The North Burdekin Water Board (NBWB) came into existence in 1965 with the South Burdekin Water Board (SBWB) being established the following year in 1966. The Boards were established in response to critically declining groundwater levels brought about by the combined effects of a major increase in the area assigned to sugar cane and several years of inadequate natural replenishment resulting from drought conditions at that time.
A study of the geology of the 622km2 Delta showed a composition of deltaic sediments resting on an old granite surface. Test drilling revealed an extensive aquifer system which (when full) would represent a storage in excess of 1.23 million megalitres. A further study of the aquifer system deemed it possible to artificially replenish this underground basin and thus, the vision to utilise this rather unique storage was born.
Every major river system has an aquifer of some kind; the Burdekin River has one of the largest coastal aquifers within Australia. The Burdekin Delta has managed its resource wisely through replenishment activities provided exclusively by the two former Burdekin Delta Water Boards. Lower Burdekin Water is continuing to artificially replenish the Burdekin delta groundwater resource within its respective water area, which was the original charter of the former North and South Burdekin Water Boards.
At the time, the concept of recharge on the scale envisaged was unique in Australia as was the self-funding and local management aspects of the proposal. Today the Board remains an autonomous statutory groundwater resource management authority, responsible for the economic and environmentally sustainable management of the groundwater resource within its proclaimed water area.
The Board operates on a user-pays cost recovery basis spending $1 million dollars annually to replenish and manage the aquifer. The sugar industry continues to be the predominant agricultural crop grown within the Burdekin Delta, with principal revenue derived from the sugar industry by way of assessable area charges, a firm partnership between the growers and millers of sugar cane now exists, such that the Miller contributes finance equivalent to one-third of each growers annual assessable area charge, there are no concessions for those farmers who grow other crops.
The success of the Board's operations over the past 40 years can be attributed to the mechanisms that the Board employs to ensure the sustainability of the aquifer. These mechanisms include:
Direct recharge of the aquifer through artificially constructed soakage pits, where water pumped from the river is diverted into these pits and percolates into the aquifer.
Recharge through the bed and banks of natural watercourses, which form a large part of the Board's distribution system.
Direct supply of water to irrigators, thereby conserving groundwater and lessening the need for artificial replenishment.
Maintaining water levels within the aquifer and ensuring the quality of water is maintained, will provide not only sustainable practices, but environmentally beneficial practices
For the last 40 years the South Burdekin Water Board has managed the aquifer in terms of quantity and quality. The history behind the Board, demonstrates how a well managed natural aquifer can provide sustainable water supplies for domestic, stock and agricultural purposes, and through good management and past experiences, ensure this natural resource will continue to.
The Burdekin Delta is an 'Open Aquifer'. Groundwater of good quality is contained against the sea with constant leakage to that environment. The Delta Aquifer is subject to six processes which affect the water level:
Leakage to the ocean.
Rainfall is an uncontrolled event which provides natural benefit directly to crops and then percolates through the soil to the aquifer.
Groundwater extracted from the aquifer is used for crops as well as domestic water supply. Private bores lift water to the surface and on farm. Local Authority (Council) bores provide town water and industrial supply through reticulated infrastructure.
Rocks Pump Station
River pumping is a Board activity to lift water from the Burdekin River for distribution throughout the defined area. Surface water is directed into 'recharge areas' or supplied to Farmers which compliments replenishment by 'water spreading'.
Recycling irrigation tail water on farm is a limited practice due to the nature of delta soils and leakage of retention ponds to the aquifer.
Permeability of delta soils assists in the retention of irrigation excess, providing cheap drainage to the aquifer of water not taken up by the crop or transpiration process.
Groundwater moves freely through streams in porous areas of the aquifer, however texture of sedimentary deposits do vary considerably from pure coarse sand with large stones to heavy clay.
The delta area within tidal limits is a good example of progression of the flood plain where heavy clay mud islands carry vegetation and the creeks in between are gradually silting up with outflow of mostly porous sandy material. LBW has areas alike to old mangrove islands below top soil which generally have poor quality groundwater and almost no bore field potential.
Groundwater quality overall is generally good and is suitable for irrigation of sugar cane and most domestic purposes. Zones of differing quality exist and are the result of either leakage of higher salinity groundwater from adjacent bedrock on the southern boundaries or from old seawater contained within the sediments as part of a 'natural saltwater wedge'.
The district's early settlers described our underground water supply as "liquid gold" and its value to the district to date, remains high.
The Burdekin District is the largest cane growing area in Australia. Its future, and indeed the future of the Board, now depends largely on the adoption of a programme to maintain and manage this precious resource.