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The characteristic hydrology of a watershed is playing a major role in ensuring water resource availability. Rainfall and runoff responses in catchment area are part of the hydrology cycles. There are several factors to determine the characteristic of hydrology at the watershed, i.e. geological, region, soil and land cover. The existence of water resources is very substantial for surroundings. The rapid development in various sectors leads to water demands increase. Optimum utilization of water resources is needed in the sustainability of water resources or the need for integrated water resources management. The consequence of development is land use change, resulting in changes inflow characteristics, flood during the wet season and drought or discharge decrease in the dry season. Many studies associate higher watershed land cover with lower baseflows, attributed to high evapotranspiration rates, while other studies indicate increased baseflow with higher watershed land cover due to higher infiltration and recharge of subsurface storage. Adaptation and mitigation efforts are required to anticipate changes in the flow characteristics. The factors are key controls on base flow through their influence on infiltration, catchment and subsurface storage properties. This review underscores the need for more research that multiple aspects of the watershed system in explaining base flow. The result of average base flow and total flow ratio during 40 years (1971-2010) is 0.296 and the class of the hydrologic function as a BF / TF ratio value which indicated very poorly hydrology function of upstream Komering, although in certain hydrologic function was still in the good category.

In Indonesia, about 89.75% of all power stations use fossil fuels, and only 10.25% generation uses renewable energy, i.e., hydropower generation, geothermal power, solar power and wind power. The use of fossil fuels such as coal, oil, and gas will cause environmental degradation. To help reduce environmental degradation requires the use of renewable energy such as solar energy through power plants in large quantities. In this paper will discuss solar power technically and economically, in this case, the cost of generation per $\mathrm {k}\mathrm {W}\mathrm {h}$ for each solar generating scheme is rooftop Off-grid photovoltaic (PV) system and on- grid PV system. Two schemes were created to calculate the generation cost per $\mathrm {k}\mathrm {W}\mathrm {h}$ for off-grid and grid-connected PV systems based on component prices for several cities in Indonesia. Electricity generation cost per $\mathrm {k}\mathrm {W}\mathrm {h}$ for off-grid PV systems and grid-connected PV system are respectively 4,644 IDR/kWh and 1,244 IDR/kWh compared to PLN electricity tariff is 1,467.28 IDR/kWh.

The triggered vacuum gap (TVG) is a closing switch for generating large current pulse and can work in the wide range of voltage for several kV to tens kV. Main electrodes are made of Ag-WC. One of main electrode has a hole for trigger electrode (Mo). The switching time is short, if the polarity of the holed-electrode is negative. It is called polarity effect. We devised a crowbar circuit using the polarity effect of the TVGs. The crowbar current of this circuit was investigated experimentally by varying applied voltage, inductance, capacitance, gap length of TVGs, and trigger current duration. A crowbar current, crest of which is 2.4 kA and 4.9/270µs for example, was observed. The probability of generating the crowbar current was more than about 90 %, in the following condition: the trigger current duration of 6.65 µs and the gap length of 2-6 mm.

Both switching time and minimum firing voltage of a triggered vacuum gap employing a trigger electrode in the cathode and anode (double triggered vacuum gap) were measured. The double triggered vacuum gap was operated below 100 V independent of the high voltage main electrode polarity (positive or negative). This minimum firing voltage was lower than that of the conventional triggered vacuum gap. The switching time is approximately 0.5 μs in the range 3 to 18 kV. The conventional triggered vacuum gap has a trigger electrode that is placed at the center of the grounded main electrode. The polarity of the main electrode affected switching time characteristics. A trigger electrode was added to the high voltage main electrode. The double triggered vacuum gap was only slightly influenced by the polarity of the high voltage main electrode when both main electrodes were triggered at the same time.