Water supply providers are facing increasing difficulty expanding their water
supply systems to satisfy growing population and industry demands. The process of
developing a new water supply source or even expanding an existing source is often met
with opposition from environmental and special interest groups, and results in lengthy,
expensive, and difficult litigation. The outcome in some recent expansion efforts has
been a directive to "do more with what you have". In these cases, water supply providers
are instructed to operate beyond the safe yield of their system and rely on conservation
measures to satisfy water supply demands during severe drought events. Operating a
water supply system this close to the edge of its reliable limits requires an accurate
determination of the safe yield and thorough knowledge of the system's performance
during severe drought events.
The authors of this paper have recently performed detailed safe yield studies for
several large and medium-sized water supply systems. These water supply systems vary
in complexity from a system with multiple reservoirs with conjunctive use of river
intakes and wells, to a simple system with a single large reservoir. The safe yield
analyses for each of these systems involved developing a custom computer model to
simulate the daily operation of the system for a lengthy period of continuous historical
inflows, often exceeding 80 years. These site specific computer models are capable of
simulating a variety of operating assumptions, variations in monthly demand,
conservation measures, and complex regulatory restrictions. In some cases the operating
rules were dependant upon water quality variables simulated by the model.
When performing safe yield studies using a daily flow model, considerable effort
and skill are required to develop the inflow database, estimate evaporation losses,
determine useable storage, and quantify physical transmission limitations within the
system. The result can be a powerful tool that can be used to generate important system
statistics, perform "what if" analyses, test proposed conservation plans, and develop
operating procedures to maximize existing resources.
This paper discusses the procedures for developing a daily flow
model for a raw water supply system, with special emphasis on common oversights that
are important to avoid. Lessons learned from past analyses and the graphical presentation
of complex water system statistics including safe yield are also presented. The tools
discussed in this paper are provided to help water supply managers "do more with what
they have".
Includes 8 references, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 1.1 MB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 13 |
| Published : | 06/16/2002 |
