has worked with producers in the Shenandoah Valley to build and test portable, solar-powered watering systems for pumping from surface waters.

Along with partners including the Virginia Agricultural Council, our local conservation district and the Chesapeake Bay Foundation, we have focused on semi-permanent use, though solar power can easily be adapted to a permanent setup. Through this project, we’ve found solar panels to be affordable, effective and simple to install.

So far, we have built four solar-powered watering systems of similar design, which are constructed as portable setups that draw from surface water using submersible pumps. In each case, the pump is powered by a solar array about 3 by 5 feet in size, and 250 watts or greater, based on site criteria. Most solar panels come standard with quick-connections for wiring that runs from pump to panel.

Float valves and panel placement

Each system was designed to pump from a surface water source to a 1,000-gallon reservoir through 1-inch diameter or greater black plastic high-density polyethylene pipe (HDPE) laid above ground or buried to a shallow depth. The reservoir then gravity-feeds a portable stock tank governed by a float valve. We sometimes found it helpful to place the reservoir on a wagon or trailer, which provides portability as well as built-in fall for the gravity-dependent systems.

Special considerations should be made when plumbing a gravity-fed stock tank. For example, we tried several float valves before finding a full-flow option that can quickly recharge a stock tank under low-pressure situations. Valve placement proved important, as plumbing the valve through the floor of the tank and underwater kept cattle from messing with it. We used a 700-gallon stock tank to ensure plenty of water was available when the herd came to drink.

We often placed the solar panel on the wagon and ran a sensor wire to the reservoir to shut off the panel when the system was topped off. Alternatively, we also placed the panel closer to the pump and used a pressure switch to turn off the pump when the system storage was full. The solar panel can be located in any sunny location, but it may require lengthening either the pump wire or a sensor wire, depending on the setup, with pros and cons to each option.

We moved our watering systems among farms to test them under different conditions and water sources (currently over a dozen sites). Pumping capacity averaged from 3 to 6 gallons per minute, depending on the site and the system used.

This amounts to around 1,000 to 2,000 gallons per day, which is enough to meet the daily water demand for a herd of around 40 to 50 cow-calf pairs. We watered up to 60 cow-calf pairs, but were able to open a limited access point to the creek if a few days of cloudy weather set in. For complete self-sufficiency, many resources recommend sizing the system to store three days worth of water – ours only held about one day of storage for the 60-cow herd.

Water sources

We have pulled water from spring-fed ponds, springs, creeks and rivers; and pumped against anywhere from 5 to 100 feet of head (pumps are capable of tackling greater elevation, but it varies by the system). In most cases, we established new watering points 300 to 1,000 feet from the water source, which allowed producers we worked with to fence out their riparian areas and shift grazing to upland pastures.

The climate is pretty mild in Virginia, so we’ve been able to operate without worry from May to October. Some system modifications, such as adding weep holes and pressure-relief valves, have allowed us to extend the pumping season through November.

Initially, we had concerns about pumping from turbid water sources. While we would still recommend care in selecting a clean and protected location for the pump, the positive-displacement, submersible pumps we’ve used have done well in pumping water that has been muddied by storms or livestock upstream. You should always select a water source that has adequate recharge to it, and you may want to consider installing a sensor to shut off the system if the water source gets too low.

How to get started

Solar panel and pump selection begins with calculating the daily water demand of your herd, including additional water storage for overcast days. A larger panel array than the ones we used, along with a more powerful pump, would be needed to accommodate a large herd.

Site considerations including solar energy available and total head (elevation gain, friction, etc.) influence the solar system sizing and pump selection for your situation. An online NRCS publication titled, “Design of Small PV Solar-Powered Water Pump Systems” is helpful for getting started.

Solar panels and compatible pumps can be purchased from retail stores or online, as individual components or as ready-to-go kits. For our project, we purchased kits from Advanced Power Inc., and Lorentz USA. Based on the equipment we’ve priced, pump and panel systems capable of 4 to 6 gallons per minute are running around $1,500 to $3,000. With the way solar panel prices have dropped, it pays to spend some time shopping around.

While solar pumping can enable stream fencing where it hasn’t been practical before, the possibilities don’t stop there. Solar-generated watering points can open poorly used upland areas to summer grazing, allow pasture subdivision for rotational grazing and enable stockpiling of pasture to extend the grazing season. Used in this way, solar-powered watering systems can serve as powerful tools to improve grazing management.