INTRODUCTIONFrom Greek word hydropower is hydro water is vitality that originates from the power of water movement. The fall and development of water is a piece of a constant common cycle called the water cycle. Vitality from the sun vanishes water in the earth’s seas and waterways and draws it upward as water vapor. At the point when the water vapor achieves the cooler air in the environment it consolidates and shapes mists. The dampness in the long run tumbles to the earth as rain or snow recharging the water in the seas and streams. Gravity drives the water movement transporting it from above ground to below ground. The energy of water movement can be a great degree amazing. Hydropower is known as a sustainable power source on the grounds that the water on earth is ceaselessly recharged by precipitation. For whatever length of time that the water cycle proceeds with we won’t come up short on this vitality source.Worldwide, hydropower is a crucial power supply option for several reasons. First, it is a renewable energy resource that can contribute to sustainable development by generating local, typically inexpensive power. Second, hydropower reduces reliance on imported fuels that carry the risks of price volatility, supply uncertainty and foreign currency requirements. Third, hydro systems can offer multiple co-benefits including water storage for drinking and irrigation, drought-preparedness, flood control protection, aquaculture and recreational opportunities, among others. Finally, hydro can allow more renewables, especially wind and solar to be added to the system by providing rapid-response power when intermittent sources are off-line, and pumped energy storage when such sources are generating excess power.Hydro dams is easier to build a hydropower plant where there is a natural waterfall. Most dams were built for recreation, flood control, fire protection, and irrigation. A dam serves two purposes at a hydropower plant. First, a dam increases the head, or height, of the water. Second, it controls the flow of water. Dams release water when it is needed for electricity production. Special gates called spillway gates release excess water from the reservoir, during heavy rainfalls.Hydro plant as people discovered centuries ago, the flow of water represents a huge supply of kinetic energy that can be put to work. Water wheels are useful for generating motion energy to grind grain or saw wood, but they are not practical for generating electricity. Water wheels are too bulky and slow. Hydroelectric power plants are different. They use modern turbine generators to produce electricity, just as thermal (coal, natural gas, nuclear) power plants do, except they do not produce heat to spin the turbines.Percentage of all sources in 3 years in the world. First, oil is remained the world’s leading fuel, accounting for 32.9% of global energy consumption. Crude oil prices recorded the largest percentage decline since 1986 (73%). Roughly 63% of oil consumption is from the transport sector. Oil substitution is not yet imminent and is not expected to reach more than 5% for the next five years. Unconventional oil recovery accounts for 30% of the global recoverable oil reserves and oil shale contains at least three times as much oil as conventional crude oil reserves, which are projected at around 1.2 trillion barrels.Another else we can see that hydropower is the leading renewable source for electricity generation globally, supplying 71% of all renewable electricity at the end of 2015. Undeveloped potential is approximately 10 000 TWh/y worldwide. The global hydropower capacity increased by more than 30% between 2007 and 2015 accounting to a total of 1 209 GW in 2015, of which 145 GW is pumped storageHydropower is renewable source.(Figure 2-1)Hydropower is considered a renewable form of energy because it is depend on solar energy that lead to the hydrologic cycle (see Figure 2-1). The hydrologic cycle relates to the following process: the sun warms the water (about 97 percent from oceans); water vaporize; rising air flows transport water vapor to the upper atmosphere where bring down the temperatures change from gas to liquid vapor into cloud. Air flows move the clouds around the world and in the end water falls as rain. Through this procedure, water can achieve heights higher than ocean level. Gravity makes water falls from highest height making chances to utilize water energy gravitation from higher elevations energy from falling water and kinetic energy from flowing water. The total of kinetic energy accessible from water stream relies upon the range from which the water drops, the point of the slant, and the volume of water per unit of time, i.e., the release. The vitality of streaming water is bridled by turbines, which are put in the way of the water stream. The power applied by water moving over turbine sharp edges turns the turbine sprinter; the turbine sprinter pivots the generator, which produces power. Hydropower’s hypothetical potential incorporates the aggregate potential vitality from all water assets inside determined spatial limits with no physical, specialized and financial use constraints. Practically speaking, just a little level of hypothetical potential can be reaped. Hydropower’s specialized potential is characterized as the aggregate vitality that can be created under the specialized, infrastructural and biological requirements. Normally, specialized potential reaches from 20 to 35 percent of hypothetical potential [Auer 2010]. Specialized potential is lower than hypothetical potential since specialized limitations confine, for instance, utilizing surge streams for vitality creation, except if a supply with vast capacity limit is accessible, which isn’t generally the situation. Thusly, an expansive extent of surface spillover stays unexploited for vitality generation. Another factor that diminishes accessible specialized potential when biological limitations are considered is giving a base stream to safeguard environmentally and socially. (Table 2-1)History of hydropower advancement can be characterize as the mechanical vitality of water has been tackled for creation since old occasions. Early uses included water system, crushing grain, and sawing wood and assembling materials, among others. Water flow vitality was changed over by water wheels into valuable types of intensity; the development of the water wheel dates to third Century BC. Amid the mechanical upheaval hydro turbines continuously supplanted waterwheels since turbines could misuse head substantially bigger than their distance across and offered altogether higher efficiencies. Using hydropower for power age dates to nineteenth C, making it the primary sustainable power source to create electric power. Today it remains the most well-known type of sustainable power source and assumes a critical job in electric power age around the world (see Table 2-1). For a short outline of innovation improvement from old to present day times.Advantage and Disadvantage of Hydropower towards EnvironmentHydropower dams can cause a few environmental issues, despite the fact that they consume no fuel. Damming streams may for all time modify waterway frameworks and untamed life environments. Fish, for one, may never again have the capacity to swim upstream. Stores may negatively affect the immersed zone, harm waterway widely varied vegetation, or upset stream employments for example, route. Hydro plant tasks may likewise influence water quality by stirring up broken down metals that may have been saved by industry long prior. Hydropower tasks may increment silting, change water temperatures, and change the levels of disintegrated oxygen. A portion of these issues can be overseen by building fish stepping stools, digging the sediment, and precisely controlling plant activities. Hydropower has points of interest, as well. Hydropower’s fuel supply (streaming water) is spotless and is recharged yearly by snow and precipitation. Besides, hydro plants don’t transmit toxins into the air since they consume no fuel. With developing worry over ozone depleting substance emanations and expanded interest for power, hydropower may turn out to be more critical later on. Hydropower offices offer a scope of extra advantages. Numerous dams are utilized to control flooding and manage water supply, and repositories give lakes to recreational purposes, for example, boating and angling.Furthermore, hydropower is eco-friendly. Hydroelectric power is a spotless wellspring of vitality, which implies it contributes little measures of nursery gasses to the environment. At the point when contrasted with non-renewable energy sources, for example, coal, oil, and gasses, it’s by a long shot the cleanest. Using hydropower is appeared to relieve the discharge of the dimensions of nursery gasses that would ordinarily happen from what could be compared to combusting 4.4 million barrels of oil every day over the globe. In addition, hydropower creation doesn’t radiate lethal side-effects that would hurt nature.Advantage and Disadvantage of Hydropower towards EconomicHydropower is the least expensive approach to create power today. No other vitality source, inexhaustible or nonrenewable, can coordinate it. Today, it costs short of what one penny for every kilowatt-hour (kWh) to deliver power at a run of the mill hydro plant. In examination, it costs coal plants around four pennies for each kWh and atomic plants around three pennies for each kWh to create power. Delivering power from hydropower is modest on the grounds that, when a dam has been assembled and the hardware introduced, the vitality source streaming water is free. Hydropower plants likewise create control economically because of their tough structures and straightforward gear. Hydro plants are tried and true and seemingly perpetual, and their support costs are low contrasted with coal or atomic plants. One prerequisite may build hydropower’s expenses later on. The method for authorizing and relicensing dams has turned into an extensive and costly process. Numerous natural effect examines must be embraced and various state and government offices must be counseled. It takes up to seven years to get a permit to assemble a hydroelectric dam or a relicense to proceed with tasks.Contrasted and different advances, the most essential advantages/favorable circumstances of hydropower which is hydropower age depends on a solid demonstrated innovation that has been around for over a century and hydropower plants can be effectively restored or updated using late advances in hydro advances. Age is sustainable on the grounds that it doesn’t lessen the water assets it utilizes and does not require fuel. It abuses local water assets, in this manner accomplishing value steadiness by keeping away from market changes.Impediments of hydropower incorporate the high in advance speculation costs contrasted with different innovations, for example, warm power (yet low operational expenses since no fuel is required). Stores may negatively affect the immersed territory, harm stream widely varied vegetation, or disturb waterway uses, for example, route. Be that as it may, most negative effects can be alleviated through venture plan. The IFC and other multilateral money related organizations have strict obligatory necessities for appraisal and moderation of social and ecological effects. For more data, allude to the IFC Performance Standards on Environmental and Social Sustainability or the IFC Environmental, Health and Safety Guidelines for development works and transmission lines.Conclusion.We ought to support the utilization of hydropower in light of the fact that it doesn’t cause air contamination or nursery gasses. Hydropower is one of the cleanest wellsprings of vitality and is additionally the most dependable and least expensive. There are numerous reasons why utilizing more hydroelectric power or hydroelectricity is great like for example the way that hydroelectric power is spotless, inexhaustible wellspring of vitality that doesn’t add to an unnatural weather change and environmental change like petroleum derivatives, for example, oil do. Hydroelectric power plants guarantee solid conveyance of power by empowering an enduring and standard creation of power which isn’t the equivalent with other sustainable power sources like sun powered and wind vitality. Hydroelectric power plants have long history of utilization, and produce the biggest offer of sustainable power source on the planet, considerably more than sun powered, wind and geothermal vitality do. The lake that shapes because of building hydroelectric power plant isn’t utilized for creating power yet can likewise be utilized for water system and recreational the travel industry in type of water sports, angling, swimming, and drifting. Utilizing hydropower has for the most part incredible preferences. It could enable us to make greater power quicker, reliably and economically for what’s to come.