OOS 49-9
Water supply and ecosystem restoration in the Mono-Owens Watersheds: The promise and pitfalls of adaptive management
Limitations on the water gathering activities by the Los Angeles Department of Water and Power (DWP) in the Mono Lake and Owens Lake watersheds has been accompanied by prescriptions to restore flow and habitats in their influent streams. The overall goals of the restoration programs in the two terminal lake watersheds are very similar –“restoration of functional stream systems with healthy riparian ecosystem components” in the Mono Basin and “establishment of a healthy, functioning Lower Owens River riverine-riparian ecosystem”. Both programs embrace adaptive management with the Lower Owens River Program (LORP) explicitly requiring the development of an adaptive management plan. Despite the similarity in intent, the restoration trajectories are very different. In the Mono Basin, stream ecosystem recovery is well underway and a recent settlement provides for a higher capacity reservoir release facility and an adaptive management process that facilitates the restoration. In the LORP, consultants retained by DWP observed that the River “is degrading” and the flow regime is causing “ecological stagnation … limiting the ability of the river to achieve original goals”, “the adaptive management process is broken” and the compliance criteria in the legal agreements should be “rescinded” and re-negotiated.
Results/Conclusions
The different restoration trajectories can largely be explained by:
a) The relationship of the prescribed flow regime to the natural hydrology. In the Mono Basin, about 85% of the average runoff is currently required to be released into the streams, guided by the timing and duration of the natural hydrograph. The Lower Owens River releases are about 10% to 20% of the natural runoff, with an unvarying, year-round base flow in every year type. Slightly higher seasonal flows are released for several days but are dramatically attenuated in magnitude and duration by the low gradient and tule growth.
b) In the Mono Basin, adaptive management is accommodated by DWP and encouraged by water right orders that define DWP’s diversions, based upon Mono Lake levels and year types. In the LORP, adaptive management recommendations that DWP determines could impact their water supply are ignored.
The LORP is at a tipping point because with the current flow regime the ecosystem goals will likely not be achieved and DWP’s supply reliability will decrease as flow losses increase, particularly in dry years. The LORP reaffirms that ecosystem restoration with a fraction of the natural runoff requires realistic goals with a robust adaptive management program.