Innovative Use of Water Balance Models in Farm and Catchment Planning in Western Australia

Abstract

Soil salinisation in the agricultural regions of southern Australia is caused by the replacement of the deep-rooted, perennial native vegetation with shallow-rooted annual species. Its remediation requires significant changes to the water balance. The land managers with the highest potential to influence the local water balance are farmers, acting in catchment groups. In order to make changes to the water balance of a sufficient magnitude to reverse or limit salinisation, farmers require an understanding of the local effects of the treatment options available to them and the likely landscape effects of applying those treatments over whole catchments. Agriculture Western Australia is using two water balance models to assist farmer groups to understand these effects. AgET is a simple, one-dimensional model that predicts the effects of soil and vegetation type on the water balance. The groundwater model, MODFLOW, is used to predict the landscape-scale effects of changes in vegetation type and other water management practices. Using these models in an integrated way has many benefits: (1) farmers’ knowledge is included in the model calibration process; (2) farmers value the opportunity to participate in the process and learn from it, and (3) water management practices likely to succeed at the catchment scale are tested by the model simulations.