A Solar-Powered Multiparameter IoT Buoy for Dissolved-Oxygen Monitoring and Short-Term Water-Quality Forecasting in a High-Altitude Trout Raceway

In high-altitude trout raceways, dissolved oxygen (DO) declines are brief and start from a narrow margin below saturation. We built a solar-powered floating node with five water-quality channels, a serviceable probe cartridge, switched sensor rails and store-before-transmit telemetry and operated it for 89 days in a raceway at 2100 m a.s.l. (Amazonas, Peru). It recorded 25,522 five-minute observations (99.57% coverage) with 99.95% packet delivery. Under calibration transfer, DO error was 0.100 mg L−1 and the field variability of temperature, DO and turbidity exceeded it 3.5–4.2-fold. On a chronologically separated test period, three-hour DO RMSE was 0.180 mg L−1 with five-channel inputs and 0.260 mg L−1 with DO-history inputs alone, against 0.362 mg L−1 for an hour-of-day control. Six-hour gains were not resolved: departures from the diel course had decorrelated, the test period shifted toward low DO and turbidity events, and out-of-range conductivity produced spurious troughs. A three-hour DO < 6.5 mg L−1 classifier reached ROC-AUC 0.946 and, with two-sample confirmation, detected all 24 complete low-DO episodes, against 15 with DO history alone. Battery-terminal measurements showed the awake controller as the largest identified load; calculated balances indicated that the installed 15 W module sustains the five-minute cycle and that deep-sleep standby would cut daily charge by 80–91%.