Water from Shihmen Dam is distributed to 28 districts in Taoyuan City, Hsinchu County and New Taipei, with a combined population of some 3.4 million people and more than 36,500 hectares (90,000 acres) of irrigated land.
 Each year, Shihmen furnishes 181.6 million m³ (147,200 acre feet) of water for irrigation and industrial uses and about 127.4 million m³ (103,300 acre feet) for residential use in downstream areas.
In addition, an annual minimum river release of 299.6 million m³ (242,900 acre feet) is maintained to provide a baseflow in the lower Dahan River.
About 386.3 million m³ (313,200 acre feet) of the aforementioned releases are utilized for hydroelectric generation.
The dam's power station generates roughly 200 million kilowatt hours annually and is integral in meeting peaking power demands in northern Taiwan's electricity grid.
Hydroelectric power releases peak in late July and August, largely because of air-conditioning usage in Taiwan's northern cities.

Shihmen is one of several key reservoirs in the Tamsui River system used to cut peak flood flows during typhoon events.
Dam releases are coordinated with those from Feitsui Dam to the east in order to reduce the severity of flooding.
However, sediment accumulation in the reservoir has reduced its effectiveness on large flooding events.
As a result, the "frequency with which the Shih-men Dam discharges water down its spillway ranks first among Taiwan's reservoirs.
The phrase 'the Shihmen Reservoir is releasing flood water' has become a euphemism for 'your fly is open'."
Additionally, large flooding events can cause turbidity levels in the reservoir to increase by over 3,000 times of average, forcing authorities to shut down water supplies.
This problem has been exacerbated by the increasing percentage of Shihmen water going to residential and industrial users, who generally demand clearer water than the agricultural users Shihmen was originally intended to supply.

The reduction in storage capacity has also affected Shihmen's ability to provide water during droughts.
Demand often exceeds stored water in Shihmen Reservoir during the dry season, forcing frequent water-supply cuts.
For several weeks in 1994, the drought-stricken Shihmen Dam service area was limited to one day of running water in three.
This has been further exacerbated by global climate change reducing the length of the rainy season in Taiwan, while increasing the intensity of rainfall when storms do strike the island.
In 2015, Taiwan recorded its lowest winter rainfall since 1947, and the Shihmen reservoir fell to a record low of 24.5 percent of capacity, again forcing the government to enact water rationing.

Among the other benefits of the dam and reservoir is recreation.
More than 160,000 tourists visit the dam each year, especially during floodwater releases.
The reservoir, its surrounding recreation area and towns are visited by a further 1.7 million people each year.
It is said that "after its grand opening to the public in 1964, the Shihmen Reservoir has remained one of the top spots on Taiwan's sight-seeing billboards".
Recreational and commercial fishing on the reservoir produces about 80,000 kilograms (180,000 lb) of fish each year, generating an annual revenue of NT$29.33 million.
Water from Shihmen Dam is distributed to 28 districts in Taoyuan City, Hsinchu County and New Taipei, with a combined population of some 3.4 million people and more than 36,500 hectares (90,000 acres) of irrigated land.  Each year, Shihmen furnishes 181.6 million m³ (147,200 acre feet) of water for irrigation and industrial uses and about 127.4 million m³ (103,300 acre feet) for residential use in downstream areas. In addition, an annual minimum river release of 299.6 million m³ (242,900 acre feet) is maintained to provide a baseflow in the lower Dahan River. About 386.3 million m³ (313,200 acre feet) of the aforementioned releases are utilized for hydroelectric generation. The dam's power station generates roughly 200 million kilowatt hours annually and is integral in meeting peaking power demands in northern Taiwan's electricity grid. Hydroelectric power releases peak in late July and August, largely because of air-conditioning usage in Taiwan's northern cities.
Shihmen is one of several key reservoirs in the Tamsui River system used to cut peak flood flows during typhoon events. Dam releases are coordinated with those from Feitsui Dam to the east in order to reduce the severity of flooding. However, sediment accumulation in the reservoir has reduced its effectiveness on large flooding events. As a result, the "frequency with which the Shih-men Dam discharges water down its spillway ranks first among Taiwan's reservoirs. The phrase 'the Shihmen Reservoir is releasing flood water' has become a euphemism for 'your fly is open'." Additionally, large flooding events can cause turbidity levels in the reservoir to increase by over 3,000 times of average, forcing authorities to shut down water supplies. This problem has been exacerbated by the increasing percentage of Shihmen water going to residential and industrial users, who generally demand clearer water than the agricultural users Shihmen was originally intended to supply.
The reduction in storage capacity has also affected Shihmen's ability to provide water during droughts. Demand often exceeds stored water in Shihmen Reservoir during the dry season, forcing frequent water-supply cuts. For several weeks in 1994, the drought-stricken Shihmen Dam service area was limited to one day of running water in three. This has been further exacerbated by global climate change reducing the length of the rainy season in Taiwan, while increasing the intensity of rainfall when storms do strike the island. In 2015, Taiwan recorded its lowest winter rainfall since 1947, and the Shihmen reservoir fell to a record low of 24.5 percent of capacity, again forcing the government to enact water rationing.
Among the other benefits of the dam and reservoir is recreation. More than 160,000 tourists visit the dam each year, especially during floodwater releases. The reservoir, its surrounding recreation area and towns are visited by a further 1.7 million people each year. It is said that "after its grand opening to the public in 1964, the Shihmen Reservoir has remained one of the top spots on Taiwan's sight-seeing billboards". Recreational and commercial fishing on the reservoir produces about 80,000 kilograms (180,000 lb) of fish each year, generating an annual revenue of NT$29.33 million.
Shihmen Dam