This essay briefly reviews perceived values of stygofauna and benefits of their inclusion in hydrogeological surveys of groundwater, and summarises the legislative and policy framework for stygofaunal surveys. Although focused on Australia, the issues discussed are of broad, international concern. A staged approach to surveys is advocated where investigations progressively increase in complexity. This aims to overcome the current paradox of omitting stygofauna from groundwater monitoring because there is insufficient information for the interpretation of survey results — yet, if stygofauna are not sampled, then the information will never be collected to address the knowledge gaps.

As demand for consumptive use of groundwater escalates, the need for careful management becomes more pressing. Water reforms in Australia require explicit recognition of environmental needs in water resource plans, but subsurface groundwater dependent ecosystems (SGDEs) are rarely provided for. The ecological values of these sequestered ecosystems are not well documented and are readily overlooked. We review the biodiversity, ecological processes and ecosystem services of Australian SGDEs and highlight the ecological relevance of their connectivity with other ecosystems. A lack of attention to SGDEs in groundwater plans risks inadequate provision for environmental water requirements with probable impacts on ecological values, water quality and ecosystem goods and services in SGDEs and connected ecosystems. We suggest an ecohydrogeological approach to understanding the implications of anthropogenic disturbance on SGDEs based on their connectivity to other ecosystems and aquifer permeability. As well as a template for comparative research on the biogeochemistry and ecology of SGDEs in Australia and overseas, this conceptual tool has potential application in conservation planning, water resource assessment and environmental impact assessment.

Demand for groundwater is accelerating in Australia and globally. The development of guidelines to ensure ecologically sustainable use of groundwater lags behind this demand, although the broad policy and planning base for environmental water requirements is in place in Australia. Environmental water requirements in aquifers are the groundwater regimes needed to maintain or restore ecological processes and conserve biodiversity. The existing framework for environmental allocations for aquifers requires identification of groundwater dependent ecosystems and estimation of their water requirements in terms of: level (in unconfined aquifers) or pressure (in confined aquifers), discharge flux, and water quality. Of all groundwater dependent ecosystems, aquifer ecosystems are entirely groundwater dependent, but details of their biota, ecosystem processes and water requirements are the least known. This study applied the framework for determining environmental water requirements of aquifer ecosystems in a case study of the Peel Valley Alluvium, an alluvial aquifer connected to the regulated Peel River in the north-east Murray-Darling Basin, New South Wales, Australia. Eleven groundwater monitoring bores were sampled to determine whether structural indicators (abundance and taxonomic richness) of the groundwater invertebrate assemblage composition were correlated with aspects of the groundwater regime. Stygofauna (groundwater invertebrates) and physico-chemical variables were sampled quarterly in these bores from July 2006 to October 2007. Data loggers in 10 of the bores recorded groundwater level and temperature hourly for this period. Long-term stream gauge and groundwater level data were used to investigate the relationship between streamflow and groundwater regime, and to assess the degree of hydrological alteration in the river and alluvium after river regulation... A revised framework for determining environmental water requirements in alluvial aquifers is proposed which takes account of the organising principle of connectivity in delivering a compound disturbance regime, and recognizes the significance of scale and of cross-scale linkages between components of the disturbance regime. Given the current limits of distributional and taxonomic knowledge, the structural indicators of faunal assemblage composition appear inadequate to identify environmental water requirements for alluvial aquifers. The conjunctive use of functional indicators of ecosystem processes is recommended. Field-testing and further development of the framework will contribute to sustainable groundwater management, but realization of this goal relies on the collaboration of researchers, policy makers and knowledge brokers.