Managing groundwater levels in the face of uncertainty and change: a case study from Gnangara

Abstract

The Gnangara Groundwater System meets about 50% of all water needs for the Perth–Peel region of Western Australia (population 1.7 million). Much of the water is contained in an unconfined aquifer which occurs in coastal sand dunes and supports ecologically-important throughflow wetlands. The system has been subject to significant climate change since about 1975, although the persistent and unidirectional nature of the change was not recognised for some time. As well as climate, groundwater levels are affected by land use (e.g. plantation forestry, urbanisation) and land management (e.g. how plantations and stormwater are managed) as well as by the amount of groundwater abstraction from each of several inter-connected aquifers. Land, water and forests are managed by different government agencies with their own policy objectives. Maintaining groundwater levels within an agreed range of values to protect the wetlands requires informed and early adaptation by these agencies as well as a supportive community. Adaptation was hampered because there was little or no experience of managing groundwater for climate change and the causes of declining levels were neither clear nor agreed. Even when target water level decisions were agreed, their achievement required the cooperation of parties with different priorities. This paper examines some of the lessons learned from this experience and the current approach to manage the land, water and forest resources to meet multiple objectives in a system that is undergoing transitional change rather than reaching a new equilibrium. Climate change impacts have been progressive and the concept of a system that can respond in a resilient manner after a temporary perturbation is not an appropriate concept in this example. Climate adaptation involves significant social and institutional change as well as biophysical changes to make the most of a changing system.

Phreatophytic vegetation responses to groundwater depth in a drying mediterranean‐type landscape

“…A suitable data set, covering 35 yr, exists for the vegetation associated with shallow groundwater systems in south‐western Australia, recognized as one of the global regions where water resources have been most affected by climate change (McFarlane et al. ). These superficial aquifers have been receding progressively during the last 35 yr due to groundwater abstraction, changes in land use and reduced rainfall, and this has been associated with changes in vegetation, particularly at shallow depths to water table (Froend & Sommer ; Sommer & Froend ).…”

“…The rate at which vegetation composition and species abundance responds to hydroclimatic changes is often slow (Pennington 1986;Davis 1989;Huntley 1991) and therefore long sequences of vegetation assessment are required to determine the persistence of hydrotype association with groundwater availability and alternative vegetation states. A suitable data set, covering 35 yr, exists for the vegetation associated with shallow groundwater systems in southwestern Australia, recognized as one of the global regions where water resources have been most affected by climate change (McFarlane et al 2012). These superficial aquifers have been receding progressively during the last 35 yr due to groundwater abstraction, changes in land use and reduced rainfall, and this has been associated with changes in vegetation, particularly at shallow depths to water table (Froend & Sommer 2010;Sommer & Froend 2011).…”

Linking Eco-Energetics and Eco-Hydrology to Select Sites for the Assisted Colonization of Australia’s Rarest Reptile

“…All current release sites are expected to provide increasingly marginal habitat because of decreasing winter rainfall and increasing groundwater abstraction [12]. For example, constant pumping of bore water has been necessary to maintain water levels at TSNR since 2003, and this site, which formerly provided good habitat for P. umbrina in the mid-1960s, now recruits very few juveniles into the population.…”

Gestión de áreas protegidas de agua dulce, ríos, humedales y estuaries

“…No obstante, el potencial de adaptación de los GDE puede verse limitado por cambios catastróficos (y en gran medida irreversibles) en la disponibilidad de las aguas subterráneas, como la mortalidad generalizada de la vegetación dependiente del agua subterránea (freatofítica) por la extracción de aguas subterráneas en épocas de sequía (Sommer y Froend, 2011). En respuesta, las agencias de gestión evaluaron las amenazas contra la vegetación freatofítica (Barron et al, 2013) y se restringió el bombeo de aguas subterráneas cerca de ecosistemas de humedales vulnerables (McFarlane et al, 2012). Para evitar tales escenarios, se requiere integrar la gestión de la cuenca de captación y equilibrar las demandas de agua con la conservación.…”