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The Effect of Outflow Depth on Phosphorus Retention in a Small,Hypertrophic Temperate Reservoirwith Short Hydraulic Residence Time
Author(s) -
Duras Jindřich,
Hejzlar Josef
Publication year - 2001
Publication title -
international review of hydrobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.524
H-Index - 52
eISSN - 1522-2632
pISSN - 1434-2944
DOI - 10.1002/1522-2632(200110)86:6<585::aid-iroh585>3.0.co;2-h
Subject(s) - hypolimnion , stratification (seeds) , environmental science , phytoplankton , temperate climate , hydraulic retention time , nutrient , outflow , water column , phosphorus , flushing , residence time (fluid dynamics) , hydrology (agriculture) , sedimentation , epilimnion , sediment , chemistry , oceanography , geology , ecology , eutrophication , effluent , environmental engineering , biology , geomorphology , endocrinology , germination , seed dormancy , botany , geotechnical engineering , organic chemistry , dormancy
Stratification and phosphorus fluxes (input, output, sedimentation, and release from sediments) were studied in České údolí Reservoir (49°43′N, 13°21′E; V – 2.65 × 10 6 m 3 ; A – 1.04 × 10 6 m 2 ; z max – 5.5 m; surface altitude – 314 m a.s.l.) during two summer stratification periods which differed in outlet operation and in hydraulic residence time (1997: surface outlets and 14 days; 1998: bottom outlets and 23 days). Use of bottom outlets resulted in weaker thermal stratification, a less pronounced oxygen deficit in the hypolimnion, and significantly lower P retention (17%) in comparison with surface discharge (42%). Factors apparently contributing to lower retention of P during the use of bottom outlets were: (i) faster flushing of the hypolimnion which intensified longitudinal transport of particles, (ii) more intense P release from sediments due to a lower concentration of nitrate in the water column and to more frequent contact of sediments in the shallows with water of pH >9. During both periods, phytoplankton production was limited only by light, not by nutrients. Phytoplankton biomass was comparable in both years despite some differences in vertical distribution.