Socio-hydrological water balance for water allocation between human and environmental purposes in catchments

Rebalancing water allocation between human consumptive uses and the environment in water catchments is a global challenge. This paper proposes a socio-hydrological water balance framework by partitioning catchment total evapotranspiration (ET) into ET for society and ET for natural ecological systems, and establishing the linkage between the changes of water balance and its social drivers and resulting environmental consequences in the Murray– Darling Basin (MDB), Australia, over the period 1900–2010. The results show that the 100-year period of water management in the MDB could be divided into four periods corresponding to major changes in basin management within the socio-hydrological water balance framework: period 1 (1900–1956) – expansion of water and land use for the societal system, period 2 (1956–1978) – maximization of water and land use for the societal system, period 3 (1978–2002) – maximization of water use for the societal system from water diversion, and period 4 (2002–present) – rebalancing of water and land use between the societal and ecological systems. Most of management changes in the MDB were passive and responsive. A precautionary approach to water allocation between the societal and ecological systems should be developed. The socio-hydrological water balance framework could serve as a theoretical foundation for water allocation to evaluate the dynamic balance between the societal and ecological systems in catchments.