There is no way of knowing how much water will be available in the rivers in the future. All we can do is study the past trend of river flows from available records and assume that more or less similar pattern will manifest in the future. Fortunately we have historic records of river flows available since the year 1922-23. A study of these records shows that flow pattern of our rivers has been highly erratic. This is evident from the fact that the highest annual flow in the recorded history of 72 years (1922-1994) was 186.79 MAF in the year 1959-60 as against the minimum of 97.74 MAF in the year 1974-75, with an annual average of 138.69 MAF, of which 83.6% is in Kharif and 16.4% in Rabi. There has been a drought cycle of nine continuous years from 1924-25 to 1932-33, when the river flows were below the average. Under these circumstances it is very necessary to have a cautious approach in undertaking any scheme for construction of a high dam in consideration of the vagaries of the river water availability.