Kaveri River Delta
The Kallanai Dam was “[built] during the second century AD by Karikalan, a king of southern India's old Chola Dynasty” and “is also one of the oldest irrigation systems in the world that is still in use” (Agoramoorthy and Hsu, 2008). “The purpose of the dam was to divert the waters of the Kaveri across the fertile Thanjavur delta region for irrigation via canals. Since the English arrived in the eighteenth century, the Kallanai has been tampered with and other hydraulic structures have been added nearby. It is therefore difficult to extrapolate from the current situation into the past to understand the workings of the anicut” (Bijker, 2007). Figure 1 shows the current state of the dam.
c. 200 AD
The author was not able to locate the duration of construction for the Kallanai Dam.
The Kallanai Dam is a simple check dam (Agoramoorthy and Hsu, 2008). Check dams are “small barriers using stones, cement, and concrete built across the direction of water flow on rivers to harvest rainwater in remote villages” and “are usually smaller than 15 m” (Agoramoorthy and Hsu, 2008). The Kallanai in particular “is an anicut of unhewn stone that stands in the Kaveri parallel to the riverbank; it is more than 300 meters long, 20 meters wide, and 4.5 meters high” (Bijker, 2007). It is believed that Kallanai initially irrigated about 69,000 acres, though it now irrigates close to 1 million acres (Arulmani). Because the Kallanai has been altered after the 1800s, it is difficult to understand more about its construction (Bijker, 2007). However, “[in] her pioneering study, [Dr. Chitra] Krishnan combined historical studies of old descriptions of the anicut from a variety of archives with archaeological and anthropological field surveys and original hydraulic research. This enabled her to piece together a picture of the Kallanai…” (Bijker, 2007). “Krishnan’s reconstruction suggests that the original Kallanai had some very peculiar design features: the curved shape of the masonry section, a sloping crest, and an irregular descent from front to rear” (Bijker, 2007), which is shown in Figure 2.
The Kallanai was built to divert floods from the Kaveri branch of the river into the Kollidam branch “via a short connecting stream” “when the water level in the river rose above its crest” (Bijker, 2007). The Kollidam “was the wider (also the steeper, straighter, and hence faster) of the two [river] branches, and…the flood carrier. It was barely used for irrigation. Almost all of the 600,000 acres irrigated by the river in 1800 were delta lands south of the Kaveri branch. So the Kaveri branch was the lifeline for delta farmers, while the Kollidam was of little consequence for them” (Bijker, 2007). Once the floods were diverted to the Kollidam, they “[flowed] directly to the sea, causing minimal damage to agriculture” (Bijker, 2007). Figure 3 shows the relation between the Kollidam and Kaveri (labeled “Cauvery”).
In her analysis of anicut practices in India, Chitra Krishnan concluded “ that the old anicuts worked so well because they sophisticatedly reshaped water currents and sedimentation processes, rather than trying to control all natural elements by force” (Bijker, 2007).
Agoramoorthy, G. (2008). "Can India meet the increasing food demand by 2020?" Futures, 40(5), 503-506.
Agoramoorthy, G., and Hsu, M. (2008). "Small size, Big Potential: Check Dams for sustainable development." Environment (Washington DC), 50(4), 22.
Arulmani, M., and Latha, V. R. H. (2014). "The Global Politics?...A New Theory on "Universal Dam"." American Journal of Engineering Research, AJER, 3(7), 66.
Bijker, W. E. (2007). "Dikes and Dams, Thick with Politics." Isis, 98(1), 109-123.
Given the rate and direction of full dip of a pla...
Given the rate and direction of full dip of a plan...