A new framework for assessing clean water supply

As climate change and a growing global population are putting increased pressure on our already stressed water resources, improving the ways we assess and manage clean water supply has quickly become one of our generation’s most pressing issues. While the emergence of new water treatment- and extraction techniques has allowed previously unobtainable water resources to be made accessible, there are still large quantities of water, while available at first glance, are unavailable from an allocation perspective. This includes water needed for the continued maintenance and operation of vital ecosystems services, water under quality constraints, and water deemed to be technically unfeasible or economically too expensive to obtain.

 

In this study we introduce a new flexible framework for assessing the total clean water supply for a predefined area and time period. We first defined the stored volume of water within the area through the spatial delineation of relevant water bodies, for which the maximum capacity and current storage was calculated. Next, a water budget was constructed on the basis of the stored volume and involving the assessment of societal and environmental needs within the area, local priorities, and constraining factors, including water under quality constraints and technical constraints. We then assessed the difference between the total allocated volume of water and actually water usage to account for and to identify areas of potential reuse and/or targeted measures. Finally, the total reclaimed and reusable water supply at the end of the period was assessed accounting for any legal and regulatory constraints, as well as any potential additional losses due to evapotranspiration. This finally resulted the quantification of  “clean water supply”.

 

To test the performance of the framework, a case study was carried out in the Goulburn River catchment, Australia, over the period of July 1^st, 2023, and June 30^th, 2024. Preliminary results show the potential of combing hydrological assessments with detailed data on water usage, water quality and technical constraints to better support water management and decision making. Furthermore, we found that of the total storage of 3.67 km³ available at the start of the period, roughly 50 % (1.88 km³) were either left unused or unclaimed at throughout the period. Of this, 0.09 km³ (5%) were removed to account for losses due to evapotranspiration. Next, a total volume of 1.73 km³ (92%) in the form of carryover rights and storage requirements were removed from the assessment, resulting in a mere 0.06 km³ (3%) of the remaining water were categorized as “Available clean water supply”.  While this suggest that there is a misconception of clean water supply in the Goulburn River catchment, more importantly the result of the assessment suggests that the framework to a great extent can be used to assess a wide range of technical, qualitative, and managerial constraints, while at the same time tracking water usage. This combined with the possibility to adjust both the spatial and the temporal aspects, suggest that the framework could be useful for clean water supply calculations throughout multiple regions around the world.