Farmland irrigation is critical to people's livelihoods. Taiwan has a wide range of farmland and is one of the most successful countries in the world with rice production as its main crop. As a result of long-term development, existing operating organization is considerable and irrigation engineering facilities comprehensive, with irrigation technology, water allocation and operational management organizations underscoring Taiwan’s success in this area. In order to effectively allocate and utilize irrigation water resources, the country has 17 Irrigation Agency management offices. In addition to allocating water, these are also responsible for maintaining irrigation facilities within their jurisdiction to ensure the supply of farmland irrigation water and remove excess water. At present, the most important facilities under the management offices include irrigation channels, trunk lines, branch lines, sub lines, small and medium water channel, tunnels and drainage channels, barrages, water gates, weirs, headworks, water bridges, hydraulic drop structures, sewer and water measurement devices etc., all of which are operated by local offices.
Natural environment and water resources utilization
1. The natural environment
Taiwan has a total area of about 36,000 square kilometers. The central mountain range runs from north to south, forming a narrow and long valley in the east and a wider plain in the west. It has a subtropical island climate. As a result of the influence of continental airflows, high temperatures, frequent rain and strong winds, climate changes are highly complicated as seasonal rain varies by region. The northeast is dry in summer and rainy in winter, while the southwest is rainy in summer and dry in winter.
2. Hydrometeorological environment
Climate:
Taiwan has a subtropical climate with high temperatures and humidity throughout the year. Plains are suitable for the growth of crops, but the northeast monsoon prevails from October to March the following year, and there are typhoons and torrential rain in summer and autumn. Although these bring abundant rainfall, they can also cause disasters.
Hydrology:
Taiwan has abundant rainfall, with an average annual rainfall of 2,510mm. However, due to the uneven distribution of precipitation in terms of location and time, nearly 80% of the annual rainfall is concentrated in the rainy season from May to October each year. In order to mitigate typhoon flood disasters, it is necessary to collect relevant information to respond more effectively. This work is undertaken by observation facilities, including 915 rainfall stations and 134 flow stations, which are distributed in various important hydrometric points as a network that monitors hydrometric changes.
Rivers:
Taiwan's rivers are divided by the central mountain range, with all flowing east to west and extend to the sea. There are 29 major rivers, which are the main sources of irrigation water, but tend to be short and steep, with turbulent water flows. As a result, the flow rate fluctuates rapidly along with the amount of rainfall and changes can be extreme. The flow rate is low during the dry season, but during the flood season, due to fragile upstream geology, narrow and steep river valleys and floods carrying large amounts of soil down to rivers, causing flooding in the lower reaches of those rivers, it is difficult to manage.
3. Development and utilization of water resources
The average annual total rainfall in Taiwan is 90.5 billion cubic meters, and annual water consumption is about 19.5 billion cubic meters, accounting for 22% of total annual rainfall, including 15.4 billion cubic meters of agricultural water consumption, 2.4 billion cubic meters of water for human consumption and industrial water consumption of 1.7 billion cubic meters; Sources include river runoff of 8.8 billion cubic meters, extracted groundwater of 6 billion cubic meters, and the use of reservoirs to store 4.7 billion cubic meters of water.
4. Development and improvement of land resources
The average annual total rainfall in Taiwan is 90.5 billion cubic meters, and annual water consumption is about 19.5 billion cubic meters, accounting for 22% of total annual rainfall, including 15.4 billion cubic meters of agricultural water consumption, 2.4 billion cubic meters of water for human consumption and industrial water consumption of 1.7 billion cubic meters; Sources include river runoff of 8.8 billion cubic meters, extracted groundwater of 6 billion cubic meters, and the use of reservoirs to store 4.7 billion cubic meters of water. The total area of Taiwan is 3.6 million hectares, including 950,000 hectares of inner plains, 970,000 hectares of hilly areas and 1.68 million hectares in alpine regions. Originally, there was about 1 million hectares of arable land, but that was reduced due to large scale industrial and commercial use. Fortunately, the government has developed more than 13,000 hectares of riverside reclaimed land and more than 4,300 hectares of coastal reclaimed land. At present, there are still about 870,000 hectares of arable land. The irrigation area under the jurisdiction of the Irrigation Agency management offices is about 371,233 hectares, and the privately established irrigation works about 100,000 hectares.
In order to increase the utilization of agricultural land, the government has adopted comprehensive and multi-targeted land reform measures - farmland re-adjustment. At present, 75% of paddy field land has been subject to farmland re-adjustment, and research is ongoing into the feasibility of rezoning dry fields.
5. Existing farmland irrigation facilities
Agriculture has been the major means of production since Taiwan was an agrarian society. The current agricultural irrigation operation organization is substantial and irrigation facilities comprehensive. It is one of the most successful countries in the world in terms of irrigation technology, water allocation and operation management organization. There are 17 Irrigation Agency management offices throughout Taiwan. In addition to allocating water, these are also responsible for maintaining and managing irrigation facilities within their jurisdiction to maintain the supply of farmland irrigation water and remove excess water. At present, there are about 67,000 waterways under Irrigation Agency management offices, including irrigation channels, trunk lines, branch lines, sub lines, small and medium water channels and drainage channels, with a total length of about 67 million meters; There are about 180,000 important facilities such as barrages, headworks, water gates, weirs, water bridges, hydraulic drop structures, sewers and water measurement devices, which are operated by local offices.