By: Benedikt Ahner
Understanding and managing water resources can be a challenging task for decision makers and others without a professional background in water studies. Concepts like the blue water footprint aim to make water quantity related issues easier to understand by calculating a water stress index. For groundwater management similar problems exist. Existing global models use grid-based approaches to estimate (ground)water withdrawal and use. While giving a fair overview about water stress on a global-scale, the grid approach gives the impression of a homogeneous data density. Regionally and locally high-resolution statistical data are available, bearing potentials for management and policy-making as well as for refinement and validation of existing global water models.
This study presents a scheme on how to process sub-national water withdrawal and use datasets, specified by source and sectoral use, for (ground)water stress calculations at various scales. The scheme was applied on a dataset for federal states and sub-watersheds in Germany and the respective groundwater stress value was calculated. The groundwater stress calculations indicate high groundwater stress for federal states exceeding 100 %, whereas sub-watersheds show moderate values up to 85 % stress. Sub-watersheds therefore appear as a more suitable spatial unit compared to federal states. The amount of used water with determinable source in a spatial unit highly depends on water import dependence of the respective spatial unit. Information on the spatial unit of origin of transferred waters will lead to a higher accuracy in the estimation of a spatial unit’s groundwater stress based on groundwater use.