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Maintaining open ditches and culverts keys to draining lowlands

Water boards part of Dutch system

Tags: Excerpts from the Windmill

LEEUWARDEN, the Netherlands – A small army of inspectors recently checked up on the condition of Dutch ditches, particularly those with water running below sea level. Over 8,300 property owners in Friesland alone have failed to meet the November 1 deadline for the annual clean-up of such drainage ditches bordering or running through their fields. To allow better water level control during the winter, farmers and other proprietors must clear these ditches of vegetation, trim the banks and clean culverts.

Water management board Fryslan, which now covers the entire province, sent every non-compliant property owner a summons to get the work done within two weeks. Alternatively, the board could hire a contractor for the work and pass along the cost. About half of the delinquents are farmers of whom some complained they had not been able to complete harvesting their cash crops (such as sugar beets) by the general deadline.

Boards in other parts of the country face similar compliance issues. The boards blanket the waterways in their respective territories with a visual inspection. Many ditches without running water fall outside the regulations, although farmers could still benefit from an annual clean-up by improving the drainage of potentially water-locked fields. The Boards, which for somewhat similar reasons also are concerned with areas lying above sea level, have a very long history and are a key part of the Dutch government system.

Runoff a greater problem

The Dutch water management boards maintain dikes, canals and sluices, and operate pumping stations, which control water levels behind the dikes, mostly by discharging excess water. In addition to rainwater, the drainage systems also dump run-off water from the hinterlands into the Frisian and the North seas. In recent decades, such run-off from notably Germany has been compounded by the canalization of rivers, and by expanding cities, which quickly dump rainwater into rivers and streams and more rapidly fill up Lowlands’ deltas.

In recent years, the Boards also have incorporated an elaborate approach to fish stock enhancement in Dutch waterways. Many pumping stations discharging inland water attract inbound migrating saltwater fish, which seek ways to surmount dikes and dams. There now are fish ladders in many places, which particularly take the glass eel inland to mature before migrating back to Bermuda where they spawn, and sticklebacks. This specie spawns in Dutch waterways. The boards also operate water treatment plants.