Given below are brief explanations of each monitoring variable, shown in the table for number of measurements. See Data List for method details (available in PDF format).
| Variables | Unit | Explanation |
|---|---|---|
| Time | Fiscal year when water samples are collected. | |
| Station | Location number of sampling. See "Sampling points" for details. GPS is used for locating since 1994. | |
| Depth | m | Depth measured with a plummet. |
| Sonar Depth | m | Depth measured by sonar. |
| Transparency | cm | Depth when Secchi disc is no longer visible from the surface. |
| E.C. | μS/cm | Electric conductivity; the higher the electric conductivity is, the more ions are dissolved in water. |
| W. Temp. | °C | Water temperature at each depth, measured every 1m from the surface (0m) to the bottom of the lake. |
| Air.Temp. | °C | Air temperature. |
| D.O. | mg/l | A concentration value of dissolved oxygen in water, measured every 1m from the surface (0m) to the bottom of the lake. |
| PAR | lux (until 1981-06-08), μmol-photon/m2/s (since 1981-06-24) | Luminous intensity, measured every 1m from the surface (0m) to the bottom of the lake. This value shows how far the light can reach inside the water, which is important for estimations of depths where phytosynthesis can occur. |
| pH | pH (Potential of hydrogen), measured every 1m from the surface (0m) to the bottom of the lake. A pH of 7 is neutral, less than 7 is acidic and greater than 7 is alkaline. | |
| PO4-P | μg/l | A concentration of phosphate-phosphorus. This value indicates a concentration of phosphorus in phosphoric acid ion, which mainly originates from wastewater or chemical fertilizers. |
| DTP | μg/l | A concentration of dissolved total phosphorus, which includes inorganic phosphoric acid in filtered water samples and organic phosphorus. |
| T-P | μg/l | A concentration of total phosphorus, which includes total inorganic phosphoric acid, dissolved organic phosphorus, and phosphorus in suspended solids. |
| T-N | μg/l | A concentration of total nitrogen, which indicates a concentration of nitrogen compounds (including suspended solids), except for molecular nitrogen (N2) in lake water |
| NH4-N | μg/l | A concentration of ammonium nitrogen. |
| NO2-N | μg/l | A concentration of nitrite-nitrogen, produced by reduction of nitrate ion or oxidation of ammonia. |
| NO3-N | μg/l | A concentration of nitrate-nitrogen. Rivers in agricultural areas, where water holds more oxygen, might indicate high value of this variable. Eutrophication will be accelerated at downstream areas when nitrogen pollution occurs, even though the water seems clear. |
| DON | μg/l | A concentration of dissolved organic nitrogen, which exists as amino acid or protein in filtered water samples. |
| DTN | μg/l | A concentration of dissolved total nitrogen, which represents nitrogen compounds except for molecular nitrogen (N2) in filtered water samples. |
| D-COD | mg/l | A dissolved chemical oxygen demand, which is indicated by an oxygen consumption value during oxidation by potassium permanganate. |
| T-COD | mg/l | Total chemical oxygen demand. |
| Chlorophyl-a | μg/l | A concentration of Chlorophyll-a, which indicates an index of phytoplankton biomass. |
| Phycocyanin | μg/l | A concentration of phycocyanin, which is a blue-green pigment of algae, such as Cyanophyceae, Rhodophyceae, and Cryptophyceae. |
| Phaeophytin | μg/l | A concentration of phaeophytin, which indicates an index of phyceae biomass. |
| Suspended Solid | mg/l | A concentration of solids in water which is suspended as floating matter. |
| POC | mg/l | Particulate organic carbon, which represents a concentration of suspended organic carbon. Dissolved organic carbon is called as DOC. |
| PON | μg/l | Particulate organic nitrogen, which represents a concentration of suspended organic nitrogen. Dissolved organic nitrogen is called as DON. |
| C/N | CN ratio, which represents a ratio of carbon and nitrogen in suspended solids. | |
| Heterotrophic Bacteria | MPN/ml | Number of heterotrophic bacteria (one of the methods for counting bacteria). |
| Total Bacteria | cells/ml | Total number of bacteria. |
| Gross Production | gO2/m3/day gC/m2/day (since 1981) | Production rate of oxygen (or carbon) in 1m3 per day |
| Net Production | gO2/m3/day gC/m2/day (since 1981) | Net production rate. |
| Respiration | gO2/m3/day gC/m2/day (since 1981) | Respiration rate. |