Coes Ford flowing again as Selwyn River rejoins Lake Ellesmere
The Selwyn River is flowing all the way across the Canterbury Plains on its way to Lake Ellesmere/Te Waihora for the first time in years.
On April 7, rainfall from ex-Cyclone Debbie got the river flowing under the State Highway 1 bridge for the first time in nearly three years, but was not enough for the water to reconnect with the lake.
The recent rain caused by ex-Cyclone Cook provided the extra boost needed for the river to rejoin, allowing aquatic animals to move up and downstream once again.
On Saturday, water flow at Coes Ford went from about 0.2 cubic metres per second (cumecs) at 8am to a peak of about 12 cumecs at 5pm the same day.
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It has since receded to about 3 cumecs as of 7pm Tuesday.
Environment Canterbury (ECan) chief scientist Dr Tim Davie said it was likely the river would dry up again across the plains, but he expected it to continue flowing at Coes Ford for the rest of the winter, as that part of the river was groundwater fed.
The river would "reconnect more easily" with future rainfalls though, he said.
"This rain has been good for recharging the groundwater. It hasn't fully recharged it; it would be good to get more rain over the winter."
Record low flows this summer had been caused by two things – the most significant being the three very dry winters Canterbury had experienced in the last three years, meaning there had been little ground water recharge across the Canterbury Plains.
The second was irrigation, which accounted for about 15 to 20 per cent of the flows in all groundwater fed streams, Davie said.
"Without irrigation it would have been really low, but it probably would have flowed at Coes Ford. But it still would have been really really low."
The water flow was good news for aquatic life now able to head up or down the river, and especially for eels which move down river at this time of year.
In early March, a mission to rescue thousands of fish in danger from the receding water was mounted, saving about 2500 fish and 500 eels.
ECan councillor John Sunckell said he was always confident the river would recharge "once we got some serious rainfall".
"We're early in the autumn, so any rainfall on top of that will keep it going."