KOPPRIO German Adolfo
congresos y reuniones científicas
An ecohydrological approach to manage an unstable coastal lake in semiarid grasslands of Argentina
KOPPRIO, G. A.; FREIJE, R. H.; LARA, R. J.
Figueira da Foz
Simposio; Integrative tools and methods in assessing ecological quality in estuarine and coastal systems worldwide; 2010
IMAR-Institute of Marine Research (U.Coimbra) and CO-Centre of Oceanography (U.Lisbon)
The pampean lakes have underwent the effects of increasing rainfall and severe floods during the last 3 decades. Lake Chasicó belongs to an endorreic basin particularly sensitive to hydrologic alterations, and responded with dramatic changes in extension and salinity. Further, the moderate salinity in the 1980s favoured a high fish biomass and Lake Chasicó was declared a nature reserve in order to protect fish population. However, since 2007 a rigorous drought began to affect the region, severely damaging the agricultural structure of the semiarid grasslands, with high cattle mortality, loss of vegetation coverage and soil erosion in the south of the Pampas. The drought period worsened the natural eutrophic state of water bodies and increased their salinity. Pampean lakes suffered fish mortality likely due to impacts of eutrophication such as toxic cyanobacteria blooms or anoxia. In order to manage Lake Chasicó, during the wet period, some projects had proposed the creation of a channel connected to the Bahía Blanca estuary to prevent floods. This low-cost solution was officially favoured by Municipal authorities. However, an alleviation channel alone lacks the hydraulic tools to regulate lake water salinity and nutrient concentrations during drought periods. The construction of a dam would help regulate lake level and salinity through controlled water release. Further, a combination with wetland creation in the Chasicó River basin would allow nutrient regulation, plant biomass production, control of toxic algal blooms in the lake and habitat creation for endangered fauna. However, the last two projects imply flooding of agricultural land, indemnifications and an unknown risk of disease vector proliferation (e.g. mosquitoes). The construction of a dam and a channel would combine the benefits of both and supply water Bahía Blanca city, which suffers recurrent shortages. Nevertheless, although this project was favoured by the State Government, it was not supported at Municipal level. Thus, in order to avoid a fragmented water management, an integrated project involving stakeholders, central and local governments, academia, private sector and civil society is urgently needed at transboundary basin level.