Open Cut » Environment
Repeated flooding of the tailings dam at Mangoola mine under project C27009 led us to apply for additional funding to investigate how we could better produce flood adapted plants for the long term dewatering of the dam. The need to develop procedures to aid adaptation and survival of plants during the extreme hydrological fluctuations on tailings dams has become necessary.
Six species were tested for survival and physiological responses during flooding at different levels in crates and transferred to the dam to determine survival and function should a flood occur. Flooding in crates were at levels up to 200mm above the soil.
Several contributing factors to the responses observed were identified that advance the knowledge of both the basic and applied science of these species, including elucidating their capacity to contribute to the 'Vegetative Water Pump'. Most species selected proved to have hydathodes in the epidermis of their leaves. These glands allow water to always leave the plant, day or night, down the water potential gradient to the air. The consequences of this, is that stomatal control of water loss, typically seen in terrestrial plants, e.g., related to water stress, is lost. Thus, hot, or drying winds can affect their leaf survival if conditions are inappropriate. Another consequence of loss of stomatal control is that there is a disjunct between transpiration rate and photosynthetic activity in many of the species studied. In a terrestrial species it would be expected that these processes are tightly linked, however, the hydathodes cause this disjunction.
The focus of this and project C27009 was to establish a 'Vegetative Water Pump' to enable drying of tailings dams and to make them safer. The water pump has been clearly shown to be active in both projects. An aim now is to expand its application across tailings dams in Australia with a current focus on the coalfields of Queensland and New South Wales. Future studies need to expand the species available to further broaden the range to cover other coal fields including the Bowen Basin and Western NSW.