Seasonal Stratified Characteristics of Water Bodies in a Sub-deep Reservoir

PurposeIn order to explore the thermal stratification structure, water quality response characteristics and their formation mechanism of a subtropical sub-deep reservoir.

MethodWe conducted on-site measurements and laboratory tests on the vertical changes of water temperature, dissolved oxygen (DO), pH, and chlorophyll a in the Changtan Reservoir (in Taizhou City) in 2018. Then the seasonal physical structure characteristics of thermal stratification were analyzed, and its impact on water quality was discussed.

ResultChangtan Reservoir has a three-layer stratification period from May to June, and a two-layer stratification period from July to November. The relative water column stability (RWCS) was the highest (521) in August, the thermocline was the largest in August, accounting for 85.19% of the water depth, and the intensity was the largest (0.70 ℃/m) in June. The vertical distribution of DO showed a 3-peak characteristic from July to September, and a 2-peak characteristic from October to November. The surface water was weakly alkaline from May to September, and was neutral in other months, the bottom water was weakly acidic from July to November, and was neutral in other months. The vertical distribution of chlorophyll a in December, January and February, and June was more discrete, and other months showed a single peak characteristic.

ConclusionThe thermal stratified structure of Changtan Reservoir presents a single-cycle mixed pattern throughout the year, and presents structural characteristics different from those of deep-water reservoirs during the stratified stable period. The special layered structure of the sub-deep reservoir has a certain special effect on the vertical changes of DO, pH and chlorophyll a.