Page:History of the Periyár project. (IA historyofperiyar00mack).pdf/26

10 channel were actually begun for diverting a small tributary of the Periyar, the Chinna Muliyár, but the work was stopped by fever among the coolies and by the excessive wages demanded by them, a forecast of two of the principal obstacles which were afterwards encountered.

It was not till 1862 that the project was revived by Major Ryves R.E., in a practical form. This officer and Major Payne spent several seasons in local investigations, experiencing great difficulty from the uninhabited and in hospitable nature of the country, the incessant rain, the absence of paths, the denge jungle and elephant grass, and the swarms of leeches, and also from the fever which was exceedingly rife during the dry months. In 1867 Major Ryves submitted detailed proposals including an earthen dam 162 feet in height at the site marked No. 1 in the map. An escape was to be made at 142 feet above the river-bed, and the water was to be diverted into the valley of the Vaigai by a cutting through the watershed at the point marked A, having its sill 17 feet below the escape crest and a maximum depth of cutting of about 52 feet. No provision was made for controlling the discharge through the watershed cutting; but in order to prevent a flow into the Suruliyar beyond what that stream could safely carry, it was proposed to construct a reservoir with a capacity of 945 millions of cubic feet at some point not fixed between the Suruliyar and the watershed. No other provision for storage was made, the project being essentially one for the diversion of the river and not for storage of water. Then, as afterwards, the principal difficulty was foreseen to be the control of the river during the construction of the dam, and it is interesting to note the manner in which Major Ryves proposed to deal with it. The unhealthiness of the country limited the working season to the period between June and February and the dryest and best months of the year were thus lost for working in the river-bed when the discharge was at its lowest. The high discharge during the South-West and North-East Monsoons still further limited the time available for foundations to a possible 30 days in August and September, and the 31 months commencing with December. Starting with these premises Major Ryves proposed to begin work in June by depositing large rough stone in the river-bed to a height of +32, leaving a clear opening of 45 feet on the left flank through which he judged the river would flow with a velocity of about 5 feet a second, with a surface level of + 3. As soon after the North-East