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Lower Murrumbidgee River floodplain at Yanga NP, Balranald
vegetation that received water in 2005 (right), vegetation that didn't receive water (left) |
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Full Title
Determining watering regimes to protect floodplains under hyper-drought conditions
Contact Person
Darren Baldwin
Project Team
Gavin Rees, Todd Wallace, Jessica Wilson
Funding Body
Department of the Environment, Water, Heritage and the Arts, Commonwealth Environment Research Facilities (CERF) Significant Projects
Duration
March 2008 to December 2010
Outcomes
Details
Summary
Soil moisture is important for facilitating numerous biogeochemical cycles in the soil, which in turn leads to enhanced primary and secondary production on the floodplain. Increased vegetative biomass functions in a positive feedback loop increasing the soils ability to retain moisture. Reduced flooding has resulted in a dramatic decline in floodplain vegetation, leading to a decline in standing litter, soil organic matter and consequently the floodplain soil's ability to retain moisture.
Floodplain ecosystems in the lower-rainfall regions of Australia derive much of their soil moisture from periodic floods. River regulation and over-extraction of water resources has limited the frequency and duration of small to medium floods, imposing a long-term artificial drought regime on floodplains. Because the store of soil moisture is not being regularly replenished by flooding events, they become more susceptible to drought-induced degradation than they would be under natural flow regimes (hence the term 'hyper-drought'). Consequently, the current drought cycle is having a greater impact than would have occurred under pre-regulation flow regimes.
Current projects investigating environmental flows for floodplains have focused on the impact of floods on vegetation, birds and fish. This project will examine the impacts of flooding regime on soil biogeochemical processes, soil biota and how changes in soil health impact ecosystem function. The purpose of the project is to determine if critical thresholds exist in soil condition, which, if exceeded lead to irreversible changes in ecosystem function and stability. These thresholds can be used by floodplain managers to set minimum flooding requirements for restoration of floodplain ecosystems, leading to more efficient use of the limited volumes of environmental water available.
