Cranberries are one of the worlds ‘super fruits’ and demand for berries and juice has never been higher. They require a wetland habitat which means striking a delicate balance between gaining the highest possible yields and avoiding flooding in surrounding areas. In Canada’s largest growing area, specialist pumps have been called in to assist with harvesting and flood alleviation.

The North American variety of cranberries dominates the world market and is mainly cultivated in the USA and Canada where it grows on trailing vines and thrives in natural wetlands. Canada’s largest growing area is in the City of Richmond on Lulu Island, British Columbia.

Occupying 129.66 sq km over 15 islands in the Fraser River delta, the City of Richmond has a natural average elevation of one meter above sea level, so flooding has always been a major concern. This has both advantages and disadvantages. The challenge that faces the City’s Engineering and Public Works Department is maintaining the equilibrium between residential/commercial and agricultural activities.

This involves keeping the farmers happy while simultaneously maintaining water levels in the island’s drainage channels so other parts of the island do not flood. It is a delicate balancing act that combines irrigation, drainage and flood control and involves the running of a network of pumping stations located around the city.

Over the years many areas have been raised out of the flood plain through land development. The ongoing program of dike construction, together with the installation and upgrade of pumping stations, prevents significant flooding in the community. It has also contributed to the development of the cranberry industry and other agricultural crops.

Harvesting cranberries

It is a popular misconception that cranberries grow underwater because all that is seen of the vines are the berries floating on top of the water in the bogs and marshes. What is actually being seen is part of the harvesting process. Wet harvesting involves the farmers using water reels to churn up the water and loosen the berries from the vines so they float to the surface for collection and transfer into trucks.

Flooding is important in cranberry cultivation and growers use it as a management tool to protect plants from the cold winter winds and for harvesting in the autumn, when the water levels in the bogs and marshes need to be raised. Equally as important to the growing of cranberries is keeping a sufficient level of water in the bogs when temperatures can be high during the summer. This dual requirement is where the pumping stations deliver their roles of preventing the City from flooding and maintaining perfect growing conditions for the farmers.

The City of Richmond operates 41 pumping stations providing a total pumping capacity of 85,000litres/sec. A programme of new build and reinvestment in older stations is now being undertaken, with specialist submersible pumps being the preferred equipment.

“We first brought in specialist pumps around 12 years ago and since then they have proved to be durable and reliable. We have experienced very little downtime, maintenance is easy and the customer service is good, plus our staff like working with the pumps,” said Romeo Bicego, manager, Sewerage and Drainage Engineering and Public Works. To date 28 Amacan pumps have been commissioned and more are on order, which will bring the commitment up to 37 units.

Located at strategic intervals around the island, the pumping stations are called into service as and when required and all are fitted with flood gates and flood boxes. The ground water levels can be very high during the winter and this is exacerbated when there is heavy rainfall and tides are high. At high tides, the pumps transfer drainage water into the Fraser River Delta and at low tide drainage water discharges through the flood boxes via gravity outflow gates.

Such is the importance of cranberry growing to the local economy, the flood management scheme ensures fresh water is available for irrigation and raising water levels in the growing bogs as required.