Irrigation in the Mountainous Cordilleras

Large ranges of mountains that host grand forests. Sharp ridges on which heart-stopping highway systems were built. Mountain peaks on which picturesque seas of clouds amaze locals and tourists alike.

Such were the usual sights when passing through the challenging roads of the Cordillera, especially along the 150-kilometre stretch of the Halsema Highway, traversing twelve municipalities of Benguet and Mountain Province.

With this rolling and mountainous topography, just like the world-famous rice terraces, it is always a wonder for tourists and visitors who pass by Halsema Highway’s terraces of agricultural areas how these are cultivated and irrigated for crop production.

CAR’s irrigation systems

Pipe irrigation is a more common scheme of development in the mountainous areas of the Cordilleras.

While big irrigation systems in the country are understandably found in the flatter regions, the Cordillera Administrative Region’s rolling and mountainous topography still facilitates irrigation development and farm cultivation in areas of higher elevation. The rice and vegetable terraces in various provinces of the region are perfect examples of this.

With the unique landscape in the region, NIA-CAR covers only four national irrigation systems. These are the Upper Chico River Irrigation System (UCRIS) with service areas in Kalinga and Isabela, West Apayao Abulug Irrigation System (WAAIS) in Apayao and Cagayan, Hapid Irrigation System in Ifugao and the Abra River Irrigation System in Abra. The rest of the irrigation systems are considered communal as they irrigate terraced fields or patches of farmlands with aggregate areas of less than 1,000 hectares.

Various centuries-old rice terraces in the region are part of the service areas of communal irrigation systems assisted by the National Irrigation Administration from various fund sources through the improvement of the water sources, and canal systems. Several allocations from various funds were rationed for the repair, restoration or improvement of irrigation facilities of various rice terraces in Ifugao, Mountain Province, Kalinga and Benguet.

Meanwhile, the equally picturesque vegetable terraces especially when bathed with morning or afternoon fog are usually found in the provinces of Benguet, Mountain Province and parts of Ifugao. Located usually along mountain sides, these are irrigated through pipe lines.

Pipe Irrigation

Some portions of pipelines are embedded into the forest ground such as this one in Camiding Communal Irrigation System in Tinongdan, Itogon, Benguet.

Necessity for food staple and livelihood obliged people in the highlands to carve mountain sides, into stair-like irregular rice areas, and then later on, for vegetable cultivation. 

Establishment of pipe irrigation in the mountainous Cordillera remains labor-intensive since access involves strenuous and extensive hiking with carried loads. Pipes used in NIA irrigation are high-density polyethylene (HDPE) in various sizes. HDPE pipes with sizes of up to 2.5” in diameter have a cutting length of 60 to 100 meters and are packaged in rolls. For pipes with diameter ranging from 3” to 12”, these have a cutting length of six meters. Two laborers are sometimes needed to carry the load uphill or downhill along steep trails to the construction site. Other construction materials, like cement, rebars and aggregates, also had to be brought to the remote worksite by carrying them on shoulders or heads. Whenever possible, makeshift pulleys are established by constructors to facilitate easier mobility of materials.  The added hauling and handling charges make the unit cost of construction or rehabilitation works a bit higher than those of the projects in the flat areas.

Rivulets with small watersheds and discharges, sometimes located in the remotest part of the forest, are tapped as water sources for gravity irrigation of vegetable areas. Intake structures or siltation tanks are established along streams or creeks to create adequate hydraulic head and to which the main pipeline will be connected. Depending on the proximity of the water source and the service area, pipelines usually run for about three to five kilometers. There are a few irrigation systems that have pipeline with a total length of about nine kilometers crossing in between mountains, such as that of the Taloy Sur Communal Irrigation System in Tuba, Benguet.

Suspended pipelines are supported by cable wires as these traverse creeks, rivers or cliffs.

From the water source, main pipelines, usually two to eight inches in diameter depending on the area to be served are either suspended, embedded or laid on the ground. Suspended pipelines are carried by cable wires, and supported with concrete tower and blocks on both sides to cross waterways, rivers or cliffs. For some portions of the pipelines, the pipes are embedded into the grounds to prevent damaged from forest fires. Parts of pipelines can just be laid on the ground especially those passing through rocky areas.

Reservoir tanks, such as this one in Babalak Communal Irrigation System in Kabayan, Benguet, are constructed in strategic areas to enable the collection and storage of irrigation water before these are distributed to individual farms.

Main pipelines are then connected to a concrete reservoir tank, typically with rectangular sizes ranging from 2.4 meters to 6 meters with a height of 2.4 meters, where water is collected and stored. A main reservoir tank can be distributed to smaller reservoir tanks where farmers can connect their own individual pipes usually ½ to ¾ inches in diameter towards their vegetable gardens.

Sprinkler irrigation generally offers the only method of obtaining adequate distribution of water on certain rolling lands where leveling for surface irrigation is not feasible.

A sprinkler head with small orifices or nozzles is then connected to the end of the lateral pipes which will then produce water under pressure in the form of spray, simulating that of rain.