Evaluation of some physico-chemical paremeters of Almus Dam Lake with geographic information systems and modeling its phosphorous carrying capacity

The physical (temperature, turbidity, secchi disk visibility, conductivity) and chemical (dissolved oxygen, pH, Nitrate-Nitrogen, Nitrite-Nitrogen, Ammonium-Nitrogen, Orthophosphate, total phosphorus) parameters of Almus Dam Lake located in the district Almus of province Tokat were seasonally determined at nine stations located along the lake. The parameters were analyzed using ARGIS 9.1 software in order to create spatial and seasonal maps of all parameters with Kriking Interpolation Method. The water quality class and trophic status of Almus Dam Lake were determined by comparing the results of our measured parameters with the values of Intercontinental Water Sources Quality Classification and OECD, respectively. The spatial and seasonal variations in physical and chemical parameters were analyzed with the Two-Way ANOVA, the relationships among these parameters were evaluated using Pearson Correlation Analysis, and water quality parameters which were important in the determination of water quality class of the Lake were identified using Principal Component Analysis. Results of statistical analyses were compared with the GIS maps. In the second phase of the research, phosphorous carrying capacity were determined using Beveridge suggested phosphorus loading model recognized by OECD.The GIS maps created for all parameters allowed us to estimate the water quality of the lake areas that were not sampled. The results obtained by correlation and other statistical analyses were overlapped with the results of GIS maps. The results of PCA analyses demonstrated that temperature, dissolved oxygen, conductivity, secchi depth, pH, Nitrate-Nitrogen, Orthophosphate, and total phosphorus were important parameters affecting water quality of the Lake. According to Intercontinental Water Sources Quality Classification, Almus Dam Lake has Class I water quality when considering parameters of temperature (14,30±7,44 C°), dissolved oxygen (10,15±2,67 mg / L), conductivity (304,43±19,71?S.cm-1), pH (8,20±0,18), Nitrate-Nitrogen (1,3±0,28 mg / L) and Class II in relation to orthophosphate (0,16±0,10 mg / L) and total phosphate (0,03±0,01 mg / L). According to OECD criteria, the lake has the mesotrophic trophical structure when taking the phosphorus concentrations into account and eutrophic structure when considering the secchi depth value (2,59±1,33 m). With the examination of seasonal temperature-depth profile, it was observed that winter stagnation and spring and fall vertical mixing occurred during the January and March and spring May and November, respectively. Temperature stratification was clearly observed during the July and September. Epilimnion, Metalimnion (thermocline) and hypolimnion were well clearly visible at the first 10 meters, between 10-20 meters, and below 20 meters, respectively.Phosphorus carrying capacity of the Lake was determined as 2275,21 mg.m-2 per year. It has been concluded that the lake will renew itself without going to eutrophication when the total production of aquaculture is between 4023,33 (Food Conservation Ratio (FCR):1.5-1) and 6981,76 (FCR: 1:1).