Woodland and Davis are two of only a very few cities in California that still rely entirely on groundwater for water supplies. In the past, groundwater was plentiful enough to meet community needs, and also state and federal water quality regulations. By itself, it is not expected that groundwater will be able to meet future state drinking water quality and wastewater discharge regulations. The quality of local groundwater supplies is deteriorating. Our groundwater has an increasing amount of salts and other minerals that threaten the environment and public health. The Cities cannot meet anticipated future regulations for the water coming into homes, or for water returned to the environment after leaving the wastewater treatment facilities, using groundwater only. An alternative, high-quality water source is needed to largely replace and supplement the groundwater supplies.
The many benefits include health and safety of drinking water supplies, reduced costs from avoidance of wear and tear on water using appliances, compliance with treated wastewater discharge requirements, and environmental benefits associated with improvements to discharged wastewater and with the replacement of an antiquated intake on the Sacramento River with an intake with state-of-the-art fish screens. Resulting improvements in the quality of treated wastewater will increase the opportunity for water reuse, advance environmental stewardship in the Yolo Bypass, and potentially lower wastewater treatment costs from what they otherwise would be in the future. Additionally, there will be opportunities to implement aquifer storage and recovery, which involves injecting high-quality, treated surface water into wells for later use. This will allow the cities to maximize the use of surface water supplies by storing the surface water in the ground during the winter months when more water is available, and delivering that water to customers during summer months and other dry times when surface water supplies are not as readily available.
It’s the quality of the water – not the quantity – that’s driving the shift from groundwater to surface water. It’s also getting more and more difficult to meet demands for water use and water quality regulations using existing infrastructure. A number of groundwater wells in Davis and Woodland have been shut down and destroyed because they no longer work and can’t be fixed, or because they exceed drinking water quality limits. Over the past several years numerous wells in Woodland and in Davis have had to be removed from service due to excessive nitrate levels. It is also likely that a number of wells in both cities will be unable to meet pending hexavalent chromium limits. Even with major improvements to groundwater facilities (wells and pumps, for example), we would still fall short of meeting future water quality regulations for drinking water and treated wastewater. In short, we need a higher-quality source of water.
An acre-foot of water – a common unit of measure for water – is about 325,000 gallons. That’s roughly the amount of water used by two households in a year, including landscape water use.
WDCWA’s water right permit authorizes it to utilize up to 45,000 acre feet of water per year. However, diversions will be limited during summer months and other dry periods. During these times, WDCWA will utilize up to 10,000 acre feet of water under a senior water right purchased from the Conaway Preservation Group (see below). WDCWA is also exploring the possibility of implementing aquifer storage and recovery facilities, which involves the injection of high-quality, treated surface water into water wells for later extraction and delivery to water users. Injection into the wells would occur during the winter months when more surface water is available, and could be extracted and used in summer months and during other times when diversions are restricted.
WDCWA purchased a senior water right for 10,000 acre feet of surface water from the Conaway Preservation Group. This water is subject to fewer restrictions between April and October and will be used during times when water under the primary water right is not available. Existing groundwater sources will continue to be used along with higher-quality groundwater from the deep aquifer to help meet peak summer demands. Combined use of surface and groundwater sources, referred to as “conjunctive use,” and the blending of supplies will result in substantial year-round improvements in water quality, including the summer months.
Fluoride is a naturally occurring element found in water supplies throughout California. Optimum levels of fluoride have been shown to improve oral health and decrease tooth decay. In California, state law requires that optimum levels of fluoride be added to any public water systems with 10,000 or more connections. Currently, neither Woodland or Davis add fluoride to their water supplies since they lack a central treatment location where fluoride can be added, monitored and adjusted as needed. The construction of the surface water supply project, with its state-of-the-art treatment facility, offers both cities the option to add fluoride to their respective water supplies. Fluoride would be added post water supply treatment and would be done independently for each city. For this reason, each City Council will have the opportunity to consider whether or not it should fluoridate its water, taking into account a variety of factors such as cost and ability to effectively regulate fluoride levels when using a blend of groundwater and surface water. Recently, the Yolo County Board of Supervisors cited community health benefits when it adopted a resolution encouraging both cities to add fluoride to their water supplies.
There is some controversy around the fluoridation of water supplies. Supporters emphasize the proven health benefits of fluoride supplementation, along with the reduced medical costs and cases of dental disease in communities with fluoridated water systems. Opponents cite concerns that consumers who drink fluoridated water may get too much of the substance since it is added to toothpastes and other personal care products. Ingesting too much fluoride can present health risks. For that reason, the state and federal governments have adopted maximum limits on how much fluoride – the total of naturally occurring and added – can be present in tap water delivered into homes. This maximum limit takes into account the fluoride that consumers are receiving from other sources.
The City Councils for both Woodland and Davis will provide an opportunity for public consideration and input into their decisions about whether or not to fluoridate their water supplies, and what factors will be considered in making those determinations. The Woodland-Davis Clean Water Agency will be responsible for implementing the decisions of the cities.
Reclamation District 2035 and the Woodland-Davis Clean Water Agency are ...
WDCWA Board Meeting, April 20, 2017 - Davis at 3:00 p.m.