The Waipara – Kowai groundwater allocation zones (referred to as zones) are located 50
kilometers north of Christchurch. Land use in the Waipara zone has evolved from dry land
farming towards horticultural and irrigated pastoral farming, and as such the demand for
groundwater resources has increased significantly. Recent 14C age dating has shown that
deep wells tap >1000 years old water, raising concerns about possible resource mining.
The Kowai groundwater allocation zone has had minimal regional hydrogeological
investigations and previously little is known about the groundwater resources here.
The Waipara – Kowai groundwater allocation zones are located near obliquely convergent
plate margin and the Porters Pass Fault System. Recent (early Quaternary) deformation
has been noted by workers along margins and associated with emerging structures within
basins. These emerging faults and folds within the basin are acting as hydrological
barriers, hindering the passage of groundwater within the basin.
A geomorphic map was constructed for this study based on existing soils maps, limited
field soil surveys and morphometric analysis. Nine geomorphic surfaces are described,
with inferred ages of modern to >73 ka. The geomorphic investigation revealed that the
Kowai groundwater allocation zone surface is stepped, with increasing thickness of loess
up gradient on the downlands. Near the coast there is intercalated terrestrial and marine
sediments, to the west overlying the Kowai Formation are small alluvial fans. In the
Waipara Basin the Waipara fan dominates the central portion of the basin, with smaller
fluvial and alluvial fans building out from the margins.
Groundwater recharge was investigated using chemical, isotopic, water level observations
and a simple water balance. It was found that in the Kowai zone the major recharge
sources were the rainfall, losses from the rivers and streams. The southern region of the
Waipara zone is recharged by rainfall with small contributions from the Kowai River
(North Branch). In the South region of the Waipara Basin groundwater recharge is derived
from rainfall and losses from streams. The groundwater systems are conceptualized as
being topographically driven, with slope – basin floors interactions being an important
source of groundwater recharge.
| Identifer | oai:union.ndltd.org:canterbury.ac.nz/oai:ir.canterbury.ac.nz:10092/3193 |
| Date | January 2009 |
| Creators | Dodson, Matthew Michael |
| Publisher | University of Canterbury. Geological Sciences |
| Source Sets | University of Canterbury |
| Language | English |
| Detected Language | English |
| Type | Electronic thesis or dissertation, Text |
| Rights | Copyright Matthew Michael Dodson, http://library.canterbury.ac.nz/thesis/etheses_copyright.shtml |
| Relation | Accompanying this thesis are electronic appendices 2 - 5 which are available on CD via InterLibrary Loan, NZCU |
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