8.1: Reading/Media

The pyramids of Giza. It was widely believed that a river must have been involved for transporting the massive building materials. But it wasn't until 2024 that a sand-buried river branch connecting most of the pyramids was discovered---the ancient Ahramat branch of the Nile river. (Photo by kennyOMG, Wikimedia)

Pyramid Building Along Nile Branch in Kingdoms-Era Egypt, 4,500 BP

Excerpts from "The Egyptian pyramid chain was built along the now abandoned Ahramat Nile branch" by Eman Ghoneim, Timothy J. Ralph, Suzanne Onstine, et al. Communications Earth & Environment 5, 233 (2024). CC BY-NC-ND

Excerpts from "Nile waterscapes facilitated the construction of the Giza pyramids during the 3rd millennium BCE" by H. Sheisha, D. Kaniewski, N. Marriner, et al. Proc. Natl. Acad. Sci. U.S.A. 119 (37) e2202530119 (2022). CC BY-NC-ND

Ancient climate and environmental conditions in the Nile valley

Excerpt (Ghoneim et al.): The landscape of the northern Nile Valley in Egypt, between Lisht in the south and the Giza Plateau in the north, was subject to a number of environmental and hydrological changes during the past few millennia. In the Early Holocene (~12,000 years before present), the Sahara of North Africa transformed from a hyper-arid desert to a savannah-like environment, with large river systems and lake basins due to an increase in global sea level at the end of the Last Glacial Maximum (LGM).The wet conditions of the Sahara provided a suitable habitat for people and wildlife, unlike in the Nile Valley, which was virtually inhospitable to humans because of the constantly higher river levels and swampy environment. At this time, Nile River discharge was high, which is evident from the extensive deposition of organic-rich fluvial sediment in the Eastern Mediterranean basin. Based on the interpretation of archeological material and pollen records, this period, known as the African Humid Period (AHP) (ca. 14,500–5,000 years ago), was the most significant and persistent wet period from the early to mid- Holocene in the eastern Sahara region, with an annual rainfall rate of 300–920 mm yr⁻¹. During this time the Nile would have had several secondary channels branching across the floodplain, similar to those described by early historians.

Excerpt (Ghoneim et al.): During the mid-Holocene (~10,000–6,000 years ago), freshwater marshes were common within the Nile floodplain, causing habitation to be more nucleated along the desert margins of the Nile Valley. The desert margins provided a haven from the high Nile water. With the ending of the AHP and the beginning of the Late Holocene (~5,500 years ago to present), rainfall greatly declined, and the region’s humid phase gradually came to an end with punctuated short wet episodes. Due to increased aridity in the Sahara, more people moved out of the desert towards the Nile Valley and settled along the edge of the Nile floodplain. With the reduced precipitation, sedimentation increased in and around the Nile River channels causing the proximal floodplain to rise in height and adjacent marshland to decrease in the area estimated the Nile flood levels to have ranged from 1 to 4m above the baseline (~5,000 BP). Inhabitants moved downhill to the Nile Valley and settled in the elevated areas on the floodplain, including the raised natural levees of the river and jeziras (islands). This was the beginning of the Old Kingdom Period (ca. 2,686 BCE) and the time when early pyramid complexes, including the Step Pyramid of Djoser, were constructed at the margins of the floodplain. During this time the Nile discharge was still considerably higher than its present level. The high flow of the river, particularly during the short-wet intervals, enabled the Nile to maintain multiple branches, which meandered through its floodplain. Although the landscape of the Nile floodplain has greatly transformed due to river regulation associated with the construction of the Aswan High Dam in the 1960s, this region still retains some clear hydro-geomorphological traces of the abandoned river channels.

Since the beginning of the Pharaonic era, the Nile River has played a fundamental role in the rapid growth and expansion of the Egyptian civilization. Serving as their lifeline in a largely arid landscape, the Nile provided sustenance and functioned as the main water corridor that allowed for the transportation of goods and building materials. For this reason, most of the key cities and monuments were in close proximity to the banks of the Nile and its peripheral branches. Over time, however, the main course of the Nile River laterally migrated, and its peripheral branches silted up, leaving behind many ancient Egyptian sites distant from the present-day river course. Yet, it is still unclear as to where exactly the ancient Nile courses were situated, and whether different reaches of the Nile had single or multiple branches that were simultaneously active in the past. Given the lack of consensus amongst scholars regarding this subject, it is imperative to develop a comprehensive understanding of the Nile during the time of the ancient Egyptian civilization. Such a poor understanding of Nile River morphodynamics, particularly in the region that hosts the largest pyramid fields of Egypt, from Lisht to Giza, limits our understanding of how changes in the landscape influenced human activities and settlement patterns in this region, and significantly restricts our ability to understand the daily lives and stories of the ancient Egyptians.

Position of the Khufu branch in relation to the Giza pyramids

Excerpt (Sheisha et al.): The pyramids of Khufu, Khafre, and Menkaure, located on the Giza Plateau, overlook the west bank of the Nile River. Built during the Fourth Dynasty (Old Kingdom 2,686–2,160 BCE), they are one of the world’s most iconic cultural landscapes and constitute ancient engineering feats that have fascinated humanity for millennia. To edify the plateau’s pyramids, tombs, and temples, it now seems that ancient Egyptian engineers took advantage of the Nile and its annual floods, using an ingenious system of canals and basins that formed a port complex at the foot of the Giza plateau. The harbor complex currently lies >7 km west of the present-day Nile, but it is widely accepted that Fourth Dynasty engineers exploited a now defunct branch of the Nile, which flowed along the western edge of the Nile floodplain during the Egyptian Old Kingdom and that we refer to as the Khufu branch. These canals and basins had to be deep enough to accommodate shallow-draft vessels all year round. Larger cargo ships could probably only navigate during the flood season (August–October), when water levels in the Nile channel rose by ∼7 m.

The fluvial-port-complex hypothesis postulates that pyramid builders cut through the western levee of the Khufu branch of the Nile and dredged basins down to river depth in order to harness the annual 7-m rise of the flood like a hydraulic lift, bringing the higher water levels to the base of the Giza plateau. In this way, it was possible to transport supplies and building materials directly to the pyramid complex. These canals and ports would also have been key for the longer-distance transport of materials via the Nile, facilitating transport logistics and for the continuous supply of the plateau’s diverse building projects and linking Giza with nearby cities in the Memphite region and on the delta. Nonetheless, the interactions between ancient Egyptian societies and environmental changes along the Khufu branch are complex and poorly understood. We evaluate its water levels during the last 8,000 y, with a particular focus on the Dynastic Period and the Old Kingdom, using sediment cores and long-term ecosystem dynamics. Our data shed light on previous reconstructions because environmental and historical data are more closely coupled; such resolution has never been achieved in this region. Furthermore, our sequence can be extrapolated to upstream and downstream areas of the Egyptian Nile, allowing comparison with other archaeological sites.

To estimate variations in the water level of the Khufu branch, five cores were drilled on the present Giza floodplain, east of the pyramid complex (Fig. \(\PageIndex{1}\)). Bioindicators (pollen grains) were extracted from cores G1 and G4 situated in what has been geographically defined as the Khufu branch of the Nile. We identified 61 taxa grouped into seven pollen-derived vegetation patterns (PdVs) based on their ecological affinities. Among the defined PdVs, the Cyperaceae (papyrus, sedge; located on the banks of the Nile), tropical Nilotic taxa (pollen carried downstream by the Nile from tropical areas of the watershed), and helophytes reveal the presence of a permanent waterbody on the Giza floodplain... The highest water levels are attested by high abundances of Cyperaceae and helophytes, with a higher input of tropical pollen from the Nile River, while the low levels are framed by an increase in terrestrial taxa. Nile flow variations, as deduced from the PCA-Axis 1, are correlated with changes in the lithofacies.

Figure \(\PageIndex{1}\): Location of the cores on the Giza floodplain. The two cores used to reconstruct Holocene variations in Khufu-branch levels (cores G1 and G4) are located where the Khufu basin was connected to the Nile. The Giza Pyramid Complex currently lies >7 km from the present-day Nile branch. Harbor remains were previously found at the site of G3;. (From Sheisha et al. 2022.)

Our score-based reconstruction shows that the water level of the Khufu branch (termed K-1) was higher during the African Humid Period, with a local termination estimated at 3550 ± 80 BCE (5,500 ± 80 BP) and a later peak recorded at 2,950 ± 80 BCE after a significant drop at 3,450–3,250 ± 80 BCE. During this period, it has been shown that conglomerations of predynastic and early dynastic settlements (3,550–3,250 BCE) existed along the east bank of the Khufu branch and on the floodplain between the paleo-channel and the pyramid plateau. We suggest that the environmental attractivity of Giza during the fourth millennium resulted from a decrease in fluvial levels following the end of the African Humid Period. The reconstructed higher level of Khufu branch is also supported by Nile Delta sedimentation rates, is attributed to increased rainfall over Lake Tana, the source of the Blue Nile and Lake Victoria, the source of the White Nile. Nile flow is mediated by monsoon activity in tropical Africa. The Holocene intensity of the East African Monsoon, as reconstructed at Lake Abiyata and Lake Rutundu in Ethiopia, is modulated by the north–south movement of the Intertropical Convergence Zone (ITCZ), with higher rainfall levels during the early Holocene consistent with a more northward migration of the monsoon rain belt driven by higher insolation. We found that the Khufu branch has recorded the same trend, with a high-stand level that correlates with greater summer insolation and a northward migration of the ITCZ, which reinforced the intensity of the East African Monsoon over the Nile Valley and created higher flow regimes in the Khufu branch. The peak in the Khufu-branch level at 2950 ± 80 BCE, while not documented in Lake Abiyata (Fig. \(\PageIndex{2}\)), is recorded at Lake Rutundu, Lake Tana, and Lake Victoria, and on the Nile Delta (Fig. \(\PageIndex{2}\)). Higher Khufu-branch levels at Giza are also in phase with higher levels in North African lakes (high and intermediate lakes; Fig. \(\PageIndex{2}\)). The most significant negative fluctuations in Khufu-branch levels during this period (∼8,000–5,500 y ago) are correlated with volcanic forcing ( leading to diminished Nile summer flooding. Moreover, a drought episode recorded in Lake Tana at 5,550 BCE, due to a southward shift in the monsoon front, is also documented by a drop in the Khufu-branch level at Giza 5,550 ± 80 BCE.

Figure \(\PageIndex{2}\): (A) Level of the Khufu branch (K-1, blue line) compared to the number of archaeological sites in Sudan and Egypt (light purple line). Archaeological site numbers were transformed into z-scores. The two datasets are shown as 1,000-y averages (with a 95% confidence interval). Long-term trends are represented by polynomial models (order 3, P_value < 0.001). (B) Level of the Khufu branch (blue line; Loess smoothing scores with 2.5 and 97.5 percentiles) compared to archaeological sites in Lower and Upper Egypt (orange line). The number of archaeological sites is shown as a 1,000-y sum, transformed into z-scores. Long-term trends are illustrated by polynomial models (order 3). (C) Khufu-branch levels (2.5 and 97.5 percentiles) during the construction of the pyramids of kings Khufu, Khafre, and Menkaure (blue line). The long-term trend is represented by a polynomial model (order 3). The background colors show the transition from the African Humid Period to the aridification of Egypt (A and B). (From Sheisha et al. 2022.)

Position and morphology of the Ahramat branch

Excerpt (Ghoneim et al.): Synthetic Aperture Radar (SAR) imagery and radar high-resolution elevation data for the Nile floodplain and its desert margins, between south Lisht and the Giza Plateau area, provide evidence for the existence of segments of a major ancient river branch bordering 31 pyramids dating from the Old Kingdom to Second Intermediate Period (2,686−1,649 BCE) and spanning between Dynasties 3–13 (Fig. \(\PageIndex{3}\) a). This extinct branch is referred to hereafter as the Ahramat branch, meaning the “Pyramids branch” in Arabic. Although masked by the cultivated fields of the Nile floodplain, subtle topographic expressions of this former branch, now invisible in optical satellite data, can be traced on the ground surface by TanDEM-X (TDX) radar data and the Topographic Position Index (TPI). Data analysis indicates that this lateral distributary channel lies between 2.5 and 10.25 km west from the modern Nile River. The branch appears to have a surface channel depth between 2 and 8 m, a channel length of about 64 km and a channel width of 200–700 m, which is similar to the width of the contemporary neighboring Nile course. The size and longitudinal continuity of the Ahramat branch and its proximity to all the pyramids in the study area implies a functional waterway of great significance.

A trace of a 3 km river segment of the Ahramat branch, with a width of about 260 m, is observable in the floodplain west of the Abu Sir pyramids field (Fig. \(\PageIndex{3}\) b–d). Another major segment of the Ahramat branch, approximately 20 km long and 0.5 km wide can be traced in the floodplain along the Western Desert Plateau south of the town of Jirza (Fig. \(\PageIndex{3}\) e). The visible segments of the Ahramat branch in TDX are now partially occupied by the modern Bahr el-Libeini canal. Such partial overlap between the courses of this canal, traced in the 1911 historical maps (Egyptian Survey Department scale 1:50,000), and the Ahramat branch is clear in areas where the Nile floodplain is narrower (Fig. \(\PageIndex{3}\) b–d), while in areas where the floodplain gets wider, the two water courses are about 2 km apart. In light of that, Bahr el-Libeini canal is possibly the last remnant of the Ahramat branch before it migrated eastward, silted up, and vanished. In the course of the eastward migration over the Nile floodplain, the meandering Ahramat branch would have left behind traces of abandoned channels (narrow oxbow lakes) which formed as a result of the river erosion through the neck of its meanders. A number of these abandoned channels can be traced in the 1911 historical maps near the foothill of the Western Desert plateau proving the eastward shifting of the branch at this locality (Fig. \(\PageIndex{3}\) b–d). The Dahshur Lake, southwest of the city of Dahshur, is most likely the last existing trace of the course of the Ahramat branch.

Figure \(\PageIndex{3}\): The water course of the ancient Ahramat branch. a Shows the Ahramat branch borders a large number of pyramids dating from the Old Kingdom to the 2nd Intermediate Period and spanning between Dynasties 3 and 13. b Shows Bahr el-Libeini canal and remnant of abandoned channel visible in the 1911 historical map (Egyptian Survey Department scale 1:50,000). c Bahr el-Libeini canal and the abandoned channel are overlain on satellite basemap. Bahr el-Libeini is possibly the last remnant of the Ahramat branch before it migrated eastward. d A visible segment of the Ahramat branch in TDX is now partially occupied by the modern Bahr el-Libeini canal. e A major segment of the Ahramat branch, approximately 20 km long and 0.5 km wide, can be traced in the floodplain along the Western Desert Plateau south of the town of Jirza. Location of e is marked in white a box in a. (From Ghoneim et al. 2024.)

Alignment of old- and middle-kingdom pyramids to the Ahramat branch

Excerpt (Ghoneim et al.): The royal pyramids in ancient Egypt are not isolated monuments, but rather joined with several other structures to form complexes. Besides the pyramid itself, the pyramid complex includes the mortuary temple next to the pyramid, a valley temple farther away from the pyramid on the edge of a waterbody, and a long sloping causeway that connects the two temples. A causeway is a ceremonial raised walkway, which provides access to the pyramid site and was part of the religious aspects of the pyramid itself. In the study area, it was found that many of the causeways of the pyramids run perpendicular to the course of the Ahramat branch and terminate directly on its riverbank.

In Egyptian pyramid complexes, the valley temples at the end of causeways acted as river harbors. These harbors served as an entry point for the river borne visitors and ceremonial roads to the pyramid. Countless valley temples in Egypt have not yet been found and, therefore, might still be buried beneath the agricultural fields and desert sands along the riverbank of the Ahramat branch. Five of these valley temples, however, partially survived and still exist in the study area. These temples include the valley temples of the Bent Pyramid, the Pyramid of Khafre, and the Pyramid of Menkaure from Dynasty 4; the valley temple of the Pyramid of Sahure from Dynasty 5, and the valley temple of the Pyramid of Pepi II from Dynasty 6. All the aforementioned temples are dated to the Old Kingdom. These five surviving temples were found to be positioned adjacent to the riverbank of the Ahramat branch, which strongly implies that this river branch was contemporaneously functioning during the Old Kingdom, at the time of pyramid construction.

Analysis of the ground elevation of the 31 pyramids and their proximity to the floodplain, within the study area, helped explain the position and relative water level of the Ahramat branch during the time between the Old Kingdom and Second Intermediate Period (ca. 2,649–1,540 BCE). Based on Fig. \(\PageIndex{5}\) , the Ahramat branch had a high-water level during the first part of the Old Kingdom, especially during Dynasty 4. This is evident from the high ground elevation and long distance from the floodplain of the pyramids dated to that period. For instance, the remote position of the Bent and Red Pyramids in the desert, very far from the Nile floodplain, is a testament to the branch’s high-water level. On the contrary, during the Old Kingdom, our data demonstrated that the Ahramat branch would have reached its lowest level during Dynasty 5. This is evident from the low altitudes and close proximity to the floodplain of most Dynasty 5 pyramids. The orientation of the Sahure Pyramid’s causeway (Dynasty 5) and the location of its valley temple in the low-lying floodplain provide compelling evidence for the relatively low water level proposition of the Ahramat branch during this stage. Thewater level of the Ahramat branch would have been slightly raised by the end of Dynasty 5 (the last 15–30 years), during the reign of King Unas and continued to rise during Dynasty 6. The position of Pepi II and Merenre Pyramids (Dynasty 6) deep in the desert, west of the Djedkare Isesi Pyramid (Dynasty 5), supports this notion.

In addition, our analysis shows that the Qakare Ibi Pyramid of Dynasty 8 was constructed very close to the floodplain on very low elevation, which implies that the Nile water levels were very low at this time of the First Intermediate Period (2,181–2,055 BCE). This finding is in agreement with previous work conducted by Kitchen, which implies that the sudden collapse of the Old Kingdom in Egypt (after 4,160 BCE) was largely caused by catastrophic failure of the annual flood of the Nile River for a period of 30–40 years. Data from soil cores near Memphis indicated that the Old Kingdom settlement is covered by about 3m of sand. Accordingly, the Ahramat branch was initially positioned further west during the Old Kingdom and then shifted east during the Middle Kingdom due to the drought-induced sand encroachments of the First Intermediate Period, “a period of decentralization and weak pharaonic rule” in ancient Egypt, spanning about 125 years (2,181–2,055 BCE) post Old Kingdom era. Soil cores from the drilling program at Memphis show dominant dry conditions during the First Intermediate Period with massive eolian sand sheets extended over a distance of at least 0.5 km from the edge of the western desert escarpment. The Ahramat branch continued to move east during the Second Intermediate Period until it had gradually lost most of its water supply by the New Kingdom.

Key Geologic Concepts:

Sedimentation; floodplain; river migration; Pleistocene-Holocene climate change.

Supplemental Materials:

Archeology News: "New study reveals Egyptian pyramids were built along a now-abandoned Nile branch", May 17, 2024.

New York Times: "A Long-Lost Branch of the Nile Helped in Building Egypt’s Pyramids", August 30, 2022.