Technical and contextual information about the canton's water system.
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Location and general context
The canton is located within the Grande de Tárcoles River sub-basin, which drains the Central Valley's waters to its outlet on the Pacific Ocean. It has a territorial area of 73.84 km², spread across a strip approximately 15 km long by 5 km wide, with elevations ranging from 600 m a.s.l. in Rincón de Carrillos to 2,838 m a.s.l. in Poás Volcano National Park.
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Main rivers and boundaries
The courses of the Poasito and Poás rivers define the eastern boundary with the canton of Alajuela, while the Achiote, Tacares and Prendas rivers define the western boundary with the canton of Grecia.
With Grecia, Poás shares the sub-basins of the Tacares and Prendas rivers — an area of great abundance of groundwater, springs and water intakes, including the Los Chorros spring, located in the protected area of the same name.
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Poás River micro-watershed
Located between Barva volcano and Poás volcano, down to the confluence with the Grande River near Alajuela. It has high potential for the formation of high-quality aquifers.
Over the past 14 years, water production in the micro-watershed has increased by 1.6%, specifically in runoff and hydrological gain.
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Poás Aquifer and human consumption
Water for human consumption comes from wells and springs, primarily from the Poás aquifer. Despite the intrinsic vulnerability of this aquifer to contamination, livestock and agricultural activities have been developed across a large part of the sub-basin's territory.
Population centres primarily use septic tanks as sanitation systems, which represents a contamination risk for both groundwater and surface water.
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Socio-environmental pressures
The micro-watershed has a socioeconomic structure based on agro-productive activities: cattle ranching, poultry farms, sugarcane, coffee and non-traditional crops such as flowers, strawberries and vegetables, which exert pressure on water resources.
Six socio-environmental pressures with a negative impact on water were identified, originating from both households and productive activities. Despite this, water quality parameters showed majority compliance with established quality criteria.
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Natural risks to water
Flash floods and landslides are associated with the presence of deeply incised river valleys with steep slopes in elongated micro-watersheds over recent volcanic deposits.
Identified risks range from volcanic eruptions, tectonic faults and landslides to human-induced threats that have caused degradation and contamination of soils and surface and groundwater.
