110 SOCIAL SCIENTIST For example, the official census of minor irrigation 1986-87 reports that there are only 6523 tanks in Tamilnadu. In fact the actual figure is 36523. Such reporting errors are likely to misguide policy planning. Another source of confusion is the frequent changes in definitions and concepts of measurement. The term 'other sources', used in data reporting presents such a heterogeneous mix that it lacks comparability and lends inconsistency. Jhil and iaalabs are regarded as negligible source, and are put sometimes under the 'other sources' and at other times under 'tanks'. Actually the South Indian tanks which are dominant in number and size are a kind of dammed reservoir which need special treatment. Therefore proper recording and documentation of the regional entity can correct the deficiencies to some extent. Basically the water appropriation is done through the diversion works, storage works and lift system. (i) Diversion works: Some of the prominent diversion works in hilly terrain are Kuhl in Himachal Pradesh and in the hill districts of Uttar Pradesh, Phad system in Maharastra and Western ghat, thodus in Kerala, pyne in Bihar. As the yield of the rivers in South India is not sufficient and there are very few perennial rivers, therefore the diversion works are not seen in this region. However, the spring channel diversion works of Grand Anicut on the Kaveri river is a notable one. The ingenuity of the local people to develop a system of water harvesting in the Lahoul spiti region in Himachal Pradesh demonstrates a technology which irrigates more than 2000 hectare of land through Kuhl. Lahaul Spiti has annual rainfall less than 127 mm. The area where the natural gravity flow is not possible, lift systems are developed. However, the traditional lift system has undergone dramatic changes on the introduction of modem pumpsets. The energised pumps have completely replaced lift systems. (ii) Storage works: The retention of rain water is easier in the North and North East monsoon plain of the country, while it is not at all easy in the rocky Gondwana parts of peninsular India. The absence of perennial rivers, poor retention of rain water and high run off make the water situation precarious in this region. Thus the storage works have been the first choice for many centuries in the region. The numerous tanks in South India till recently were considered a remarkable means of irrigation and water supply. The rich heritage and respect for cultural value system of water resource signifies the importance of the structures. A few inscriptional records indicate the poetic description of the tanks in the Sangam period of 5000 years ago. It was a common practice to build storage tanks in the name of Gods, in memory of royal family members to celebrate the victory of war (Jala Stambha), and in recognition of high merits etc. The high level of technological consideration (Jala sutrada) and participation of common people evolved the system to be sustainable. The elaborate