CHANGES IN WATER QUALITY IN THE NEWLY IMPOUNDED SUBTROPICAL FEITSUI RESERVOIR, TAIWAN¹

Abstract

Water quality and trophic conditions in the Feitsui Reservoir, a subtropical reservoir, were evaluated with data from a ten‐year data base to depict the impacts of river impoundment upon the chemical and biological characteristics of a reservoir, and to discuss the effects of flushing rate on in‐lake phosphorus concentrations and phytoplankton growth. The results of the investigation showed that during the incipient impounding period, the water quality in the Feitsui Reservoir was significantly affected by internal loadings from submerged vegetation and soil in the flooded area. Studies of the changes in phosphorus compounds indicated that total phosphorus concentration appeared to approach equilibrium after the seventh year of impoundment and that orthophosphate stabilized after the sixth year of impoundment. Concentrations of both phosphorus forms varied seasonally after attaining stability. Nitrogen compounds (NH3‐N, NO3‐N and NO2‐N) approached equilibrium within three years after impoundment. The seasonal variation in carbon was correlated to the number of phytoplankton. The mean value of the N:P mass ratio has remained over 110 since year seven of impoundment (1990), indicating that phosphorus constitutes the potential limiting nutrient in the growth of phytoplankton. The rapid flushing rate (132.11 and 110.43 yr‐1) in Feitsui Reservoir during the first and second impounding stages was a critical factor influencing the phytoplankton growth response to available nutrients.

Effects of mountain tea plantations on nutrient cycling at upstream watersheds

“…The vegetation is primarily composed of secondary-growth, mixed broad-leaf forests dominated by Fagaceae and Lauraceae (Chen, 1993). Approximately 16 % of the FRW is agricultural land with tea plantations covering an area of 1200 ha, or 25 % of all agricultural lands (Chang and Wen, 1997;Chou et al, 2007). In 1986 the FRW was designated as a water resource protection area, followed by the construction of the Feitsui Reservoir in 1987.…”

“…2 for details). Many studies have demonstrated substantial nutrient efflux and sediment production from surrounding tea plantations to the reservoir over the past 2 decades (Chang and Wen, 1997;Lu et al, 1999;Kuo and Lee, 2004;Li and Yeh, 2004;Yang, 2006, 2007;Zehetner et al, 2008;Chiueh et al, 2011;Wu and Kuo, 2012). Yet, to our knowledge none examined both the effects of spatial configuration of agricultural lands on nutrient export and the effects of agriculture on atmospheric deposition.…”

Integrating isotopic, microbial, and modeling approaches to understand methane dynamics in a frequently disturbed deep reservoir in Taiwan

“…Beginning in November 2004, we conducted field sampling at Feitsui Reservoir (FTR) (120.34E, 24.54N; maximal depth 120 m) in northern Taiwan. The FTR is a good model system for deep monomictic lakes in subtropical regions because (1) it is well-protected from anthropogenic pollution and therefore habitat destruction, and its nutrient status is oligotrophic to mesotrophic (Chang and Wen 1997); and (2) the region has substantial interannual variations in winter mixing intensity, degree of summer stratification, and thickness of hypoxic hypolimnion depending on weather conditions (Itoh et al 2015;Ho et al 2016). In addition, typhoons are a major disturbance of summer stratification in this region (e.g., Fan and Kao 2008).…”

The Effect of Developing a Tunnel across a Highway on the Water Quality in an Upstream Reservoir Watershed Area—A Case Study of the Hsuehshan Tunnel in Taiwan

“…The upstream watershed of the Feitsui Reservoir has a long history of tea plantations. Due to the favorable soil and water conservation, vegetation is sustained [2,5,6,14]. The Shihmen Reservoir, adjacent to the Feitsui Reservoir, has similar meteorological and hydrological conditions, and the volume of water currently held is 49.8% of the effective storage capacity.…”