Implications of water resources management on the long-term regime of Lake Garda (Italy)

• Published in: Journal of environmental management Vol. 301; p. 113893
• Main Authors: Hinegk, Luigi, Adami, Luca, Zolezzi, Guido, Tubino, Marco
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-01-2022
• Subjects: European perialpine lakes; Lake levels and outflows; Lake regulation; Multi-decadal analyses; Water resources management; Water resources management; European perialpine lakes; Multi-decadal analyses; Lake levels and outflows; Lake regulation
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2021.113893

Amongst different climatic and anthropogenic drivers, water resources management can cause massive changes to the natural regime of a lake after its regulation, thereby affecting the quantity and quality of water intended for satisfying the multiple basin water requirements. Here, we investigate the multi-decadal variation of the water levels and outflows of Lake Garda, the largest in Italy, where the dam operational rules and the related basin water needs heavily altered the annual and seasonal trend of the lake regime since its regulation in 1951. Daily lake levels and outflows were first collected and digitized for the period 1888–2020, thus providing a unique database of 133 years that allowed a consistent comparison between natural and regulated periods. Statistical analyses highlighted a significant change of the inter-annual trend of the lake outflows, which passed from upward to downward after regulation, against a constant increasing trend of the water levels. Conversely, water levels showed a more remarkable shifts on a seasonal scale if compared to the outflows, revealing the influence of summer and winter basin water needs. Additional analyses on the inter-annual variation of the main downstream water demands regulated by the dam, i.e. the irrigation, hydropower and fluvial ecosystem requirements, outlined their relevance in changing the lake regime, influencing dam operational policies, which progressively limited the share of water released for ecosystem integrity. A comparison between the lake levels and outflows recorded for the pre-regulation and post-regulation periods of some selected European perialpine lakes finally highlighted different effects on the lake regime, drawing attention to the importance of defining the role of the dam operational policies within the current scenario of climate change and changing water demands.
•Dam management and water basin needs changed Lake Garda regime from 1888 to 2020.•Conversely to lake levels, outflows passed to a significant decreasing trend after regulation.•Massive seasonal shifts of the lake levels reflect summer and winter basin water needs.•Dam management has limited the share of water releases to sustain river integrity.•Comparison with other European perialpine lakes draw attention to future management policies.