Groundwater maintains healthy levels, irrigation from rivers beginning to be affected
Latest well measurements by Environment Canterbury indicate that, with a few exceptions, groundwater levels are at or above average levels for January-February, and still much higher than at this time last year.
Environment Canterbury hydrogeologist, Dr Howard Williams says the region’s groundwater levels reflect the high level of winter recharge tempered by generally low rainfall in the post-Christmas period. He says shallow and intermediate depth wells generally show high groundwater levels, but they are decreasing in most instances from readings taken just after Christmas, due to a seasonal downturn. He says deeper wells show average or just below average groundwater levels but are also now showing a seasonal downturn.
According to NIWA, the rainfall for January and early February was generally far below average, unlike December rainfall, which was mostly above average. At Winchmore, Waimate, Kaikoura and Lincoln monitoring sites between a third and a half of the expected rain fell in January and early February. Soil moisture levels at Lincoln and Winchmore are at average levels for the time of year but at Waimate, soil moisture levels are slightly below average. Rangiora on the other hand, received an average rainfall and shows soil moisture levels above average. “This reflects the higher rainfall in that area,†says Dr Williams.
Below is a summary of the state of groundwater levels in different parts of the region.
Waipara
Groundwater levels in monitoring wells are generally displaying low levels as a result of strong demand.
Ashley-Waimakariri
Groundwater levels in aquifers of all depths are at average or above average levels.
Central Plains
Groundwater levels in aquifers of all depths are at average or above average levels and are, in general exhibiting a declining trend; very deep wells are showing slight declines.
Christchurch City
Groundwater levels are generally at average or above average levels throughout the area for this time of year.
Ashburton-Rangitata Plains
Monitored groundwater levels, for both shallow and deep aquifers, across the Ashburton-Rangitata Plains are above or at average for this time of year. Groundwater in very deep wells inland of Ashburton is now declining.
Orari shallow aquifer system
Shallow groundwater levels between the Waihi River and Coopers Creek, and immediately south of the Waihi River, have slowly declined since January 2007 and are at average levels for this time of year.
The most recent monitoring data is available at:
< http://www.ecan.govt.nz/Our+Environment/Water/Groundwater/Groundwater+Levels/>
Irrigation restrictions
Irrigation restrictions are just beginning to be imposed on irrigators taking water from rivers across Canterbury region. For an updated list go to the ECan home page (www.ecan.govt.nz ) and click on Irrigation restrictions bottom right.
Irrigation restrictions as at February 21, 07:
North Canterbury: Hurunui River Band 1 irrigators - 80% allocation; Hurunui River Band 3 - 67% allocation; four takes on the Ashley River/Rakahuri at Ashley Gorge are on full restriction; Little Ashley at State Highway 1 is on 50% allocation; some takes from the Waimakariri River at the Old Highway Bridge are on full restriction, others are partially affected;
Banks Peninsula: one take on the Kaituna River at Kaituna Valley Rd is on full restriction;
Central Canterbury:Miles Drain at Pannetts Rd is on full restriction; Band 5 irrigators on the Rakaia River at Fighting Hill are on full restriction and Band 4 irrigators same site are on 2% allocation; Band 2 irrigators from Selwyn River at Coes Ford are on full restriction.
Mid Canterbury: Band 2 irrigators from the Ashburton River at SH1 are on full restriction; the North Ashburton River at the Old Weir is also on full restriction.
South Canterbury: Opihi River at SH1 - BN consent holders are on full restriction, AN consent holders are at 51% restriction; South Opuha River at Monument Bridge is on full restriction; two consents from the Waihao River at McCullochs Bridge are on restriction - one on full the other 50%; Band 1 irrigators at the same site are on 50% restriction; one consent from the Ahuriri River at South Diadem is on full restriction; Band 2 irrigators from the Hakataramea River at SH 82 full restriction; Band 1 irrigators same site 50% restriction; two consents linked to Pareora River are on full restriction.
Environment Canterbury hydrogeologist, Dr Howard Williams says the region’s groundwater levels reflect the high level of winter recharge tempered by generally low rainfall in the post-Christmas period. He says shallow and intermediate depth wells generally show high groundwater levels, but they are decreasing in most instances from readings taken just after Christmas, due to a seasonal downturn. He says deeper wells show average or just below average groundwater levels but are also now showing a seasonal downturn.
According to NIWA, the rainfall for January and early February was generally far below average, unlike December rainfall, which was mostly above average. At Winchmore, Waimate, Kaikoura and Lincoln monitoring sites between a third and a half of the expected rain fell in January and early February. Soil moisture levels at Lincoln and Winchmore are at average levels for the time of year but at Waimate, soil moisture levels are slightly below average. Rangiora on the other hand, received an average rainfall and shows soil moisture levels above average. “This reflects the higher rainfall in that area,†says Dr Williams.
Below is a summary of the state of groundwater levels in different parts of the region.
Waipara
Groundwater levels in monitoring wells are generally displaying low levels as a result of strong demand.
Ashley-Waimakariri
Groundwater levels in aquifers of all depths are at average or above average levels.
Central Plains
Groundwater levels in aquifers of all depths are at average or above average levels and are, in general exhibiting a declining trend; very deep wells are showing slight declines.
Christchurch City
Groundwater levels are generally at average or above average levels throughout the area for this time of year.
Ashburton-Rangitata Plains
Monitored groundwater levels, for both shallow and deep aquifers, across the Ashburton-Rangitata Plains are above or at average for this time of year. Groundwater in very deep wells inland of Ashburton is now declining.
Orari shallow aquifer system
Shallow groundwater levels between the Waihi River and Coopers Creek, and immediately south of the Waihi River, have slowly declined since January 2007 and are at average levels for this time of year.
The most recent monitoring data is available at:
< http://www.ecan.govt.nz/Our+Environment/Water/Groundwater/Groundwater+Levels/>
Irrigation restrictions
Irrigation restrictions are just beginning to be imposed on irrigators taking water from rivers across Canterbury region. For an updated list go to the ECan home page (www.ecan.govt.nz ) and click on Irrigation restrictions bottom right.
Irrigation restrictions as at February 21, 07:
North Canterbury: Hurunui River Band 1 irrigators - 80% allocation; Hurunui River Band 3 - 67% allocation; four takes on the Ashley River/Rakahuri at Ashley Gorge are on full restriction; Little Ashley at State Highway 1 is on 50% allocation; some takes from the Waimakariri River at the Old Highway Bridge are on full restriction, others are partially affected;
Banks Peninsula: one take on the Kaituna River at Kaituna Valley Rd is on full restriction;
Central Canterbury:Miles Drain at Pannetts Rd is on full restriction; Band 5 irrigators on the Rakaia River at Fighting Hill are on full restriction and Band 4 irrigators same site are on 2% allocation; Band 2 irrigators from Selwyn River at Coes Ford are on full restriction.
Mid Canterbury: Band 2 irrigators from the Ashburton River at SH1 are on full restriction; the North Ashburton River at the Old Weir is also on full restriction.
South Canterbury: Opihi River at SH1 - BN consent holders are on full restriction, AN consent holders are at 51% restriction; South Opuha River at Monument Bridge is on full restriction; two consents from the Waihao River at McCullochs Bridge are on restriction - one on full the other 50%; Band 1 irrigators at the same site are on 50% restriction; one consent from the Ahuriri River at South Diadem is on full restriction; Band 2 irrigators from the Hakataramea River at SH 82 full restriction; Band 1 irrigators same site 50% restriction; two consents linked to Pareora River are on full restriction.