Current evidence suggests that Indigenous farmers in the North American Southwest began canal irrigation in the second millennium BC, marking an important change in food production technology. Early ...canal systems are preserved in alluvial floodplains of the US-Mexico Borderlands region, tend to be deeply buried, and can appear as natural fluvial features. Here I discuss some of the challenges in identifying early canals and associated fields and present case studies from the Santa Cruz River in southern Arizona where buried channels dating as early as 1600–1400 BC were likely human constructed. These small channels share several stratigraphic properties and are consistent with hypotheses of early canal irrigation practiced by small family groups reliant on mixed farming and foraging. Through time, irrigation canal systems expanded in size, resulting in increased labor investment, sedentism, and productivity and facilitating the development of larger irrigation communities. Stratigraphic and geomorphic properties of early canal systems thus far identified along the Santa Cruz River provide a framework for identifying potential early canal evidence in other fine-grained floodplains of the Southwest, thereby improving our understanding of Indigenous agricultural intensification.
We present 12 accelerator mass spectrometry (AMS) 14C and five quartz single-grain optically stimulated luminescence (OSL) ages from three Early Agricultural period irrigation canals recently ...discovered in the floodplains of the Santa Cruz River and Rillito Creek in Tucson, Arizona. Significant discrepancies in the AMS 14C ages are associated with fluvial redeposition of charcoal, producing at times, age overestimates of ∼1000 years. Single-grain OSL ages on canal sediments and application of a minimum age model accurately date the final operation of the canals but have relatively large standard errors of several hundred years. Based on single-grain OSL, one canal dates 730–310 B.C. and the other two date 560–100 B.C. This corresponds with a period of predominant floodplain aggradation (∼500 B.C.–A.D. 1) conducive to water control and irrigation agriculture. Stratigraphic evidence of uncontrolled flooding and rapid sedimentation is present in all three canals and marks the abandonment of two canals. Determining the age of the earliest canals is important for understanding the origins of water management and the transition from foraging to intensive agriculture in the North American Southwest. Due to potential problems with reworked organic material for 14C dating and partial bleaching (resetting) of luminescence signals in fluvial settings, we recommend a combined AMS 14C and single-grain OSL approach for dating early canals.
•Three prehistoric canals near Tucson, AZ were dated with AMS 14C and single-grain OSL.•While 14C ages from charcoal were more precise, they were up to 1000 years too old.•Single-grain OSL methods provided more accurate ages for canal use.•Canals date to ∼700–100 B.C., relate to floodplain aggradation and early agriculture.
•Anthropogenic soils produced by centuries of Hohokam (450–1450 CE) canal irrigation underlie the city of Phoenix.•Age and origin of a hypothesized buried anthropogenic soil tested with ...morphological, micromorphological, pollen, and chronometric analyses.•Results indicate that Indigenous irrigation agriculture produced a 70+ cm cumulic soil in ∼500 years in our study area.•Evidence suggests application of organic materials to help maintain soil productivity.•We hypothesize that farming ceased in our study area ∼1200 CE due to reduced soil quality.
Over 1000 years of irrigation agriculture by the Hohokam (450–1450 CE) left an indelible mark on soils of the lower Salt River Valley in Arizona. Defining the nature, extent, and formation of these anthropogenic soils, named Salt River Adobe during the valley’s first soil survey, is important for understanding human impacts to the environment and agricultural history of arid lands. Towards that objective, we describe an undisturbed, buried example of the Salt River Adobe from the Salt River floodplain and present evidence for its anthrogenesis based on archaeological context, age, physicochemical properties, micromorphology, and pollen content. We determined that the Salt River Adobe at this location represents approximately 500 years of irrigation sedimentation and pedogenesis resulting in a 70+ cm thick cumulic soil. Cessation of irrigation within the project area occurred in the 1200s CE at a time of peak Hohokam population. Our evidence suggests fairly continuous multi-century irrigation farming by the Hohokam at one location with soil productivity maintained by irrigation sedimentation and possible fertilization. We hypothesize that cessation of farming at this location during a time of high food-demand was due in part to gradually reduced soil permeability and tilth. More research is needed to better understand the geographic extent and genesis of Salt River Adobe and the role it played in Hohokam farming and cultural history.
El Niño resilience farming on the north coast of Peru Caramanica, Ari; Mesia, Luis Huaman; Morales, Claudia R. ...
Proceedings of the National Academy of Sciences - PNAS,
09/2020, Volume:
117, Issue:
39
Journal Article
Peer reviewed
Open access
El Niño–Southern Oscillation has been treated as a disruptor of environmental and socioeconomic equilibrium both in ancient times and in modern-day Peru. Recent work in the coastal desert plain, ...known as the Pampa de Mocan, challenges this view by demonstrating that prehispanic irrigation systems were designed to incorporate floods and convert them into productive waters. Archaeological investigations in this landscape reveal a 2,000-y history of floodwater farming embedded in conventional canal systems. Together with a pollen record recovered from a prehispanic well, these data suggest that the Pampa de Mocan was a flexible landscape, capable of taking advantage of El Niño floodwaters as well as river water. In sharp contrast to modern-day flood mitigation efforts, ancient farmers used floodwaters to develop otherwise marginal landscapes, such as the Pampa de Mocan, which in turn mitigated risk during El Niño years. These archaeological data speak to contemporary policy debates in the face of increasingly intense and frequent natural disasters and question whether El Niño Southern Oscillation events should be approached as a form of temporary disorder or as a form of periodic abundance.
Here we present the first
14
C ages for the Ascope Canal System (ACS), a large prehispanic hydraulic network in the Chicama Valley on the north coast of Peru. Composed of multiple alignments that ...irrigated areas north of the river, our results indicate that the ACS was constructed and operated in the Late Intermediate Period, ca. a.d. 1000-1400. This overlaps in time with the Chicama-Moche Intervalley Canal that diverted water on the south side of the Chicama River and extended to the city of Chan Chan. Conservative estimates of discharge capacity indicate that the combined flow through the canals would have exceeded stream flow in the Chicama River during half of the year. The ACS appears to have functioned for several centuries and would have been in direct competition with the Intervalley Canal. There was, apparently, insufficient water for both systems and other Chicama Valley canals during most of the year. This study underscores the complexities of understanding the operations and histories of irrigation systems in complex societies.
A field-based course at the University of Arizona called Sense of Place (SOP) covers the geology, ecology and cultural history of the Tucson area. SOP was quantitatively assessed for pedagogical ...effectiveness. Students of the Spring 2008 course were given pre- and post-course word association surveys in order to assess awareness and comprehension of the geology, ecology and cultural history of the Tucson area. Students who had previously taken SOP (2005-2007) and students who had never taken SOP also completed the survey. The survey consisted of 12 stimulus terms, all of which represent concepts integral to an understanding of environmental geography of the Tucson area. The students wrote words that they associate with each stimulus term. Differences between the pre- and post-course responses showed clear improvement in awareness and comprehension of the geology, ecology and cultural history of the Tucson area. Results from students who took SOP in past years indicate that long-term retention of course content is good. The word association technique proved to be effective for collecting data and evaluating the course. The field trips of SOP are described in the Appendix, which also contains the word association survey used in this research.
A buried canal system AZ AA:12:1077 (ASM) dated AD 350-550 was identified north of Tucson, Arizona and traced over 700 m across the southern piedmont of the Tortolita Mountains at the multi-component ...(Early Agriculture to Hohokam) Dairy Site. Unlike most pre-Hispanic canal systems in southern Arizona which originate on medium to large drainages, the Dairy Site Canal System harvested runoff from small, ephemeral alluvial fan channels with < 100 ha catchment areas and directed it towards the Santa Cruz River floodplain. Multiple channels indicate at least four episodes of remodeling and northward shifting of irrigation water through time. The Dairy Site Canal System is interpreted as an effort to diversify water procurement and reduce the risk of crop failure along an ephemeral reach of the Santa Cruz River. Although short non-riverine canals on alluvial fans have been ethnographically documented in the region, systems of this length and complexity are unknown historically. Non-riverine canals likely played an important role in water harvesting and food production in the deserts of southern Arizona but are poorly known due to low archaeological visibility.
Un sistema de canales de riego encontrado bajo la superficie AZ AA:12:1077 (ASM) que data de 350-550 d. C. fue identificado al norte de Tucson, Arizona y rastreado a más de 700 m. a través de la pendiente de la Sierra Tortolita en el sitio Dairy que tiene multi-componentes (Inicios Agricolas a Hohokam). En contraste a la mayoría de sistemas de canales de riego prehispánicos en la parte sur de Arizona que origínan cauces de medianos a grandes, el Sistema de canales de riego del Sitio Dairy capturó agua de canales abanicos aluviales con < 100 ha de cuencas hidrológicas guiándolas hacia el plano de inundación del Río Santa Cruz. Los canales múltiplos indican por lo menos cuatro episodios de reparación y movimientos de agua de riego hacia el norte a través del tiempo. El sistema de canales de Riego del Sitio Dairy está interpretado como un esfuerzo para diversificar la procuración de agua y reducir el riesgo de un fracaso de cosechas por un segmento efímero del Río Santa Cruz. Aunque los canales temporales de riego ubicados en abanicos aluviales han sido etnografiamente documentados en la región, los sistemas de esta longitud y complejidad son desconocidos historicamente. Es probable que los canales temporales de riego jugaron un papel importante en la estrategia de la procuración de agua y producción de comida en los desiertos del sur de Arizona, pero son desconocidos debido a una pobre visibilidad arqueológica.
A buried canal system AZ AA:12:1077 (ASM) dated AD 350-550 was identified north of Tucson, Arizona and traced over 700 m across the southern piedmont of the Tortolita Mountains at the multi-component ...(Early Agriculture to Hohokam) Dairy Site. Unlike most pre-Hispanic canal systems in southern Arizona which originate on medium to large drainages, the Dairy Site Canal System harvested runoff from small, ephemeral alluvial fan channels with < 100 ha catchment areas and directed it towards the Santa Cruz River floodplain. Multiple channels indicate at least four episodes of remodeling and northward shifting of irrigation water through time. The Dairy Site Canal System is interpreted as an effort to diversify water procurement and reduce the risk of crop failure along an ephemeral reach of the Santa Cruz River. Although short non-riverine canals on alluvial fans have been ethnographically documented in the region, systems of this length and complexity are unknown historically. Non-riverine canals likely played an important role in water harvesting and food production in the deserts of southern Arizona but are poorly known due to low archaeological visibility. Publication Abstract
The scale of prehistoric canal construction in the North American Southwest peaked in a.d. 450-1450, during what has been named the Hohokam Millennium. Explanations for the eventual Hohokam ..."collapse" remain elusive. Environmental disturbances, such as floods, that were once manageable may have become unmanageable. Recent archaeological excavations of Hohokam canals in Phoenix identified stratigraphic evidence for three destructive floods that date to a.d. 1000-1400 within two large main canals in System 2, Hagenstad and Woodbury's North. Woodbury's North Canal was flood-damaged and abandoned sometime after a.d. 1300. Thereafter, no main canals of similar size were constructed to supply villages within System 2 and the area was depopulated. Our investigation provides the first stratigraphic evidence for a destructive flood during the late Classic period in the lower Salt River Valley and is compatible with the hypothesis of diminished resilience to environmental disturbance at the end of the Hohokam Millennium.
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