On this "rain island" with an annual rainfall of 2,500 mm, water resources are often insufficient. Springs where the meiyu (plum rain) fails to arrive, and summers where typhoons bypass the island, have made "tight water conditions" a recurring annual keyword in Taiwan. From Shimen Reservoir to Zengwen Reservoir, and from Feicui Reservoir to Nanhua Reservoir, Taiwan's reservoir systems sustain the water lifelines of 23 million people.
Natural Conditions of Taiwan's Water Resources
Abundant but Uneven Rainfall
Taiwan is located in a subtropical monsoon climate zone, with an average annual rainfall of approximately 2,500 mm—about 2.6 times the global average. However, this figure is deceptive because precipitation is extremely uneven in both time and space.
In terms of timing, about 80% of Taiwan's rainfall is concentrated during the wet season from May to October, with the highest concentration occurring during the typhoon season. A single medium-sized typhoon can bring over 1,000 mm of rain, but this water often arrives too suddenly and intensely, flowing directly into the ocean without being effectively utilized.
In terms of space, annual rainfall in eastern Taiwan can exceed 4,000 mm, while southwestern Taiwan may receive less than 1,500 mm. The blocking effect of the Central Mountain Range creates distinct rain shadows. Major agricultural areas, such as the Chianan Plain and Kaohsiung Plain, are located in the relatively dry southwest, where water demand is high but natural supply is insufficient.
Impact of Topography on Water Resources
Taiwan features high mountains and steep slopes with short rivers; the average distance from the Central Mountain Range to the coast is less than 100 km. This topographical characteristic causes rainwater to flow rapidly into the ocean, resulting in poor natural storage capacity.
Rivers west of the Central Mountain Range, such as the Zhuoshui River, Gaoping River, and Zengwen River, have relatively large catchment areas, but due to the steep terrain, discharge rates fluctuate wildly between dry and wet seasons. Severe flooding can occur during the wet season, while rivers may run dry during the dry season.
Geological conditions also affect water resource utilization. The western plains consist mainly of alluvial layers, where groundwater is abundant but prone to subsidence from over-extraction; the east consists mostly of hard rock, which does not store water easily but offers better water quality; the south features limestone terrain, which facilitates groundwater systems but is also susceptible to contamination.
History of Reservoir Development in Taiwan
The Japanese Colonial Period: The Starting Point of Modern Hydraulics
Modern reservoir construction in Taiwan began during the Japanese colonial period. Completed in 1930, Wushantou Reservoir was the first large-scale reservoir, designed and built by Yoichi Hatta to primarily supply irrigation water for the Chianan Irrigation System. The construction technology used was quite advanced for its time, employing a semi-hydraulic earth-and-rockfill dam with a storage capacity of 150 million cubic meters.
The success of Wushantou Reservoir transformed the Chianan Plain from land dependent on unpredictable weather into fertile farmland, significantly increasing rice production. This project also established the technical foundation for Taiwan's hydraulic construction and cultivated local water engineering talent.
During this period, Sun Moon Lake Reservoir was also constructed, though its primary purpose was power generation rather than water supply. Utilizing the natural topography of Sun Moon Lake, a hydroelectric power plant was built, becoming a vital foundation for Taiwan's electrical development.
Post-War Reconstruction: Focus on Domestic Water Supply
Following World War II, Taiwan experienced rapid population growth and increased urbanization, leading to a surge in demand for domestic water. The government began planning and constructing reservoirs primarily for water supply purposes.
Completed in 1964, Shimen Reservoir was Taiwan's first large-scale multi-purpose reservoir built after the war. It serves functions including water supply, power generation, flood control, and tourism, serving as a model for reservoir construction in Taiwan. Shimen Reservoir mainly supplies water to parts of Taoyuan and New Taipei City, playing a crucial role in the development of northern Taiwan.
Feicui Reservoir was planned in 1973 and completed in 1987. Built specifically to supply the Taipei area, it employs strict catchment area controls to ensure excellent water quality. The success of Feicui Reservoir has allowed Taipei to become the only major city in Taiwan that does not face water shortages.
1980s–1990s: The Era of Large-Scale Construction
As Taiwan's economy took off in the 1980s, industrial water demand increased sharply, prompting large-scale reservoir construction by the government. This period saw the completion of important reservoirs such as Zengwen, Deji, and Wushe.
Completed in 1973, Zengwen Reservoir is Taiwan's largest reservoir, with a storage capacity of 700 million cubic meters. It primarily supplies agricultural and industrial water to the Chianan region, holding a critical position in the development of southern Taiwan.
Located upstream on the Dajia River, Deji Reservoir was completed in 1974 to mainly supply the Taichung area. This high-altitude reservoir sits at an elevation of over 1,000 meters and offers excellent water quality, but it also faces issues with sediment accumulation caused by typhoon rains.
Recent Developments: The Rise of Environmental Awareness
Since the 1990s, rising environmental awareness has met with increased resistance to new reservoir projects. Plans such as the Meinong Reservoir and the Jiyang Artificial Lake were halted due to environmental controversies. The public began to question the necessity and environmental costs of large-scale reservoirs.
Recent reservoir construction has focused on small and medium-sized projects, such as Hushan Reservoir and updates to the Agongdian Reservoir. Simultaneously, the government has begun to emphasize the maintenance and management of existing reservoirs, promoting dredging and facility upgrades.
Introduction to Major Reservoir Systems
Northern Water Resource System
Feicui Reservoir is the most important water source for the Taipei metropolitan area and is one of Taiwan's most successfully managed reservoirs. Development within its catchment area is strictly controlled, maintaining high water quality over the long term. The reservoir utilizes dual-layer intake facilities, allowing operators to select different layers based on water quality to ensure supply standards.
Shimen Reservoir serves parts of Taoyuan and New Taipei City and is a vital source for northern Taiwan. However, it faces serious sedimentation issues, with its effective storage capacity declining annually. The government is promoting the Shimen Reservoir Renewal Project, which includes dredging and dam heightening.
Small and medium-sized reservoirs like Xinshan Reservoir and Chengfu Reservoir provide supplementary water supply functions. Although small in scale, they play a critical role during dry seasons.
Central Water Resource System
Deji Reservoir, located upstream on the Dajia River, is the primary water source for the Taichung area. While it offers excellent water quality, its catchment area's fragile geology often leads to massive amounts of sediment entering the reservoir during typhoons, causing severe siltation.
Liyu Tan Reservoir supplies the Miaoli area and utilizes a "off-stream" reservoir design to avoid sedimentation issues in the main river channel. This design concept was later applied to other newly built reservoirs.
Hushan Reservoir is Taiwan's most recently completed large-scale reservoir, having begun operations in 2016 to primarily supply the Yunlin area. It features modern design, complete monitoring systems, and environmental protection measures.
Southern Water Resource System
Zengwen Reservoir is Taiwan's largest reservoir and operates in conjunction with Wushantou Reservoir as the Zengwen-Wushantou Reservoir System. This system is the primary source of agricultural and domestic water for the Chianan region, covering an irrigation area of 150,000 hectares.
Nanhua Reservoir supplies parts of Tainan and Kaohsiung. It employs more modern design concepts with good water quality protection measures, though its catchment area is relatively small, limiting its supply capacity.
Agongdian Reservoir was Taiwan's first earth-and-rockfill dam; it has a long history but features aging facilities. Recent years have seen renewal and reconstruction efforts to improve supply capacity and safety.
The Gaoping River Weir, while not a reservoir, is an important water facility for the Kaohsiung area. By raising the water level through the weir, it increases the stability of water intake.
Challenges in Water Resource Management
Sedimentation: The Chronic Disease of Reservoirs
Taiwan's reservoirs generally face serious sedimentation problems. Due to the fragile geology of catchment areas, typhoon rains often bring massive amounts of soil and rock that accumulate in reservoirs, reducing storage capacity.
Sedimentation is most severe at Shimen Reservoir, where effective storage capacity has dropped from its original design of 200 million cubic meters to 170 million cubic meters. Deji Reservoir faces an even higher sedimentation rate of up to 47%, seriously impacting its supply capacity.
Dredging is the primary method for addressing siltation, but it is costly and has limited effectiveness. In recent years, the government has promoted the "Enhanced Catchment Area Conservation and Management Program" to reduce sediment inflow at the source. Simultaneously, new dredging technologies such as hydraulic sediment discharge and land-based dredging are being developed.
Water Quality Protection: The Dilemma of Development vs. Conservation
Protecting water quality in reservoir catchment areas is an eternal challenge. Activities such as agriculture, livestock farming, and tourism within these areas can all impact water quality. The government must strike a balance between economic development and water protection.
Management of Feicui Reservoir is the strictest; development is prohibited within the catchment area, and even visitor access is restricted. This strict control ensures excellent water quality but limits local development.
Other reservoirs have relatively relaxed catchment controls and face greater pollution pressure. For instance, the Zengwen Reservoir catchment includes agricultural and tourism activities, making water quality management more complex. The government is promoting ecological engineering methods and pollution reduction measures to balance development with conservation.
New Challenges from Climate Change
Climate change presents new challenges for Taiwan's water resource management. As precipitation patterns shift and extreme weather events increase, traditional water planning methods may no longer be applicable.
In recent years, Taiwan has frequently experienced the phenomenon of "spring rain failure," where reduced rainfall during the meiyu season prevents reservoirs from storing enough water. The historic drought of 2021, which saw several reservoirs hit record-low storage rates, highlighted the threat posed by climate change.
Changes in typhoon paths also affect water resources. Typhoons that used to bring abundant rain to Taiwan have recently been passing by at the periphery, reducing rainfall replenishment. Even when typhoons do strike, they may be so intense that the rain arrives too rapidly to be effectively captured and stored.
Regional Imbalance and Allocation
The North-South Gap: A Contrast in Abundance
Taiwan's water resources are distributed very unevenly, creating a distinct north-south gap. Northern Taiwan has large reservoirs like Feicui and Shimen, providing relatively sufficient water; while the south, despite having large reservoirs like Zengwen, faces much greater water pressure.
The Taipei metropolitan area, thanks to the abundant supply from Feicui Reservoir, has almost never faced a water crisis. Even during the severe drought of 2021, the Taipei area was able to maintain normal supply. In contrast, central and southern regions frequently struggle with tight water conditions.
This gap is not only caused by natural conditions but is also related to historical development. Because of its political importance, the north has received more investment in hydraulic infrastructure; while the south is agriculturally developed, its hydraulic facilities are relatively insufficient.
Competition Between Agricultural and Domestic Water
Agricultural water accounts for over 70% of Taiwan's total water usage, yet agriculture's contribution to GDP is less than 2%. As the economic structure transforms, pressure is increasing to shift agricultural water toward domestic and industrial use.
Water resource allocation in the Chianan region is the most complex. The Zengwen-Wushantou Reservoir System primarily serves agricultural irrigation, but industrial zones like the Tainan Science Park also require massive amounts of water. Meeting these diverse needs within limited resources is a major challenge for management authorities.
The government has promoted policies to transfer agricultural water, encouraging farmers to reduce irrigation during dry seasons to redirect water to domestic and industrial users. However, this has sparked backlash from farmers who feel it hinders agricultural development.
Technical Challenges of Inter-regional Water Transfer
To solve regional imbalances, the government has planned several inter-regional water transfer projects. However, Taiwan's complex terrain poses significant technical challenges for such transfers.
The "South-to-North" plan aims to move southern water resources to the north, but it has been suspended due to high costs and technical difficulties. The "East-to-West" plan seeks to use the abundant rainfall of the east to supplement western demand, but faces similar topographical obstacles.
Currently, short-distance regional allocation is more feasible, such as joint allocation between Taipei and New Taipei, or support between Taoyuan and Hsinchu. While these measures are small in scale, they prove effective during emergencies.
Development of Alternative Water Sources
Desalination: Getting Water from the Sea
Faced with water shortages, desalination has become an important alternative. Surrounded by sea on all sides, Taiwan can leverage desalination as a stable source unaffected by climate patterns.
Several desalination plants are currently operational in Taiwan, including on offshore islands like Penghu, Kinmen, and Matsu, as well as in Yongkang (Tainan) and Hsinchu. These facilities primarily use reverse osmosis technology, and the cost of desalination continues to decline.
However, desalination has limitations. It is energy-intensive, requiring 3–5 kWh of electricity per ton of fresh water produced; the discharge of high-salinity brine may affect the marine environment; and maintenance costs are high, requiring specialized expertise. Whether desalination can be developed on a large scale in the future depends on overcoming these challenges.
Reclaimed Water Utilization: Practicing a Circular Economy
Reclaimed water involves treating wastewater for reuse, serving as an important method of water recycling. In Taiwan, reclaimed water is mainly used for industrial cooling, landscape irrigation, and toilet flushing.
The Hsinchu Science Park is a pioneer in reclaimed water use, having built reclamation plants as early as the 1990s to supply its resident companies. This successful experience has since been promoted to other science parks.
Promoting reclaimed water for domestic use is more difficult, primarily due to public acceptance. Although treated reclaimed water is of high quality, many people still have psychological barriers. The government is promoting education and awareness campaigns to change public perception.
Rainwater Harvesting: Wisdom in Local Sourcing
Rainwater harvesting is an ancient but effective method of water utilization. In highly urbanized Taiwan, rainwater harvesting can not only increase water sources but also reduce the risk of urban flooding.
The government promotes "Standards for Installing Rainwater Harvesting Facilities in Building Sites," requiring new buildings to install such facilities. These systems can collect rooftop rainwater for uses like irrigation and cleaning.
Community-scale rainwater harvesting systems are also being gradually promoted. By installing large storage facilities, entire communities can collectively utilize rainwater resources. This approach is particularly suited to Taiwan's climate of high but unevenly distributed rainfall.
The Future of Smart Water Management
Application of IoT Technology
Internet of Things (IoT) technology is bringing revolutionary changes to water resource management. By installing sensors in reservoirs, pipe networks, and at the user end, data such as water levels, quality, and flow rates can be monitored in real-time, enabling precision management.
The Taiwan Water Corporation is promoting a "Smart Water Network" project, using smart water meters, pressure monitoring, and leak detection technologies to improve supply efficiency. These technologies can detect leaks early, reducing water waste.
Reservoir management is also incorporating IoT. Through meteorological monitoring, water level early warning systems, and automated operations, water resources can be allocated more precisely. The application of Artificial Intelligence (AI) can further predict water demand and optimize supply strategies.
Digital Twin Technology
Digital Twin technology reconstructs physical hydraulic facilities in a virtual space, allowing for the simulation of various scenarios to evaluate the effectiveness of different strategies.
This technology is particularly suited for reservoir operational management. By creating a digital model of a reservoir, operators can simulate water level changes under different rainfall scenarios to formulate optimal operating strategies. It can also evaluate the effects of engineering improvement plans, reducing risks during actual construction.
Pipe network management can also utilize Digital Twin technology. Building a complete digital model of the network allows for the simulation of water pressure changes and the impact of leaks, assisting in the formulation of maintenance plans.
Artificial Intelligence Prediction
AI shows immense potential in water resource prediction. By analyzing historical meteorological and usage data, it can more accurately predict key indicators such as rainfall and water demand.
In terms of short-term forecasting, AI can predict water demand for the coming days to assist in water allocation. Long-term forecasting can assess the impacts of climate change to plan future hydraulic infrastructure.
Early warning for extreme events is a vital application of AI. By analyzing meteorological data, it can provide advance warnings for droughts or heavy rains, gaining precious response time. This is particularly important for a region like Taiwan where climate variability is intense.
International Experience and Lessons for Taiwan
Singapore's Four National Taps Strategy
Singapore is a model of successful water resource management, and its "Four National Taps" strategy is worth learning from. The four taps include local catchment water, imported water, reclaimed water, and desalinated water, ensuring water security.
Singapore's reclaimed water technology is particularly advanced; the quality is high enough to be directly potable. Through the branding of "NEWater," the government successfully changed public perception of reclaimed water. This experience provides great inspiration for Taiwan's promotion of reclaimed water.
Regarding desalination, Singapore continuously improves its technology to reduce costs and energy consumption. Its desalination plants use the most advanced membrane technologies, significantly increasing efficiency. Taiwan can refer to its technical and management expertise.
Israel's Water-Saving Agriculture
Israel has developed advanced water-saving agricultural technologies in arid regions, including drip irrigation, micro-sprinklers, and fertigation (integrated water and fertilizer application). These technologies greatly increase water use efficiency, turning deserts into oases.
While Taiwan is not an arid region, its agricultural water consumption is massive, making water-saving agricultural technology equally important. The government is promoting smart agriculture, including precision irrigation and soil monitoring, to improve agricultural water efficiency.
Israel's water pricing policy is also worth considering. Through tiered pricing, it encourages water conservation; heavy taxes are imposed on excessive usage to curb waste. This market mechanism is often more effective than administrative regulation.
A Sustainable Future for Taiwan's Water Resources
Faced with the challenges of climate change and population growth, Taiwan must establish a more sustainable water resource management system. This requires the collective effort of the government, enterprises, and the public.
Technologically, there must be continuous development in reclaimed water, desalination, and smart management to improve efficiency. Simultaneously, existing facilities must be improved through reservoir dredging and pipe network replacement.
Institutionally, a more reasonable water pricing mechanism must be established to reflect the true cost of water resources. At the same time, water rights systems should be perfected to allow for effective allocation among different uses.
Socially, public education on water conservation must be strengthened to cultivate a culture of saving water. Enterprises must also assume social responsibility by adopting water-saving technologies and reducing waste.
Water is the source of life and the foundation of economic development. On this beautiful island, we must cherish every drop, manage our water resources wisely, and ensure that future generations can also enjoy sufficient clean water. This is not just the responsibility of the government, but a mission for everyone.
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