In the coming months the District will begin work on the East Adams/Acacia Canal Improvement Project. This project is in partnership with the Yolo Subbasin Groundwater Association and is being made possible by a grant from the California Department of Water Resources through the Sustainable Groundwater Management Act (SGMA) grant program.
One of the grant program’s objectives is to provide funding for projects that provide multiple benefits while improving groundwater supply and quality. The focus of this article is a component of the more comprehensive project that seeks to improve China Slough and convey excess storm flows through the Slough to enhance groundwater recharge and sustain groundwater levels. In order to route excess storm flows in this area, the District must upgrade the East Adams and Acacia Canals’ infrastructure, and plans are underway to begin this spring. The infrastructure upgrades include enlarging culverts, and installing five new automated gates and check structures which will allow for automated control of the canal. The spill structure at the terminus of the Acacia Canal will also be replaced with an automated unit which will allow District staff to gain more control over the amount of spill into China Slough. The upgrades will allow for more flow into this part of the canal system and make it possible to divert storm flows from Cache Creek to facilitate groundwater recharge. The new infrastructure will help to achieve other goals of the project which include alleviating groundwater depletion and subsidence and help to minimize unintended water losses.
The new programmable gates will make it possible to responsibly divert excess storm flows from Cache Creek into the canal system for groundwater recharge. Although there are frequent excess flows in Cache Creek during the winter months, it can’t always be diverted into the canal system because certain regulatory and operational conditions must be met first. These conditions include that flows in Cache Creek at the Yolo gauge near Highway 5 must exceed 50 cfs, water flows in the Delta must “be in excess”, and the stormwater cannot contain too much sediment which will silt up the canals. Due to these constraints, District staff need to be able to act quickly when the right conditions are present, and the automated gates and check structures make it possible to implement recharge efforts when these requirements are met. Also, since the gates can be controlled remotely, flow changes can be made in locations where muddy roads at remote sites prevent staff from being able to access them.
The installation of the controlled gates is scheduled to begin this spring as soon as District staff can safely access canal roads and get heavy equipment into the project sites. The new culverts and check structures are also scheduled to be installed this spring, but Operations & Maintenance Supervisor Sal Espinoza says that the real schedule is set by Mother Nature. If springs rains persist into late March and April, then the culvert improvements and new spill structure will need to be delayed until the end of the 2024 irrigation season.
Other longer-term goals of the project include a feasibility study, cost-benefit analysis, and an environmental review to rehabilitate China Slough in order to facilitate groundwater recharge. The concept is to use China Slough to convey water and divert it onto cooperating farmers’ fields to maximize recharge area. In this way, the District and the YSGA hope to demonstrate that an expanded program could recharge up to 7,200 acre-feet of water per year, elevate groundwater levels, reduce the rate of land subsidence, and help to maintain at least 88 domestic wells.