|Design and Operation of Smallholder Irrigation in South Asia (WB, 1995, 134 p.)|
|Chapter 18 - Ecological and riparian factors in irrigation development|
Any new consumptive diversion from a river reduces downstream flows and may adversely affect existing or prospective downstream users. Conversely a proposed project may be adversely affected by future upstream diversions or storage. Such circumstances may be the cause of serious disputes. They may occur between neighboring projects within the same state, or between states, or across international boundaries. There is no universally-accepted legal framework for settling such disputes, particularly at the international level. Development agencies consequently endeavor to avoid becoming involved in such problems by requiring, in principle, that riparian issues be addressed, and agreement between the riparian parties be reached, before a project is accepted for appraisal. However, there may be little incentive for the riparian parties, other than the one desiring the new development, to reach such an agreement. A downstream riparian can almost always find some disadvantage, and withhold consent on that account. Thus, the prospective financing agency, while seeking to avoid involvement, may nevertheless have to inject some judgement as to the relative merits of a case, to avoid needed development being held up indefinitely on insignificant grounds. In exercising that judgement, the agency can provide a forum for airing the positions of the parties concerned and for technical fact-finding.
Not only consumptive diversions but also flood protection works can be the subject of riparian dispute. For instance, embankment construction to prevent a river from flooding across adjacent agricultural lands reduces the flood storage in that reach of the river and correspondingly increases the downstream flood-flow. Where the river crosses an international boundary between the upper and lower areas, a riparian dispute may result, requiring evaluation of respective upstream and downstream effects.
An international financing agency can have an important role in riparian disputes concerning major international rivers by funding the works required to provide a mutually acceptable solution. Division of the waters of the Indus River following partition of India, involving extensive works funded by the World Bank, is a notable example. However, decades of negotiation and the prospect of major Bank financing have failed to result in a solution elsewhere.
Turning to very much smaller works, riparian issues may be encountered in the improvement of village-constructed diversions from a small stream. There are frequently a number of diversions down the length of the stream, each having its own primitive brush-wood weir. The weirs frequently fail, passing on the flow to downstream diversions. An informal system of priorities of water rights has been established by tradition, based largely on the nature of the weirs. Any effort to improve the most upstream weir to provide more security to the diversions at that point reduces diversions at downstream weirs, upsetting the traditional balance of water use. It may be necessary, in these circumstances, to supply the downstream areas by canal, from the upstream improved diversion weir. However, the formal division of the water between upper and lower areas, taking the place of the traditional informal division, may involve protracted village-level negotiation.