Agno River
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The Agno River, also known as the Pangasinan River, is a river on the island of
Luzon Luzon ( , ) is the largest and most populous List of islands in the Philippines, island in the Philippines. Located in the northern portion of the List of islands of the Philippines, Philippine archipelago, it is the economic and political ce ...
in the
Philippines The Philippines, officially the Republic of the Philippines, is an Archipelagic state, archipelagic country in Southeast Asia. Located in the western Pacific Ocean, it consists of List of islands of the Philippines, 7,641 islands, with a tot ...
. Traversing the provinces of
Benguet Benguet (), officially the Province of Benguet ('';'' ; ; ; ), is a landlocked Provinces of the Philippines, province of the Philippines located in the southern tip of the Cordillera Administrative Region in the island of Luzon. Its capital cit ...
, Pangasinan, and Tarlac, it is one of the largest river systems in the country, with a drainage area of . The river originates in the Cordillera Mountains and empties into the
South China Sea The South China Sea is a marginal sea of the Western Pacific Ocean. It is bounded in the north by South China, in the west by the Indochinese Peninsula, in the east by the islands of Taiwan island, Taiwan and northwestern Philippines (mainly Luz ...
via
Lingayen Gulf Lingayen Gulf is a large gulf on northwestern Luzon in the Philippines, stretching . It is framed by the provinces of Pangasinan and La Union and sits between the Zambales Mountains and the Cordillera Central (Luzon), Cordillera Central. The Agno ...
. The river is long, making it the sixth longest river in the country. Roughly two million people live in the Agno River Valley, making it one of Philippines' larger population clusters. The river is dammed by three hydroelectric power plants: the Ambuklao Dam in Bokod, the Binga Dam in Itogon, and the San Roque Dam in San Manuel.


Geography

The Agno River is the main drainage system of the area and has a catchment area of . It is the third largest river in Luzon (next to
Cagayan River The Cagayan River, also known as the Río Grande de Cagayán, is the longest river and the largest river by discharge volume of water in the Philippines. It has a total length of approximately and a drainage basin covering . It is located in ...
and Pampanga River) and the fifth largest river in the Philippines. The Agno is the largest Philippine river in terms of water discharge, draining around 6.6 cubic kilometers of
fresh water Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salt (chemistry), salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include ...
into
Lingayen Gulf Lingayen Gulf is a large gulf on northwestern Luzon in the Philippines, stretching . It is framed by the provinces of Pangasinan and La Union and sits between the Zambales Mountains and the Cordillera Central (Luzon), Cordillera Central. The Agno ...
, or almost 70% of the total fresh water input into the gulf. The
headwaters The headwater of a river or stream is the geographical point of its beginning, specifically where surface runoff water begins to accumulate into a flowing channel of water. A river or stream into which one or many tributary rivers or streams flo ...
of Agno River are at the slopes of Mount Data in the Cordillera Mountains at an elevation of , where it drains
Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...
to
Paleocene The Paleocene ( ), or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), ...
igneous basement rocks, and marine siliciclastic and
carbonate rock Carbonate rocks are a class of sedimentary rocks composed primarily of carbonate minerals. The two major types are limestone, which is composed of calcite or aragonite (different crystal forms of CaCO3), and Dolomite (rock), dolomite rock (also kn ...
s. Of its total length, about runs through mountainous terrain and
canyon A canyon (; archaic British English spelling: ''cañon''), gorge or chasm, is a deep cleft between escarpments or cliffs resulting from weathering and the erosive activity of a river over geologic time scales. Rivers have a natural tendency t ...
s. As the river descends following a southerly course, it exhibits a braided channel pattern. It then transforms into a southwest-directed meandering river as it crosses the Central Luzon Plain. From its
confluence In geography, a confluence (also ''conflux'') occurs where two or more watercourses join to form a single channel (geography), channel. A confluence can occur in several configurations: at the point where a tributary joins a larger river (main ...
with the Tarlac River emanating from the south, the Agno River then veers northward while draining the eastern flanks of the
Zambales Mountains The Zambales Mountains is a mountain range in western Luzon. The mountains spread along a north-south axis, separating Luzon's central plain from the South China Sea. The range extends into five Provinces of the Philippines, provinces: Zambales, ...
. The Agno's principal
tributaries A tributary, or an ''affluent'', is a stream or river that flows into a larger stream ('' main stem'' or ''"parent"''), river, or a lake. A tributary does not flow directly into a sea or ocean. Tributaries, and the main stem river into which the ...
include the Pila, Camiling, Tarlac and Ambayoan Rivers. The main branch of the Agno River is Tarlac River which originates from
Mount Pinatubo Mount Pinatubo is an active stratovolcano in the Zambales Mountains in Luzon in the Philippines. Located on the tripoint of Zambales, Tarlac and Pampanga provinces, most people were unaware of its eruptive history before the pre-eruption volc ...
(elevation ) in Tarlac and joins the Agno River at Poponto Swamp near Bayambang. The swamp has an area of about and temporarily retains flood waters from Tarlac River. After passing through mountains at an average elevation of some ASL, the Agno River forms a vast
alluvial fan An alluvial fan is an accumulation of sediments that fans outwards from a concentrated source of sediments, such as a narrow canyon emerging from an escarpment. They are characteristic of mountainous terrain in arid to Semi-arid climate, semiar ...
and
delta Delta commonly refers to: * Delta (letter) (Δ or δ), the fourth letter of the Greek alphabet * D (NATO phonetic alphabet: "Delta"), the fourth letter in the Latin alphabet * River delta, at a river mouth * Delta Air Lines, a major US carrier ...
called the Pangasinan Plain, a historically vital economic hub on Luzon Island. A number of faults of local and regional significance cut across the river. Joint systems are also found in the area. These faults and joints reduce the rock strength and rock coherence through which water could pass or slippage could occur. The Philippine Fault System, including the Digdig Fault, which has been assessed as the causative fault of the July 16, 1990 Luzon earthquake, and the San Manuel Fault, Bulangit Fault and the San Roque Fault are some of the major fault lines crossing the river. The river's headwaters and upstream basin in the Cordillera Central range are designated conservation areas that lie within the Mount Data National Park, the Upper Agno River Basin Resource Reserve and the Lower Agno Watershed Forest Reserve.


Flora and fauna

Spanish explorers who documented the catchment area of the river in the 16th century say the mouth of the Agno was an extensive
marshland In ecology, a marsh is a wetland that is dominated by herbaceous plants rather than by woody plants.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p More in general ...
with rich alluvial soil. It was thickly covered with
mangrove A mangrove is a shrub or tree that grows mainly in coastal saline water, saline or brackish water. Mangroves grow in an equatorial climate, typically along coastlines and tidal rivers. They have particular adaptations to take in extra oxygen a ...
and nipa palm trees which served as habitat to many marshland wildlife species. But the catchment area is now severely deforested. Primary forest has almost completely disappeared apart from a few areas above ASL. The forests have been replaced by
grassland A grassland is an area where the vegetation is dominance (ecology), dominated by grasses (Poaceae). However, sedge (Cyperaceae) and rush (Juncaceae) can also be found along with variable proportions of legumes such as clover, and other Herbaceo ...
and riceland.


Flooding

Since the Agno River basin is characterized by mountainous topography, the Ambuklao water reservoir was built to keep it from gushing down and causing devastating effects on the lower levels of the river, the flood runoff estimated annually at about 6,654 million cubic meters reaches the plain in several hours in the river mouth in about a day. Average annual rainfall varies from in the neighborhood of Tarlac to in the upper reaches of the Agno River. The Pangasinan Plain suffers from recurrent and destructive floods. The catastrophic floods of July–August 1972, May 1976, and September 2009 inundated the entire Pangasinan Plain, including the floodplains of the Tarlac River. The
PAGASA The Philippine Atmospheric, Geophysical and Astronomical Services Administration (, abbreviated as PAGASA , which means "hope" as in the Tagalog language, Tagalog word ''pag-asa'') is the National Meteorological and Hydrological Services (NMHS ...
, the national weather bureau, has established a flood monitoring and warning center in Pangasinan.


People

The Agno traverses several towns in Benguet province where some 35,000 indigenous Ibaloi, Kankanaey and Kalanguya people live. The Ibaloi people of Benguet regard the river as sacred because it gives life.
Barangay The barangay (; abbreviated as Brgy. or Bgy.), historically referred to as ''barrio'', is the smallest Administrative divisions of the Philippines, administrative division in the Philippines. Named after the Precolonial barangay, precolonial po ...
Dalupirip, Itogon in Benguet province is held sacred by its people. Portions of the land serve as the burial grounds of their ancestors. The place holds great historical value and is considered one of the remaining seats of Ibaloi culture. Archaeological sites were discovered at Sitio Camanggaan, Barangay San Roque in San Manuel, Pangasinan and in surrounding areas. Yields consisted of tradeware and earthenware shards and
Palaeolithic The Paleolithic or Palaeolithic ( years ago) ( ), also called the Old Stone Age (), is a period in human prehistory that is distinguished by the original development of stone tools, and which represents almost the entire period of human prehist ...
and
Neolithic The Neolithic or New Stone Age (from Ancient Greek, Greek 'new' and 'stone') is an archaeological period, the final division of the Stone Age in Mesopotamia, Asia, Europe and Africa (c. 10,000 BCE to c. 2,000 BCE). It saw the Neolithic Revo ...
stone tool Stone tools have been used throughout human history but are most closely associated with prehistoric cultures and in particular those of the Stone Age. Stone tools may be made of either ground stone or knapped stone, the latter fashioned by a ...
s.


Economic importance

Gold panning was common along the river, with gold found along the river from Kabayan, Benguet, to San Manuel, Pangasinan, and along its tributaries in Tublay, Benguet, and Bokod, Benguet. The river has three hydroelectric plants: Binga Dam in Itogon, Benguet ( upstream); Ambuklao Dam in Bokod, Benguet ( upstream) and the San Roque Dam in San Manuel, Pangasinan. Binga has been operational since 1960 and Ambuklao since 1956. There are several
mining Mining is the Resource extraction, extraction of valuable geological materials and minerals from the surface of the Earth. Mining is required to obtain most materials that cannot be grown through agriculture, agricultural processes, or feasib ...
concessions in the upper reaches of the river. The government has also established the Agno River irrigation system to provide
irrigation Irrigation (also referred to as watering of plants) is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has bee ...
water to some 60 to 100 square kilometers of ricelands in Pangasinan.


Crossings

This is listed from mouth to source. # Domalandan Bridge (Lingayen–Labrador Road, Lingayen) # Bugallon Bridge (, Bugallon) # Bocboc Bridge (Gallego Street, AguilarSan Carlos boundary) # Mangatarem–Urbiztondo Road ( Mangatarem, PangasinanUrbiztondo, Pangasinan boundary) # President Carlos P. Romulo Bridge (Camiling–Malasiqui–Santa Barbara Rd, Bayambang–
Camiling, Tarlac Camiling, officially the Municipality of Camiling, (; ; ), is a municipality in the Philippine province, province of Tarlac in the Philippines. According to the 2020 census, it has a population of 87,319 people. Camiling is one of the fastest-g ...
boundary) # Calvo Bridge (Alcala–Bayambang Road, BayambangBautista boundary) # Teofilo Sison Bridge (, Rosales–Villasis boundary) # Tomana Underpass (, RosalesVillasis boundary) # Narciso Ramos Bridge (Santa Maria–Binalonan Road, Asingan, Pangasinan) # Ambuklao By-pass Bridge (, Bokod) # Liboong Hanging Bridge ( Bokod) # Bokod–Kabayan–Buguias–Abatan Road ( Buguias, Benguet)


Cities and municipalities

The following list shows the cities and towns traversed by the Agno River, ordered upstream going downstream: * Buguias, Benguet ''(location of Mount Data)'' * Kabayan, Benguet * Bokod, Benguet ''(drains into the Ambuklao Dam)'' * Itogon, Benguet ''(drains into the Binga Dam)'' * San Manuel, Pangasinan ''(drains into the San Roque Dam)'' * San Nicolas, Pangasinan * Santa Maria, Pangasinan * Asingan, Pangasinan * Villasis, Pangasinan * Rosales, Pangasinan * Santo Tomas, Pangasinan * Alcala, Pangasinan * Bayambang, Pangasinan * Bautista, Pangasinan *
Camiling, Tarlac Camiling, officially the Municipality of Camiling, (; ; ), is a municipality in the Philippine province, province of Tarlac in the Philippines. According to the 2020 census, it has a population of 87,319 people. Camiling is one of the fastest-g ...
* Urbiztondo, Pangasinan * Mangatarem, Pangasinan * San Carlos City, Pangasinan * Aguilar, Pangasinan * Bugallon, Pangasinan * Lingayen, Pangasinan ''(location of river mouth)'' * Labrador, Pangasinan


References


Further reading

* Siringan, Fernando P. and Mateo, Zenon Richard P. ''Sediment load partitioning of the Agno River and changes in the shoreline position,'' National Institute of Geological Sciences, University of the Philippines, Diliman, Quezon City * Torres, Ronnie C.; Paladio, Ma. Lynn O.; Punongbayan, Raymundo S.; and Alonso, Rosalito A. ''Mapping of Areas Affected by Liquefaction during the July 16, 1990, Earthquake'' Philippine Institute of Volcanology and Seismology and University of the Philippines National Institute of Geological Sciences


External links

*
Philippine Atmospheric, Geophysical and Astronomical Services Administration

Institute of Philippine Culture's Case Study of San Roque Multipurpose Project

International Rivers
{{Authority control Rivers of the Philippines Landforms of Benguet Landforms of Pangasinan