Evaluating sustainable groundwater management options using the MIKE SHE integrated hydrogeological modelling package

Abstract The Wakool Irrigation District consists of 74,000 ha of agricultural land, a large part of which is affected by a rising watertable. Irrigation in the district started in 1936 when the watertable depth was about 9 m. Over the past 30 years, the watertable has risen as a consequence of irrigation, wet winters and inadequate drainage. In addition, the Wakool Irrigation District is underlain by the Calivil and Renmark aquifers of the Murray Basin. Rising groundwater pressures in these deeper aquifers are also contributing to the rising shallow watertable. Since 1981, a sub-surface drainage scheme with 48 bores pumping shallow saline groundwater into a 2000 ha evaporation basin has been developed in two stages to control the watertable in the Wakool Irrigation District. This paper describes the development and application of an integrated hydrogeological model for the Wakool Irrigation District, where management of rising watertable levels and land salinisation is a continuing problem. The model development is considered to be an important part in the establishment of sustainable water management policies for the Wakool Irrigation District. The Wakool model was developed by using the MIKE SHE integrated catchment-modelling package. The developed model enables analysis of the complex hydrogeological regime in the region, and prediction of the environmental impacts of various management options. It is able to describe temporal and spatial variations in the exchange of water between the land surface, drainage and supply systems, and the aquifers within the area. Management options proposed in the Wakool Land and Water Management Plan have been analysed for the period between 1975 and 2020. Various scenarios such as the implementation of on-farm recycling ponds in conjunction with laser levelling, deep-rooted perennials, tree planting, installation of deep groundwater pumps and the effect of shallow groundwater pumping, were investigated. The results from these simulations indicate that the best option is the implementation of shallow pumping.