Nahua reservoir is an important water resource for supplying drinking water to the Tainan area and a part of Kaohsiung in Taiwan. In recent years, Nanhua reservoir suffers eutrophication problems as many other reservoirs in Taiwan. In order to study eutrophication problems in reservoirs, a three-dimensional hydrodynamic and water quality model has been constructed using the FVCOM (Finite Volume Coastal Ocean Model) model to simulation the hydrodynamics, the nutrient dynamics and the phytoplankton growth in the Nanhua reservoir.
The modeling of 3D hydrodynamics is the basic module dominating the circulation in the reservoir. The 3D eutro-dynamics are also calculated by the water quality module, which includes the dynamic variations of chlorophyll-a (Chl-a), dissolve oxygen (DO), carbon biological oxygen demand (CBOD), ammonia nitrogen (NH3-N), nitrate nitrogen (NO3-N), organic nitrogen (ON), phosphate (PO4) and organic phosphorus (OP).
The model was first calibrated with the data measured in 2007 and, then, verified with the 2008 data. The model results are in reasonable agreement with the field measurements, both in the calibration and the verification phases. The water level variations are influenced by daily supply for the drinking water treatment and the inflows from the catchment and from Chiashian aqueduct during the dry season in spring. Nutrients are mainly carried into the reservoir through these routes. The residence time in the reservoir and the phytoplankton response with the nutrient loads are calculated.
The model results indicated that phytoplankton growth is limited by low temperature and long residence time during the winter. The chlorophyll levels are getting higher from spring through out summer, which is due to enough sun lights and high nutrient loads carried by the catchment runoff. Surface temperatures are higher then the bottom layers causing stratification that worsen the eutrophication problems.
Besides the comparisons by hydrodynamic and water quality parameters, the Carlson Trophic State Index (CTSI) has been calculated to categorize the eutrophication levels in the reservoir, which have shown good agreement with the CTSI calculated from EPA sampling data. Therefore, the model can be used as a tool for water quality management in the Nanhua reservoir.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0806109-132813 |
| Date | 06 August 2009 |
| Creators | Su, Chih-yuan |
| Contributors | Jimmy C. M. Kao, Jason C. S. Yu, Lei L. Yang |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0806109-132813 |
| Rights | off_campus_withheld, Copyright information available at source archive |
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