Long-term sustainability of groundwater resources: An approach using integrated hydrogeological and economic models

Abstract

Groundwater is an important but under-utilised water resource. Its use is growing. Approaches to the management of groundwater are evolving, with sustainability as the current approach in New Zealand, and other countries. Models of aquifer geometry, geology, groundwater flow, and groundwater quality are developed from observed data. These models are integrated using an economic model of groundwater use and groundwater quality to predict the total economic value of groundwater. This approach to modelling the sustainability of groundwater is demonstrated for the Delta Zone of the groundwater system in the Waimea Plains, Nelson, New Zealand. Four scenarios of use are investigated; actual, allocated, two-times allocated and five-times allocated. It is predicted that the economic value of irrigation from groundwater in the zone is $2 million with actual and allocated water usage. With use of two-times allocated, the economic value of irrigation from groundwater is $3.5 million. The Waimea River is predicted to be dry for at least one week in a dry year with this scenario. The economic value of irrigation from groundwater is -$1.3 million with water use of five times irrigation. This economic loss is due to land being taken out of production because of saltwater intrusion, and the costs of moving a water supply system caused by predicted saltwater intrusion. This research provides key information to assist the water management agency in setting allocation limits for groundwater resources.