The guidelines presented below are intended as concise summaries of the major practical findings of the analyses carried out in the text. For justification of each guideline reference should be made to the text section indicated.
Objective
Each guideline is aimed at optimizing fish yield (i.e. a composite resultant of biological fish production and extractive fishing activity) from a particular environment under the control of the dam.
Applicability
Each guideline is given without regard to its applicability to any particular situation, or its compatibility with other guidelines. Each particular dam/reservoirs/downstream river situation requires comprehensive assessment to see which guidelines can be integrated into the design and operation of the dam in order to achieve an optimal compromise.
Crest elevation
The maximum possible dam height is preferable. Beyond a certain critical crest elevation littoral fish catch will probably remain fairly constant, but total reservoir catch will increase significantly due to the creation of a pelagic environment with a significant fishery resource potential (see sections 5.1 and 5.2.6 - Physical concentration effect).
Discharge structures
Flood water discharge structures which draw water from the epilimnion are preferable to those which draw water from deeper layers. Turbine intakes should be positioned at the highest possible elevation compatible with their operation in order to reduce as much as possible the discharge of deoxygenated (or H2S laden) water to the downstream river channel (see section 6.1.1 - Water quality).
Discharge water reoxygenation
Equipment to oxygenate the deeper water layers in the vicinity of the dam and/or to oxygenate the tailrace discharge water should be installed to ensure that the downstream river channel receives water of adequate quality at all times of the year (see section 6.1.1 - Water quality).
Fish ladders
By-pass structures to allow downstream fish stocks to ascend the dam wall and enter the reservoir should only be installed if there is adequate justification to do so since they may result in a net loss in yield of both the downstream river channel and the reservoir. If a fish ladder is found to be desirable its design should be optimized for only those species requiring the access and should exclude other species (see section 6.1.3 - Fish ladders).
Reservoir water level fluctuation
Water level management should be guided by a target type curve rather than a design rule type curve. A re-evaluation of the design rule curve should also be carried out. Total annual fluctuation should be within the range of 2.5–4.0. Changes in water level (either impounding or drawdown) should be done slowly and smoothly. There should be only one peak and one trough in the annual water level curve. Drawdown rate should not exceed 0.6 m/month during any one month (see section 5.2.1, 5.2.4 - Submerged macrophytes, and 5.2.6).
Downstream discharge
Changes in the magnitude of downstream discharge should not be abrupt. During initial reservoir filling (and during any subsequent special period) discharge magnitude must never drop below a minimum safety limit which is to be determined by a fishery biologist. The release of an artificial flood annually is desirable as it creates spawning opportunities for several important fish species. Timing, magnitude and duration of the artificial flood must be determined by a fishery biologist. Termination of the flood must be gradual (see sections 6.1.1 - Discharge regulation, and 6.1.3 - reproduction).
