Impacts of dam discharge on river environments and phytoplankton communities in a regulated river system, the lower Han River of South Korea

Abstract

To understand the effects of fluctuations in dam discharge due to river environments and phytoplankton communities, we monitored such environments and phytoplankton communities biweekly, from February 2001 to February 2002 and from February 2004 to February 2005, in the lower Han River (LHR), South Korea. The phytoplankton abundance during the dry season was approximately two times higher than that during the rainy season. In particular, fluctuations in diatom assemblages, which constituted over 70% of the total phytoplankton abundance, were affected severely by the changes in the discharge. When a large quantity of water in a dam was discharged into the LHR, the conductivity and the concentrations of total nitrogen (TN), total phosphorus (TP), and dissolved inorganic phosphorus (DIP) decreased rapidly, whereas the concentrations of suspended solids (SS), dissolved inorganic nitrogen (DIN), and dissolved silica (DSi) increased immediately. Time-delayed relationship also revealed that the dam discharge had an immediately significant negative relationship with phytoplankton abundance. On the whole, fluctuations in phytoplankton communities in the LHR were influenced much more by hydrodynamics such as dam discharge than by the availability of nutrients. Thus, the variability in these concentrations usually parallels the strength of river flow that is associated with summer rainfall, with higher values during periods of high river discharge.

Impact of chemical and microbiological water quality on bacterial community assemblage of San Juan River (Sierra del Rosario, Biosphere Reserve, Cuba)

“…In the San Juan River, a negative correlation was observed between dissolved oxygen concentrations and precipitation. Similar results were obtained by Jung et al (2014) On the other hand, there was a positive correlation between nitrite and phosphate concentrations, which were higher in S-3 station compared to S-1 and S-2 stations. A cause that could contribute to these concentrations of nutrients, are the runoff from the aerobic oxidation lagoon that is located between stations S-2 and S-3, which presents ruptures and receives volumes of domestic wastewater that are superior to its retention capacity, as observed during the sampling.…”

Response of the Changjiang (Yangtze River) water chemistry to the impoundment of Three Gorges Dam during 2010–2011

“…The riverine DSi fluxes to the ocean can be drastically changed by damming retention effect (Conley et al, 1993;Humborg et al, 2000Humborg et al, , 2006Beusen et al, 2009;Harrison et al, 2012;Maavara et al, 2014). The dammed reservoirs could retain more nutrients than natural water body (Palmer and O'Keeffe, 1990;Josette et al, 1999;Cook et al, 2010;Bayram et al, 2012) by increasing algae growth in these artificial reservoirs (Schelske et al, 1983;Conley et al, 1993;Gao et al, 2013;Sun et al, 2013;Zhu et al, 2013;Jung et al, 2014) and increasing assimilation and burial of DSi in the riverbed (Conley et al, 1993;Tallberg et al, 2012;Ran et al, 2013a;Sun et al, 2013;Zhu et al, 2013;Domingues et al, 2014). With > 45,000 dams built in the Changjiang catchment (Chen and Huang, 2008), the increased water residence time and corresponding photosynthetic DSi consumption and sedimentation in the reservoirs (Duan et al, 2007) could cause great retention of DSi as well as dissolved nitrogen (DIN) and total phosphorous (TP) Ran et al, 2013aRan et al, , 2013bSun et al, 2013).…”

Hydro-ecological controls on riverine organic carbon dynamics in the tropical monsoon region

“…3b), and that phenomena both happened in the dry season and the wet season. The construction of DGB reservoir in the basin had changed the hydrological situation and largely multiplied the aquatic algae 34–36 , which increased the endogenous sources of DOC in middle reaches. After discharging from DGB reservoir, the riverine DOC concentration gradually decrease towards to the lower reaches (30#~26#), which was likely because that the impact of reservoir gradually weakened.…”