Rivers of Data

An automated river monitoring system that alerts New Zealand residents about floods - or good fishing conditions - has been upgraded to make it more resilient.

On March 18, 2007, a natural dam burst on Mount Ruapehu, a volcano on New Zealand’s North Island. As a result, 1.4 million cubic metres of rock, mud and water cascaded downhill, some of it in the direction of Horizons Regional Council, a region that is home to 220,000 people.

For the many farmers in the region, floods on this scale represent a considerable risk: cattle grazing lowlying pastures risk being drowned. Farmers therefore appreciate any early warning system that can notify them of looming emergencies.

Horizons Regional Council provides just such a service, thanks to a network of 150 telemetry devices that measure water temperature, turbidity and rate of flow in its rivers.

“The telemetry devices all connect to Council,” explains William Gordon, Team Leader for Infrastructure Technology at Horizons Regional Council. “Some of the sensors are polled by modems from a computer system.

Most dial in and upload data automatically.” Some connect using wireless telephony. “Some of the sites are quite remote and the hydrology guys have built solar panels to power them, plus a timer to turn the sensors on, take a reading and upload it,” Gordon says.

Information collected from the sensors is distributed to residents who request notifications of times when rivers reach certain thresholds.

“The application is based on a set of triggers,” Gordon explains. “Members of the public can sign up to be told if a river gets to a certain level. When the sensor data says the trigger point has been reached, people who are on the list are contacted.” That contact arrives in the form of an inbound telephone call, which uses a library of pre-recorded phrases to inform subscribers about the information they’ve requested.

The system is not only useful in emergencies: the sensors can also measure low river flows to inform farmers that their irrigation quotas cannot be used.

“When river flows get lower, we can issue low flow warnings,” Gordon explains.

Anyone can also dial in to the system and request information from any of the Council’s sensors.

“Normal members of the public want to know if they can go for a swim, so they want to know the temperature of the water or how murky it is. Fisherman want to know what their favourite spot is doing.” Callers to this service navigate menus before the application speaks its information to them.

Toughening up

While some of the service’s users don’t rely on it for information related to emergencies, the importance of this warning system to Council is highlighted by the fact that it has recently rebuilt in a more resilient, fault-tolerant fashion.

“The latest revisit is really around getting some resiliency into the system,” Gordon says. “We only had one node for the warning system and it was here in council headquarters at Palmerston North. But if we had an incident, the warning system went out.” Installing a second node to provide failover in case of an outage or emergency therefore made a lot of sense. The Council maintains an office in nearby Woodville, a town 27 kilometres from Palmerston North and in a different valley that is unlikely to be affected by an emergency that hits the Council’s headquarters. Woodville’s proximity also made connectivity cost-effective.

The new system uses an IP PBX from Interactive Intelligence, with the use of IP meaning council can take advantage of session initiation protocol (SIP) to route calls between its two locations.

“Our previous systems didn’t have that redundancy,” Gordon says. “Now we know this important service has the reliability it needs.”