Libros

To search for former inlets or outlets at the West Baray, GPR transects were conducted around and over the north-east corner, over the east and partly over the south embankment, within the dry part of the reservoir parallel to the embankment; and because of the immense height of the reservoir a large number of N-S transects were conducted on the east side of the embankment, corresponding to the two parallel earthworks inside the baray.

Inlet

A breach in the north-eastern corner of the baray was indicated by Groslier⁹²⁰ and later identified by Pottier as a potential inlet,⁹²¹ as it could be associated with earthen embankment outside the baray that were recognized as part of the canal network. The embankment at this location is relatively narrow and some material at the eastern side is removed forming a chasm.

The GPR surveys in the area outside the baray, see Fig. [108], did not detect anomalies that referred to channels in association to the inlet. GPR profiles on top of the baray embankment, crossing the side of the breach, displayed a large anomaly representing presumably the sand-filled part of the breach.

FIG.[108]:LOCATION AND GPR SIGNAL OF WEST BARAY INLET (BACKGROUND:FINNMAP).

Outlet

GPR surveys inside the reservoir between the two small embankments in the central part of the eastern embankment showed no evidence for a continuation of the channel from the West Mebon. Surveys on top of the baray embankment revealed large anomalies over the complete east embankment, possibly corresponding to breaches in the wall that had been refilled. The largest breaches were measured in this central area, fewer and smaller in the profile covering the eastern part of the southern embankment. The signal penetration depth of about 300cm did not, however, reach to the base of the baray embankment 10m below therefore hindering the search for potential outlets. Due to the embankment height and flooding inside the reservoir, the main focus was directed onto the east side of the embankment. Seven parallel north-south transects were conducted crossing the central axis of the baray. The majority reveal slightly dipping feature that could emphasise an about 40 m wide but shallow channel. This feature was measured independently from the rising slope of the embankment. Transects further north to this area reveal evidence of small distributor channels but no similar channel feature was detected.

An excavation⁹²² following the GPR survey did not discover masonry structures, however, a soil change was detected which is associated to the remains of a former outlet. Two excavation trenches that crossed the central axis of the baray further investigated this potential outlet. The excavation revealed the extent of a channel that dips down in the centre, corresponding to the results from the GPR survey. The construction had later been buried with sand deposits which are clearly different to the clayey sand of the embankment.⁹²³

When looking for the potential extension of an outlet at this location, aerial photos reveal a linear feature east of the modern road which runs parallel to the east embankment between the baray and Angkor Thom. GPR survey at this site was not possible due to too much vegetation, therefore GPR transects was conducted in the southwest quadrant of Angkor Thom. The only anomaly recognizable in the over 1.5km long transect is a channel feature in alignment with the central E-W axis of the West Baray. This could indicate the extension of the canal towards the east before construction of Angkor Thom. Arguably however, the inside of the massive enclosure was heavily transformed at the time of its construction, and is today difficult to interpret solely with GPR; see Chapter (8).

Further south Pottier mapped two parallel earthworks leaving the southwest corner of the West Baray towards Angkor Thom, which have the same width as the southern Angkor Thom moat, therefore apparently a later addition. Only one of the two GPR profiles crossing the connecting two embankments between the West Baray shows an anomaly (PB_DAT_0005_312-324m) that may refer to a small channel. Pottier also mapped 180m earthen ramps on the south of the western side of the southern embankment, and described them as potentially related to exit channels.⁹²⁴ The southwest corner of the baray embankments was breached by Trouvé in the 1930s in an effort to empty the reservoir. The excavations also discovered large wooden posts inside the embankment that, according to Pottier may have been associated with water management,⁹²⁵ but alternatively they may have had a supportive function for the baray embankment.

FIG.[109]:LOCATION AND GPR ANOMALY (WB_DAT_0109_12-48M) OF POTENTIAL WEST BARAY OUTLET (BACKGROUND: FINNMAP).

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The last of the giant reservoirs, the Jayatataka, was built under Jayavarman VII (AD1181 -

~1218)⁹²⁶ to the north of the Yasodharatataka and east of the large monastery of Preah Khan (consecrated AD1191).⁹²⁷ Neak Pean, the mebon in the centre of the reservoir, and the temple of Ta Som, have been linked with the same ruler.⁹²⁸ Ta Som is located east of the eastern embankment and north of the central axis of the baray, its outline is slightly inclined to the baray embankment. ⁹²⁹ To address whether the last baray was ever finished and if and how long it was in use, Dumarçay quotes Zhou Daguan, who possibly described in AD1296 the temple of Neak Pean inside the Jayatataka: “The northern lake is five li to the north of the walled city. In the middle is a square golden tower, and several dozen stone chambers.” ⁹³⁰

The 3640m long and 960m wide reservoir is considerably smaller than its two predecessors, but is comparable in size to the Indratataka. The Jayatataka has recently been investigated further. Several excavations were conducted by APSARA at Neak Penh and the baray; from 2009 on the reservoir was filled again with water, which is directed through a modern concrete inlet in the northern embankment.

FIG.[110]:JAYATATAKA AND ASSOCIATED FEATURES (BACKGROUND:POTTIER/DTM FROM JICA TOPOGRAPHY).

The GPR Survey

Following the findings in the other reservoirs, GPR surveys were conducted on the road of the north and east embankment of the Jayatataka to look for additional inlets and outlets former of the reservoir. The survey concentrated on the area around Ta Som temple due to its location in relation to the baray.

Inlet

There is a known masonry inlet located about 400m to the west of the north-eastern corner of the reservoir, ⁹³¹ see Fig. [111]. The central part is covered by the asphalt surface of the modern road; however the southern part of the structure is exposed, showing two parallel masonry walls of carved laterite blocks, about 2m apart, and a few laterite blocks are visible to the

north.⁹³² The GPR survey over the road provides a clear signal of the outline of the structure below the surface. The resultant anomaly served as a sample signal to identify additional masonry inlets at the other reservoirs. Other anomalies that were measured over the complete length of the northern embankment by GPR could not be clearly identified as masonry structures or potential inlets.

FIG.[111]:GPR ANOMALY OF JAYATATAKA INLET (JB_DAT_0043_324-342M) AND IMAGE OF SOUTH SIDE. A Potential Outlet and Ta Som Temple

Trouvé described laterite remains near the western end of the south of the Jayatataka he interpreted as the former outlet of the baray, supported by the presence of a depression along the East West axis, a potential channel that might be related to the moat of Angkor Thom.⁹³³ There is also a gap in the JICA topography data displayed 600m east of the south-western corner of the reservoir. ⁹³⁴

FIG.[112]:DUMARÇAY’S INTERPRETATION OF THE NORTH-EASTERN BARAY. K) ORIGINAL STELA LOCATION O) OUTLET YASODHARATATAKA N) OUTLET JAYATATAKA (SOURCE:DUMARÇAY,2003, P.50).

In Dumarçay’s model of the construction chronology of the baray, an outlet is displayed close to the south-western border on the southern embankment towards Siem Reap River; see Fig.

[112].⁹³⁵ Dumarçay saw it as a later addition to the baray.⁹³⁶ The area was however not accessible for the GPR at the time of the survey.

FIG.[113]:ANOMALIES DISPLAY POTENTIAL OUTLET AT TA SOM (BACKGROUND:POTTIER/FINNMAP),ANOMALY JB_DAT_0124-20-92M.

The search for a potential outlet was concentrated on the eastern side of the baray, see Fig.

[113]. The GPR results give no evidence of a potential outlet associated to the central E-W axis of the baray, nor to the extended central E-W axis of Neak Pean, which both are in line with the southern moat of the Ta Som. However, GPR profiles in- and outside the southern part of the west wall of Ta Som display a 60m wide linear feature dipping towards the middle of the radargram with an approximately 15m wide channel feature in its centre at about 60ns depth (approximately 3m depth). Additionally a drill core down to the feature was taken in front of the

southern wall at the slopes of the channel feature; the bottom of the core was a compact surface at about 150cm depth, approximately at the same depth as the recorded anomaly. The two profiles were not sufficient to determine either the direction or extent of the potential channel, but several additional N-S transects inside the baray, on the road, each parallel to transects at wall, showed similar anomalies that supported the hypothesis of an E-W outlet of the Jayatataka in this area.

GPR surveys to the east of Ta Som show no sign of any channel that could have directed the water to the Siem Reap River. However, if there had been a channel, it could have run beside the embankment to the south, thereby corresponding to the channels found at the Yasodharatataka and Indratataka. Evidence of a channel was revealed on an E-W transect south of Ta Som. The problematic issue however is that an outlet at this location would have run into the west wall of the outer end of Ta Som. The fact that it is situated in front of a temple, construction of which has been associated with the same ruler as the Jayatataka, makes the existence of a former outlet at this location unlikely. Presuming, however, it is a former outlet, it could be explained by assuming a different chronological order of construction:

 Ta Som temple was built after the baray, and the original outlet was moved to a different location, which has not been discovered. Several aligned laterite blocks next to the road south of the temple indicate other preceding constructions that were removed.

 The outer enclosure wall was built later than Ta Som temple⁹³⁷ and the baray; the structure could have been used therefore as an outlet over a period of time. The southern part of the outer enclosure of Ta Som is lower than the rest of the enclosure, indicating that this could have been the original channel. The inclined angle of the moat compared to the baray and the location of the temple being off the centre axis, speak for a later addition compared to the temples of Preah Khan and Neak Pean, which align exactly with the baray.

Support for a later construction of the Ta Som comes from architectural comparison of the Bayon style monuments by Cunin⁹³⁸ and magnetic susceptibility measurements on the sandstone by Uchida et al.,⁹³⁹ who place Preah Khan (described by them as period: VIa and VIb) and Neak Pean (VIc), the two temples associated with the construction of the Jayatataka, into an earlier construction period than Ta Som (VIII). Only archaeological excavations could clarify the existence of a potential former outlet.

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From the evidence presented several conclusions can be drawn about the baray as part of the water management system:

 Each of the baray has evidence of inlet/outlet structures. Several are masonry structures, and close to the northeast corner of the reservoir, which at Angkor are the most elevated point of the interior of the baray and the general topography. Some of the inlets have been known before.⁹⁴⁰ All historic inlets were buried under embankments that serve now as roads, which might have been one of the reasons that they were sometimes not observed by other scholars.

 The geophysical survey and subsequent excavations have shown that at some point in time each baray had at least one exit channel in their eastern embankment. While the role of Krol Romeas in the construction history of the Yasodharatataka is now relatively well understood, the outlets in other baray are not as apparent. It seems to be quite clear however, that water was distributed from the baray to other locations when the reservoir was filled.

 The existence of inlets and outlets shows that the baray were embedded in a vast network of canals - originating from redirected former natural rivers, which channelled the water into the reservoirs, and reaching a high water level, directed the water out of the baray east and then southwards. Additional canals further down slope could have distributed water across the landscape or disposed it in the Tonle Sap.

 Most inlets and outlets were at some point in time covered by the embankment as the function of the reservoirs changed when they were disconnected from the water source and the water management system.

(b) O THER W ATER R ESERVOIRS

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