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Opinion: Mayor Oberg Explains Water Levels at Watson and Willow Lakes
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01 March 2017   Mayor Harry Oberg

What governs the levels at Watson and Willow Lakes?

Water is always an important subject in Arizona, and there is an old saying here in the West: “Whiskey is for drinking and water is for fighting.” As Mayor, I receive many comments and emails from constituents asking the water levels in the Willow Lake and Watson Lake reservoirs not be lowered, but left "as they are." Present water levels are at a six-year high, making these community assets particularly scenic. The sentiments expressed in emails and verbal comments are understandable. With those in mind, I thought that it would be opportune to review for your readers the various factors and complexities in determining water levels throughout each year.

The dams that created Watson and Willow Lakes were constructed in the early 1900s, at elevations favorable to create a gravity-flow irrigation system for agriculture and ranching in Chino Valley. The water in these reservoirs was routinely drawn down to the levels of their outlet pipes to provide the supply needed by agricultural lands in the Chino Valley Irrigation District (CVID). In 1998, the City of Prescott purchased the reservoirs for two principal reasons: as a source for our municipal water supply, and recreation. Prescott entered into an agreement with CVID and its shareholders (the property owners within the District) in order to utilize surface water flowing into the reservoirs The agreement held the surface water was to be used for recharging the local aquifer, and subsequent recovery to serve our utility customers. It is important to note that the CVID Agreement, and the manner in which Prescott uses the water, is subject to Arizona water law, water rights held by other parties, and ongoing obligations to CVID and its property owners. This agreement includes an annual "recharge window" from April 1st through November 30th, during which water may be sent from the reservoirs to the City's recharge facility near the Airport. The reservoir water levels are reduced to minimum "conservation pools" (depths below the spillway of each water body, but well above the outlet pipes) enabling continued recreational uses, while providing capacity for subsequent refilling from monsoonal and winter moisture. Within the recharge window, out flow is stopped for fish spawning and other natural events.

The voter-approved 2015 Prescott General Plan, available on the City website (www.prescott-az.gov), contemplates further growth of our community, and provides information on the water resources necessary to facilitate it. Unless prior groundwater rights exist for a parcel land, the only source of water that is presently physically available for new subdivisions is recharge/recovery. And an average annual quantity has been pledged for that purpose, hence its importance.

As will be evident, the reservoir levels reflect not only the annual recharging, but weather conditions (precipitation and evaporation) and their uncertainties. These make reservoir operations highly challenging. However, I believe the City has worked, with success, to maintain the balance between water supply requirements and recreation. Since acquisition, reservoir levels have not been reduced below the conservation pools.

The City's Water Resource Manager is scheduled to present the Annual Water Report to the City Council at our 1:00 pm Study Session on Tuesday, March 28, 2017, which will provide more information on several topics, including operation of the reservoirs. That presentation can also be viewed remotely by accessing the City website, and clicking on the "City Meetings" homepage link.

Our lakes, and the water they provide, are a resource that affects all citizens of Prescott. I hope this sheds some light on the purpose of the lakes, and the City’s ongoing management efforts.