Eutrophication and Sedimentation Patterns in Complete Exploitation of Water Resources Scenarios: An Example from Northwestern Semi-arid Mexico

摘要: Water requirements to supply human needs lead water stakeholders store more during surplus periods fulfil the demand – not only scarcity periods. At reservoirs, mostly those in semi-arid regions, level then fluctuates extremely between rises and downward one single year. Besides of management implications, changes on physical, chemical biological dynamics these drawdown refilling are little known yet. This paper shows results, throughout a year, solids, nutrients (N P), chlorophyll-a, sedimentation dynamics, when former policy was applied reservoir from Northwestern Mexico. sinusoidal trend impinged thermal stratification mixing, modifying nutrient cycling primary producer responses. According nitrogen phosphorus concentration as well mesotrophic, becoming hypertrophic drawdown. Nutrient concentrations were high (1.22 ± 0.70 0.14 0.12 mg P l−1), increasing lowering N:P significantly study period, although no intensive agricultural, urban development, neither industrial activities take place watershed. suggests recycling complex mechanisms, including release sediment–water interface main pathway shallowness, at same time mineralization, increases. Outflows controlled availability ecosystem while organic matter depended river inflows. As other subtropical aquatic ecosystems, limited productivity (Spearman correlation R = 0.75) but chlorophyll-a seasonal pattern showed an irregular trend, prompting no-nutrient related limitants. Shallowness induced homogeneous temporal quality. observed variability mainly explained statistically by solids (mineral organic), flows (62.3%). Annual rates total ranged 11.73 16.29 kg m−2 year−1 with comprising around 30%. ratio could be expected resuspension dominated ecosystem, spatially inverse bottom sediments. Distance inlet into reveals marked spatial heterogeneity solid sedimentation, showing system dependence inflows supporting pathway. Accretion (2.19 0.40 cm year−1) hydrological decreased distance input. Total sediment accumulation (9,895 tons km−2 denotes siltation serious environmental problem reservoirs possibly operational procedures.