Research project Water quality impacts water scarcity - accounting for freshwater salinity on water scarcity
This project aims to target the major scientific challenge of assessing main drivers of freshwater salinization and quantify present and future salinity-driven water scarcity in basins around the world. This is needed because elevated salinity of freshwater resources is a common water quality issue, which could strongly affect water use and water scarcity.
Because no studies have accounted for salinity impacts on water scarcity in critical global drylands, current water scarcity estimations risk being severely underestimated. This study will achieve the aim by; 1) conducting the first coherent assessment of present freshwater salinity in global drylands; 2) combining water- and mass balance approaches to develop projections of future changes in water quantity and salinity, accounting for impacts of agricultural development and climate change, and; 3) estimate where and to what extent salinity-driven water scarcity will occur during the 21st century, through novel development of a data-driven modelling framework, considering salinity thresholds for different human water uses and ecosystems.
Project description
The overall aim of this project is to assess main drivers of freshwater salinisation and quantify salinity-driven water scarcity in global drylands. Increasing salinity of freshwater resources is a main cause behind water quality deterioration globally. Such salinization is in turn frequently driven by agricultural development and climate change, which cause evapoconcentration of salts as evapotranspiration increases and remaining water quantities decrease. Although many studies have highlighted the need to account for water quality in water scarcity assessments, few attempts have been made to quantify salinity impacts on water scarcity, and no studies have assessed critical global drylands. Excluding such water quality aspects is expected to cause severe underestimations of present and future water scarcity.
The specific objectives of the project are to:
1) Combine and interpret global datasets in new ways to conduct the first assessment of current salinity levels of different parts of the surface water component (rivers, lakes, reservoirs) in global drylands.
2) Quantify salinity-driven water scarcity in global drylands, through novel development of a data-driven modelling framework, considering salinity thresholds for different human water uses and ecosystems.
3) Develop projections of future changes in water quantity and salinity in global drylands, accounting for impacts of agricultural development and climate change.
4) Estimate where and to what extent salinity-driven water scarcity will occur during the 21st century and compare this to water scarcity projections without consideration of salinity.
Specifically, a novel data-driven modelling framework will be developed, where salinity changes due to evapo-concentration effects will be quantified (Box 1). This will be done through novel couplings of globally applicable water and mass balance approaches, assessing the impact of both agricultural development and climate change on changing evapotranspiration and water volumes. From this, evapo-concentration of salt is proportional to decreasing water volumes (Box 1, approach 3, illustrated conceptually in b).
This framework will allow novel large-scale assessments of future freshwater salinisation in global drylands. This action will then develop further and tailor to salinity, the first globally applicable water quality-driven water scarcity framework, where thresholds for different sectoral water uses are explicitly accounted for7 (Box 1, approach 2). This framework has so far mainly been focused on thermal pollution and its impact on water scarcity for the energy sector, using globally available projections of water temperature. Until now, addressing salinity-driven water scarcity in global drylands has not been done.
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Box 1. Conceptualisation of the observation-driven modelling framework developed for assessing freshwater salinisation and salinity-driven water scarcity. The top part of the figure (a) shows the previous traditional approach for estimating water scarcity (1) and the new approach (2) will here be further developed and tailored specifically to salinity as a water quality component and its future changes due to evapo-concentration effects (3). Part (b) shows a conceptualisation of how future agricultural development and climate change act as main drivers of increasing evapotranspiration and associated evapo-concentration of salts in shrinking water volumes. Panel (c) highlights a current example of salinity-driven water scarcity that the Experienced Researcher is currently working on; the drying of Lake Urmia (Iran) due to climate change and irrigation expansion and associated salinity-driven water scarcity. This framework will (as illustrated in part b of the figure), provide a first globally applicable approach for quantifying the combined effects of climate and agriculture on changing water quantities and salinity and estimating their joint impact on salinity-driven water scarcity.