Moving water was one of the earliest energy sources to be harnessed to reduce the workload of people and animals. No one knows exactly when the waterwheel was invented, but irrigation systems existed at least 5,000 years ago, and it seems probable that the earliest waterpower device was the noria, a waterwheel that raised water for irrigation in attached jars. The device appears to have evolved no later than the fifth century B.C., perhaps independently in different regions of the Middle and Far East.

The earliest waterpower mills were probably vertical-axis mills for grinding corn, known as Norse or Greek mills, which seem to have appeared during the first or second century B.C. in the Middle East and a few centuries later in Scandinavia. In the following centuries, increasingly sophisticated waterpower mills were built throughout the Roman Empire and beyond its boundaries in the Middle East and northern Europe. In England, the Saxons are thought to have used both horizontal0 and vertical-axis wheels. The first documented English mill was in the eighth century, but three centuries later about 5,000 were recorded, suggesting that every settlement of any size had its mill.

Raising water and grinding corn were by no means the only uses of the waterpower mill, and during the following centuries, the applications of waterpower kept pace with the developing technologies of mining, iron working, paper making, and the wool and cotton industries. Water was the main source of mechanical power, and by the end of the seventeenth century, England alone is thought to have had some 20,000 working mill.

There was much debate on the relative efficiencies of different types of waterwheels. The period from about 1650 until 1800 saw some excellent scientific and technical investigations of different designs. They revealed output powers ranging from about 1 horsepower to perhaps 60 for the largest wheels and confirmed that for maximum efficiency, the water should pass across the blades as smoothly as possible and fall away with minimum speed, having given up almost all of its kinetic energy. (They also proved that, in principle, the overshot wheel, a type of wheel in which an overhead stream of water powers the wheel, should win the efficiency competition.)

But then steam power entered the scene, putting the whole future of waterpower in doubt. An energy analyst writing in the year 1800 would have painted a very pessimistic picture of the future for waterpower. The coal-fired steam engine was taking over, and the waterwheel was fast becoming obsolete. However, like many later experts, this one would have suffered from an inability to see into the future. A century later the picture was completely different: by then, the world had an electric industry, and a quarter of its generating capacity was water powered.

The growth of the electric-power industry was the result of a remarkable series of scientific discoveries and development in electrotechnology during the nineteenth century, but significant changes in what we might now call hydro (water) technology also played their part. In 1832, the year of Michael Faraday’s discovery that a changing magnetic field produces an electric field, a young French engineer patented a new and more efficient waterwheel. His name was Benoit Fourneyron, and his device was the first successful water turbine. (The word turbine comes form the Latin turbo: something that spins). The waterwheel, unaltered for nearly 2,000 years, had finally been superseded.

Half a century of development was needed before Faraday’s discoveries in electricity were translated into full-scale power stations. In 1881 the Godalming power station in Surrey, England, on the banks of the Wey River, created the world’s first public electricity supply. The power source of this most modern technology was a traditional waterwheel. Unfortunately this early plant experienced the problem common to many forms of renewable energy: the flow in the Wey River was unreliable, and the waterwheel was soon replaced by a steam engine.

From this primitive start, the electric industry grew during the final 20 years of the nineteenth century at a rate seldom if ever exceeded by any technology. The capacity of individual power stations, many of them hydro plants, rose from a few kilowatts to over a megawatt in less than a decade.

流水是人类最早利用的能量来源，以减少人和牲畜的工作负担。无法知晓水轮是什么时候发明的，但灌溉系统至少在五千年前就已存在。最早的水力设施很可能是戽水车，一种通过附带的瓦罐将水举起以便灌溉的水轮。这种设备在公元前十五世纪就可能独立的出现在中东和远东的一些地区了。

最早用于研磨谷物的水力磨可能都是垂直轴的，比如可能在公元前一到二世纪出现在中东的希腊磨以及几个世纪之后出现在斯堪的纳维亚的斯堪的纳维亚磨。后来的几个世纪里，更加先进的水磨在整个罗马帝国及其边界以外的中东和北欧各地兴建起来。在英国，撒克逊人可能既有水平轴的也有垂直轴的水磨。有记录的最早的英国磨出现在八世纪，但三百年后大约有5000口水磨记录再案，也就是说几乎每一处居民聚集地，无论规模大小如何都有自己的水磨。

举升水和研磨谷物绝不是水力磨的唯一用途，在后来几个世纪中，对水力的利用与采矿、炼铁、造纸以及棉毛纺织工业的技术进步同步。水力是机械能的主要来源，在十七世纪末，光英国就有约两万座水磨。不同类型水轮的效率的高低向来争议很多。从1650到1800年间，人们设计了一些在科学和技术上都很先进的水轮。它们的输出功率从1马力到最大的60马力，并且人们确信要想产生最高效率，水应该从叶轮上尽可能光滑的流过，并以最小的速度落下，以便输出其几乎所有动能。（已经证明从原则上，上射水轮，一种利用从顶部倾泻的水流驱动叶轮的水轮，的效率最高。）

但当蒸汽动力进入历史舞台，水力的前途就备受怀疑了。一位能源分析者在1800年写的一篇论文给水力的前途铺上了一层悲观的色调。燃煤蒸汽动力正在普及，而水轮则被迅速遗弃。然而，正如后来很多专家所言，这位分析者对未来过于短视。一个世纪之后，情况完全不同：那时世界已经有了电力工业，而四分之一的发电能力都来自水力。

十九世纪电力工业的崛起源自一系列的科学发现和电工业的发展，但我们现在目睹的水力技术的重大进步也发挥了重要作用。在1832年，当Michael Faraday发现了变化的磁场能够产生电场理论时，一位年轻的法国工程师申请了一种新型的更有效率的水轮专利。他的名字叫Nenoit Fourneyron，而他的设备是最早的成功的水力涡轮。水轮在保持了近2000年的原始模样后终于被超越了。

在半个世纪里的时间里，法拉第的电学理论终于发展成了设施齐备的发电厂。1881年在英国的萨里，在卫河河畔建成了世界上第一座公用水力发电站----Godalming 发电站。这种现代化的发电站所用的仍是传统的水轮。不幸的是，这座早起的水力发电站也遭受了所有可再生能源的共同弊端：卫河的水流极不稳定，而水轮很快被蒸汽机代替了。

从这次原始的尝试开始，电工业在十九世纪最后的二十年中以比任何其它技术都快得多的速度发展起来。单个发电站，很多都是水力发电站，的发电能力从几千瓦在不到十年时间内就发展到了几兆瓦。