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 Sự phú dưỡng hoá cho hồ chứa đục nhiệt đới. Mô hình toán cho hồ chứa Cointzio, Mexico
Tác giả hoặc Nhóm tác giả:  Doan, P.T.K., Némery, J., Schmid, M., and Gratiot, N
Nơi đăng: Ecological Modelling for Ecosystem Sustainability in the context of Global Change; Số: October 28-31;Từ->đến trang: 1;Năm: 2013
Lĩnh vực: Môi trường; Loại: Báo cáo; Thể loại: Quốc tế
TÓM TẮT
ABSTRACT
The overall water quality of lakes and reservoirs continues to deteriorate in many regions of Mexico. The Cointzio reservoir, located in the southern part of the Mexican Central Plateau on the Trans-Mexican Volcanic Belt (TMVB), is no exception. This turbid tropical reservoir behaves as a warm monomictic water body (area = 6 km2, capacity 66 Mm3, residence time ~ 1 year). It is strategic for the drinking water supply of the city of Morelia, capital of the state of Michoacán, and for downstream irrigation during the dry season. The reservoir is threatened by sediments accumulation and nutrients originating from untreated waters in the upstream watershed. The high content of very fine clay particles and the lack of water treatment plants lead to serious episodes of eutrophication (up to 70 μg chl. a L-1), high levels of turbidity (Secchi depth < 30 cm) and seasonal periods of anoxia (from May to October).Based on intensive field measurements in 2009 (sampling in the watershed, deposited sediment, water vertical profiles, reservoir inflow and outflow) we presented an integrated study of the hydrodynamics and biogeochemical functioning of the Cointzio reservoir. Water column measurements of temperature, TSS, DO, chlorophyll a, carbon and nutrients undertaken during the year 2009 were used to assess internal cycling in the reservoir.To complete field data analyses we examined the ability of some vertical one dimensional (1DV) numerical models (Aquasim biogeochemical model coupled with k-ε mixing model) in order to (i) reproduce the main biogeochemical cycles in the Cointzio reservoir and (ii) assess scenarios of nutrients (P and N) and eutrophication reduction in the coming decades. The k-ε model reproduced nicely the low to moderate temperature stratification which characterizes this turbid reservoir. The Aquasim model was able to reproduce the main patterns of DO, nutrients and chlorophyll a during the year 2009. The different simulations pointed out the negative long-term impact of global warming. By the end of the century (2090), an increase of air temperature as high as 4.4°C was predicted from Global Circulation Models. When coupled with a dry hydrological year, this scenario could lead to critical conditions with a severe depletion of DO and important blooms of chlorophyll a (up to 94 μg L-1). Various simulations showed that a drastic reduction of nutrients input (by 90%) would be required to significantly reduce chlorophyll a concentrations. If such mitigation measures are adopted, the maximum peak of chlorophyll a would reduce significantly, from 94 μg L-1 to 40 μg L-1after a five-year period of efforts.
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