Critical Mixing Depth Models for Eutrophicated Inland Water Bodies to Prevent Harmful Cyano-Bacterial Blooms

Abstract

Critical depth hypothesis (CDH) is a predictive criterion for primary production of phytoplanktons by photosynthesis, not only in the ocean but also in inland water bodies like lakes and reservoirs. In this study, a review of general models for estimating the critical depth (zcr) is studied with the selection of saturated-type Photosynthesis–Irradiance (P-I) curve equations. A comparison of the various zcr equations has revealed a remarkable quantitative difference between the zcr values. From the point of view of engineering applications, a bilinear-type P-I curve equation has been given more emphasis considering its accuracy. Finally, implications of the importance of zcr in determining the air diffuser depth in eutrophication countermeasure are discussed, such as artificial circulation methods in lakes and reservoirs. Application of Critical depth hypothesis (CDH) shall provide a framework to interpret blooms of harmful cyanobacteria which will lead to further design and management of bubble circulation countermeasures.KeywordsCritical depthP-I equationsArtificial circulationCyanobacteria