The feasibility study must also analyse carefully the hydrology of the project site. This involves establishing the expected flow in the river that is being harnessed for the project.
The only sure way of determining flows is from historical records. Some countries, particularly, European countries and countries that were once colonies of European powers, will often have good hydrological records. In other areas the records will be non-existent.
If there are no records, then it is possible to reconstruct them by secondary means but this will never be as reliable as an accurate set of records. Opinions differ about the length of record needed but 10 years is normally thought too short a period and 40 years barely sufficient.
The historical record will show how river flows have varied. It will indicate the maximum and minimum flows to be expected and the average flows. These figures will not allow prediction of the amount of water in the river at any specific date in the future but they will allow average generation levels to be computed. It must, nevertheless, be borne in mind that there will be days and months when flow is minimal or none existent. And there will always be a risk of flood.
Hydrological records provide the data upon which to base a power purchase agreement for a hydropower plant. However the records cannot take account of one factor, future upstream use of water.
When Turkey built the Ataturk dam on the Euphrates, flow through Syria and Iraq was seriously affected. In fact it stopped completely for a month in 1990 when the reservoir was filled. This is a risk that cannot be tackled at a project level. Risks of this sort are extremely difficult to predict. If upstream development does occur, then legal recourse represents the only way of gaining adequate compensation.
Global climate change can also affect rainfall patterns and hence river flows. Changes are likely to take place slowly and can be predicted with careful analysis. This is another effect that should be taken into account in any feasibility study.
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Do we really want the one thing that gives us its resources unconditionally to suffer even more than it is suffering now? Nature, is a part of our being from the earliest human days. We respect Nature and it gives us its bounty, but in the recent past greedy money hungry corporations have made us all so destructive, so wasteful.