Basin Management Objectives (BMOs)

Basin Management Objectives (BMOs) developed in 2001 are the heart of the Glenn County Groundwater Management Plan. The Basin Management Objective (BMO) concept was developed to overcome many of the problems of defining safe yield and overdraft in the Sacramento Valley by the Department of Water Resources, Northern District Groundwater Section.

Ordinance 1115 requires that management objectives for minimum groundwater levels, minimum water quality and maximum inelastic subsidence be established for each of the 17 sub-areas. The management objectives can be considered a set of trigger points where action will be taken if the BMO levels are exceeded. Representatives from each sub-area established the objectives, the methodology used, and the wells to be monitored for their own area. A “one size fits all regulation” does not exist in Glenn County, rather the individual BMOs for each sub-area were compiled into a countywide BMO, which was approved by the Board of Supervisors after holding public workshops and a public hearing. The management objectives for each sub-area are evaluated annually and any changes must be approved by the Board of Supervisors. A basic tenet of the BMO for each sub-area is that water management practices or activities in one management sub-area shall not negatively impact the water management objectives of another sub-area.

At this time sub-area BMOs have been established for groundwater levels only. Sub-area BMOs for water quality and subsidence will be adopted when the monitoring system is in place. It is anticipated that the BMOs will change as more data becomes available and experience is gained in evaluating the data.

In January 2010, Sub-areas 8, 9 and 10 were revised. The revisions are included here:

In April 2012, Sub-area 4 and Sub-area 5 revisions from March 2010 were approved by the Board of Supervisors. The revisions are included here:


There are various methods for determining the BMO for groundwater levels. There is no definitive method that should take precedence over the others because of the uncertainty in the data. However, some methods may be preferable based on variability of the data, simplicity, operating procedures, or availability of data. The value of having historical data cannot be over-emphasized. Data from wells in sub-areas without historical data must be obtained in dry precipitation cycles in order to establish and have confidence in BMOs for those sub-areas. The methods used to calculate BMOs for Glenn County sub-areas are described in the BMO document adopted August 2001.