Relationship between the Water Quality Elements of Water Bodies and the Hydrometric Parameters: Case Study in Lithuania

The larger and deeper lakes and ponds are, the better the conditions for spontaneous water purification, slower hydrobiological processes and slower accumulation of sediment. The goal of this research was to assess the ecological status of selected Lithuanian lentic water bodies and the impact of morphometric indicators on water quality. Multiple studies were conducted on 29 lakes and 10 ponds located throughout Lithuania in 2014-2018. The study proved that higher maxima and average depths of lakes correlate with lower P-total. N-total yield and macrophyte taxonomic composition values, indicating higher ecological status class. Higher chlorophyll a EQR, ichthyofauna taxonomic composition indicator for Lithuanian fish index LFI and Lithuanian lakes' macroinvertebrate index indicates a higher ecological class. Larger lake areas contain smaller amounts of P-total and N-total, indicating better ecological status class; higher ichthyophane taxonomic composition in LFI, zoobenthos taxonomic composition indicator for Lithuanian lakes' macroinvertebrates index (LLMI) and taxonomic composition of macrophytes MRI indicate better ecological status class. Larger lake areas contain lower chlorophyll a EQR values. Rapid water exchange improves the condition of the lake in addition to nitrogen, phosphorus and chlorophyll a EQR values. The faster the water exchange in the lake is, the lower the P-total and N-total values; faster water exchange in the lake also means higher chlorophyll a EQR values. However, slower water exchange indicates better ecological status of the macrophytic taxonomic composition of the MRI, the ichthyofauna taxonomic composition and the Lithuanian lakes' macroinvertebrates index indicator of zoobenthos.