Generally, the synthetic unit hydrograph had to be developed just like a kind of Snyder that found accord empire scientific in the United States. Determination of their parameters has been presented by various criteria, but so far, the results are still relatively deviated for watershed-watersheds in Indonesia. The study was conducted to Bionga Kayubulan sub-watershed that has properties and characteristics that need to be conducted regarding irregularities by comparing models HSS Snyder with unit hydrograph observations on sub-watershed. Hydrograph water level readings AWLR derived from a flood hydrograph, using the are discharge. to separate the base flow with runoff straight-line method is used to produce direct runoff hydrograph. From the data obtained ARR hourly rainfall records were then analyzed, using the equation effective rainfall of index Φ. Direct runoff hydrograph and rainfall effectively revealed to be the observation unit hydrograph using collins method. Based on topographic maps obtained watershed physical factors were then used to analyze HSS Snyder. Further comparison of the HSS Snyder constant adjustments made using software Microsoft Excel-Solver. Observation unit hydrograph Bionga Kayubulan sub watershed has a peak time (Tp) of 4.5 hours with a peak discharge (Qp) of 2.81 m3/sec while Snyder HSS obtained from the analysis of Tp and Qp of 5.15 hours of 0.33 m3/sec. The test results showed that the predicted ratio Snyder HSS HSS calibration better than Snyder before calibration. CE adjusted value is 0.11 and as adjusted to 0.93. The value of EV adjusted is 65.20% before and after adjustment to 2.70%. EQP value addition, AETR values, and values after adjusting widened AETp 0 hours.

This study aims to analyze the water quality of Lake Perintis and Lake Limboto as irrigation water sources in Gorontalo Province. This study was carried out by considering the importance of water from these two lakes for irrigating the rice fields. 2 lakes became the locations for sampling in this study, namely Lake Limboto and Lake Perintis. Because this study was an initial survey, the researchers only applied one-site and one-time sampling for each lake. The observed parameters were temperature, TDS, COD, turbidity, phosphate, pH, nitrate, iron, manganese, cyanide, arsenic, fluoride, chlorine, manganese, magnesium, calcium, sodium, potassium, total coliform, and E. coli. The analysis was carried out at the Water Quality Laboratory, Health Office of Gorontalo and Integrated Research & Testing Laboratory of Gadjah Mada University. The sampling for total coliform was carried out aseptically, while measurements in the laboratory applied the MPN method. The way of taking chemical and physical samples followed SNI 8995-2021. Furthermore, the collected data were analyzed following Government Regulation No. 22/2021 Appendix VI regarding Lake Water Quality Standards. In analyzing water for irrigation purposes, the researchers applied the Sodium Adsorption Ratio (SAR) classification. Results showed that the water quality of Lake Perintis and Lake Limboto did not meet the requirements stipulated in Government Regulation No. 22/2021 because the chlorine, COD, and phosphate parameters were above the required quality standard. In addition, we also found that the pollution level in Lake Limboto was higher than that of Lake Perintis. Moreover, the results of the SAR analysis indicated a score of 7.975 for Lake Perintis (classified in the low sodium criteria) and a score of 11.23 for Lake Limboto (classified in the medium sodium criteria).

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Heavy precipitation is among the causes of flooding. Bone Bolango is one of the flooding areas in Gorontalo. Since the parameters determining the discharge of the flood is precipitation, an analysis method for determining the distribution pattern and precipitation that fits the situation in the watershed area of Bolango Bone is required. Thereby, the present study aimed at analyzing the distribution pattern and the precipitation in the area. The analysis methods of rainfall distribution were the normal, log-normal, log Pearson type III, and Gumbel methods. In addition, the precipitation was examined using Talbot method, Sherman method, and Ishiguro method. The data consisted of daily precipitation data (the data from the last 10 years at minimum) from Alale station, Boidu, Longalo, Dulamayo Selatan, and Sogitia Permata. According to the results of parameter statistical analysis, the value of Cs, Cv, and Ck of the precipitation in 5 stations did not meet the requirements for normal distribution, log-normal, and Gumbel. The Cv value of Alale station, Boidu station, Longalo station, Dulamayo Selatan station, and Sogitia station is 0.3, 0.32, 0.19, 0.23, and 0.28, respectively. The Cs value of those stations, in consecutive order, is 3.45, 2.21, 1.33, 0.92, and 1.11, and the Ck value is 18.58, 6.64, 4.55, 2.08, and 3.99. On that ground, the distribution pattern that best fits the watershed area of Bone Bolango us the Log Pearson III. Further, the most appropriate measurement of the precipitation in the area is the Sherman method. This method has the lowest standard deviation value at 67.3 mm and the best correlation value at 1. The heaviest rainfall occurred in the duration of 5 minutes and the return period of 100 years. The precipitation in Alale station, Boidu, Longalo, Dulamayo Selatan, and Sogitia is 378.15 mm/hr, 250.78 mm/hr, 188.98 mm/hr, 300.76 mm/hr, and 358.82 mm/hr, respectively.