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With narrowing snowmaking windows and increasingly efficient snow gun productivity, water pumping capacities have been rising at a significant rate. However, water sources have generally remained the same, and water regulations often limit or restrict usage. That has made water storage both a higher priority and a more common solution for meeting the surge capacities needed during high production snowmaking operations.

The common practice of drawing water from creeks or streams has become higher risk, even in the traditionally water-abundant states of the East, since local or state agencies have been imposing restrictions in order to maintain minimum downstream flow to protect fisheries. This practice has long been in place across much of the West. 

Reservoirs as insurance. Reservoirs provide surge capacity to allow for high pumping rates to be sustained during brief snowmaking windows. They enable high productivity and recovery during these peak periods, without having to rely on vulnerable small streams. 

Water storage reservoirs can be filled at slow rates when not making snow or during the spring and fall, staying below regulatory flow rate or volume thresholds and minimizing the impact on stream flows at the most inopportune times.

Mid-mountain storage has value. If the location allows, on-mountain storage at higher elevations above the water source can provide an additional advantage by reducing peak power demand during snowmaking. Filling an on-mountain pond ahead of the season can be considered a form of pre-season energy storage. 

CASE STUDY: MOUNT PLEASANT OF EDINBORO, PA.

In 2020, Mount Pleasant ski area in northwest Pennsylvania installed a new 3.5-million-gallon pond 300 vertical feet above its existing base pumphouse and primary water source. The existing pumps drew from a small stream-fed creek at the base of the ski area. During dry periods or very cold periods when recharge rates were very low, the ski area struggled to maintain maximum capacity from the main snowmaking pumps.

Mount Pleasant of Edinboro, Pa., built a 3.5-million-gallon on-mountain reservoir and pumphouse 300 vertical feet above its original pumphouse and water source, which doubled the pumping capacity and reduced reliance on an existing low-recharge water source.

Efficient storage. With the installation of a new on-mountain reservoir, the area doubled its pumping system capacity by adding a pump at the upper reservoir. Throughout the year, the lower pumps were operated during off-peak power rates and at lower pressures to fill the reservoir.

Since the water pump at the upper pond is 300 vertical feet above the base pumps and pumps downhill, the upper pump operates at about a third less horsepower than the base pump for the same water flow.

Flexible productivity. During peak snowmaking, the pumphouses can operate independently or simultaneously, the latter providing double the snowmaking production rate. This capacity has been crucial to open terrain quickly and recover during narrow snowmaking opportunities.  

CASE STUDY: WOODS VALLEY, N.Y.

A similar project was undertaken in 2019 at Woods Valley Ski Area in Westernville, N.Y. A 4.5-acre, 9.5-million-gallon on-mountain storage pond was constructed 370 vertical feet above the existing pumphouse and water source.

Efficiency gains. Instead of installing pumps at the on-mountain pond site, Woods Valley connected a dedicated supply pipeline from the pond to the base pumphouse. While the pond can be filled by natural recharge, the supply line does double duty by allowing the base pumps to fill the pond when water is available from the existing water source. The main snowmaking pump fills the pond at a lower speed using a VFD, minimizing power consumption.

The pumping capacity at the base was expanded and configured to accept both the gravity-fed water from the upper pond as well as from the existing water source. Due to the gravity pressure available from the on-mountain storage, the pumping rate was increased more than 45 percent, and pressure increased more than 80 PSI with only a 20 percent increase in pumping power. With the increase in pressure, high efficiency guns were implemented on more terrain, with a corresponding increase in average water pumping flow rates.

Greater production. President and GM Tim Woods reports great success in the three seasons of operation since the pond went into service. In the past, water was always limited, and when it was cold, snow gun production had to be constantly reduced or curtailed to match the incoming recharge rate. With the pond full at the start of the season, Woods Valley has 60 percent of its average seasonal water usage “in the bank,” which has allowed for significant gains in production rates, fewer operating hours, and a more reliable product for customers. 

CASE STUDY: ARIENS NORDIC CENTER

In 2022, Ariens Nordic Center in Brillion, Wis., installed a new nine-million-gallon snowmaking storage pond and pumphouse. The pond is needed due to the center’s limitations on water recharge. It is fed primarily by drilled wells, but is restricted to a monthly cap on water usage by state regulators. 

This 9-million-gallon reservoir, built in 2022, services a 5K Nordic/biathlon course at the new Ariens Nordic Center in Brillion, Wis., and is recharged by drilled wells.

Operations manager Sean Becker notes that the weather has been a challenge this season, requiring much more water pumping than anticipated. Having the storage in conjunction with the well recharge has allowed the center to maintain production even under difficult weather conditions.

Well water is not ideal for snowmaking, since ground water temperatures hover close to 50º F throughout the season in most regions of North America, and warm water can hamper snow production, particularly with energy efficient snowmaking equipment. A reservoir can allow well water to naturally cool prior to being pumped.

That cooling affect may need some assistance, though.  

CHILLING OUT

In order to be space efficient, greater storage volumes mean deeper ponds. However, deeper ponds tend to retain heat. Water temperatures at the bottom will be fairly close to the ground temperature, which could be in the upper 40ºs to 50º F. Water intakes are typically close to the bottom, so pumps would be drawing in the warmest water. This can hamper the performance of high efficiency guns. 

Aerators can be used to cool the water at the intake. Surface water temperatures will be fairly close to the ambient air temperature, and there could be ice formation. Circulation strategies can mix the cold surface water with the warmer, deep water to provide the coolest possible water at the pump intakes.

Surface aerators. Smaller or shallower ponds can benefit from surface aerators. These devices consist of a submersible motor and impeller suspended on a float, which draws water from a few feet deep and circulates it to the surface, exposing it to cold ambient air. 

Brattleboro Ski Hill in Vermont outfitted its small snowmaking pond with a surface aerator manufactured by Otterbine. Ski hill VP Zach Rounds reports promising results in the first season with the area’s eight-foot-deep, one-acre pond. Water temperatures dropped from 46º F on the first of November to the low-30ºs by the second week in December.

Bubble aerators. Although surface aerators can be used for both small and large installations, bubbler aeration is more effective for larger or deeper ponds. Bubblers use a small, low-pressure air compressor to create fine bubbles at the bottom of the pond. The column of small bubbles will induce a flow from the very deepest sections of the pond to the surface, again exposing the warmer water to the cold ambient air. 

Kendra Holmes, VP of operations for Aqua Sierra in Morrison, Colo., says that Aqua Sierra’s product consists of a weighted tubing with calibrated slits that generate the bubbles. The tubing can be supplied in coiled modules, or simply laid on the bottom. Application and layout depend on a number of factors, such as pond depth and composition of the pond bottom.

In Western states where water supply is highly valuable, bubblers have the advantage of minimal evaporation as opposed to mechanical surface aerators.  

Aeration suppresses ice formation on the surface, too. Ice sheets can damage pond liners, and also insulate the water surface from the cold ambient air, inhibiting natural cooling.  

CLEANER WATER

Another not so obvious advantage of a storage pond is the settling of debris. Water drawn directly from a running stream can carry debris into water pumps, clogging impellers and hampering performance. Reservoirs allow suspended debris to settle out and lower the risk of pumps clogging.

Mount Pleasant’s base supply pump encountered clogging this fall. Within a few hours of startup, GM Andrew Halmi noted the flow and pressure of the pump dropped dramatically, with a corresponding drop in motor current. Upon investigation, he found leaves packed into the pump impeller set. The leaves were drawn in from the adjacent creek when low water levels were present—a common occurrence in fall 2022 due to low water levels in many areas. 

POND LINERS

The use of a pond liner may be useful, depending on the site’s soil type and local geology. Local engineers can usually offer the best guidance on whether a particular site will require a liner or not. 

Generally, pond liners are more common in the Western U.S., where more permeable soil and less predictable soil types are prevalent. In the East, less permeable soils or a greater prevalence of clay often provide a natural pond lining.

Reinforced polyethylene. When liners are required, a common, modern material for large applications is reinforced polyethylene (RPE), which is a polymer membrane with a woven reinforcement. 

Nolan Wilson of BTL Liners in Oregon cites various advantages for this material, primarily its thickness and strength. It is relatively thin compared to older EPDM rubber materials; very large factory-fabricated sections can be made, which minimizes seaming, site installation, and shipping costs. The material has a high tensile strength and good UV resistance. 

Covering it with soil increases the longevity of the material dramatically since it is not exposed to UV light and is less subject to damage from foot traffic and ice.

Clay liners. Clay has advantages of longevity, resistance to damage caused by traffic, rocks, and ice, and it is not affected by UV light. However, it costs more for material and installation, primarily due to trucking expenses. Mount Pleasant, for example, used bentonite clay to seal portions of its reservoir from leaks. 

HEIGHTENED ATTENTION TO WATER

Managing water resources is becoming increasingly important, even in historically water-abundant regions of North America. Snow production demands and governmental regulations are driving the need for implementing or planning for water storage infrastructure. 

Water pumping capacities are increasing to take full advantage of shrinking snowmaking opportunities and to respond to competitive pressures to open terrain. Water storage offers solutions to these and other challenges, regardless of geographic location.

Ski areas considering adding or implementing additional storage should consider consulting with a snowmaking planning engineer, in conjunction with a local civil engineering firm, to design a storage reservoir that will enhance the ski area’s long-term viability and sustainability.