Trophic state modeling for shallow freshwater reservoir: a new approach

• Published in: Environmental monitoring and assessment 2019-09, Vol.191 (9), p.586-586, Article 586
• Main Authors: Markad, Adinath T., Landge, Asha T., Nayak, Binaya B., Inamdar, Arun B., Mishra, Akhil K.
• Format: Article
• Language: English
• Subjects: Agricultural economics; Agricultural management; Agricultural runoff; Agriculture; Algae; Algal blooms; Atmospheric Protection/Air Quality Control/Air Pollution; Chlorophyll; Chlorophyll - analysis; Chlorophylls; Climate; Climate change; Climatic conditions; Earth and Environmental Science; Ecology; Economic impact; Economics; Ecotoxicology; Environment; Environmental degradation; Environmental Management; Environmental monitoring; Environmental Monitoring - methods; Environmental science; Eutrophic environments; Eutrophic reservoirs; Eutrophic waters; Eutrophication; Eutrophication - physiology; Freshwater; Inflow; Inland water environment; Lake management; Lakes; Lakes - chemistry; Limnology; Low water levels; Mineral nutrients; Modelling; Models, Theoretical; Monitoring/Environmental Analysis; Monsoons; Morphometry; Nutrient loading; Nutrients; Oceanography; Phosphorus; Phosphorus - analysis; Reservoirs; Runoff; Seasons; Surveys; Trophic state; Turbidity; Water inflow; Water levels; Water Pollutants, Chemical - analysis; Water Quality; Water Supply
• ISSN: 0167-6369; 1573-2959
• DOI: 10.1007/s10661-019-7740-5

Lakes and reservoirs around the world are facing a substantial water quality degradation problem that poses significant environmental, social, and economic impacts. Reservoir productivity is influenced primarily by the climatic, morphometric, and hydro-edaphic features. High nutrient loadings in the reservoir from agriculture runoff often provide ideal conditions for algal blooms, leading to eutrophication. Reservoir and lake management to prevent or reduce eutrophication, therefore, has become the need of the hour. The traditional approach of trophic state monitoring by rigorous field surveys and eutrophication modeling has been revised in the present study by developing a new trophic state index (TSI)-based model for tropical shallow freshwater reservoirs. The new model has been constructed based on Carlson’s Limnology and Oceanography, 22 , 361-369, ( 1977 ) guidelines by establishing an empirical relationship between trophic parameters including total phosphorus (TP), Secchi disk depth (SDD), and chlorophyll (Chl- a ). After comparing the new model with various earlier models for its applicability and validation with actual field conditions, it was found to be most precise over previous TSI models. Temporal and spatial fluctuations in the water quality of the Tiru reservoir were primarily attributed to the changing climatic conditions during the study period. Seasonal monsoon with less frequency, heavy nutrient loading from agriculture runoff, and increased turbidity due to a high level of sediment inflow during monsoon raised the TSI (SDD) values of the Tiru reservoir to place it in the hyper-eutrophic class. Average TSI values during winter for SDD, Chl- a , and TP were indicative of the meso-eutrophic to eutrophic state. Saturation of nutrients due to low water level during summer season caused the poly-eutrophic condition for TSI (SDD)- and TSI (TP)-based estimates and eutrophic condition as per TSI (Chl- a ) estimates. However, seasonal deviations of the TSI values based on the relationship between TSI (Chl- a ) and TSI (SD) indicated a predominance of smaller particles (non-algal turbidity) during all seasons. Even though TP present in the Tiru reservoir is controlling the algal production, it is also affected by low-light conditions due to non-algal turbidity. The recommendation from this study is that the TSI method for estimating the health of the water bodies is the efficient, cost-effective, and time-saving approach. The model developed duri