Reservoir

A hydraulic facility that stores water by blocking rivers or valleys to supply agricultural and domestic water and control floods

Reservoir

Overview

A reservoir is a hydraulic facility that artificially confines and stores water from rivers or valleys, with the main purposes of supplying agricultural irrigation water, domestic water, and industrial water and controlling floods. Unlike natural lakes, it consists of artificial structures such as embankments (dams), spillways, and intake facilities, and is classified into agricultural reservoirs, multipurpose reservoirs, and tidal-barrage-type freshwater lakes, etc., according to scale and purpose. Thousands of agricultural reservoirs are distributed in Korea, most of which were intensively constructed in the 1960s–1970s, making aging and response to climate change key tasks.

Main Content

Definition and Classification

A reservoir is an artificial freshwater body that stores water, and in Korea's Act on the Maintenance and Improvement of Agricultural and Fishing Villages (농어촌정비법), an agricultural reservoir is defined as 'a facility installed to store and supply water necessary for agriculture.' Generally, facilities with a storage capacity of 300,000 tons or more at full water level are classified as reservoirs, while smaller ones are called small reservoirs (소류지, 小溜池) or ponds. The boundary with dams differs according to administrative definitions, but facilities with a height of 15 m or more or a total storage capacity of 3 million tons or more are often managed as dams.

Components

The core structures of a reservoir are as follows.

  • Embankment (Body): The main structure that impounds water, with homogeneous, zoned, and fill-dam types. Seepage cutoff performance and slope stability are key to design.
  • Spillway: A facility that safely discharges excess water when overflow occurs, preventing embankment failure. Types include overflow, side-channel, and chute spillways.
  • Intake facilities: Conduits (waterways) and intake towers that draw reservoir water for irrigation and water supply.
  • Outlet facilities: Facilities that supply maintenance water and ecological flow to downstream rivers; recently, eco-corridor-type fishways are installed together.
  • Measurement and management facilities: Safety management equipment such as water level gauges, seepage line gauges, CCTV, and remote monitoring terminals.

Functions and Uses

Reservoirs are largely divided into supply functions and regulation functions. On the supply side, agricultural water supply centered on rice farming accounts for the largest share, and they are also used for domestic and industrial water, livestock water, and river maintenance water. On the regulation side, there are flood control functions that temporarily store inflow during flood season to lower downstream peak flow, and low-flow supplementation functions that replenish river flow by releasing water during droughts. Some reservoirs are also used in combined ways, such as floating solar power generation on the water surface and fishing and tourism.

Types

  • Curved (valley-type) reservoir: Built across a valley, with deep water and a small water surface area. Advantageous for water quality management.
  • Plain-type reservoir: A form surrounding a wide lowland with an embankment, common in downstream river areas or reclaimed land.
  • Tidal-barrage-type freshwater lake: Large-scale artificial lakes created by reclamation projects (e.g., Saemangeum Lake, Sihwa Lake), with salinity management as a major task.
  • Underground reservoir: A method of artificially recharging and storing groundwater, also used to reduce urban flooding.

Management and Safety

In Korea, most agricultural reservoirs are managed by the Korea Rural Community Corporation (한국농어촌공사), and their condition is assessed through regular safety inspections and detailed safety diagnostics. The storage rate (current storage / effective storage capacity) is a key indicator for drought response, and before the spring farming season, storage rates compared with normal years are checked to establish water supply plans. Embankment leakage, slope cracks, and spillway blockage can lead to failure, so real-time measurement and evacuation systems are important during heavy rains.

Recent Trends

The main trends in 2024–2025 can be summarized as climate-change-responsive smart management and rehabilitation of aging reservoirs. First, as localized heavy rains and long-term droughts repeat due to abnormal climate, the roles of reservoirs in flood control and drought buffering are being emphasized simultaneously. Second, the Korea Rural Community Corporation is expanding a 'smart water management system' that collects reservoir water levels and rainfall in real time and predicts discharge volumes with AI, and pre-simulates failure scenarios with virtual reservoir models based on digital twins. Third, as reservoirs more than 50 years after completion exceed half of all reservoirs, the 'Aging Reservoir Safety Enhancement Project' is underway, with comprehensive improvements such as embankment reinforcement, spillway expansion, and creation of walking trails and ecological parks. Fourth, 'energy reservoir' models combining floating solar power and small hydropower are increasing, and urban storage facilities such as underground reservoirs and rainwater storage tanks are also spreading. However, water quality deterioration (eutrophication), reduction of storage capacity due to sedimentation (soil deposition), and conflicts over water allocation between regions remain unresolved tasks.

Related Topics

  • [[댐|Dam]]
  • [[수자원|Water resources]]
  • [[가뭄|Drought]]
  • [[홍수|Flood]]
  • [[관개|Irrigation]]
  • [[한국농어촌공사|Korea Rural Community Corporation]]