What Is Reservoir? Purpose And Types Of Reservoir

A reservoir is a natural lake or a man-made outdoor storage space where water is collected and stored in a limited quantity for later use.  Reservoirs are an integral part of many water supply systems worldwide, which play an important role in supplying water to domestic, industrial, and agricultural demands. In this post, we will discuss different types of reservoirs.

types of reservoir

Purpose Of Reservoir

Sometimes weather fluctuations cause the natural flow of streams and rivers to change over time. The excess water flow and valley floods can vary according to short flow or drought. The main purpose of water storage or reservoirs is to store the excess water during periods of higher flow.

This way, floods can be controlled, and the stored water can be released gradually for longer periods. This stored water can be used for domestic, industrial, and agricultural purposes.

The reservoir supplies water to cities and towns and provides basic human needs. Population growth plays a significant role in designing reservoirs.

The demand for water increases with the increase in population, leading to the construction of roads, supply centers, schools, shopping malls, and community facilities. All this is not possible without a permanent and secure water supply.

Simple storage tanks were probably created in the early history of mankind for drinking water supply and irrigation. From South Asia and North Africa, reservoirs have spread to Europe and other continents.

The large reservoirs serve high demands but can be of small size to serve individual demands. This can be seen in the agricultural sector, where the individual pond is built to store the water and use it for later needs.

Though reservoirs are designed for irrigation, flood control, and water supply, some common purposes of reservoirs are as follows:

  • Prevent or control the flood.
  • Hydroelectric or Power generation
  • Fishing and Boating
  • Irrigation
  • Water Supply
  • Water Storage
  • Water Sports
  • Wildlife habitat
  • Bird sanctuary
  • Wildlife Parks

Types Of Reservoir

The types of reservoir are as follows:

  1. Valley-dammed reservoir or Storage reservoir
  2. Flood control reservoirs
  3. Service reservoirs or Distribution reservoir

1. Valley Dammed Reservoir

Valley-dammed reservoirs are formed in valleys in the middle of the mountains. There is often an existing lake or water, and the sides of the mountain are used as reservoir walls to hold water. A dam or artificial tank wall is built at the narrowest point to hold water.

Before constructing Valley-dammed reservoirs, the water flow or river must be diverted. The dam construction process involves laying the foundations for the dam, and then the concrete cladding is laid and the construction of the dam can proceed.

The construction of the dam usually takes many years, but when it is finished, valley ponds and a large water source can be used to serve the purpose of irrigation, hydropower generation, and domestic and industrial water supply.

2. Flood Control Reservoir

This type of reservoir, also known as a flood mitigation reservoir, is built to store the floodwater from a high-flow water stream to reduce flooding in protected areas or populated areas.

The entire stream entering the water storage is discharged until the outflow reaches the safe capacity of the lower channel. The excess inflow is stored in the reservoir, and the stored water is gradually resealed to create a storage capacity for the next flood. There are two types of flood control reservoirs:

  1. Storage Reservoir
  2. Retarding Reservoir
i) Storage Reservoir

A reservoir where gates and valves are installed at its spillways and sluice outlets is known as a storage reservoir. This reservoir requires a manual operation to open and close the gate, which gives complete control over the amount of water discharged.

ii) Retarding Reservoir

A reservoir that has ungated outlets and the flow is uncontrolled is known as retarding reservoir or retarding basin. The retarding reservoir has some advantages over the storage reservoir, such as no necessity of installing gates at sluiceways and spillway crests.

During maximum floods, the water present in the land is submerged temporarily and driven out in a few days after the flood is controlled or minimized.

3. Distribution Reservoir or Service Reservoir

Distribution Reservoir connected to the main water supply channels(pipelines). The main purpose of this type of reservoir is to serve or supply water to consumers according to changing demands or requirements of the local population.

It also serves as local storage in the event of an emergency. Here the water is stored in the reservoir by pumping at a specific rate, and later, this stored water can be used or supplied at a rate higher than the inflow rate during high demands.

The main advantage of this type of reservoir is it can store water during the demand period and supply water during the demand period. Distribution reservoirs mainly depend on the population’s demand for water at a particular period.

Multi-purpose Reservoirs

As the name suggests, these reservoirs are built to store and supply water to meet more than one purpose; hence they are known as Multipurpose Reservoirs.

For Example, multi-purpose reservoirs are designed for irrigation, flood control, power generation, etc. In India, Bhakra Dam and Nagarjuna Sagar Dam are examples of important multi-purpose projects that serve more than two purposes.

FAQs On Reservoirs

Q. Which is the first man-made reservoir?

Ans – Jawa dam, located in Jordan, is said to be the first man-made reservoir built in 3000 BC to store and supply water for irrigation, watering crops, etc.

Q. What is the largest man-made reservoir?

Ans – Lake Kariba is the largest man-made lake in the world, located in Zambia and Zimbabwe. It has a storage capacity of 180.6 cubic kilometers of water.

Q. How many types of Reservoirs are there?

Ans- There are mainly three types of reservoirs which are as follows:

  1. Valley-dammed reservoir or Storage reservoir
  2. Flood Control reservoirs
  3. Service reservoirs or Distribution reservoir

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