Mill Creek: Sharing Scarce Water
by Heidi Hopkins
Lee Vining's public meeting places-the grammar school's gymnasium, the local fire hall-have become key venues for discussing the proposal to rewater Mill Creek (see Mill Creek Proposal), one element of the Department of Water and Power's Mono Basin restoration plans. County supervisors, community residents, scientists, resource agency staff, and the Mono Lake Committee have come together to review questions raised during recent months as parties to the Mono Basin restoration planning process focus on how to restore Mill Creek.
The community discussion-at times highly charged and contentious-is about how the limited water of the north Mono Basin should be allocated and whether there is a way to use part of that water to restore Mill Creek while retaining existing water-dependent landscapes and habitat.
While all impacts relating to any change of water use will be addressed in the environmental review process stipulated by D-1631-the 1994 Water Board decision that established the target lake level for Mono Lake and called for restoration-the community's questions have been brought to the fore by a soon-to-expire option to purchase the Conway Ranch.
Conway Ranch acquisition linked to restoration proposal
As mentioned in the last newsletter, the Mill Creek restoration proposal is linked to a proposed public land acquisition project in the northwest corner of the Mono Basin. The Trust for Public Land (TPL) has acquired an option on the thousand-acre Conway Ranch, including the ranch's 18 cubic feet per second (cfs) Mill Creek water right. At present, TPL is working with Mono County to develop grants to fund the acquisition; if the purchase is successful, the land will be set aside as public open space. The series of public meetings held in Lee Vining is TPL's attempt to bring the community to some sort of consensus about Conway Ranch so that TPL can move forward with its project in advance of the Water Board process.
The essential question under discussion is: What will be done with the property's 18 cfs of Mill Creek water? In the D-1631-mandated restoration plans, DWP recommended the rewatering of Mill Creek (see sidebar) and suggested that the Conway Ranch water rights were critical to this effort. Conway Ranch's water, then, has become the link between the open space project and Mono Basin restoration.
The benefits
The restoration proposal is to re-establish the natural hydrology of Mill Creek, Mono Lake's third largest tributary. Evidenced by dry channels and remnant stumps, Mill Creek once provided lush, wooded bottomland and deltaic habitat such as that formerly found along Rush and Lee Vining creeks, a type that is rare today in the Great Basin.
If restored, Mill Creek's bottomland would once again develop riparian vegetation, meadows, and willows underneath a canopy of cottonwoods and Jeffrey pines. Deer, bobcat, coyotes, and all sorts of water-loving birds would find cover in the multi-storied habitat. Summer recharge would keep groundwater tables high and maintain backwater pools for fish and ducks into the fall and winter. With creek flows continuing through the winter, Mill Creek's brown trout population would thrive.
Down by the lake, where Mill Creek has cut two separate trenches across the existing delta, two embayments, or rias, would fill with water and extend upstream. Creek flows into these embayments would provide protected freshwater refuge for waterfowl in the fall and winter months, as recommended by the restoration scientists.
100 years of diversions
But because of historical water diversions from Mill Creek, the restoration proposal raises questions. As described in past newsletters, Mill Creek has been diverted for over 100 years. Its water has been used to irrigate north Mono Basin pastures and to generate hydroelectric power in the Lundy power plant. (DWP, which has rights to Mill Creek water, diverts its water for north Mono Basin irrigation, not for export.) As a consequence, Mill Creek has disappeared into the sand several miles from the lakeshore for most of this century. Its bottomland and deltaic habitat-rich wooded wetlands, marshes, open water ponds, and a freshwater environment off the creek's mouth-was lost.
In part because it was dry, Mill Creek's bottomland was less affected by the type of stream incision that DWP's operations caused on Rush Creek. At present, the underlying physical structure of the Mill Creek bottomland is relatively intact and offers an excellent opportunity to compensate for irreparable physical and biological damage to Rush Creek-just by reinstating natural flows and opening side channels.
But rewatering Mill Creek could affect landscapes currently benefiting from Mill Creek water. The diversion ditch in which Mill Creek's water has flowed for 100 years has taken on some of the attributes of a functioning stream with riparian habitat; it is now known as Wilson Creek. Additionally, a number of pastures irrigated with Mill Creek water lie scattered across the north Mono Basin landscape.
Questions raised
Whenever a change to the way water is distributed is proposed, there are questions. Not surprisingly, then, a number of people-fishermen, homeowners on the Conway Ranch, residents interested in protecting the basin's historical pastures-have raised questions. Some locals have formed a loose organization called People for Mono Basin Preservation as a means of participating more effectively in the Mill Creek decisions. Many of the questions relate to change.
The most pressing question asked by those concerned with the basin's historical landscapes is: Can you maintain the historical green meadows of Conway Ranch? The answer is an emphatic "yes!" For the last decade, roughly 85 percent of Conway Ranch-the entire meadow section north of Wilson Creek-has been irrigated with Virginia Creek water, diverted over from the Walker River system to the north, as well as with natural springs and runoff. Even during recent droughts, the meadows stayed green. The remaining 15 percent of Conway Ranch land to the south of Wilson Creek could be kept green using water-saving irrigation techniques.
Birdwatchers fond of the willows that meander across Conway Ranch ask: Can you return water to Mill Creek and still retain riparian habitat values on Wilson Creek? Again, yes, due to the property's hydrologic features. Runoff from natural springs and irrigation eventually ends up in the meadow depression through which Wilson Creek runs, actually increasing the creek's flow as it crosses the property. This, combined with a base-level release of Mill Creek water into Wilson Creek during the summer growing season, should maintain the important visual and habitat qualities of the riparian vegetation along the upper reaches of Wilson Creek.
Local fisherman ask: Can you maintain a productive year-round fishery on both Wilson Creek and Mill Creek? Probably not. In a recent study, the California Department of Fish & Game recommended streamflows for Mill Creek that would provide a healthy ecosystem for its existing brown trout population. To achieve these flows, virtually all of Mill Creek's available water in the fall and winter would need to be returned to Mill Creek, at least in dry years. This timing is additionally important because the fall and winter are precisely when water will make the most difference to migrating waterfowl. A Wilson Creek seasonal fishery could likely exist, however.
Duck hunters ask whether the rich waterfowl habitat at the Wilson Creek delta will disappear. It won't. The freshwater springs in the area existed before the diversion of Mill Creek water into Wilson Creek, as evidenced by the old age of the spring-formed tufa towers in the area. These springs will continue regardless of where Mill Creek water flows.
Others pose legal questions. How secure is the Virginia Creek water right? Apparently, Conway Ranch's 6 cfs right has high priority due to its having been established in the 1870s.Furthermore, the right is so small that it is unlikely to be challenged.
And people ask practical questions. For example, the ditch that carries Virginia Creek water over to the Conway Ranch cannot carry the full 6 cfs. Despite this, the 2-3 cfs that is brought over, combined with natural accretion from the ravine through which the ditch descends, has been sufficient to keep the meadows green.
Another practical issue is that the Mill Creek return ditch, which returns water to Mill Creek after a brief diversion through the Lundy hydropower facility, has limited capacity. If a substantial amount of the Conway Ranch water right were to be dedicated to Mill Creek, could the water physically get there? Not as the ditch is currently configured.
Furthermore, summer peak flows in excess of the water rights of Conway Ranch and others currently run down Wilson Creek by default. To return these flows to Mill Creek-where they belong by right-clearly requires restoring the capacity of the ditch if not expanding it to a greater capacity.
Those with historical interests have questions that are separate from the Conway Ranch proposal but part of the restoration proposal-and they are definitely part of the current debate.
For example, as part of its restoration plan, DWP proposed dedicating its north basin irrigation rights back to Mill Creek. If DWP did so, some have asked, wouldn't the meadows and old cottonwoods dry up on the historic Thompson Ranch, whose scenic meadows lie immediately adjacent to Highway 395 on Mono Lake's north shore? The Committee thinks not, if the current irrigation system is modernized. In fact, most agree that Thompson Ranch has been overwatered for many years, encouraging shallow root growth in its cottonwoods and proliferation of water-loving plants unpalatable to the sheep that graze there. With water-saving irrigation methods, the scenic values could be maintained, the meadow composition for grazing improved, and stronger-rooted trees developed.
A decision-making process
At the most recent community meeting, the Mono Lake Committee proposed that the Water Board be asked to help design a process that all can agree upon that will both (1) allow the community to move forward to protect Conway Ranch as open space under the tight timeline of the current option and (2) provide for thoughtful analysis of the Mill Creek restoration proposal and all its potential benefits and impacts.
As it stands now, December is a critical month. TPL's option expires at the end of January 1997; the county board of supervisors has agreed to make a decision on whether to move forward with the Conway Ranch project in December. Fires will continue to burn in the Lee Vining Fire Hall's wood stove as the parties struggle to reach some sort of consensus on a process for making decisions before the December deadline.
Heidi Hopkins, the MLC's Eastern Sierra Policy Director, is determined to keep hiking despite the snow.
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