View source for Pastaza River

{{Short description|River in the Amazon Basin of South America}}
{{distinguish|Pastaza province, Ecuador}}
{{Redirect|Sumatara|the Indonesian island|Sumatra}}
{{Infobox river
| name               = Pastaza River
| native_name        ={{native name|es|Río Pastaza}}
| name_other         = 
| name_etymology     = 
<!---------------------- IMAGE & MAP -->
| image              = RioPastaza.JPG
| image_size         = 270
| image_caption      = The Pastaza at [[Mera, Pastaza|Mera]], Pastaza Province
| map                = Amazonriverbasin basemap.png
| map_size           = 270
| map_caption        = [[Amazon Basin]] with Pastaza River in the far west
| pushpin_map        = 
| pushpin_map_size   = 270
| pushpin_map_caption= 
<!---------------------- LOCATION -->
| subdivision_type1  = Countries
| subdivision_name1  = {{hlist|[[Ecuador]]|[[Peru]]}}
| subdivision_type2  = 
| subdivision_name2  = 
| subdivision_type3  = 
| subdivision_name3  = 
| subdivision_type4  = 
| subdivision_name4  = 
| subdivision_type5  = 
| subdivision_name5  = 
<!---------------------- PHYSICAL CHARACTERISTICS -->
| length             ={{cvt|786.41|km|mi|abbr=on}}<ref name="Perú: Anuario de Estadistícas Ambientales 2022">{{cite book|url=https://www.inei.gob.pe/media/MenuRecursivo/publicaciones_digitales/Est/Lib1877/libro.pdf|title=Perú: Anuario de Estadistícas Ambientales 2022|year=2022}}</ref>
{{cvt|710|km|mi|abbr=on}}<ref name=fao>{{cite book |last1=Ziesler |first1=R. |last2=Ardizzone |first2=G.D. |title=The Inland waters of Latin America |year=1979 |url=http://www.fao.org/docrep/008/ad770b/AD770B05.htm |publisher=[[Food and Agriculture Organization|Food and Agriculture Organization of the United Nations]] |isbn=92-5-000780-9 |chapter=Amazon River System |archive-url=https://web.archive.org/web/20141108152358/http://www.fao.org/docrep/008/ad770b/AD770B05.htm |archive-date=8 November 2014 |url-status=live}}</ref> 
| width_min          = 
| width_avg          = 
| width_max          = 
| depth_min          = 
| depth_avg          = 
| depth_max          = 
| discharge1_location=Confluence of [[Marañón River|Marañón]] (near mouth) 
| discharge1_min     = 
| discharge1_avg     =(Period: 1965–2013){{cvt|2,438.23|m3/s|cuft/s|abbr=on}}<ref name="Evaluación de recursos hídricos en la cuenca Marañón">{{cite web|url=https://repositorio.ana.gob.pe/handle/20.500.12543/39|title=Evaluación de recursos hídricos en la cuenca Marañón|year=2015}}</ref>
{{cvt|2,769|m3/s|cuft/s|abbr=on}}<ref name="Oficina Nacional de Evaluación de Recursos Naturales (ONERN)">{{cite web|url=https://hdl.handle.net/20.500.12543/1063|title=Oficina Nacional de Evaluación de Recursos Naturales (ONERN)|year=1980}}</ref> 
| discharge1_max     = 
<!---------------------- BASIN FEATURES -->
| source1            = [[Cotopaxi Province]]
| source1_location   = 
| source1_coordinates= {{coord|0|40|0|S|78|27|0|W|display=inline}}
| source1_elevation  ={{cvt|3,762|m|abbr=on}}<ref name="Perú: Anuario de Estadistícas Ambientales 2022">{{cite book|url=https://www.inei.gob.pe/media/MenuRecursivo/publicaciones_digitales/Est/Lib1877/libro.pdf|title=Perú: Anuario de Estadistícas Ambientales 2022|year=2022}}</ref> {{cvt|4,570|m|abbr=on}}<ref name=fao/>
| mouth              = [[Marañón River]]
| mouth_location     = 
| mouth_coordinates  = {{coord|4|54|29|S|76|24|32|W|display=inline,title}}
| mouth_elevation    ={{cvt|125|m|abbr=on}}<ref name="Perú: Anuario de Estadistícas Ambientales 2022">{{cite book|url=https://www.inei.gob.pe/media/MenuRecursivo/publicaciones_digitales/Est/Lib1877/libro.pdf|title=Perú: Anuario de Estadistícas Ambientales 2022|year=2022}}</ref> {{cvt|120|m|abbr=on}}<ref name="SanIsidro" />
| progression        = [[Marañón River|Marañón]] → [[Amazon River|Amazon]] → [[Atlantic Ocean]]
| river_system       = [[Amazon River|Amazon]]
| basin_size         = {{cvt|39,504|km2|mi2|abbr=on}}<ref name="Oficina Nacional de Evaluación de Recursos Naturales (ONERN)">{{cite web|url=https://hdl.handle.net/20.500.12543/1063|title=Oficina Nacional de Evaluación de Recursos Naturales (ONERN)|year=1980}}</ref>
{{cvt|41,793|km2|mi2|abbr=on}}<ref name="Evaluación de recursos hídricos en la cuenca Marañón">{{cite web|url=https://repositorio.ana.gob.pe/handle/20.500.12543/39|title=Evaluación de recursos hídricos en la cuenca Marañón|year=2015}}</ref>
| tributaries_left   = 
| tributaries_right  = 
| custom_label       = 
| custom_data        = 
| extra              = {{Designation list
| embed = yes
| designation1 = Ramsar
| designation1_offname = Complejo de humedales del Abanico del río Pastaza
| designation1_date = 5 June 2002
| designation1_number = 1174<ref>{{Cite web|title=Complejo de humedales del Abanico del río Pastaza|website=[[Ramsar Convention|Ramsar]] Sites Information Service|url=https://rsis.ramsar.org/ris/1174|access-date=25 April 2018}}</ref>}}
}}
The '''Pastaza River''' ({{langx|es|Río Pastaza}}, formerly known as the '''Sumatara'''<ref name="Enock">Enock, Charles Reginald (1914) ''Ecuador: its ancient and modern history, topography and natural resources, industries and social development'' Charles Scribner's sons, New York, [https://archive.org/details/ecuadoritsancie00enocgoog/page/n205 pages 177–178], {{OCLC|2453173}}</ref>) also known as the Patate, flowing in Ecuador and Peru is a large [[tributary]] to the [[Marañón River]] in the northwestern [[Amazon Basin]] of [[South America]].<ref name="COPESCAL-T-1">Ziesler, R. and G.D. Ardizzone, G.D. (1979) [http://www.fao.org/docrep/008/ad770b/AD770B05.htm "Amazon System"] ''Las Aguas Continentales de America Latina / The Inland Waters of Latin America'' (COPESCAL Technical Paper No. 1) Fisheries and Aquaculture Department, Food and Agriculture Organization of the United Nations (FAO), Rome, {{ISBN|92-5-000780-9}}, in English and Spanish</ref>

It has its headwaters in the [[Ecuador]]ian province of [[Cotopaxi Province|Cotopaxi]], flowing off the northwestern slopes of the volcano [[Cotopaxi]] and known as the Patate River. The Patate flows south and in [[Tungurahua Province]] it is joined by the [[Chambo River]] just upstream from the town of [[Baños de Agua Santa]] just north of the volcano [[Tungurahua|Mount Tungurahua]] and becomes the Pastaza.<ref>Instituto Geografico Militar del Ecuador, Mapa Tungurahua 50,000:1</ref><ref name="Baños">Topographic map [http://www.lib.utexas.edu/maps/topo/ecuador/banos-ecuador-50k-2000.pdf Baños, Ecuador, Series J721, Sheet 3989 IV, 1:50,000] Instituto Geográfico Militar (IGM), Quito, Ecuador, September 2000, reprinted by the U.S. National Imagery and Mapping Agency</ref> Seven kilometers east of Baños, it is dammed for the [[Agoyán]] hydroelectric project, which has created a silty lagoon by the village of La Cieniga.<ref name="Baños" /> The Agoyán dam was placed in that location specifically to leave the famous Falls of Agoyán, about 5&nbsp;km further downstream, intact.  After the waterfall the river enters a gorge where there is very fast whitewater with class-4 rapids; it is often used for whitewater [[rafting]] although it is not considered to be of the same quality as the [[Tena River]] and is therefore less popular for the sport.<ref>Guia Turistica del Tungurahua, Ministerio de Turismo Ecuador</ref>

From the junction with the Chambo, the Pastaza flows almost due east for about {{convert|275|km|mi|0}} where it then turns south-east, as it is joined by the Topo River.<ref name="Rio Negro">Topographic map [http://www.lib.utexas.edu/maps/topo/ecuador/rio_negro-ecuador-50k-1987.pdf Rio Negro, Ecuador, Series J721, Sheet 3990 II, 1:50,000] Instituto Geográfico Militar (IGM), Quito, Ecuador, June 1996, reprinted by the U.S. National Imagery and Mapping Agency</ref> The Troncal Amazonas highway parallels the river from Baños to Puyo, passing through seven tunnels, and four major waterfalls that are touristic destinations for many Ecuadorians (Agoyán and Pailón del Diablo being the most popular.)  Just past the town of Santa Inez, the Pastaza River crosses into the province of [[Pastaza (province)|Pastaza]], where it forms the boundary between that province and [[Morona-Santiago]]. At the town of [[Mera, Pastaza|Mera]], shortly before reaching Puyo, the river exits the mountains and flows into a wide valley, becoming wider and shallower.<ref name="Mera">[https://archive.today/20130106065342/http://www.igm.gob.ec/site/files/cartabase/enie/imagenes/ENIEIV_D2_ALTA.jpg Topographic map Mera, Ecuador, Series J721, Sheet 3989-I, 1:50,000, Instituto Geográfico Militar (IGM), Quito, Ecuador, 1989, a reduced image is available from IGM] </ref> After [[Shell, Ecuador|Shell]] the river becomes [[Braided river|braided]] and [[meander]]s, leaving [[Oxbow lake|oxbows]] and [[Slough (hydrology)|sloughs]] along its route across the Amazonian floodplain.

After cutting through Ecuador, the Pastaza passes into [[Peru]] at the village of Hito Zoilaluz on Isla Zoilaluz<ref name="Checherta">Topographic map [http://www.lib.utexas.edu/maps/topo/peru/checherta-peru-1565-100k-1995.pdf Checherta, Peru, Series J632, Sheet 1565, 1:100,000] Instituto Geografico Nacional (IGN), Lima, Peru, June 1995, reprinted by the U.S. National Imagery and Mapping Agency</ref> and flows south into the [[Marañón River]] near Puerto Industrial.<ref name="SanIsidro">Topographic map [http://www.lib.utexas.edu/maps/topo/peru/san_isidro-peru-1661-100k-1993.pdf San Isidro, Peru, Series J632, Sheet 1661, 1:100,000] Instituto Geografico Nacional (IGN), Lima, Peru, October 1993, reprinted by the U.S. National Imagery and Mapping Agency</ref>

==Tributaries==
The Pastaza has numerous tributaries, both above and below the hydroelectric dam.  These contribute to its rapid flow and to its tendency to flood.  On the highway side of the Pastaza, a tributary river occurs about every 3–4&nbsp;km for a stretch of about 50&nbsp;km; on the opposite bank, the number of tributaries is slightly lower. The major tributaries are the Chambo, Bobonaza, and Huasaga,<ref name="COPESCAL-T-1" /> also important are the Ambato, the Pindo, and the Puyo.

==Economy==
[[File:Ecuador bridgeoverthePastazas2.JPG|thumb|Bridge over the Pastaza River between [[Puyo, Pastaza|Puyo]] and [[Macas (city)|Macas]]]]
There are no major fisheries on the Pastaza River - it is primarily used as a means of transport by canoe.<ref name="Enock" /> Its rise and fall are rapid and uncertain, and it is shallow and full of sandbanks and snags.<ref>{{Cite EB1911 |wstitle=Amazon |volume=1 |page=788}}</ref>  Flooding occurs seasonally.<ref name="Enock" />

==Bridges==
{{unreferenced section|date=August 2025}}
In Ecuador, there are very few bridges across the Pastaza. The most significant ones are in Tungurahua province - namely a large span over the exact point of headwaters, just north of Baños, and the secondary span created by the Agoyán dam.  After this, bridges tend to be of the suspension type, suitable for foot or small vehicle passage only.  However, it is notable that the Pastaza can be forded during the dry season in a 4x4 truck, going across the floodplains below the town of Mera.

==See also==
*[[Agoyán]]

==References and notes==
{{Reflist}}

[[Category:Tributaries of the Amazon River]]
[[Category:Rivers of Ecuador]]
[[Category:Rivers of Peru]]
[[Category:International rivers of South America]]
[[Category:Ramsar sites in Peru]]
[[Category:Upper Amazon]]
[[Category:Rivers of the Department of Loreto]]