Determining the causes for the dramatic recent fall of Lake Prespa (southwest Balkans)

Abstract

Mediterranean lake-wetland systems are threatened by climate change and intensive human impacts. Individual lake responses to these threats are poorly known but urgently required to steer preservation strategies. The dramatic water-level fall (~8 m since 1987) of Lake Megali Prespa endangers this global biodiversity hotspot and the wider catchment's water resources. Annual lake fluctuations are found to be strongly related to wet-season (Oct.-Apr.) precipitation variability, which is linked to the North Atlantic Oscillation. The lake primarily adjusts to sustained inflow changes through amending surface evaporation. Cumulative water abstraction since 1951 (~19 × 10 6 m 3 /year:~0.006% of lake volume) explains~70% of the long-term decrease in surface evaporation; climate variability explains the remainder. Persistent low lake levels after 1995 are caused by water abstraction. Compared to 1952Compared to /53-1977, the period 1978/79-2003/04 experienced significant decreases in wet-season precipitation, snowfall and discharge; the number of very dry years increased. ARTICLE HISTORY

The Impact of Warming and Nutrients on Algae Production and Microcystins in Seston from the Iconic Lake Lesser Prespa, Greece

“…Hence, in deciphering what should be controlled and how to mitigate eutrophication, a thorough diagnosis, or system analysis, is required [ 38 ]. In that view, also the observed decrease in wet-season precipitation and increase in number of dry years can be expected to further aggravate eutrophication symptoms [ 6 ]. Those climate change effects probably will exert a stronger impact on water quality deterioration than a direct warming effect on the cyanobacteria as shown from our warming incubations.…”

“…Guanotrophication is already reflected by the excessive chlorophyll-a and nutrient levels which have been measured within the small isolated Vromolimni Pond (0.25 km 2 ), where large mixed populations of pelicans and cormorants breed annually [ 1 , 5 ]. In the Prespa basin altered rainfall patterns and ongoing water abstractions are also expected to speed-up eutrophication [ 6 ]. The resulting over-enrichment of the water with nutrients is leading to cyanobacterial blooms and in a recent study, the occurrence of occasionally high microcystin concentrations (MC) in the lake—as well as MC in the tissue of carp, pelicans and otters—was determined [ 5 ].…”

Reconstructing absolute water-level variability of Lake Prespa (SW Balkans) during the Medieval Climate Anomaly and ‘Little Ice Age’ from a prograding beach ridge complex

“…Significant lake highstands (>851m) after AD ~1650 (ridge 2) and AD ~1790 (unit Q5, ridge 1) may correlate with two ‘LIA’ phases with lower temperatures as registered in the annually laminated stalagmites in N Italy (Frisia et al, 2003), from AD1650 to 1713 and AD 1798 to 1840, which coincide with low solar activity (Maunder Minimum and Dalton Minimum). Low lake levels since the 1980s were caused by water abstraction compounded by a long drought episode from 1987 to 1995 (Van der Schriek and Giannakopoulos, 2017).…”

“…Several studies have shown the strong influence of the NAO on (declining) winter precipitation and snowfall over the previous decades in the Pindos and Rhodope mountain chains (SW Balkan), including the wider Lake Prespa catchment (Grunewald et al, 2009; López-Moreno et al, 2011; Popovska and Bonacci, 2007). NAO-forced wet season precipitation has been shown to drive multi-decadal water-level variability of Lake Prespa (Van der Schriek and Giannakopoulos, 2017). Given the strong extra-regional (North Atlantic) signal in the lake-level movements, which drives regional wet season precipitation, reconstruction of past Lake Prespa water-level variability will inform on hydro-climatic changes in the SW Balkan mountains.…”

“…The total annual lake variability is ~0.5 m, with maximum levels in May/June (related to snow melt) and minimum levels in October/November. NAO-forced wet season precipitation drives multi-annual lake-level variability (Van der Schriek and Giannakopoulos, 2017).…”