As the Marin Municipal Water District nears the end of a nearly yearlong study of potential new water supplies, some district leaders say more information is needed on the costs and benefits of bolstering water conservation investments.

“I’m concerned that we are, as a board and as the public, still lacking the data we need about what’s feasible,” district board member Cynthia Koehler said during a board meeting on Tuesday.

The district has been studying new water supplies since March after facing the prospect of depleting local reservoir storage following two years of severe drought. Rains in late 2021 helped to nearly refill the district’s seven reservoirs, giving it time to review new sources of water.

The district hired the Jacobs Engineering firm to conduct the water supply study. The study seeks to compare estimated costs and water yields for several options, including desalination, recycled water, enlarging reservoirs and new connections to outside water agencies. The results and recommendations are expected to be released in January and likely will include various portfolios of water supply options, according to staff.

However, the study does not include a similar review of water conservation programs as board members had expected. In response, district staff presented their own estimates in August and September on potential water savings and costs from investing in conservation programs such as installing wireless water meters, turf replacement rebates, rain barrels and grey water reuse systems.

Staff estimated, based on the historical performance of these conservation programs and those of other water agencies, that total annual water use could be reduced by about 15% by 2045 to a total of 27,400 acre-feet per year.

By comparison, annual water use in 2020 was 26,500 acre-feet, with an acre-foot equating to about 326,000 gallons. The cost estimate per acre-foot of water saved would be about $1,800 for the district and $2,883 for the district’s ratepayers, mostly from hardware installation and maintenance costs, according to the district.

In September, the board directed staff to hire the Maddaus Water Management consulting firm to conduct a further review of the estimated water savings from conservation under a contract not to exceed $14,000. The study was in addition to the Jacobs Engineering water supply study, which could cost up to $620,200.

On Tuesday, Maddaus Water Management presented its findings. It largely found that the district staff’s estimates were reasonable, with some exceptions. The study recommended increased installation of wireless water meters, known as AMI meters, throughout the district, while calling on the district to shy away from funding programs such as pool cover rebates that it said are unlikely to generate high participation or water savings.

The study did include cost estimates, and Koehler expressed concern on Tuesday that the latest study also did not account for increasing participation in conservation programs through time.

“There were assumptions that were made that do not seem to have been questioned,” she said during the meeting.

Board member Larry Bragman said conservation program spending has been capped because of financial impacts caused by the drought, but that he has never assumed the conservation budget was set in stone.

“Moving forward I have not assumed that as a policy of this board,” Bragman said Tuesday. “I really disagree with that statement about our philosophy and what staff is directing.”

Board member Monty Schmitt said he agrees there is “room for further sharpening” on the water savings and the costs of these conservation programs.

“I think that would be time well spent,” Schmitt said on Tuesday. “We really want to be cost effective here. That’s going to be a key driver, among other things.”