The influence of fish-rearing ponds on surface water eutrophication

摘要

The thesis discusses the problem of eutrophication in the aquatic environment, which occurs due to excessive intake of nutrients, i.e. nitrogen and phosphorus, which results in excessive algae growth. In our case we treat rearing ponds, as a source of phosphorus for downstream recipients. Ponds are hydraulically connected. In addition to high amount of phosphorus from the environment, fishing family also adds phosphorus with the feeding in the second and fourth pond. In the five rearing ponds, we first performed the basic physical and chemical analysis of water and produced simple Vollenweider's model. Phosphorus in the model stands as the only limiting factor for eutrophication. With the model we attempted to quantify and assess the impact of the introduction of phosphorus in the ponds, but also in the aquifer in which the water from the ponds flows into. We compared the results of the analysis of water and the model with each other and placed them in state of trophic rearing ponds. By comparison with the model and measurements, trophic states differ a bit in the third pond. In all other ponds, the trophic states are the same. The model results show, that the first and the second pond are in eutrophic state and the fourth pond is in mesotrophic state. Measurements show that the third pond is in eutrophic state, while the model shows mesotrophic state. The highest concentration of phosphorus is in the last pond as expected. The measurements show eutrophic state, as confirmed by the model. The last pond contains high quantity of total phosphorus. Due to excessive concentrations of total phosphorus, during the summer, the process of eutrophication appears. This is the reason, why phosphorus from the last pond affects downstream on first recipients and causes the eutrophication process.