Historically, broadacre agriculture has dominated the Midlands area; mainly cereal cropping and pastures for sheep and cattle. More recently it has been recognised for its potential to support horticultural production, particularly annual vegetable crops such as carrots, onions, potatoes and leafy vegetables, with perennial tree crops such as citrus, nuts, mangos and olives. Besides meeting the expansion needs of vegetable growers, the government also receives investor inquiries regarding large-scale fruit tree production, beef feed lots and feed-on dairy facilities.
The Midlands Land and Water assessment project sought to provide information on water availability and land suitability for irrigated horticultural growth, and identify one or more 2000 to 3000 hectare areas suitable for intensive horticulture in the coastal Midwest. The project area covered approximately 17 000 square kilometres, located 120 kilometres north of Perth, stretching along the coast from Dongara to Lancelin and inland from Mingenew to Moora.
Due to the extensive project area, a Community Reference Group was established to help identify two focus areas. The Irwin Valley and Dinner Hill areas were chosen based on their potential suitability. Irwin, in the north of the project area, is approximately 15km east of Dongara, underlain by the Yarragadee aquifer. The area is aligned with the Irwin River valley alluvial soils, straddling the Twin Hills, Allanooka and Eneabba Plains groundwater sub-areas of the Arrowsmith Groundwater Area. Dinner Hill is in the south of the study area over the Leederville - Parmelia aquifer. It covers 502 square kilometres between Moora, Dandaragan and Badgingarra. Along its western border lies the Dandaragan Scarp. The Dandaragan plateau, on which the focus areas sits, is crossed from south to north by the Minyulo Brook, and contains a number of springs and soaks. Established irrigated horticulture producers are found across the area.
Water investigation results within the Irwin focus found, shallow groundwater occurs primarily near the Irwin River and its tributaries. However, this water is relatively saline and is more suited to stock water than irrigated agriculture.
Soil studies in the Irwin area have generally concluded that, due to the relatively high salt levels of the underlying water sources and the saline and poor draining subsoils, the area is suited to broadacre agriculture rather than irrigated agriculture which would require careful site selection and substantial soil management if undertaken. The Midlands land, water and crop reports are now available.
Groundwater investigations identified additional water is available in the northern and western parts of Dinner Hill, however, the volume is insufficient to support significant expansion of land under intensive horticulture. It was also found that existing groundwater allocations are currently under utilised. Since 2000, water abstraction in the south east corner of the focus area closest to Moora has resulted in reduced groundwater levels. The studies highlight the need to manage local scale abstraction to avoid adverse effects on water quality, water supply and groundwater-dependent ecosystems. Water allocation limits in the broader Dinner Hill/Gingin area will be reviewed again following the completion of Department of Water and Environmental Regulation's East Midlands project.
The Dinner Hill groundwater allocation statement defines the water availability and the rules to access it. The Department of Water and Environmental Regulation website has relevant reports, more information on water allocations and the rules and process of the water register.