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Construction of the reservoir serves as the most important form of utilizing and managing water resources by human beings. Hydro-power projects usually coming after the construction of reservoir also provide people with clean energy. But still a lot of people have some kind of misunderstandings regarding questions as what is water ？ What is the water resources？ Why do we build reservoirs？ How will Hydro-power station affect people’s lives？ Let’s read the experts’ explanation .
The construction of reservoirs is an important way to the develop water resource
First we have to understand the fact that reservoir and hydro-power are not necessarily connected. In reality， for some reservoirs or dams， there are no hydro-power station built on them. For example， China owns more than 80，000 reservoirs， however， only over 40，000 hydro-power stations. So why do we on the Earth build reservoirs？
Water resources， in the strict definition， doesn’t include those that cannot be controlled or accessed
Natural resource generally refers to the resources which can bring benefits to human beings under certain technical and economic environmental conditions. By this definition， the water in nature （such as rain） can really become water resources theoretically only if it forms surface runoff or groundwater. Unlike the groundwater resources with a relatively stable amount， river water resource is constantly changing together with the shift of time and space. If the contradiction between its spatial and temporal distribution cannot be solved， and it cannot “bring benefits to human beings under certain technical and economic environmental conditions”， it cannot be called water resource in the strict sense
To take advantage of the water in the river， we need to have control measures in place. The process to control， in other words， is the development of water， turning natural water into water resources. In general， the development of river water resource means the construction and retaining of reservoirs， therefore， in reality， the extent of how development the river water resources reaches， often can be represented by a ratio of the average annual runoff of the river and the storage capacity of the reservoirs. The ratio of water resources utilization of the river， however， should be calculated by the ratio of the annual runoff of the river and the total amount of water extracted and consumed by people.
The reservoirs are built to meet the human’s need of using water resources Why do people have to build reservoirs？ This is due to the fact that the amount of water in nature is always changing with time and space， however， human society requires strict amount of water resources， neither not too much （flooding）， nor too little （few rain and drought threatening life）. So far， with the limitations of science and technology， only two artificial ways are available to massively adjust the space-time contradiction of water resources， that is to build reservoirs and to retain or adjust water. Therefore， the construction of reservoirs， especially large ones are essential to modern social civilization. In ancient times， due to the low population density of the society and the small demand in each region for water resources， the space-time contradiction is not as sharp as in modern society. Since we enter into modern society， uneven distribution of natural water resources in terms of time and space， and the shortage of water resources as well， have become one of the most principal contradiction in the development of human civilization.
Hydro-power serves as the most significant way of water use
According to a survey in 2007 by the UN， the number of dams in a country and its per capita reservoir capacity is closely tied to the country's social and economic development. China has a similar total water resources and land area to US， but its total usable capacity of reservoir is only about half of that in the US， while the per capital water conservation is less than tenth of that of the U.S. Compared to the U.S.， China lacks reservoirs， therefore we could see flood disasters somewhere and severe drought elsewhere. In essence， this is due to the lack of water resources that can be controlled. By contrast， the better natural environment and less natural disasters in the U.S.， is largely due to their large reservoir capability， which allow them to retain more flood water while resist bigger droughts.
The construction of reservoirs is an important way to the develop water resource
First we have to understand the fact that reservoir and hydro-power are not necessarily connected. In reality， for some reservoirs or dams， there are no hydro-power station built on them. For example， China owns more than 80，000 reservoirs， however， only over 40，000 hydro-power stations. So why do we on the Earth build reservoirs？
Water resources， in the strict definition， doesn’t include those that cannot be controlled or accessed
Natural resource generally refers to the resources which can bring benefits to human beings under certain technical and economic environmental conditions. By this definition， the water in nature （such as rain） can really become water resources theoretically only if it forms surface runoff or groundwater. Unlike the groundwater resources with a relatively stable amount， river water resource is constantly changing together with the shift of time and space. If the contradiction between its spatial and temporal distribution cannot be solved， and it cannot “bring benefits to human beings under certain technical and economic environmental conditions”， it cannot be called water resource in the strict sense
To take advantage of the water in the river， we need to have control measures in place. The process to control， in other words， is the development of water， turning natural water into water resources. In general， the development of river water resource means the construction and retaining of reservoirs， therefore， in reality， the extent of how development the river water resources reaches， often can be represented by a ratio of the average annual runoff of the river and the storage capacity of the reservoirs. The ratio of water resources utilization of the river， however， should be calculated by the ratio of the annual runoff of the river and the total amount of water extracted and consumed by people.
The reservoirs are built to meet the human’s need of using water resources Why do people have to build reservoirs？ This is due to the fact that the amount of water in nature is always changing with time and space， however， human society requires strict amount of water resources， neither not too much （flooding）， nor too little （few rain and drought threatening life）. So far， with the limitations of science and technology， only two artificial ways are available to massively adjust the space-time contradiction of water resources， that is to build reservoirs and to retain or adjust water. Therefore， the construction of reservoirs， especially large ones are essential to modern social civilization. In ancient times， due to the low population density of the society and the small demand in each region for water resources， the space-time contradiction is not as sharp as in modern society. Since we enter into modern society， uneven distribution of natural water resources in terms of time and space， and the shortage of water resources as well， have become one of the most principal contradiction in the development of human civilization.
Hydro-power serves as the most significant way of water use
According to a survey in 2007 by the UN， the number of dams in a country and its per capita reservoir capacity is closely tied to the country's social and economic development. China has a similar total water resources and land area to US， but its total usable capacity of reservoir is only about half of that in the US， while the per capital water conservation is less than tenth of that of the U.S. Compared to the U.S.， China lacks reservoirs， therefore we could see flood disasters somewhere and severe drought elsewhere. In essence， this is due to the lack of water resources that can be controlled. By contrast， the better natural environment and less natural disasters in the U.S.， is largely due to their large reservoir capability， which allow them to retain more flood water while resist bigger droughts.