1. The Effects of Lake Hydrology on Reservoir Design and Operation Michael Robinson UCSB Graduate Student

2. Acknowledgements Dr. Hugo Loáiciga, advisor. Dr. Keith Clarke, department chair. 200B cohort for feedback and recommendations.

3. Structure Description of linear model/reservoir design and operation problem. Preliminary results. Conclusions / Future work.

4. Methodolgy Purpose: »Develop and implement a design and annual operation model for the Lake Cachuma reservoir (Santa Barbara County, CA) »Inspired and extending H. Loáiciga’s Reservoir Design and Operation with Variable Lake Hydrology (2002).

5. Methodolgy Use linear programming to formulate the reservoir design and operation problem. »Without evaporation, E, and precipitation, P; streamflow, R, treated deterministically. »With E & P; R treated deterministically. »Without E & P; R treated stochastically. »With E & P; R treated stochastically.

6. Methodolgy Basic equation without lake evaporation and precipitation: Basic equation with lake evaporation and precipitation: where: S i = reservoir storagew i = releases R i = streamflowP i = precipitation D i = diversionsE i = evaporation i = 1, 2, …, n

7. Methodolgy Each component will minimize: where: K = cost of reservoir ($/10 6 m 3 ) C = reservoir capacity s = discount rate, 0.07 Gi = value of release ($/10 6 m 3 ) F = fisheries requirement, 2.932 x 10 6 m 3 /yr

8. Results Previous research (Loáiciga, 2002). »Lake hydrology plays major role on: Optimal reservoir capacity Average annual water release This research. »Further explore and develop these relationships. »Better understand capabilities and limitations.

9. Results Comparison of Lake Cachuma annual rainfall and evaporation. It is important to note that evaporation consistently exceeds rainfall.

10. Results Initial comparison of Model I and Model II data suggests that optimal capacity and average annual releases decrease when lake hydrology effects are considered. 50% initial capacity 100% initial capacity 50% initial capacity 100% initial capacity

11. Conclusions Significant impact on reservoir storage attributable to the effects of precipitation and evaporation. This affects: »Initial capacity of the reservoir. »Annual storage and releases. Future work may include an examination of this application to a variety of reservoirs in different locales and with different hydrologic conditions, again with the intent of helping policy makers and water supply managers better understand, protect and utilize their water supplies.

12. References Ahlroth, J.H., and Naftaly, M. (1997). Santa Ynez River hydrology model manual, Santa Barbara County Water Agency, Santa Barbara, Calif. Loáiciga, H. (2002). Reservoir Design and Operation with Variable Lake Hydrology. Journal of Water Resources Planning and Management, vol. 128, no. 6, pp. 399-405. Santa Barbara County Water Resources (rainfall data) United States Bureau of Reclamation (evaporation data) United States Geological Survey (streamflow data)