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Published: 2003-09-12 00:00:00

Environment Waikato has analysed how long it takes for substances to travel down the Region’s major rivers.

The information will be used to warn downstream users of impending trouble following a spill or accident on nearby major roads and railways. Hydrologist Dr Edmund Brown told this week’s Environment Committee meeting that there had been a number of recent vehicle accidents which put hazardous substances into waterways in the Region.

There was little information readily available to estimate the time for a spill to travel downstream and this would be useful in advising downstream users of how much time they had before they were affected. The charts detail times for the Region’s major rivers – the Waikato, Waipa, Waihou, Piako, Awakino and Mokau – and are designed to be used quickly in emergencies. The information also covers tributaries to the rivers.

Travel times are based on river length, discharge and velocity both in high and low flow, conditions and large rivers are split into different sections. For instance, under low flow water leaving Lake Karapiro will take about 75 hours to reach Waikato Heads. Allowances are also made for tidal influences.

The charts already had their first use with the recent urea spill from a truck crash at the Narrows Bridge and were found to be accurate.