An analysis of groundwater quality in the Morven, Glenavy and Ikawai area, South Canterbury, New Zealand

Abstract

The quality of groundwater beneath land surfaces can be influenced by activities carried out on the land. The combination of these activities and effects of the physical environment can cause groundwater contamination, being the threshold at which human or animal health is at risk. The physical environment can induce unacceptable levels of chemicals to groundwater and these may be measured by indicators such as pH and hardness. Particular activities leading to contamination in rural environments include farming activities utilising irrigation and chemicals to enhance production. An outcome of these activities may include the disposal of animal wastes which is a direct contaminant input having the potential to reach groundwater. Settlement patterns, in particular small settlements which are unsewered, can also contribute to groundwater contamination through sewage disposal from septic tanks. This thesis explores how these activities may influence groundwater quality of the Morven, Glenavy and Ikawai area in South Canterbury, New Zealand. In doing so it utilises groundwater measurements taken by the Canterbury Regional Council from 90 wells in February and May 1996. The results from these measurements are related using a Geographic Information System to various human activities, namely farm type, irrigation, waste disposal and settlement patterns and two physical parameters, soil permeability and groundwater depth or piezometric surface. Patterns emerge which indicate contamination from settlement patterns and activities such as waste disposal, but not so much from dairying or irrigation. Levels of hardness are highest near the Waikakahi Downs, coinciding with the pattern of less permeable soils near the Downs. It is important that other factors, such as temporal changes, are not overlooked or neglected.